development of a cast 50 ksi (345 mpa) yield strength …

Pennsylvania State University

The Graduate School

DEVELOPMENT OF A CAST 50 KSI (345 MPa) YIELD

STRENGTH LOW ALLOY STEEL WITH A LOW CARBON

EQUIVALENT

A Thesis in

Materials Science and Engineering

by

Cody Daniel Snyder

copy 2019 Cody Daniel Snyder

Submitted in Partial Fulfillment

of the Requirements

for the Degree of

Master of Science

December 2019

II

The thesis of Cody Daniel Snyder was reviewed and approved by the following

Robert C Voigt

Professor and Graduate Program Coordinator of Industrial Engineering

Thesis Advisor

Allison M Beese

Associate Professor of Materials Science and Engineering

Jingjing Li

Associate Professor of Industrial Engineering

Amy C Robinson

Associate Teaching Professor of Materials Science and Engineering

Special Signatory

John C Mauro

Professor of Materials Science and Engineering

Associate Head for Graduate Education of Materials Science and Engineering

Signatures are on file in the Graduate School

III

Abstract

The purpose of this research was to develop a 50 ksi (345 MPa) Yield Strength

(YS) cast steel with a carbon equivalent (CEAWS D11) of le 045 wt CE to ensure that

optimum weldability is maintained A database of conventional C-Mn cast steel (ASTM

A216 WCB grade specific cast steel) compositions and mechanical properties was

analyzed to determine if these can meet YS and CE requirements or if microalloying was

needed The database analysis found that only 041 of the cast steels reached YS and

CE requirements thus microalloying was needed to achieve YS and CE requirements

Microalloying effects of vanadium were understood further with Modified C-Mn and

Modified C-Mn-V cast steels that had compositions based on previous literature work1

These alloys were subjected to NampT and QampT heat treatments (austenitizing at 1750 ˚F

(955 ˚C) for 2 hr) a tempering study and special heat treatments that included thick-

section analysis normalizing cooling rate study and double normalizing Optical

microscopy was performed on both samples and there was precipitation hardening

observed in the Modified C-Mn-V alloy for both NampT and QampT conditions The targeted

chemistry for both alloys was not achieved by the casting foundry this resulted in high

CE for both alloys 048 and 051 wt CE for Modified C-Mn and Modified C-Mn-V

respectively Further work continued because these alloys did not meet YS and CE

requirements Next Alloys C-F were developed with a focus on how much variation in

composition is allowable to still achieve YS requirements and they were tested for

mechanical properties in the NampT and QampT conditions Alloy C and Alloy E met CE

requirements with 039 and 044 wt CE respectively Alloy C achieved a YS of 81 ksi

(558 MPa) in the QampT condition but did not reach 50 ksi (345 MPa) in the NampT

IV

condition Alloy E reached YS requirements in both the NampT and QampT conditions Thus

Alloy E has the optimum composition to achieve high weldability and 50 ksi (345 MPa)

YS with the following composition 012 wt C 104 wt Mn 025 wt Si 036

wt Cr 006 wt Ni 003 wt Mo 006 wt Cu and 011 wt V

V

Table of Contents

List of Figures IX

List of Tables XIII

List of Equations XV

Acknowledgements XVI

Chapter 1 Introduction - 1 -

11 Project Overview - 1 -

12 Metals Casting Background - 2 -

121 A Brief History of Iron and Steel Production - 3 -

122 Todayrsquos Metals Casting World - 4 -

1221 Contemporary Furnaces - 4 -

1222 Casting Techniques - 5 -

12221 Continuous Casting - 6 -

12222 Ingot Casting - 7 -

12223 Shape Casting - 8 -

122231 Green Sand Casting - 9 -

122232 Permanent Metal Mold Casting - 15 -

1223 Production Rates of Todayrsquos Metal Casting World - 16 -

13 Relevant Phases and Microstructures - 17 -

131 Ferrite (α-Fe) and Cementite (Fe3C) - 17 -

132 Austenite (γ-Fe) - 17 -

133 Pearlite - 18 -

14 Strengthening Mechanisms in Steels - 20 -

141 Increasing C Content - 21 -

142 Refinement of Ferrite Grains - 24 -

143 Addition of Solid Solution Strengthening Elements - 26 -

144 Addition of Precipitation Hardening Elements - 27 -

145 Formation of Dislocations - 28 -

15 Cast Metal vs Wrought Metal - 30 -

151 Cast Metal - 31 -

152 Wrought Metal - 32 -

VI

16 Solidification Dynamics - 32 -

161 Nucleation Mechanisms - 32 -

1611 Homogeneous Nucleation - 34 -

1612 Heterogeneous Nucleation - 36 -

162 Solidification Dynamics of a Cast Pure Metal - 38 -

163 Solidification Dynamics of a Cast Alloy - 40 -

164 Solidification Zones in a Casting - 41 -

1641 Chill Zone - 41 -

1642 Columnar Zone - 42 -

1643 Central Equiaxed Zone - 43 -

17 Solidification Defects - 44 -

171 Macroporosity - 44 -

172 Macrosegregation - 46 -

173 Microporosity - 47 -

174 Microsegregation - 48 -

175 Gas Porosity - 48 -

18 Heat Treating of Steels - 50 -

181 Homogenization - 52 -

182 Full Anneal - 53 -

183 Process Anneal - 53 -

184 Normalization - 54 -

185 Austenitize-Quench-Temper - 54 -

1851 Hardness vs Hardenability - 54 -

1852 Martensite - 56 -

1853 Tempering Kinetics - 59 -

186 Spheroidizing - 60 -

187 Stress Relieving - 60 -

19 Introduction to High Strength Low Alloy (HSLA) Steels - 60 -

191 Precipitation Hardening - 61 -

110 Weldability and Carbon Equivalent (CE) - 61 -

1101 Weldability - 61 -

1102 Carbon Equivalent (CE) - 62 -

VII

Chapter 2 Literature Review - 63 -

21 Microalloying of Steels - 63 -

211 Early Microalloying History with Vanadium - 63 -

22 HSLA Steels - 64 -

221 Strengthening Mechanisms of Microalloys - 65 -

222 Carbides Nitrides and Carbonitrides - 66 -

2221 Vanadium Microalloy Additions - 69 -

2222 Niobium Microalloy Addition - 72 -

2223 Titanium Microalloy Additions - 73 -

2224 The Roll of Manganese in HSLA Steels - 73 -

23 HSLA Cast Steels - 74 -

231 Temperaging - 76 -

232 Weldability and Carbon Equivalent in Previous Work - 76 -

233 Pertinent Cast Steel ASTM Standards - 78 -

234 Key Findings from Previous Work - 79 -

Chapter 3 Hypothesis and Statement of Work - 82 -

31 Hypothesis - 82 -

32 Statement of Work - 82 -

Chapter 4 Experimental Procedure - 83 -

41 Heat Treating Modified C-Mn and Modified C-Mn-V - 83 -

42 Tempering Study - 84 -

43 Special Heat-Treating Options - 85 -

431 Thick-Section Study Part I (Keel Block) - 85 -

432 Thick-Section Study Part II (Normalizing Cooling Rate Effect) - 85 -

433 Double Normalize - 86 -

44 Heat Treating of Factorial Design Alloys - 86 -

45 Metallography of Samples - 87 -

Chapter 5 Results and Discussions - 89 -

51 SFSA Database for Conventional C-Mn (WCB) Steel - 89 -

52 Modified C-Mn and Modified C-Mn-V - 98 -

53 Thermocalc CALPHAD Modeling - 100 -


VIII

55 Initial Round of Heat Treating - 109 -

551 Analysis of Modified C-Mn - 109 -

552 Analysis Modified C-Mn-V - 112 -

553 SEM Analysis of Modified C-Mn and Modified C-Mn-V - 115 -






571 Analysis of Alloy C-F - 129 -

58 Weldability and Carbon Equivalent Analysis - 135 -

59 ASTM Considerations - 139 -

Chapter 6 Summary Conclusion and Future Work - 141 -

61 Summary - 141 -

62 Conclusion - 147 -

63 Future Work - 149 -

Appendix A - 150 -

Appendix B - 153 -

References - 154 -

IX

List of Figures

FIGURE PAGE

Figure 1 Continuous Casting Process Schematic 7

Figure 2 Hierarchy Chart of Shape Casting Processes 9

Figure 3 Horizontal Green Sand-Casting Mold Illustration11

Figure 4 Green Sand-Casting Flow Chart 12

Figure 5 Diagram of a Green Sand-Casting Shake-out System 14

Figure 6 Green Sand Reclamation and Cooling Diagram15

Figure 7 Graph of Casting Sales per Year 16

Figure 8 Eutectoid Cooling Diagram for Steel 18

Figure 9 Hypoeutectoid Cooling Diagram for Steel 19

Figure 10 Hypereutectoid Cooling Diagram for Steel 20

Figure 11 Illustration of Interstitial Carbon in BCC α-Fe 22

Figure 12 Illustration of Interstitial Carbon in FCC γ-Fe 23

Figure 13 Iron-Carbon Phase Diagram 23

Figure 14 Solid Solution Strengtheners Effecting Yield Strength 27

Figure 15 Illustration of an Edge Dislocation 29

Figure 16 Illustration of a Screw Dislocation 30

Figure 17 Graph of the Four Stages of Nucleation and Growth 34

Figure 18 Image of a Thermodynamically Stable Nuclei 35

Figure 19 Graph of Gibbs Free-Energy as a Function of Nuclei Radius 36

Figure 20 Wetting Diagram Showing Surface-Energy Affect 37

Figure 21 Graph of Nucleation Growth and Transformation Rates 37

Figure 22 Graph of Solidification Latent Heat Profile 38

Figure 23 Illustration of Primary and Secondary Dendritic Arms 39

Figure 24 Solidification Properties Influenced by Composition Graph 41

Figure 25 Illustration Depicting Different Casting Solidification Zones 42

Figure 26 Metal Shrinkage as a Function of Phase and Temperature 45

X

Figure 27 Illustration of Pipe Defect Formation Inside a Casting 46

Figure 28 Lever Rule Example for Two-Phase Region 47

Figure 29 Illustration of Microporosity in the Inner-Dendritic Region 48

Figure 30 Graph of Gas Solubility in Metal as a Function of Phase 49

Figure 31 Micrograph of Gas Hole Porosity 50

Figure 32 Heat Treating Temperature Ranges Fe-C Phase Diagram51

Figure 33 TTT Diagram for Steel 55

Figure 34 Illustration of Interstitial Carbon in BCT Martensite 57

Figure 35 Diagram of Martensitic Bain Strain 58

Figure 36 Graph of MS Temperature and Lath vs Plate Martensite 59

Figure 37 Chart Displaying Common Stoichiometric Steel Carbides 68

Figure 38 Bar Chart of Carbide and Martensite Hardness 68

Figure 39 Graph of Mole Fraction of VCN vs Temperature 70

Figure 40 Recrystallization Temp vs Solute Content for Microalloys 72

Figure 41 Graph of Solubilities of Common Carbides vs Temperature 73

Figure 42 Optimum Alloying Range with Mechanical Properties 75

Figure 43 Complete Scatterplot Heat Treat vs CE for SFSA Sprdsht 90

Figure 44 YS vs C Content for SFSA Spreadsheet 91

Figure 45 YS vs Mn Content for SFSA Spreadsheet 91

Figure 46 Normalized Condition YS vs Weldability 93

Figure 47 NampT Condition YS vs Weldability 94

Figure 48 QampT Condition YS vs Weldability 95

Figure 49 Modified C-Mn Thermo-Calc Phase Fraction vs Temp 101

Figure 50 Modified C-Mn-V Thermo-Calc Phase Fraction vs Temp 101

Figure 51 Modified C-Mn-V with Nb Thermo-Calc Phase Fraction 102

Figure 52 Modified C-Mn NampT Tempering Graph 104

Figure 53 Modified C-Mn QampT Tempering Graph 104

Figure 54 Modified C-Mn-V NampT Tempering Graph 105

Figure 55 Modified C-Mn-V QampT Tempering Graph 105

Figure 56 Modified C-Mn NampT vs QampT Tempering Graph 106

XI

Figure 57 Modified C-Mn-V NampT vs QampT Tempering Graph 106

Figure 58 NampT Condition Modified C-Mn vs Modified C-Mn-V 107

Figure 59 QampT Condition Modified C-Mn vs Modified C-Mn-V 107

Figure 60 NampT Condition HRB vs Temp Mod C-Mn amp C-Mn-V108

Figure 61 QampT Condition HRB vs Temp Mod C-Mn amp C-Mn-V108

Figure 62 Micrograph of Modified C-Mn in NampT Condition 111

Figure 63 Micrograph of Modified C-Mn in QampT Condition 111

Figure 64 Micrograph of Modified C-Mn-V in NampT Condition 114

Figure 65 Micrograph of Modified C-Mn-V in QampT Condition 114

Figure 66 SEM Micrograph Modified C-Mn NampT Condition 116

Figure 67 SEM Micrograph Modified C-Mn-V NampT Condition 116

Figure 68 SEM Micrograph Modified C-Mn-V NampT Condition (2) 117

Figure 69 Modified C-Mn Attached to Keel Block Micrograph 122

Figure 70 Modified C-Mn-V Attached to Keel Block Micrograph 123

Figure 71 Modified C-Mn Separated from Keel Block Micrograph 123

Figure 72 Modified C-Mn-V Separated from Keel Block Micrograph 124

Figure 73 Modified C-Mn Double Normalize Micrograph 126

Figure 74 Modified C-Mn-V Double Normalize Micrograph 126

Figure 75 Alloy C in NampT Condition Micrograph 131

Figure 76 Alloy C in QampT Condition Micrograph 131

Figure 77 Alloy D in NampT Condition Micrograph 132

Figure 78 Alloy D in QampT Condition Micrograph 132

Figure 79 Alloy E in NampT Condition Micrograph 133

Figure 80 Alloy E in QampT Condition Micrograph 133

Figure 81 Alloy F in NampT Condition Micrograph 134

Figure 82 Alloy F in QampT Condition Micrograph 134

Figure 83 ISO-YS Graph NampT Condition 00 wt V 136



Figure 86 ISO-YS Graph QampT Condition 00 wt V 137

XII



Figure 89 Extra Micrograph of Cast Steel Appendix A

Figure 90 As-Cast HSLA Steel Micrograph Appendix A

Figure 91 Original Estimate for Vanadium ISO-YS Graph Appendix A

Figure 92 Original Attempt at YS Surface Appendix A

XIII

List of Tables

TABLE PAGE

Table 1 Chemistry Range for Low-C V-Alloyed Cast Steel 75

Table 2 SFSA Database Mechanical Property Extrema92

Table 3 SFSA Database Heat Treatment per Designation 93

Table 4 Normalized Condition Average Chemistries per Designation 94

Table 5 NampT Condition Average Chemistries per Designation 95

Table 6 QampT Condition Average Chemistries per Designation 96

Table 7 Top amp Bottom Quart Ave and Std Dev SFSA Database 96

Table 8 Summary of SFSA Database 97

Table 9 Spectro Comp of Modified C-Mn and Modified C-Mn-V 99

Table 10 CE Values for Modified C-Mn and Modified C-Mn-V 99

Table 11 Target C vs Mult Spectro Modified C-Mn amp C-Mn-V 99

Table 12 Mechanical Properties Modified C-Mn NampT and QampT 110

Table 13 Mechanical Properties Averages from Table 11 110

Table 14 Mechanical Properties Modified C-Mn-V NampT and QampT 112

Table 15 Mechanical Property Averages from Table 13 113

Table 16 Brinell Hardness Profiles Across Keel Blocks119

Table 17 Brinell Hardness Profile Est Midway and Edge Values 119

Table 18 Mechanical Prop Thin Section Attached to Keel Block 121


Table 20 Mechanical Prop Thin Section Separated from Keel Block 121


Table 22 Mechanical Prop Double Normalize C-Mn amp C-Mn-V 125


Table 24 Alloys C-F Designations 127

Table 25 Alloys C-F Compositional Targets 127

Table 26 Alloys C-F Spectrometer Composition 128

XIV

Table 27 CE Values for Alloys C-F 128

Table 28 Target C vs Multiple Spectro Data Alloys C-F128

Table 29 Mechanical Properties Alloy C NampT and QampT 129


Table 31 Mechanical Properties Alloy D NampT and QampT 129


Table 33 Mechanical Properties Alloy E NampT and QampT 129


Table 35 Mechanical Properties Alloy F NampT and QampT 130


Table 37 ASTM Standard Summary 139

Table 38 Alternate CE Table Mod C-Mn and Mod C-Mn-V Appendix B

Table 39 Alternate CE Table Alloys C-F Appendix B

Table 40 Original Database Quartile Analysis Data Appendix B

XV

List of Equations

EQUATION PAGE

Equation 1 Hall-Petch Yield Strength Grain Size Relation 26

Equation 2 Gibbs Free-Energy for a Sphere 34

Equation 3 ldquoYoungrsquos Equationrdquo for Wetting of a Material 37

Equation 4 AWS D11 CE 77

Equation 5 General ASTM and IIW CE 77

Equation 6 HSLA C-Mn Steels CET 77

Equation 7 ASTM A529 CE 77

Equation 8 Japanese Welding Engineering Society CE 77

Equation 9 Regression Equation for ISO-YS Lines NampT 135

Equation 10 Regression Equation for ISO-YS Lines QampT 135

XVI

Acknowledgements

First and foremost I have to thank the best advisor I could ever ask for Dr

Robert Voigt I cannot thank him enough for having faith in me and accepting me as a

graduate student Itrsquos an honor to learn from one of the best metallurgists in the field The

metals casting world owes you a great deal you are a great conduit supplying nearly

endless knowledge from academia to industry In addition to being a great advisor he

also has a job lined up for me at the Benton Foundry upon completion of my Masterrsquos

Next this research would not have gotten off the ground if it wasnrsquot for the

organizations foundries and partners who contributed funding heats of material and

other resources and services Raymond Monroe David Poweleit Ryan Moore and Diana

David from the SFSA Charlie and Greg from Regal Cast in Lebanon PA Bill and

Maynard from Effort Foundry in Bath PA my boy Robert Haldeman (shock the world)

with Car-Tech in Reading PA and Andrew and Ken who worked for Dr Voigt as

undergraduates and lent helping hands when they could

Next due to my limited computer literacy and my difficulty with coding I have to

thank the following Brandon Bocklund and Hongyeun Kim from Dr Luirsquos group (thanks

for the Thermo-Calc help) And most importantlyhellip my dear friend fulltime MatSE

partner and part-time math tutor Nick Clarks

Finally most importantly my family Thank you for your endless love constant

support enduring patience and never-ending encouragement I love you

Chapter 1 Introduction

11 Project Overview

This research was conducted in hopes of creating a cast steel alloy with a

minimum nominal yield strength (YS) of 50 ksi (345 MPa) and a maximum carbon

equivalent (CEAWS D11) of 045 wt C for military and construction applications This

is in response to the recent transition from 36 ksi (248 MPa) highly weldable wrought

steels to 50 ksi (345 MPa) highly weldable wrought steels It is desired that complex

shapes of 50 ksi (345 MPa) cast steel be cast into the final form and welded into place to

expedite construction processes The CE limit will ensure a high weldability and prevent

preheating requirements for welding purposes A primary goal is creating an alloy that

can be readily cast at any steel foundry in the United States This implies simple

chemistries not requiring special furnaces or abnormal heat treatments to attain

mechanical properties Foundries often find difficulty with targeting chemistries

accurately thus detailed heat-treating protocols will be designed so a corrective heat

treatment can be performed by the foundry to correct variance with chemistry

Cast steels are not afforded the luxury of receiving strengthening and defect

correction from thermomechanical deformation as are wrought steels Therefore

mechanical properties of the cast steel developed will be influenced solely from

chemistry and heat treatments Additionally casting defects that otherwise could be

deformed out of a wrought steel will often remain with the casting There are multiple

advantages to using cast steels that justify the metallurgical hurdles such as cost savings

because of fewer production steps The strength of 50 ksi (345 MPa) will be reached by

- 2 -

developing a High Strength Low Alloy (HSLA) steel This effectively uses microalloying

additions such as vanadium to refine strengthen and toughen the ferrite matrix while

maintaining a high weldability1

Finally since there are no current existing standards or codes for a 50 ksi (345

MPA) YS cast steel with CEAWS D11 le 045 wt CE an attempt will be made to

establish composition ranges and heat-treating directions in a current American Society

for Testing of Materials (ASTM) Standard The newly developed material grade will

mimic an already existing wrought or cast standard such that it is compatible with

wrought steels with similar performance To enable the goal of casting the steel into its

final form and assembling via welding to come to fruition the cast steel must also be

introduced into the AWS D11 Structural Code for Steel

12 Metals Casting Background

Metals casting in the most generalized definition is the act of pouring molten

metal into a shaped mold such that upon solidification the metal retains the shape of the

mold in which it was poured In reality there are many mechanisms and unseen forces at

work during the melting pouring and solidification of a metal The art and science of

metals casting has its roots traced back to antiquity and it has been an ever-evolving

process ever since its inception Ancient metallurgists did not possess an extensive

knowledge of metallurgy thermodynamics kinetics fluid dynamics and heat transfer

however expertise in these areas are essential for modern metal casting facilities to be

competitive efficient and successful2

- 3 -

121 A Brief History of Iron and Steel Production

The metallurgists of antiquity were only able to utilize seven metals copper lead

silver mercury tin iron and gold all but tin being in an elemental form Ancient

metallurgist called ldquoalchemistsrdquo at the time were first able to use elemental gold in

approximately 5000 BC3 Iron smiths at the time of approximately 1200 BC were able to

produce tools and weapons from iron and steel Surprisingly this was before technology

allowed for the melting of iron Metallurgists of this time period were aware that if iron

ore was heated with charcoal strength improved This is because carbon reduces the iron

ore into iron Consequently carbon migrated its way into the crystal of iron through solid

state diffusion and it increased the strength Then blacksmiths forged this primitive

version of steel into desired shapes which unknown to them also helped the mechanical

properties while creating a wrought iron34

Cast iron was first melted in the seventeenth century when coal replaced charcoal

in the smelting of iron because of the higher temperatures that were enabled by the coal

Cast iron due to its eutectic point at 41 wt C has a lower melting point as observed

in Figure 13 and was melted over a century before steel Metallurgists of the time soon

discovered that the cast iron was very brittle and efforts were made to remove some of

the carbon in the cast iron to decrease its brittleness Carbon was oxidized out of the cast

iron and wrought iron was created3

Even though steel has been used by peoples for over 3000 years similar to iron

the technology was not available to create steel in the modern sense until about 1740 AD

In 1856 Henry Bessemer created the process by which modern steel is produced The

ldquoBessemer Processrdquo forces heated air into the molten pig iron to initiate decarburization

- 4 -

This oxidized the carbon resulting in CO2 production and a reduction in the amount of

carbon content in the melt Now the remaining metal can be shape casted or cast as steel

into ingots and then forged into shapes3

122 Todayrsquos Metals Casting World

Today even though the principles of melting metals are unchanged the

metallurgy knowledge would be unrecognizable to a metallurgist of antiquity Metallurgy

in the past was utilitarian and even a poorly casted bronze tool was better than one made

of wood so improvement was easy to achieve Contemporary metallurgists have strict

requirements to follow and their products are met with a high demand for excellence by

consumers who require failure-free parts delivered at a competitive price Metallurgical

engineering of today focuses on producing lighter-weight materials to reduce the overall

weight of a system while obtaining optimal strength and performance levels without

sacrificing safety The reduced weight of an entire system will limit raw materials

consumed energy during production shipping costs while increasing fuel economy in a

progressively environmentally conscience world

1221 Contemporary Furnaces

In conjunction with advanced engineering teams the modern castings world

utilizes state-of-the-art furnaces to efficiently produce metals as pure and clean as

possible The furnace used is dependent upon type of metal produced desired tonnage of

metal production and the facility layout

Large modern steel facilities producing virgin steel ie do not re-melt scrap often

require two different furnaces First pig iron must be created in a blast furnace Iron ore

- 5 -

coke and lime are added to the blast furnace and hot air is forced into the furnace Coke

behaves as a reducing agent to iron ore producing what is known as pig iron which is a

high carbon content steel Additionally lime has an affinity for impurities and will bond

with them resulting in a slag compound less dense than molten pig iron Consequently it

floats to the top of the melt where it can be removed Next the pig iron is poured into

pigs In these holding vessels the pig iron will solidify be transported and await re-melt

in a Basic Oxygen Furnace A Basic Oxygen Furnace is a modern version of the

Bessemer Converter such that the molten pig iron is oxidized to reduce carbon and

impurities exothermically to produce steel45

Steel can also be created from scrap while being melted in Electric Arc Furnaces

which are the most common furnace used in todayrsquos iron and steel foundries They

provide better metallurgical control and are nearly emissions free The process for

melting in an Electric Arc Furnace is as follows A charge of scrap metal is loaded into

the furnace which is refractory lined with a high voltage coil surrounding the outer

refractory This coil produces a magnetic field inducing eddy currents in the metal such

that the inherent electrical resistance of the metal creates heat Given time the melting

temperature is reached Once the metal is in its liquid state the induction along with

buoyancy driven flow create currents inside the melt that encourage mixing of alloying

elements This type of furnace is scalable and it can be used to melt ferrous and non-

ferrous metals56

1222 Casting Techniques

Contemporary metals casting is completed in one of three ways continuous

casting ingot casting and shape-casting2

- 6 -

12221 Continuous Casting

Continuous casting is different from the other two forms of metals casting

because it is not a batch process It is normally performed in tandem with wrought

processing The process is as follows and a schematic can be observed in Figure 1

Molten metal from a furnace is transferred to a ladle which pours into a tundish The

tundish is a critical component to the continuous casting process because this

intermediate container enables a steady-state flow of molten metal to occur It drains

slowly into a highly thermally conductive mold of water-cooled copper while a crane

operator retrieves another ladle of molten metal The flow rate is timed perfectly such

upon exiting the copper mold the steel already has a solidified outer shell in the desired

shape of the slab that will be sold It continues on this line to a sizing mill where the slab

can be thermomechanically deformed to a more exact dimension2

- 7 -

Figure 1 Continuous casting process from start to finish Observe that it is not a batch process The entire

process will seamlessly transition via conveyor system such that from liquid metal to finished slab it is

continuous Over 75 percent of steel is created by this process2

12222 Ingot Casting

Most modern steel is manufactured via continuous casting methods however

ingot casting was the original primary method for raw steel production Currently ingot

casting has its niche in producing specialty steels tool steels re-melted steels and steels

for forging Ingots are created by pouring molten steel from a ladle into large ingot

molds Consequently ingots have high specific heat capacities resulting in extended

solidification times This leads to a broad array of microstructures within the ingot The

kinetics of casting solidification and its influence on microstructure will be discussed

extensively later However thermomechanical deformation additional processing and

subsequent heat treatments remedy the microstructural issues in ingots7

- 8 -

12223 Shape Casting

Ingot casting (as-casted) and continuous casting are severely limited in their

capable casting geometries Therefore shape casting is often the production method

chosen for any complex shape or any metal not sold as slab or bulk piece destined for

thermomechanical deformation This process is metal casting in the most traditional

sense such that the metal is casted directly into the final desired shape Once solidified

the microstructure can only be refined by heat treatment because a casting is not

subjected to any wrought processing such as forging as are ingots and slabs produced

via continuous casting2

All contemporary shape casting can be divided into two primary mold types

Expendable and Permanent Metal each with many sub-groups The hierarchy of this

system can be summarized in Figure 2 Although it is possible to produce the same end-

result with multiple casting methods the advantages and disadvantages must be

considered by the metallurgist to decide which method is most appropriate for each

situation In this report special interest will be devoted to discussion on the green sand-

casting process which is a specific sub-set of expendable molds The cast steel samples

for this project were produced exclusively via green sand casting therefore it is

important to have a comprehensive understanding of green sand casting28

- 9 -

Figure 2 Hierarchy chart of the many sub-sets of shape casting It splits from expendable mold and metal

(permanent) mold into many specific types of molds each with their own niche use The permanent mold

side is comprised mostly of the multiple variations of die casting while expendable molds are dominantly

sand molds Sand molds require much attention because of their implementation of cores and the multiple

ways to cure sand8

122231 Green Sand Casting

Expendable molds are not reusable the most common type of expendable mold

shape casting is green sand casting Other common methods of expendable mold shape

castings are lost foam and investment castings The following will be a summary of the

typical green sand molding process used by steel foundries Green sand casting is the

most basic and common type of shape casting method utilized today and accounts for

almost 75 of all shape casted metal Green sand casting utilizes pattern and mold

materials that are inexpensive cost-effective at high production rates and can be used for

ferrous and non-ferrous metals There are also disadvantages to using green sand casting

a new sand mold needs to be created for each casting the dimensional accuracy is not as

exact as for permanent molds and the entire green sand system introduces substantial

- 10 -

variation into the process and must be constantly monitored Additionally an engineering

team is needed to design the pattern which includes the gating risers chills and cores89

The primary ingredient in green sand mold material is sand however green sand

requires clay water seacoal and other additions to obtain properties conducive for ideal

metals casting The clay normally a southern or western bentonite or blend of both

behaves as a binder when mixed properly with water It binds to the sand enabling the

sand to retain its shape and provides strength such that the mold can support the weight of

liquid metal Seacoal is a biproduct of bituminous coal and behaves as a carbonaceous

material (reducing agent) Its addition will improve the surface finish of the casted metal

ie it will not be oxidized8910

A description of the typical green sand mold is as follows The mold itself is

always two-piece In horizontal green sand mold casting the upper-part of the mold is

called the cope and the lower-part of the mold is called the drag these two will meet at a

parting joint During the molding process the cope and drag will receive imprints on

their mating side from the pattern The pattern imprints the negative-space of the desired

part on the cope and drag such that any volume of the mold that is not sand will be filled

with metal Sand is compacted around the pattern thus filling the cope and the drag

Next the pattern is removed and the cope and drag are placed together again a flask is

necessary to ensure that the cope and drag remain aligned A schematic of the entire mold

and its parts can be observed in Figure 3 and a flow chart of its assembly is illustrated in

Figure 4 The assembly process must happen seamlessly in a production facility8910

The actual pattern itself is more complex than just the negative-space of the

desired part it must include liquid metal passageways In every green sand mold there is

- 11 -

a sprue which is the fill-hole through the cope where the molten metal can be poured

Liquid metal pathways called gates extend from the sprue and direct the liquid metal to

the casting itself Solidification defects predominantly exist in the last part of the casting

system that solidifies Effort is taken during design to ensure that the casting itself will

not solidify last A sacrificial riser is implemented into the system such that it becomes

the last to solidify and in theory should contain most of the systemrsquos solidification

defects The riser and the rest of the gating system which also includes the sprue and

gates will be removed from the casting later in the process A good design for the system

is to have the sprue opposite the riser such that directional solidification occurs to further

ensure that the riser is the last part to solidify8911

Figure 3 A typical horizontal green sand mold It should be observed that the riser is opposite of the sprue

This is to encourage directional solidification such that the riser is the last part of the mold to solidify This

helps to prevent solidification defects from forming inside the casting Often there is a need to apply mold

weights to the top of the mold to prevent the hydrostatic pressure of the liquid metal from pushing its way

through the parting joint This will be dependent upon the mold and the geometry and size of the casting10

- 12 -

Figure 4 Flow chart of the green sand molding and casting process for a part from its inception as the

mechanical drawing to the final casting that is ready for shipment to the customer This illustrates a manual

horizontal green sand molding process but the concept will always be similar In a high-production facility

a vertical molding system is sometimes used such that each cope is also a drag to the next part ie each

mold is double-sided such that it becomes a continuous line of molds that gets poured9

There are certain green sand castings that require additional attention Sometimes

implementation of a riser is not enough to ensure that complete solidification of the

casting occurs before all metal in the system is solidified In certain cases a chill may

need added during the molding process A chill is a piece of metal with appropriate

chemistry that is strategically placed inside the casting It behaves as an ldquoice cuberdquo to the

molten metal such that when the molten metal comes into contact with the chill it cools

the metal faster9

Green sand molding can also get more complex when a core is needed A core is

used to produce a cavity inside of the mold itself The core is also made of sand

however a green sand process is not normally utilized in its production but rather a resin

- 13 -

bonded sand This is because resin bonded sands are much more strongly bonded The

sand grains are coated with a resin that is either gas-catalyzed liquid-catalyzed or heat-

catalyzed These processes are colloquially known as core box no-bake and shell

process respectively The core needs to be placed inside of the mold prior to the

assembly of the cope to the drag911

In a production facility the sand molding system is on a conveyor such that one

mold follows the other All of the aforementioned steps happen in succession After the

mold is poured the next one in line pushes the already-poured molds farther down the

line This allows the mold ample time to cool At the end of this line the mold is dumped

onto another conveyor system to begin shake-out which begins the sand reclamation

process and recovery of the metal part Shake-out consists of tumblers and spring

conveyor systems that utilize resonance to break apart the mold separating the sand from

the casting The ldquocastingrdquo at this point includes the casting itself and the entire gating

system that is still attached gates risers and sprue9

Heat from the molten metal will dry and burn-out the clay surrounding the

casting This makes the mold disintegrate much easier The strength of the mold after the

metal is poured is known as the dry strength The casting continues through shake-out

where it may finish cooling and then it goes to the grinding room The casting at the time

of shake-out may still be at an elevated temperature because sand is insulative Slow

cooling for sand molds needs consideration because it influences the mechanical

properties of the ldquoas-castrdquo metal In the grinding room the sprue gating system and

risers are removed from the casting such that it can assume its final form Depending on

the toughness of the metal casted some of the gating system may be broken off during

- 14 -

shake-out but attention in the grinding room is always required Fig 5 illustrates the

shake-out process9

Figure 5 A typical shakeout system in a green sand mold metal casting facility The complete mold enters

the rotating drum from the left The sand subsequently breaks apart freeing the casting Depending on the

facilityrsquos machinery the finer clumps of sand fall through the rotating drum and get sent to reclamation

while the larger clumps and the complete casting move down the line The castings will enter tumblers

where ideally some gating and risers will break apart from the casting This is also dependent upon the

metal casted For example a gray iron gating system is more apt to breaking apart in the tumbling drum

than a ductile iron gating system This conveyor leads to the final line where workers separate the castings

Then the castings move to grinding room where the gating systems will be removed and the part will be

finished9

After the sand is separated from the casting in shake-out it is sent to sand

reclamation and recovery The pouring and shake-out processes are detrimental to the

sand grains which are slowly broken down into finer grains The first step in the

recovery system is to remove fines which are sand grains that have eroded beyond the

point of re-use Next because sand is a good insulator and has a high specific heat

capacity it must be cooled Cooling is normally done by pouring water over the sand

while on conveyor transport to the muller This is better understood with Figure 6 which

is a diagram of the cooling process The muller is the mixing machine where clay water

seacoal and other additives for the green sand mixture are combined This prepares fresh

green sand which is monitored by the on-site laboratory ensuring it is prepared

consistently When the fresh green sand meets laboratory approval it enter into the

molding machines to begin the process over again9

- 15 -

Figure 6 Cooling the sand as soon as possible is paramount for maintaining a healthy sand system This

ensures that sand is not too hot by the time it re-enters the muller This illustration is of a typical sand

cooler 1) The entry from hot shakeout 2) The rifling of the drum makes the sand cascade as the drum

rotates this accelerates cooling 3) Sand of the acceptable size falls through this grate where it falls to the

next screen 4) This screen discharges the acceptable sized sand to a conveyor where it will head to the

muller 5) Sand cores remain and other sand that did not dissociate will be removed through this area where

it will be discarded9

There is as much knowledge and effort dedicated to maintaining an efficient sand

system as there is to the metallurgy of the metal In fact a quality sand system is essential

in the production of quality green sand casted metal The foundryrsquos laboratory will need

to continually monitor clay percentages percentage of fines remaining in the sand

compactability of the green sand pH of the system and other factors9 The facility must

also consider seasonal effects on the sand For example sand will cool faster in the

winter than in the heat of summer9

122232 Permanent Metal Mold Casting

Permanent mold casting as the name implies utilizes a permanent reusable metal

mold The molten metal can be fed to the molds in a variety of ways gravity fed vacuum

- 16 -

fed or pressure fed Permanent metal molds are known for their very high initial cost

however when production numbers are high they become more cost-effective A

common form of permanent mold casting is die-casting These processes produce high

dimensional accuracy and precision as well as fast cooling rates due to the high thermal

conductivity of the metal mold Fast cooling rates create a fine grain size and a refined

microstructure which is favorable for mechanical properties512

1223 Production Rates of Todayrsquos Metal Casting World

The United States is currently one of the world leaders in metals casting with

1915 foundries and a nationwide output of 14 million tons of castings per year In 2017

the United States produced 97 million metric tons while China and India shipped 494

and 1206 million metric tons respectively Figure 7 which is a graph of the production

volumes of select metals is shown13

Figure 7 The number of castings of aluminum ductile iron investment cast steel gray iron and steel as a

function of year It can be observed that casting production has increased in recent years and according to

the American Foundry Society (AFS) industry growth is projected into the following years Aluminumrsquos

high strength-to-weight-ratio places the metal in high-demand13

- 17 -

13 Relevant Phases and Microstructures

A quick overview of relevant steel phases and microstructures will be covered for

a comprehensive metallurgical presentation It should be understood that in steels a

ldquophaserdquo is only accurate vernacular when it can be seen on the Fe-C phase diagram

everything else is a microstructure For all of the following the phase diagram in Figure

13 should be a reference Additionally the microstructure of martensite will be more

appropriately discussed in substantial detail in Chapter 1852

131 Ferrite (α-Fe) and Cementite (Fe3C)

Ferrite is the pure form of iron colloquially called ldquoalpha-ironrdquo it exists in a

Body Centered Cubic (BCC) structure below temperatures of 1341 ˚F (727 ˚C) Its BCC

structure is only capable of handling 002 wt C in a solid solution once this limit is

exceeded carbon will create a second phase in the form of intermetallic cementite

(Fe3C) Cementite is characteristically hard and brittle but in small amounts it is a useful

strengthener to steel because α-Fe by itself is too weak to be structural14

132 Austenite (γ-Fe)

Austenite is the stable phase of ferrite that dominates the Fe-C phase diagram

above 1341 ˚F (727 ˚C) Austenite with its Face Centered Cubic (FCC) structure is

capable of holding up to 21 wt C in a solid solution This region is important because

it is the starting point for common steel heat treatments If a Fe-C composition passes

through this region on the Fe-C phase diagram upon heating or cooling the Fe-C is

considered a form of steel If the carbon content exceeds the austenite carbon solubility

range then the Fe-C alloy is considered a form of cast iron14

- 18 -

Figure 8 Partial Fe-C phase diagram depicting the eutectoid composition (077 wt C) cooling from the

austenite region Notice how there is a sharp transition from the austenite grains to the pearlite lamellar

structure there is no cooling through a binary region of α+γ or γ+Fe3C 15

133 Pearlite

Pearlite is a microstructure not a phase however pearlite will commonly form in

the α+Fe3C region of the phase diagram given proper cooling Pearlite can only form

when a steel cools from the austenite region and it has a characteristic lamellar structure

that alternates between colonies of α-Fe and Fe3C The size and spacing of these lamellar

is dictated by cooling rates and composition A fast cooling rate will produce fine pearlite

and a slow cooling rate will produce coarse pearlite At modest cooling rates 077 wt

C the microstructure will be 100 percent pearlite because this is the eutectoid

composition of steel which does not cool through other proeutectoid ferrite or

proeutectoid cementite zones on the phase diagram If the composition of carbon is less

or more than 077 wt then it is known as either a hypoeutectoid or hypereutectoid

- 19 -

alloy respectively Upon cooling at a modest rate a hypoeutectoid alloy will form

proeutectoid ferrite and pearlite and a hypereutectoid alloy will form proeutectoid

cementite Figure 8-10 are partial Fe-C phase diagrams displaying the differences

between 100 percent pearlite hypoeutectoid (proeutectoid ferrite) and hypereutectoid

(proeutectoid cementite) respectively The microstructures displayed are assuming that a

modest cooling rate was observed ie no quench1415

Figure 9 Partial Fe-C phase diagram showing the microstructure evolution of a hypoeutectoid alloy (less

than 077 wt C) cooling from the austenite region There is not a sharp transition between austenite

grains and pearlite but rather a solidification range through the α+γ region of the phase diagram First

proeutectoid ferrite will form at the triple points and grain boundaries Upon further cooling deeper in this

region the proeutectoid ferrite will continue to grow until cooling below the A1 temperature Once this

happens pearlite will begin to form its lamellar structure along all areas that are still austenite not

proeutectoid ferrite15

- 20 -

Figure 10 Partial Fe-C phase diagram showing the microstructure evolution of a hypereutectoid alloy

(greater than 077 wt C) cooling from the austenite region Proeutectoid cementite is formed similarly to

proeutectoid ferrite Proeutectoid cementite can have an embrittling effect on the mechanical properties of

steels and is sometimes avoided15

14 Strengthening Mechanisms in Steels

To fully appreciate the scope of this project and understand the science at work in

steel castings versus wrought steel products it is imperative to have a comprehensive

knowledge of the strengthening mechanisms used in steels The strength of low alloy

steels can be increased in the following ways higher carbon content ferrite grain

refinement addition of alloying elements that are solid solution strengtheners addition of

alloying elements capable of precipitation hardening and formation and locking of

dislocations Unfortunately increases of metalrsquos strength are normally associated with a

- 21 -

loss of toughness and it commonly becomes a metallurgical compromise between

strength and toughness1

141 Increasing C Content

Increasing the carbon content increases steelrsquos strength for two reasons The first

reason is because it enters the octahedral and tetrahedral sites in both the BCC structure

of α-Fe and the FCC structure of γ-Fe Each C atom fits snugly into the interstitial ferrite

lattice sites and induces strain fields which make slip (plastic deformation) more

difficult The location of the carbon atom interstitials in the BCC lattice and FCC lattice

are illustrated in Figures 11 and 12 respectively The solubility limit of carbon in the

BCC α-Fe phase is reached at 002 wt C due to interstitial size restraints The radius

of C is ~07 Å and the largest interstice in α-Fe is the tetrahedral site with a radius of

035 Å After this solubility point is exceeded the intermetallic compound of iron

carbide or cementite (Fe3C) is precipitated out of solution The precipitation of this

carbide into the matrix is the second reason why carbon content increases strength These

different phases and microstructures can be observed in Figure 13 which is the Fe-C

phase diagram Even though it is commonly called the Fe-C phase diagram when it

depicts cementite as a thermodynamically stable phase it is incorrect Given infinite

time metastable cementite will convert to its lowest energy state at room temperature

which is graphite However in industry and often times in academia when one mentions

the Fe-C phase diagram they generally mean carbon in the form of cementite because it

is more practical151617

- 22 -

Figure 11 Interstitial sites where carbon migrates to in the BCC structure of α-Fe below the A1

temperature transition line where the BCC structure is thermodynamically stable Carbon will assume

these respective interstitial positions up to 002 wt C as a solid solution Once this composition is

exceeded carbon will precipitate out as cementite The largest interstice in the BCC structure is the

tetrahedral site with a radius of 035 Å16

The FCC lattice of austenite (γ-Fe) which is thermodynamically stable above the

A1 temperature can accommodate up to ~21 wt C in a solid solution without needing

to precipitate out carbon as cementite The A1 temperature line is depicted on the partial

Fe-C phase diagram in Figure 15 and is 1341 ˚F (727 ˚C)18 The FCC lattice can

accommodate more carbon than the BCC lattice because the interstitial sites are larger Its

largest being the octahedral site which has a radius of 052 Å Both the BCC and FCC

lattices have to strain to accommodate carbon interstitials because the carbon atomic

radius is larger than either of the biggest interstitial sites Counterintuitively the diffusion

rates of carbon is faster in the BCC lattice because it has more open channels despite

being the low temperature allotrope and having smaller interstitial spaces16

- 23 -

Figure 12 Interstitial sites where carbon atoms migrate to in the FCC structure of γ-Fe above the A1 phase

transition temperature where the FCC structure is thermodynamically stable Carbon will assume these

interstitial positions in the FCC lattice up to ~21 wt C as a solid solution Once this composition is

exceeded carbon will precipitate out as cementite The largest interstice in the FCC structure is the

octahedral site with a radius of 052 Å16

Figure 13 The standard iron-carbon phase diagram of temperature as a function of wt C It can be

observed from this phase diagram that the solubility limit of carbon in α-Fe is 002 wt C Given infinite

time the carbon depicted in the phase diagram will be in the thermodynamically stable form of graphite

however in normal steel production the carbon in the binary region is in its intermetallic metastable form

of cementite (Fe3C) There are certain heat treatments and certain cast iron processes that do produce

carbon in its graphite form however the distinction is not normally made from the diagram itself17

- 24 -

An over-abundance of carbon will make a steel brittle because it becomes overly

hard at the expense of ductility Additionally carbon increases the steelrsquos hardenability

which is defined as the steelrsquos ability to form martensite It should be noted that the

ultimate martensite hardness for a steel is a function of its carbon content alone Steels

with a high hardenability often require a pre-heat before welding to slow the cooling rate

such that martensite does not form A high carbon content also increases the ductile-to-

brittle transition temperature (DBTT) for steels A high DBTT makes a steel more

susceptible to catastrophic failures at low temperatures Hardenability will be discussed

in greater detail in Chapter 1851 which differentiates hardness and hardneability11920

142 Refinement of Ferrite Grains

Refinement of ferrite grains can increase the strength of steels and can be

accomplished through various means In general a fine grain size increases yield strength

and ductility simultaneously Grain refinement is the only mechanism that can both

increase strength and toughness12122 This is commonly accomplished via a faster

cooling from above the A1 transition temperature during heat treating or initial cooling

Solid solution strengtheners or dispersed microalloy particles that are present before a

phase change may act as a heterogeneous nucleation site for a grain or mechanical

deformation can contribute to grain refinement211923

Faster cooling rates as seen with a normalizing heat treatment compared to a

furnace anneal encourage grain refinement because there is less time for the grain to

reach its lowest energy state which is a sphere without the presence of grain boundaries

because grain boundaries are a surface with a free-energy The kinetics involved in all

steel making do not provide sufficient time at a specific elevated temperature for a grain

- 25 -

to achieve its lowest possible energy state However longer durations at elevated

temperature will allow the grain to reduce its surface-area-to-volume-ratio This means

less grain boundaries and a coarser grain structure Faster cooling rates do not give

sufficient time for much free-energy reduction to occur and small grains limited by

kinetics are not able to grow into large grains Since small grains inherently have more

grain boundaries they are stronger because a grain boundary will interrupt slip

mechanisms due to the different orientations between grains at this interface1 However

more grain boundaries will increase diffusion along their boundaries which can increase

creep rates particularly Coble creep124

Finer ferrite grains can be obtained by other mechanisms that either work in

tandem with accelerated cooling rates or unaccompanied Increasing the number of

nucleation sites for grains will yield finer grains More nucleation sites will initiate more

simultaneous grain growth which limits overall size grain size because grains will

impede each otherrsquos growth The concept of seeding nucleation sites with inoculants is

known as heterogenous nucleation and it occurs in metals when a solute particle becomes

the nucleus of the solidifying phase These solute particles are often solid solution

strengtheners or dispersed microalloy elements such as vanadium with a higher melting

temperature than the ferrite grains Each of these nuclei will grow into a grain The ldquoas-

solidifiedrdquo grain size has an inverse relationship to the amount of heterogenous

nucleation sites ie more nucleation sites equate to a finer grain size21

The prior-austenite grain size will affect the ferrite grain size as well Prior-

austenite grains are formed in the FCC (austenite) phase of steel above 1341 ˚F (727 ˚C)

Like ferrite grains austenite grains increase in size with time and temperature Then

- 26 -

upon cooling below the A1 temperature ferrite grains will nucleate on the transforming

prior-austenite grain boundaries which have become heterogeneous nucleation sites

Therefore the smaller the prior-austenite grains the finer the resulting ferrite grains

because of more heterogeneous nucleation sites25 Prior-austenite grains can possess high

energy from being strained but not recovered This increases the driving force for more

ferrite grains to form simultaneously (resulting in a smaller grain size) because the

strained prior-austenite grains want recovery (strain-relief) and a phase change will

suffice26

The relationship between yield strength and grain size was first researched by

Hall and Petch The Hall-Petch Equation displayed in Equation 1 represents the inverse

relationship between grain size and yield strength when σy is the lower yield stress σi is

the friction stress Ky is the strengthening coefficient and d is the grain size This relation

exists because the grain boundary stops the slip plane which will help to arrest

dislocation motion The more grain boundaries that are present in a material will increase

the amount of energy needed to continue to propagate a dislocation23

120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1

143 Addition of Solid Solution Strengthening Elements

Elements that form a solid solution with ferrite must have a similar size and

electronic structure to iron ie will not form carbides or nitrides Carbon and nitrogen are

potent interstitial solid solution strengtheners present in every steel They are in solid

solution to a certain solubility limit at which point they will precipitate out as a second

phase For example the solubility limit of carbon in iron is 002 wt C Solid solution

- 27 -

strengtheners have two primary jobs grain refinement and initiating strain fields to

reduce the ease of plastic deformation Solid solution strengtheners refine grains because

they can provide a heterogeneous nucleation site for grain growth to occur if they are

solid before the dominant solidifying phase Solid solution strengtheners also initiate

strain fields similar to the way carbon strengthens steel as an interstitial Any size

difference in the radii of alloying elements creates a lattice strain which makes slip more

difficult Figure 14 presents the yield strength effect of common solid solution

strengtheners as a function of element percent123

Figure 14 Yield strength as a function of element percent for common solid solution strengtheners It can

be observed that the highest yield strengths are achieved by using carbon and nitrogen which are interstitial

solid solution elements Phosphorus is a potent substitutional solid solution strengthener that exchanges

positions iron atoms in the matrix This finite difference in size creates a strain in the lattice such that a

strengthening effect is seen because this strain impedes dislocation motion Other elements such as nickel

and aluminum have a negligible effect1

144 Addition of Precipitation Hardening Elements

Precipitation hardening also known as secondary hardening or age hardening is

the primary strengthening mechanism in non-ferrous alloys Plain carbon steels cannot

- 28 -

take advantage of precipitation hardening because of the limited solubility of carbon in

the α-Fe phase However steels alloyed with vanadium niobium titanium and a select

few other elements can precipitation harden because these elements have a high affinity

for carbon and have an overwhelming tendency to form complex carbides nitrides and

carbonitrides instead of Fe3C Precipitation hardening generally requires a two-step heat

treating process The elements are solutionized during an initial heating called

austenitizing and then the steel is rapidly cooled to trap these elements into a

supersaturated solid solution Subsequently the system is aged to precipitate out these

elements as a second phase which greatly increases the strength levels The diffusion and

mechanisms of this process will be discussed in great detail later as precipitation

hardening is the primary strengthener in High-Strength-Low-Alloy (HSLA) steels1

145 Formation of Dislocations

Dislocations are a crystallographic line defect that is a linear discontinuity in the

periodicity of the crystal Dislocation motion is the mechanism for slip which is plastic

deformation Alternatively it can be visualized as dislocations being created in a metal

whenever plastic deformation occurs All dislocations need a shear stress component in

order for them to propagate Metals are strengthened when dislocation motion is

impeded whether by grain boundaries alloying elements or other dislocations (assuming

that a metal can undergo plastic deformation without catastrophic failure) When steel is

plastically deformed below its recrystallization temperature dislocations will not anneal

away and they will remain inside of the microstructure The strength increase comes from

dislocation motion being impeded by other dislocations because they cannot slide well

over one-another Thus slip is restricted Dislocations will anneal away above the

- 29 -

recrystallization temperature because the crystal has enough thermal energy to allow

relaxation into a lower energy state thereby lowering the kinetic barrier to the lowest

free-energy for that crystal Figure 32 illustrates the annealing temperatures and

recrystallization regime316182327

There are two types of dislocations possible edge and screw dislocations The

magnitude and direction that the shear stresses displace the atoms is represented by the

Burgers vector Edge and screw dislocations are illustrated in Figures 15 and 16

respectively163 Both are activated by shear stresses however they react differently to

solid solution strengtheners and interstitial atoms An edge dislocation which is an

incomplete plane of atoms in a crystal will respond to both shear and hydrostatic

components while a screw dislocation will only react to a shear component23 The

implications are that solid solution strengthening elements give a hydrostatic distortion in

the lattice and therefore only impede edge dislocations23 Interstitial atoms initiate both a

hydrostatic and shear stress because they are asymmetrical within each unit cell

therefore these can interact with both edge and screw dislocations3162223

Figure 15 The movement of an edge dislocation along a slip plane Notice how the dislocation moves

parallel to the slip plane The ldquoextra half-planerdquo of atoms slides in response to a shear stress This type of

dislocation can be thought of as either an extra half-plane of atoms inserted into the lattice or a missing

half-plane An edge dislocation is constrained to a single slip plane16

- 30 -

Figure 16 A screw dislocation Contrary to edge dislocations there are no atoms missing from a screw

dislocation Notice how the screw dislocation rotates around its dislocation line like a spiral staircase A

screw dislocation is not confined to a single slip plane like an edge dislocation it can re-orientate itself onto

a new slip plane3

15 Cast Metal vs Wrought Metal

To completely understand this project it is important to discern the differences

between metal that was shape casted nearly into its final form and metal that was casted

and subsequently thermomechanically deformed Metals that undergo thermomechanical

deformation are known as wrought metals All metals except those produced via additive

manufacturing or powder metallurgy are cast at some point in their existence eg in the

form of an initial ingot However not all metals that are cast can easily undergo

thermomechanical deformation because of their propensity for crack formation

Additionally some metals due to their composition are highly castable and are used in

their cast form as opposed to being wrought processed2

- 31 -

151 Cast Metal

Cast metal is metal that experienced some sort of shape casting and is nearly in its

final form and will not undergo thermomechanical deformation Sometimes metals are

chosen to be shape cast because the desired metal for the job consequently casts well or

it can be that the final design of the part is too complex for forging and fabricating and

that powder metallurgy and additive manufacturing are not the best choices

The fact that cast metals do not undergo any type of thermomechanical

deformation can act as both an advantage and a disadvantage It can be an obvious

disadvantage because cast metals are not afforded the luxury of the strengthening

mechanism associated with dislocation motion impedance Therefore all casting

strengthening must be done with alloying and heat treating Cast steels can be very cost

effective because fewer steps in production of the final product will allow for larger profit

margins This cost savings can also be passed along to consumers1

The most extensively shape cast metal is cast iron the tonnage of all other shape

cast metals can be summed together and it still would not surpass the annual tonnage of

cast iron Cast iron despite the name has a higher carbon content than steel normally in

the range of 17 to 35 wt C According to Figure 13 the Fe-C phase diagram the

carbon content creates a eutectic point for cast iron at ~42 wt C Eutectic and near

eutectic compositions cast well because there is a sharp transition between liquid and

solid The more deviation in the carbon content there is from the eutectic point the

broader the solidifying temperature range Then transport phenomena will increasingly

influence properties This will be discussed more later in Chapter 163 Solidification

Dynamics of an Alloy2

- 32 -

152 Wrought Metal

Wrought metal is any metal subjected to some form of thermomechanical

deformation Thermomechanical deformation means deforming the material to

manipulate its dimensions which by nature of the process will achieve better mechanical

properties through dislocation entanglement Some interpretations of thermomechanical

deformation strictly demand strain aging processes (when dislocations are pinned by

carbon atoms during deformation) and the work hardening of austenite not be included in

definition28 While other sources strictly dissect thermomechanical deformation into

different regimes Class I being deformation below the austenite temperature Class II

deformation during the austenite transition and Class III deformation above the austenite

transition2229

16 Solidification Dynamics

Cast metals ingots included are subjected to a multitude of kinetic mechanisms

inherent with the process There are certain considerations to be realized temperature

gradient of heat flowing outward from the center of the casting solidification temperature

range of the particular alloy cast type of casting process and its inherent thermal

properties and the structure-property relationships

161 Nucleation Mechanisms

Solidification from a liquid phase requires a nucleation event so a new phase can

propagate The method of Nucleation and growth describes how a precipitate grain or

phase comes into existence starting with the origin of the phase through the nascent

- 33 -

growth period until full grain formation Nucleation and growth occurs with two

mechanisms homogeneous nucleation andor heterogeneous nucleation303132

Essentially both homogeneous and heterogeneous nucleation mechanisms can be

divided into four stages of growth either for initial cooling from a melt or nucleation of

new grains after a solid-to-solid phase change Stage I is named the incubation period

because no stable particles have formed yet At this stage only microscopic clusters or

embryos exist and they are metastable These clusters are randomly distributed

throughout the meltmatrix and they begin to grow by agglomeration It is likely that

many will revert back into the meltmatrix This is because of their small size they

inherently have a high surface-to-volume ratio and are not stable However if the embryo

grows large enough it reaches a critical size such that it becomes thermodynamically

stable then it becomes a particle These particles are now permanent and will continue to

grow Nucleation continues with Stage II which is the quasi-steady-state nucleation

regime As the name implies embryos are transitioning into particles at a constant rate

This steady-state of transitioning continues until a saturation point is reached in Stage III

By Stage IV the number of new particles decreases because as the pre-existing particles

continue to grow they devour the smaller particles This process can be described in

Figure 17 Then after a stable nucleus is formed whether by homogeneous or

heterogeneous nucleation its growth rate is determined by the degree of undercooling the

system is subjected to and how easily the existing crystal structure accommodates the

new growth3132

- 34 -

Figure 17 Nucleation rate as a function of time There is a finite amount of time that passes before the first

embryos come into existence in Stage 1 In Stage II nucleation growth increases rapidly until it hits the

saturation point in Stage III The growth of new nuclei starts to decline when smaller nuclei fall victim to

larger nuclei that are cannibalistic Thus larger nuclei grow at the expense of smaller ones31

1611 Homogeneous Nucleation

This is the primary nucleation mechanism in a one-component system It also

occurs in alloy systems but is less dominant than heterogeneous nucleation In

homogeneous nucleation the embryos are uniformly distributed throughout the entire

parent material and by randomness of agglomeration they begin to grow at the expense

of one-another If the embryos grow to reach the critical size they obtain a stable surface-

area-to-volume ratio are thermodynamically stable and known as particles The Gibbs

free-energy transitions from positive to negative at this point when the activation energy

for nucleation is reached This relation can be illustrated in Figure 18 and summarized in

Eq 2 where ∆119866 is the Gibbs free energy 4

31205871199033 is the volume of the spherical nucleus

∆119866119907 is the free energy of the volume and 41205871199032120574 is the surface area of the nucleus30

∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -

Figure 18 Image depicting a mathematically idealized form of nuclei such that it has a perfect volume and

area represented by 4

3πr3 and 4πr2γ respectively Once the nuclei grow large enough it becomes

thermodynamically stable and it will not dematerialize unless it sacrifices itself for the growth of a larger

nuclei30

This phenomenon is readily observed during solidification It is more

energetically favorable (larger negative Gibbs free energy) for particles to form via

homogeneous nucleation when a greater undercooling is performed ie faster and more

dramatic cooling rate Undercooling is defined as the offset of the cooling temperature

below the equilibrium temperature of solidification When the system experiences a large

undercooling the nucleation rate increases and this forms many solid nuclei

simultaneously Therefore many nuclei are growing concurrently and the growth rates

soon reach a saturation point where growth is impeded by competing nuclei When fewer

nuclei are growing because of a small undercooling the nuclei grow larger before

impeding one-another This can all be summarized with the graph in Figure 19 but

essentially faster cooling rates procure finer grains and smaller undercooling will be

conducive for coarse grain formation3033

- 36 -

Figure 19 Gibbs free energy of a nuclei as a function of radius of the nuclei The temperature determines

the stable radius (r) It can be observed that a larger undercooling makes nuclei more thermodynamically

stable because it forces the nuclei out of solution more easily at temperatures farther away from the melting

temperature30

1612 Heterogeneous Nucleation

Heterogeneous nucleation dominates in alloys over homogeneous nucleation

because of the insoluble particles present in the material behaving as nucleation sites

Other nucleation sites will include mold walls grain boundaries and dislocations The

pre-existing surface that initiates nucleation and growth consequently lowers the required

undercooling for heterogeneous nucleation by several hundred degrees centigrade

compared to homogenous nucleation For high heterogeneous nucleation rates upon mold

walls the liquid metal must wet the mold walls This means that the liquid phase

disperses evenly over the mold walls and does not form droplets Figure 20 is an

illustration of the wetting phenomenon and the required free-energies to make it

favorable303132

Heterogenous nucleation can be promoted through the addition of inoculants

which behave as nucleation sites These solid particles have higher melting temperatures

- 37 -

than the primary metal composition and they will either solidify first upon cooling or

precipitate out of solution before another phase change Then these heterogenous

nucleation sites that are distributed throughout the solidifying or phase-changing metal

will begin to grow larger eventually becoming grains As in homogeneous nucleation

faster cooling rates are characteristic of finer grain sizes303132

120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3

Figure 20 Diagram showing the ldquowettingrdquo action of a droplet on a surface 120574119868119871 is the liquid-solid

interfacial energy 120574119878119868 is the solid surface energy 120574119878119871 is the liquid surface energy and 120579 is the wetting

angle The lower this angle the more wettable the surface30

Figure 21 Nucleation rate growth rate and overall transformation rate of nucleation and the effect that

temperature has on all three It should be observed that growth rate and nucleation rate will hit an optimized

rate when the overall transformation rate is the highest30

- 38 -

162 Solidification Dynamics of a Cast Pure Metal

Solidification in pure metal casting will occur via two different mechanisms

planar growth and dendritic growth The creation of a solid phase from a liquid phase

requires energy expenditure ie a surface-energy associated with the liquid-solid

interface The energy required to produce a solid phase from the liquid phase is produced

from undercooling Planar growth will only exist in a turbulent-free and alloy-free

solidifying system because other mechanisms for solidification will dominate under other

conditions such as the presence of alloys Planar growth as the name implies is the

propagation of a solidifying plane throughout the melt There are areas of the melt that

will solidify ahead of this plane however the outward heat flux flowing from the

solidifying plane will cause re-melting This is caused by the latent heat-of-fusion ie the

heat radiating from the solidifying structure will make the liquid next to it hotter than the

rest of the melt This is described graphically in Figure 22 This enables the planar

interface to be maintained but only when slow cooling rates are recognized234

Figure 22 Temperature profile of a metal casting mold Particular interest should be focused on the area of

ldquotemperature increase due to latent heatrdquo because this is how planar solidification is able to re-melt

solidified areas of the casting and re-solidify as a plane The latent heat of solidification is the release of

heat energy at the solidification temperature so that the metal can solidify2

- 39 -

Dendrites are defined as ldquotree-shaped crystalsrdquo that grow and solidify along

crystallographic preferred directions and are the dominant form of non-planar front

solidification In BCC and FCC crystal structures the preferred crystallographic growth

direction is along the lt100gt orientation Dendritic growth unlike planar solidification is

present in both pure metals and alloys but the mechanism for dendritic growth is

different in both cases In pure metals dendrites form due to thermal supercooling which

occurs more predominantly with higher cooling rates Akin to the effects of latent heat-

of-fusion in planar growth the liquid next to solidifying dendrites is hotter than the rest

of the melt If the solidifying dendrite is catalyzed by any perturbations in the

solidification it will have the propensity to grow past this solidifying wall to the cooler

temperatures (just a few tenths of a degree) beyond areas experiencing the latent heat of

solidification This creates a ldquotree-likerdquo crystal This process repeats again but on a

smaller scale for secondary dendrite ldquoarmsrdquo growing off of the primary dendrite ldquoarmrdquo

that originally grew past the solidification front Figure 23 illustrates both primary and

secondary dendritic arms273536

Figure 23 The difference between primary and secondary dendritic arms Primary dendritic arms the first

dendrites that grow through the solidification front in a crystallographic preferred direction and secondary

dendritic arms are dendrites that sprout from the primary arms7

- 40 -

163 Solidification Dynamics of a Cast Alloy

In a pure metal the entire system is homogenous The system will have a

solidification point but in an alloy system the solidification will occur over a range of

temperatures except at eutectic points This introduces a new solidification mechanism

which is constitutional supercooling The first solid to form will have a different

composition than the last solid to form when cooling through a dual-phase region (α+L

region) of the phase diagram It should be noted that when cooling happens through a

eutectic point solidification occurs at one temperature This can all be understood more

clearly by observing the Fe-C phase diagram in Figure 13 As the temperature falls

through the cooling range in a dual-phase area the solidifying composition at that cooling

range can be found by drawing an isothermal tie-line to the solidus line on the phase

diagram The first solid matrix to form tends to be deplete of solute while the final

composition to solidify tends to be solute rich This phenomenon of compositional

supercooling is intensified by equilibrium cooling rates therefore a faster cooling rate

will help to reduce its effect These dual-phase regions colloquially called ldquomushy

zonesrdquo are depicted in Figure 24 The more cooling that occurs through one of these

regions increases the likelihood for defects associated with long dendrites and difficulty

feeding the solidifying shrinking metal with liquid metal 23436

Constitutional supercooling is the predominant mechanism for dendrite growth in

alloys however the mechanism of thermal supercooling is still active The solute that

drops out of solution will lower the solidification temperature of the liquid and act as a

starting point for dendritic growth and it makes dendritic growth more pronounced

Especially those that cool through large two-phase regions2

- 41 -

Figure 24 The consequences of different cooling paths as dictated by composition on the phase diagram It

is observed that the best fluidity comes from a single-phase composition and a eutectic composition

because these do not have a freezing range but a freezing point This lowest fluidity (highest viscosity) is

observed with compositions that require cooling paths through the thickest region of the dual-phase β+L

region This path is characteristic of the largest freezing range such that certain solutes are solidified out of

that specific composition while liquid still remains37

164 Solidification Zones in a Casting

Both pure metals and alloys are subject to different solidification zones in castings

due to solidification kinetics Pure metals will see two solidification zones the chill zone

and the columnar zone Alloys will experience those two zones in addition to a third

central equiaxed zone It should be kept in mind that the casting will solidify from the

inside out and heat flows from hot to cold2

1641 Chill Zone

This is region ldquoardquo in Figure 25 Liquid metal nearest the mold will experience the

fastest cooling rates due to large undercooling because the mold radiates heat away from

- 42 -

itself This effect is exacerbated in permanent metal molds with a high thermal

conductivity because the mold behaves as a heat sink that removes heat rapidly from the

solidifying metal However some molds are insulative (green sand molds) and the

amount of undercooling that the outside of the casting experiences will be minimized In

general the faster cooling rates experienced at the outside of the mold will combine with

the heterogeneous nucleation occurring at the mold wall to form fine equiaxed grains2

Figure 25 There are three different solidification zones in a typical casting a) Is the ldquochill zonerdquo this

microstructure is characteristic of fine equiaxed grains initiated via quick cooling rates seen on the outside

of the casting at the mold wall b) In the ldquocolumnar zonerdquo long grains grow because of less undercooling

additionally dendrites grow perpendicular to the mold walls which is the reason for the columnar

orientation c) The ldquocentral equiaxed zonerdquo is at the center of alloy castings These smaller equiaxed grains

are created by the combined effects of constitutional supercooling and the heat gradients flowing outward

from the center

1642 Columnar Zone

The mold walls rapidly heat up and the degree of thermal undercooling will soon

start to diminish as solidification continues This happens in the moments after the chill

zone is formed The nucleation rates decrease inside the liquid metal adjacent to the chill

zone When there are fewer nucleation sites mixed with a slow cooling rate coarse grains

- 43 -

growth will dominate This area becomes known as the columnar zone because dendrites

and grains will grow perpendicular to the mold walls The large columnar grain

boundaries have a propensity to contain embrittling impurities and porosity which

degrades the mechanical properties of the ldquoas-castrdquo material Hence the reason

thermomechanical deformation is commonly used as a post-processing step after casting

for non-shape-cast metals Deformation will break apart the continuity of the inclusions

thus reducing the embrittlement However there are ways to improve the as-casted

microstructure in this region Grain refiners (inoculants) can be added to the melt As the

name implies these refine the grain size in the columnar zone and reduce grain sizes

These inoculants solidify before the parent material of the melt and behave as another

heterogeneous nucleation site therefore creating more nucleation that will grow

simultaneously This enables the system to reach its saturation point sooner and this

yields smaller grains2

1643 Central Equiaxed Zone

This zone is only present in alloys due to the combined effects of the

constitutionally supercooled regions from the mold walls converging at the center of the

casting and the temperature gradient flowing outward form the castingrsquos center thus

creating a large undercooling effect at the center of the casting The large undercooling

both from constitutional and thermal effects yield high nucleation rates which create

fine equiaxed grains Another effect that commonly contributes to a pronounced central

equiaxed zone is buoyancy-driven convection flow in the solidifying melt This has the

capacity to break-off already solidified dendrites and transport them around the

circulating melt These broken dendritic arms act as another heterogenous nucleation site

- 44 -

within the melt Melt circulation and convection of the liquid metal can also be

artificially induced with ultrasonic vibrations or alternating magnetic fields2

17 Solidification Defects

There are five primary defects that can occur in castings because of solidification

mechanisms and they are more pronounced in alloys due to constitutional supercooling

The five primary defects are macroporosity macrosegregation microporosity

microsegregation and gas porosity Defects are combated in different ways however

most commonly is with implementation of a riser which will solidify last and contain

most defects2

171 Macroporosity

Macroporosity formation in the casting is caused by shrinking of the metal as it

cools and the inability of fresh liquid metal to fill in the void The last part of the casting

system to solidify is subject to macroporosity because no liquid metal remains to fill in

voids created by the solidification shrinkage The mechanisms that contribute to

macroporosity are liquid shrinkage solidification shrinkage and solid shrinkage which

can be summarized graphically in Figure 26 Nearly all materials whether in their liquid

solid or gas state experience a volume expansion associated with heating and a volume

decrease associated with cooling The shrinking volume of the liquid during cooling is a

nonissue when there is more liquid metal available to replenish the volume An issue

develops because there is a shrinkage associated with the transition from a liquid to a

smaller volume crystal Additionally the casting will experience further shrinkage due to

- 45 -

the thermal expansion coefficient of the solid metal that will be active from the

solidification temperature to room temperature2

Macroporosity can be combated with the addition of risers chills and insulation

placed in key areas to ensure that the casting itself is not the last to solidify Ideally the

casting will directionally solidify towards the riser such that the riser is the last part to

solidify and that it can continue to feed the shrinking casting with its remaining liquid

metal Figure 27 illustrates the macroporosity solidification defect that forms at the top of

the riser known as a pipe2

Figure 26 Volume of metal in different phases as a function of temperature Most materials shrink as they

are cooled due to the mean vibration distances decreasing because there is less thermal energy in the

bonding There is an exceptional decrease in the volume of metal during solidification shrinkage due to the

formation of the crystal structures which is ordered2

- 46 -

Figure 27 Solidifying metal will shrink this shows how a pipe forms in a cube sand casting It will begin

by forming a solidified skin on top at the mold-casting interface which isolates this section from the rest of

the casting that is still liquid Thus liquid metal cannot replenish this void2

172 Macrosegregation

The last part of the actual casting to solidify not including the riser will be at the

centerline of the thickest mass section When an alloy solidifies unless it is a eutectic

composition it will solidify over a temperature range The exact composition solidifying

is represented by an isothermal line drawn from the alloyrsquos composition line (C0) to the

solidus line this can be best illustrated with Figure 28 This solidification range creates

solute migration because the first part of the casting to solidify will be solute poor and the

last part of the casting to solidify will be solute rich Macrosegregation can be combated

by a faster solidification rate so that there is not time allowed for solute migration Heat

treating the casting will also help reduce the segregation after the casting is solidified

however solid state diffusion rates are substantially slower than diffusion rates in the

liquid238

- 47 -

Figure 28 This is an example of a two-phase solidification region where solidification happens over a

range of temperatures The lever rule can be used to determine specific composition of the solute falling out

of solution at any point in time below the liquidus line38

173 Microporosity

Solidification shrinkage will also cause microporosity When the casting is

solidifying it is common for the dendrites to grow into one-another such that they

impede liquid metal flow in the inner-dendritic region Then solidification shrinkage

occurs within the dendritic region and since liquid metal is not available to replenish the

shrinking volume a micropore will form Figure 29 provides an illustration of this

phenomenon Microporosity is exacerbated by alloys that solidify through a larger two-

phase region because these have a higher propensity for form dendrites due to the larger

freezing range This defect can be combated with any mechanism that breaks up the

dendrites such as ultrasonic vibrations magnetic eddy currents or higher velocity

pouring metal2

- 48 -

Figure 29 Dendrites are the primary cause of microporosity because the dendritic arms grow together and

liquid metal cannot replenish the micropore that forms due to the solidifying metal This action is illustrated

above The kinetics of solidification in the space between inter-dendritic arms is also a leading cause for

microsegregation2

174 Microsegregation

Microsegregation is another byproduct of the solidification kinetics of an alloy

The last composition of the alloy to solidify will have a high solute content This can

cause intermetallic phases and inclusions to form primarily between dendrites These

both have the tendency to be brittle and should be avoided if possible The primary side-

effect to the intermetallic phase and inclusions is hot shortness which is cracking that

occurs during any subsequent hot working process Microsegregation can be rectified by

the same process alterations as for macrosegregation Additionally it was reported that a

homogenizing heat treatment works well to remedy the problem The secondary-dendritic

arm spacing normally has the largest effect on microsegregation and this spacing can be

used to determine the time and temperature of the homogenization that is needed23940

175 Gas Porosity

Gas porosity is also a common defect which is caused by the absorption of gases

into the liquid phase prior to solidification The primary gases that are responsible for gas

porosity in iron and steel are H2 N2 and CO The primary mechanism for gas porosity is

- 49 -

the dramatic decrease in gas solubility at the liquid-to-solid phase change which can be

illustrated in Figure 30 These gases are soluble in liquid metal and often times

solidification happens so quickly that when gases evolve out of the solidifying metal a

gas hole is left in their wake An example of a gas porosity hole in the solidified metal

can be observed in Figure 31 the nearly perfectly round hole is indicative of gas porosity

Gas porosity can be remedied by vacuum degassing the melt Hot-Isostatic-Pressing

(HIPrsquoing) the finished part the addition of inclusion formers and all around cleanliness

of the melt241

Figure 30 Hydrogen gas content in a metal as a function of temperature illustrates that the liquid form of a

metal has a much greater gas solubility than does the solid phase There is a sharp discontinuity in the

solubility graph at the solidification temperature and this is why gas hole porosity is seen in metals The

metal is solidifying with ample amounts of gas in it and often times it solidifies before the gas has a chance

to escape Thus leaving a gas hole in its wake

- 50 -

Figure 31 Round pores seen in micrographs commonly indicate gas porosity because the gas bubble is

round and when the metal solidifies around it as the gas is escaping it leaves its own trace in the metal41

18 Heat Treating of Steels

Heat treating is commonly performed on both cast and wrought steels Depending

on categorization there are arguably seven different heat treatments that are performed

on metals homogenization full anneal process anneal normalization austenitize-

quench-temper spheroidizing and stress relieve Consult the Fe-C phase diagram in

Figure 32 that has the temperature ranges for each heat treatments superimposed upon it

for reference during each of the following sections18

Common to most every heat treatment of steels is heating first above the A1

transition line to fully austenitize the steel This is important because the FCC structure

has a higher solubility for carbon and other alloying elements Austenite can be thought

of as the ldquoparent phaserdquo to most microstructures and phases in steels because most

microstructures are formed by cooling from the austenite region It is because of the

- 51 -

austenite region that there are so many heat treatments possible for steel Cooling rate

will control the diffusion which along with the composition dictate the resultant

microstructure in cast steels Slower cooling rates will allow phases solute and particles

that were stable in the austenite region but not stable in the α+Fe3C region to precipitate

out as second phases Faster cooling rates will keep these solutes in solution in a

metastable form2542

Figure 32 Partial phase diagram of temperature vs carbon wt illustrates the ranges for each type of heat

treating and thermomechanical processes up to 15 wt C Notice this depicts the A1 temperature line at

1341 ˚F (727 ˚C) so frequently referenced18

The austenite region in steels is important for other reasons too For example it is

single phase at most temperatures and compositions that are commonly used plus it is a

high-temperature phase that it naturally more ductile This increased ductility enables

thermomechanically deformation of steels in the austenite region to be cost-effective

- 52 -

Also the austenite phase forms its own grains by a standard nucleation and growth

process There is a kinetic barrier that needs overcome for them to start growing because

α+Fe3C needs to be transformed The final size that the austenite grains grow to will

affect how easily the microstructure can be transformed back into α+Fe3C upon cooling

Therefore they have an effect on ferrite microstructure For example toughness is

sensitive to prior-austenite grains and it is reduced as the size of the prior austenite grains

are increased Once cooled the remnants of the austenite grains are called prior-austenite

grains (these grains are visible when subjected to special etches and microscopy)2542

181 Homogenization

During solidification of an alloy microsegregation and macrosegregation can be

mitigated by subsequent homogenization heat treatments Compositional supercooling

creates a multitude of problems because there is not a uniform composition throughout

the solidified metal At ambient temperatures the solute atoms will not diffuse fast

enough to achieve an equilibrium composition throughout To quicken diffusion rates a

homogenization heat treatment is performed to enable the systemrsquos concentration

gradients to equilibrate across the matrix Most ingot castings are homogenized before

hot working to improve workability mechanical properties and repeatability because the

solute atoms are dissolved Homogenization is performed approximately in the 1830-

2190 ˚F (1000-1200 ˚C) temperature range followed by an air cool which produces

larger coarse grains upon completion as opposed to a quench Homogenization normally

happens simultaneously with the nucleation and growth of the austenite grains therefore

one could argue that austenitizing and homogenizing are the same heat treatment Often

- 53 -

thermomechanical deformation is performed directly after homogenization so that the

ingot does not have to be reheated later254243

182 Full Anneal

Performing a full anneal in steels will produce a microstructure characteristic of

equiaxed ferrite and coarse pearlite that will have soft and ductile mechanical properties

The temperature ranges involved are just above the A3 temperature line for hypoeutectoid

steels and just above the A1 temperature line for hypereutectoid steels If a hypereutectoid

steel is cooled slowly through the γ + Cementite region the steel will have a tendency to

form proeutectoid cementite along the grain boundaries which is too brittle for use A

full anneal is normally held at temperature for an hour per inch thick of steel and it

finishes with a furnace cool1844

183 Process Anneal

A process anneal is also called a recrystallization anneal and it is primarily used

to restore ductility to a piece of metal that has been cold worked As explained

previously when a steel is cold worked dislocations form and they impede each otherrsquos

flow This makes the material less ductile because dislocation motion is a mechanism for

slip A process anneal can annihilate these dislocations so cold working can continue

without damaging the steel additionally increased ductility can be achieved There are

three phases of a process anneal heat treatment 1) dislocation annihilation (recovery) 2)

recrystallization 3) new grain growth The recovery phase reduces strain in the matrix

and the recrystallization phase nucleates new strain-free grains It should be made clear

that no phase change is achieved during a process anneal the upper temperature limit is

less than A1 temperature line1844

- 54 -

184 Normalization

Normalizing is used to refine the grain structure of the steel typically after cold or

hot working Steel is commonly sold in this condition because it produces fine equiaxed

grains and fine pearlite that is desirable for good mechanical properties such as strength

and ductility Normalizing involves an air cool from temperatures above the A3

temperature line but still relatively low in the austenite region The cooling rate is

dependent upon ambient conditions casting size and casting geometry1844

185 Austenitize-Quench-Temper

The highest strength and hardness microstructure in steels is called martensite

This is formed via a diffusionless transformation from the austenite region initiated via a

quench A quench is the act of cooling the material quickly in a medium that can be

water oil or brine A martensitic microstructure is not used without subsequently being

tempered due to un-tempered martensitersquos brittleness and lack of toughness that would

make the steel prone to catastrophic failure45

1851 Hardness vs Hardenability

It is important to distinguish the difference between hardness and hardenability

The ability of a steel to form martensite is called hardenability and hardness is a

materialrsquos resistance to deformation These also have different influences as well the

ultimate hardness potential of martensite is only a function of the carbon content of the

steel while hardenability is controlled by the following carbon content alloying

elements prior-austenite grain size cooling rate (severity of quench) and the size of the

steel being quenched192045

- 55 -

The factors affecting hardenability are straightforward The higher the carbon

content and alloying content the higher the hardenability because additives decrease

diffusion rates Since the formation of pearlite and bainite are diffusion dependent the

system will have a higher tendency to form martensite This can be observed on a Time-

Temperature-Transformation (TTT) diagram as seen in Figure 33 Any effect that slows

diffusion like the addition of alloying elements moves the curve to the right

Hardenability is increased with increasing prior-austenite grain size because there are

fewer grain boundaries with coarser grains which results in fewer nucleation sites for

pearlite formation19204647

Figure 33Time-Temperature-Transformation (TTT) diagram This particular TTT diagram has a Fe-C

phase diagram attached on the left This illustrates how martensite finish (Mf) decreases with C content

This is an isothermal diagram and therefore no kinetic effects during the cooling will be taken into

account ie it assumes infinitely fast cooling to the desired temperature46

Intuitively depth of hardness increases with increasing hardenability and the

severity of the quench The quenching medium affects the severity for example an oil

quench is less severe than a water quench which is the most common medium

Additionally section size will influence cooling rates A small sample will experience a

more severe quench1920454849

- 56 -

1852 Martensite

A martensitic structure in steels results from a diffusionless athermal and shear-

type formation To catalyze the formation of this hardest possible steel microstructure

the steel must undergo a severe quench from austenite to its room temperature stable

phase The austenite phase at 1674 ˚F (912 ˚C) is capable of handling up to 211 wt C

due to its more open FCC structure but the maximum carbon that the α-phase can handle

is 002 wt C because of its more enclosed BCC structure This means that with typical

cooling rates carbon will partition itself out of the α-ferrite and form the secondary phase

of Fe3C To form full martensite a quench must happen quickly such that carbon cannot

diffuse out of the octahedral sites in α-Fe into a second phase of Fe3C hence the

diffusionless transformation Carbon remains trapped in the BCC lattice however it

strains the BCC lattice deforming it into a Body Centered Tetragonal (BCT) lattice

where carbon is still in the octahedral sites This is observed in Figure 34 Martensite is

not a thermodynamically stable phase which means that martensite is metastable and that

the diffusion was only suppressed45

Martensite strengthens steel to such a high degree because of the Bain strain that

is induced by the carbon wedged into the BCT lattice The strain field that forms around

each carbon atom inhibits dislocation motion There is also a solid solution strengthening

effect from the carbon that contributes to the overall hardness of the martensite A surface

tilting is normally associated with martensite formation based upon which habit plane

that it forms upon from the austenite phase These habit planes will be dependent upon

alloy composition Figure 35 illustrates this habit plane relationship45

- 57 -

Figure 34 The Body-Centered Tetragonal (BCT) lattice of martensite Carbon atoms become stuck in the

interstices between larger atoms during the rapid quench from the FCC phase of austenite The system

wants to assume the BCC phase of ferrite however cooling happens so rapidly that carbon does not have

time to migrate and now it is trapped in this metastable phase45

It should be noted that martensite formation occurs over a range of temperatures

The alloy must first be quenched through its martensite start temperature (MS) This is

determined by a thermodynamic driving force that is required to start the shear

transformation from austenite to martensite The MS will vary directly with carbon

content the higher the carbon content the lower MS This may seem counterintuitive

because one method for increasing hardenability is to increase the carbon content

however since carbon is an interstitial alloying element in steels it places strain even on

the FCC lattice of austenite This increases austenitersquos resistance to shear Therefore

since martensite formation is a shear transformation there needs to be a larger

thermodynamic driving force to initiate this change which is catalyzed by a larger

undercooling There is also a MF which occurs when all of the austenite has transformed

into martensite Figure 36 illustrates martensite start temperature45

- 58 -

Figure 35 Martensite is characteristic of causing Bain strain The exceptionally high strains associated

with the shear transformation for the formation of martensite will twist and tilt the martensite surface to

start the formation The austenite phase that was not transformed yet has to be plastic enough to allow this

to happen45

There are two different types of martensite that exist lath and plate However

they do not exist exclusively and can mix together The type of martensite formed is

dependent upon composition Plate martensite will form above 10 wt C and lath

martensite will dominate below 06 wt C with a mix of both occurring between 06

and 10 wt C This relationship is illustrated in Figure 36 as well as the martensite start

temperature Plate martensite is characteristic of irrational habit planes macroscopic in

nature (can be seen with optical microscopy) and subject to mostly twinned planes Lath

martensite has the tendency to form in parallel packets with more dislocations than twins

and its habit plane is defined as 11145

- 59 -

Figure 36 There are two different types of martensite lath and plate Formation is dictated by carbon

content As observed a range up to 06 wt C will produce lath and a range upwards of 10 wt C will

produce plate martensite When the wt C is between these ranges a mixture of lath and plate martensite

can be expected45

1853 Tempering Kinetics

Martensitic steel must be tempered to restore ductility and toughness to prevent

possible catastrophic brittle failure Tempering must be performed cautiously because

over-tempering is possible such that the steel becomes too soft Since martensite is a

metastable phase whose diffusion was only suppressed due to kinetics it takes relatively

little thermal energy to enable the carbon to migrate out of the BCT lattice Thermal

energy is introduced to the system in the form of tempering Once carbon leaves the BCT

structure the lattice will relax and reform its thermodynamically stable BCC lattice that

has 002 wt C maximum Therefore the extra carbon that was supersaturated into the

BCT lattice will now precipitate out as the second phase of cementite (Fe3C) Since the

primary goal of tempering is to soften the metal at the expense of hardness it becomes a

balancing act between how long and at what temperatures tempering is conducted to

obtain the desired mechanical properties455051

- 60 -

186 Spheroidizing

Spheroidite is the softest and most ductile microstructure possible for a given steel

because of the formation of spherical carbides which have a low surface-area-to-volume

ratio relative to other carbide shapes Therefore there is less interaction area with the

matrix and in turn less of a strain field that is formed Steels subjected to this heat

treatment have great machining properties because of the increased ductility To achieve

this microstructure the steel is held just below the A1 temperature for multiple hours to

give ample time for carbon diffusion18

187 Stress Relieving

This heat treatment is performed to remove internal stresses induced by welding

machining cold-working etc There is no recrystallization or significant microstructural

changes as with process annealing The temperature for stress relieving is approximately

750 ˚F (400 ˚C) which is the temperature required for dislocation annihilation to

occur1844

19 Introduction to High Strength Low Alloy (HSLA) Steels

HSLA steels are low carbon content steels typically with pearlite and ferrite

microstructures that achieve relatively high strengths formability and toughness despite

the fact that they have a low carbon content Their weldability is also superb due to the

low carbon content To achieve strength an HSLA steel must be able to precipitation

harden the ferrite HSLA steels are commonly microalloyed with vanadium niobium

titanium or another strong carbide forming element and with a solid solution

strengthener such as silicon or manganese Another essential aspect to the strength of

- 61 -

HSLA steels is a fine grain structure Reduced grain size is an additional mechanism for

strength but it also increases toughness while lowering the DBTT5253

191 Precipitation Hardening

Commonly known as age hardening in non-ferrous alloys this secondary-

hardening process closely resembles an austenitize-quench-temper cycle for normal

steels Technically a solution-treat and age cannot be performed in conventional steels

because of the lack of carbon solubility However with the additions of microalloys a

true precipitation hardening can be achieved in HSLA steels A precipitation hardening

technique is similar to an austenitize-quench-temper in terms of its heat treatment cycle

During the quench the goal is to make a metastable supersaturated solid solution Then

when thermal energy is introduced to the system the precipitates (alloy carbides nitrides

and carbonitrides) age or precipitate into the matrix These processes occur at the same

time that the martensite is quenched and tempered54

110 Weldability and Carbon Equivalent (CE)

A cornerstone of this project is ensuring that the alloy developed will have

superior weldability but first the term weldability must be defined such that it can be

understood The weldability of low alloy steels is commonly expressed in terms of

Carbon Equivalent (CE) which is calculated solely from the chemical composition of a

steel The following are the definitions adopted and how they are defined for this project

1101 Weldability

Weldability is defined by the American Welding Society (AWS) as ldquoThe capacity

of a material to be welded under fabrication techniques imposed in a specific suitably

- 62 -

designed structure and to perform satisfactorily in the intended servicerdquo However there

are many characteristics of a steel that could influence its weldability55 Colloquially one

would just say that a steel which welds successfully without pre-heating has a good

weldability

1102 Carbon Equivalent (CE)

One of the best metrics for weldability assessment is through an empirically

derived formula called the carbon equivalent (CE) This was created as a way to quantify

the relative likelihood of hydrogen induced cracking problems and heat affected zone

(HAZ) martensite formation in a steel A knowledgeable welder will use the CE value as

a tool to determine how the metal is going to weld and what welding procedures to follow

to avoid weld zone problems For example if the CE is high the welder will know to pre-

heat the metal to decrease the likelihood of martensite formation upon cooling after

welding In this sense a steel with good weldability (low CE) has poor hardenability56

- 63 -

Chapter 2 Literature Review

The essence of HSLA steels was briefly introduced in Chapter 19 however this

section will serve as a review of the development of HSLA wrought and cast steels

21 Microalloying of Steels

The importance of alloying steel was discovered early in the 20th century in

Europe One of the first microalloying elements added to steel was vanadium57

211 Early Microalloying History with Vanadium

Vanadium was the first element added to microalloy steels Research in the early

1900s in England and France lead to the first commercial microalloyed steel

Metallurgists at that time learned the strength of plain carbon steel could be increased

substantially with additions of vanadium especially when a quench and temper was

performed They did not understand the strengthening mechanisms at work but they

knew that vanadium increased strength and toughness57

Steel containing vanadium made its way to America in about 1910 when Henry

Ford spectated an auto race in France and saw a violent crash He was surprised at how

little damage occurred to the racecarrsquos crankshaft and this sparked his curiosity He

managed to get a sample of the steel tested and it was found to contain vanadium Ford

deduced that additions of vanadium to steel used in Ford vehicles would improve a steelrsquos

strength and shock resistance on American roads even though they did not understand

why Thus vanadium as a microalloy enters markets in the United States however it

would be years before serious focus was applied to development and integration of

microalloy HSLA steels into more areas57

- 64 -

World War II advanced welding technologies greatly Metallurgists soon

discovered that they could not just increase the strength of steels by increasing carbon

content due to the toughness decrease observed when higher carbon content steels are

welded This catalyzed a focus to develop alternative strengthening mechanism to carbon

which lead to the development of grain refining and microalloy precipitation for an

additional strengthening mechanism in steel that required a high weldability From this

deeper investigations into the metallurgy of microalloying continued to develop57

22 HSLA Steels

Even small additions of microalloys to low-carbon steel matched with simple heat

treatments can produce mechanical properties that are comparable to more expensive

steels low alloy steels that require advanced processing steps58 High-Strength-Low-Alloy

steels are based on the microalloying principles discussed previously The term

microalloying and HSLA are used synonymously The concept for strengthening in HSLA

steels is straightforward from a metallurgical point of view there needs to be 1) a refined

grain structure present such that it encourages strength and toughness 2) lower carbon

content to improve weldability 3) strength is achieved through the addition of

microalloys such as vanadium manganese and niobium 4) finally HSLA steels take

advantage of secondary hardening that disperses fine precipitates throughout the ferrite

matrix that further strengthens the steel53

One of the first large scale uses of HSLA steels in the United States was during

construction of the Alaskan Pipeline in 1969 and 1970 It was imperative that steels used

in this pipeline remained tough during the artic conditions so that they would not be

prone to brittle failure Equally important was weldability This caused metallurgists to

- 65 -

analyze previous work done with microalloying of steels and eventually the name

ldquoHSLA steelrdquo was adopted52 The Alaskan Pipeline success with microalloying steels

initiated many investigations into microalloying effects and jump-started broad use of

HSLA steels

221 Strengthening Mechanisms of Microalloys

Microalloys work well for strengthening steel because they can combine the

strengthening mechanisms of grain refinement and precipitation hardening without

decreasing weldability These combined effects counteract the lower carbon content For

microalloys to be effective they must be able to alter the matrix of the ferrite by either

grain refinement or precipitation hardening (normally in the form of carbo-nitrides) or by

a combination of these two57

Grain refinement is the act of making the ferrite grains smaller after final

processing This is achieved when the dispersed microalloys solidify and create a

heterogeneous nucleation site to prevent prior-austenite grain growth During lower

temperature heat treatments in the austenite region often times the stable precipitates will

not fully solutionize and they act as heterogeneous nucleation sites upon cooling which

inhibits austenite grain growth Regardless the microalloying precipitate falls out of

solution before ferrite grains are nucleated57

Precipitation strengthening by microalloying occurs because the microalloys are

precipitated into the ferrite as carbonitrides (CN) but most commonly in HSLA steels as

vanadium-nitrides (VN) or vanadium-carbonitrides (VCN) through a secondary-

hardening process during aging or tempering57 Carbonitrides of vanadium niobium and

titanium can precipitate in both the austenite region and ferrite region59 Additionally

- 66 -

when some form of a CN or VCN is present and a subsequent heat treatment is

performed such as normalizing these carbonitrides will act as austenite grain stabilizers

that prevent grain growth This preserves grain refinement because smaller prior-

austenite grains lead to smaller final ferrite grains They will also pin the ferrite grains

from deformation and growth before the A1 temperature is reached during heating Both

of these mechanisms work together simultaneously to improve the microstructure6061 If

hot rolling is performed on wrought steel austenite grains become elongated which will

increase the grain boundary area Thus increasing the driving force for transformation in

addition to providing more heterogenous nucleation sites26 More nucleation sites are

added indirectly in a steel during hot rolling because it can make precipitation of carbides

happen more favorably60

Microalloying also has a profound effect on the recrystallization during hot

rolling This is important in wrought steels because if the prior-austenite grains are

pinned by microalloys and cannot coarsen then a finer ferrite structure will form upon

cooling There is also a developed argument that solute drag is responsible for limiting

recrystallization57

222 Carbides Nitrides and Carbonitrides

Elements such as vanadium niobium and titanium have tendencies to form stable

carbides nitrides and carbonitrides in steel when precipitated through a secondary

hardening reaction They are the primary microalloying elements used today in HSLA

steels62 The formation of carbides and nitrides are diffusion dependent processes

Complex microalloy carbide and nitride and phases do not diffuse as rapidly as the

conventional Fe3C phase during heat treatment This has a few important consequences

- 67 -

metallurgically First carbides reduce the rate of softening effects such as a temper

because they inhibit the diffusion driven coarsening that Fe3C would experience

Secondly metal carbides that are formed will be resistant to coarsening This limits their

size and enables them to maintain a fine dispersion throughout the matrix Finally it

provides great creep resistance at high temperatures because they will combat steel

softening at elevated temperatures63

Carbides of vanadium niobium and titanium are commonly found in the form of

MC M2C M6C and M23C6 where ldquoMrdquo is comprised of various metals and ldquoCrdquo is

carbon the common stoichiometric carbides are summarized in Figure 37 These carbides

and carbonitrides have the FCC crystal structure and comparable lattice parameters thus

they have extensive mutual solubilities The carbides and nitrides formed by vanadium

niobium and titanium are also known to be harder than martensite This is quantified in

Figure 38 which displays the hardness values of common carbides and martensite63

- 68 -

Figure 37 Chart displaying compositions of some common stoichiometric carbides present in HSLA

steels ldquoMrdquo can vary with multiple chemistries63

Figure 38 Stoichiometric carbides formed with vanadium niobium and titanium that commonly have a

hardness greater than martensite this is important especially for the strengthening effects in prior-austenite

grain pinning63

- 69 -

2221 Vanadium Microalloy Additions

Vanadium is the workhorse in the microalloyed steel families and is more soluble

in the austenite phase than niobium and titanium It has a high affinity for nitrogen and

carbon and readily forms VN VC and VCN These stable carbides and nitrides of

vanadium will have high solubilities in austenite as well compared to niobium and

titanium These solubilities are summarized in Figure 39 Solutionizing of vanadium and

its carbides and nitrides occurs at approximately 1920 ˚F (1050 ˚C) Upon cooling

vanadium will begin to precipitate out of solution at this temperature While cooling

passed the solutionizing temperature which is still in the austenite phase nearly pure VN

is the first to precipitate into the matrix Then when the nitrogen supply is all but

exhausted the system will transition precipitation of VN to VCN and finally to VC

(normally in the form of MC) as nitrogen is depleted There will be a sharp drop in the

solubility of VCN in the matrix around the A1 temperature because of the phase

transition Thus more VCNrsquos are precipitated at this temperature57 Vanadium is

commonly the alloying choice over niobium for precipitation strengthening because

niobium solutionizes at a higher temperature which means that it also precipitates out of

solution at higher temperatures It will fall out of solution during the upper region of the

austenite phase this provides the NbCN too much of an opportunity to coarsen during

cooling Therefore vanadium tends to form the finest precipitates in the ferrite matrix60

- 70 -

Figure 39 Mole fraction of nitrogen in the V-carbonitrides as a function of temperature Vanadium

preferentially bonds with nitrogen at higher temperatures until nitrogen is nearly depleted Then there is a

sharp transition at approximately 1470 ˚F (800 ˚C) to vanadium bonding with carbon preferentially over

nitrogen57

Previous work in the literature regarding microalloying with V in HSLA wrought

steels is extensive some key findings follow

bull Vanadium addition ranges from 003 to 010 wt V increase toughness in

HSLA steels because it will stabilize the dissolved nitrogen64

bull During thermomechanical deformation vanadium has been shown to

precipitate out of solution while the steel is being hot rolled in the form of a

VN60

bull VN will help to prevent austenitic grain growth and recrystallization of

austenite grains However if the solubility product of VN is too low or if the

cooling rates are too fast VN will not form in austenite It has been shown

- 71 -

that raising the nitrogen content will increase the amount of VN that

precipitates60

bull The presence of other alloying elements such as niobium titanium and

aluminum will affect how vanadium behaves Albeit vanadium has the

highest affinity for nitrogen but the other elements precipitate out sooner such

that they will consume all of the nitrogen before vanadium has precipitated60

bull Vanadium does not retard ferrite formation as do molybdenum therefore

vanadium steels are less prone to bainite formation and acicular ferrite

Vanadium reduces the embrittlement likelihood especially in high-carbon

steel Additionally vanadium alloys will not be as susceptible to Heat

Affected Zone (HAZ) embrittlement60

bull VCN precipitation in the austenite region is limited due to sluggish kinetics

therefore most VCN will be precipitated in the ferrite region57

bull Precipitation of VCN in low-carbon and low-nitrogen steels (010 wt C and

010 wt N) will occur mostly at 1292 ˚F (700 ˚C) and below57

bull VC has a higher solubility in austenite and ferrite compared to VN this is

because the thermodynamic driving force for VN precipitation is much

higher57

bull When nitrogen content is decreased the VN precipitate size increases

considerably This is an effect of nucleation rate similar to that observed in

pearlite formation The end-resulting grain size is based on the number of

nuclei57

- 72 -

bull Vanadium will form non-stoichiometric carbides and nitrides VC073 to VC089

are a common VC composition range65

bull Using orientation relationships it is possible to determine whether VCN was

precipitated during the austenite or ferrite phase When the VCN assumes the

Baker-Nutting orientation of 100α-Fe||100VCN and lt100gt α-

Fe||lt010gtVCN it was precipitated in the ferrite When the VCN assumes the

Kurdjumov-Sachs orientation of 110α-Fe||111VCN and lt111gt α-

Fe||lt110gtVCN it was precipitated in the austenite66

2222 Niobium Microalloy Addition

Niobium solutionizes at higher temperatures than vanadium 2100 ˚F (1150 ˚C)

compared to 1750 ˚F (955 ˚C) respectively The implications are that niobium will pin

austenite grains from growing until much higher austenitizing temperatures resulting in

reduced prior-austenite grain size1 Niobium as shown in Figure 40 also works better

than vanadium or titanium for inhibiting recrystallization of austenite temperatures59

Figure 40 Niobium has the optimum effect on increasing the recrystallization temperature of austenite

Vanadium performs the worst in this category This is significant because larger prior-austenite grains will

increase hardenability as well as decrease grain refinement59

- 73 -

2223 Titanium Microalloy Additions

Titanium forms the most stable nitrides in steel (TiN) of all microalloying

elements Most studies suggest that TiN will not solutionize at any temperature in the

austenite region57 Its insolubility in austenite ensures that it will prevent austenite grain

growth during welding and hot processing techniques It can be observed in Figure 41

that TiN has a very low solubility in the austenite phase compared to VC The addition of

titanium levels as low as 001 wt Ti are sufficient to perform its primary

microalloying functions57

Figure 41 Solubilities of common carbides and nitrides of HSLA steels This graph displays the logarithm

of the solubility constant (k) as a function of logarithmic temperature It should be observed that TiN has

very low solubility and that VC has the highest solubility In fact TiN has been known to resist

solutionizing even in the upper region of the austenite phase it is virtually insoluble57

2224 The Roll of Manganese in HSLA Steels

Manganese is an effective solid solution strengthener for ferrite in HSLA steels it

is usually in a range from 15-20 wt Mn67 Manganese will increase VN solubility in

- 74 -

austenite because it increases the activity coefficient of vanadium in tandem with

decreasing the activity coefficient of carbon This increases the amount of microalloying

precipitation during the phase transition from austenite to ferrite Additionally

manganese will lower the AR3 temperature which contributes to ferrite grain refinement

because ferrite grains will get less time to grow All of these factors make higher

manganese (08-14 wt Mn) HSLA steels more effective than low-carbon steels with

conventional manganese levels576063 It has also been shown that manganese additions

will not be detrimental to toughness as other microalloying elements68

23 HSLA Cast Steels

Cast steels can be considered to be at a disadvantage because they do not have the

luxury of being thermomechanically deformed to increase strength as do wrought steels

They must rely solely on heat treating and alloying Other than this there are relatively

minute differences between cast and wrought HSLA steels The 30-year development in

the metallurgy of HSLA wrought steels transcended to HSLA cast steels There are slight

differences in chemistry and heat treatment that must be considered to replace the

benefits of thermomechanical deformation in wrought HSLA steels but the

microalloying concepts between HSLA cast and wrought steels remains the same The

following will review past work specific to the development of HSLA cast steels

154676970

Most of the early work developing HSLA cast steels was done in Europe The

first major work in the United States was conducted by Voigt et al starting in 198671

The first review published on HSLA cast steels was by WJ Jackson in 1978 titled ldquoThe

Use of Vanadium in Steel Castings ndash A Review of the Literaturerdquo In this review the

- 75 -

author detailed past accounts of successful microalloying of cast steels with vanadium

compositions The optimal chemistry ranges for the mechanical properties of cast plain-

carbon and low-alloy steels reviewed by Jackson are shown in Table 1 The yield point

of these steels increased by 30 percent compared to similar plain carbon steel without

microalloying additions with only a negligible decrease in ductility and toughness

Limited research was carried out to identify optimum chemistries for these C-Mn steels

which are summarized in Figure 42 It was determined that the best properties were

obtained with 01 wt vanadium because it produced the finest ferrite grain structure72

Table 1 Chemistry Range for Low-Carbon Vanadium Alloyed Cast Steel72

Elements C Si Mn Cr V

Wt 012-050 03-06 09-15 04-06 007-015

Figure 42 Influence of vanadium on the properties of a C-Mn microalloyed steel Optimum chemistry

occurs at 01 wt V 130 wt Mn 034 wt Si and all carbon in the study was 032 or 033 wt C

At this chemistry it is evident that some properties of toughness decreased All samples were water

quenched and the subsequently tempered at 1202 ˚F (650 ˚C) The V-free steel was quenched from 1616 ˚F

(880 ˚C) and the vanadium steels were quenched from 1688 ˚F (920 ˚C)57

In this study normalizing between 1796-1976 ˚F (920-1080 ˚C) produced a

microstructure of bainite or acicular ferrite microstructure When a subsequent temper is

performed at 1112 ˚F (600 ˚C) an increase in hardness was found because of the

secondary-hardening effects of the precipitation of VCN However extended tempering

times at elevated temperature caused the system to overage which reduced hardness due

- 76 -

to coarsening of precipitates This is one of the reasons why Jacksonrsquos research suggested

that it is imperative to have better control when heat treating microalloyed steel compared

to conventional steels72

It was discussed previously that vanadium and other microalloying elements act

as grain refiners in the austenite region for wrought processed HSLA steels A similar

behavior was observed for cast steels upon initial cooling from the melt VCN acted as a

grain refiner because it fell out of solution slightly before grains grew72

231 Temperaging

To achieve the highest possible strength with HSLA steels they must be

subjected to a quench and temper heat treatment which initiates a precipitation hardening

effect The temper dually functions to soften martensite into ferrite and cementite while

simultaneously aging fine precipitates into the matrix This dual function has become

known to some metallurgists as the portmanteau ldquotemperagingrdquo17367

232 Weldability and Carbon Equivalent in Previous Work

There are different CE formulas for different welding applications however the

CE formula used in this project is AWSD11 that is displayed in Equation 4 The CE

formula which is most appropriate for structural steel welding varies between steels

because different alloying elements have different influences on weldability For

example how much they slow diffusion rates and whether or not they are carbide

formers In general the addition of other alloying elements to a C-Mn steel will have the

same hardenability and weldability influence of an increase in carbon content Individual

alloying elements directly affect the weldability of the steel to varying degrees This is

- 77 -

why the effect of each element on the CE is scaled by a factor that can be expressed as a

carbon equivalent factor for that steel This means that if a particular steel had been

alloyed with just carbon it would theoretically weld simularly56

119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4

There are other CE formulae used throughout industry but they all have a similar

goal which is being a weldability predictor High carbon content steels have low

weldabilities therefore a high CE steel will also have a low weldability The most

common CE used in industry is displayed in Equation 5 is adopted by the International

Institute of Welding (IIW) as their official CE equation5473 The following ASTM

Standards also follow CE calculated by Equation 5 A216 A352 A709 (Grade 50s)

A913 and A1043 Both ASTM A216 and A352 are cast steel specific standards

Equation 6 is the typical HSLA CE for C-Mn steels Equation 7 is used in ASTM A529

and it is the only CE equation that includes Nb This is because Nb rarely contributes to

the cold-cracking of steels54 Equation 8 is utilized by the Japanese Welding Engineering

Society for low-carbon content steels (lt 011 wt C)74

119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -

Jacksonrsquos Review analyzed CEASTM for HSLA cast steels and utilized Equation 5

with the following results72

bull CEASTM le 041 Good weldability and no need for preheating

bull CEASTM le 045 Good weldability when the welding is completed with low H2

electrodes

bull CEASTM ge 045 Preheating is required for welding use of low H2 electrodes is

required

bull CEASTM ge 060 Only specific conditions enable the steel to be weldable

One nuance that should be stressed to the reader is this project has a goal of

integrating a cast steel designed for structural applications into an existing wrought

ASTM Standard The implications are that a structural welding steel obeys the structural

welding code as seen in AWS D11 such as their CEAWS D11 in Equation 4 while most

ASTM Standards obey CEASTM as seen in Equation 5 This is bound to cause confusion

and all parties involved must be made aware

233 Pertinent Cast Steel ASTM Standards

There are ASTM Standards specifically for cast steel A27 A148 A216 A217

A352 A356 A487 and A958 Most relevant are ASTM A216 Standard Specification

for Steel Castings Carbon Suitable for Fusion Welding for High-Temperature Service

and its low-temperature counterpart of ASTM A352 Standard Specification for Steel

Castings Ferritic and Martensitic for Pressure-Containing Parts Suitable for Low-

Temperature Service Both standards obey the CEASTM in Equation 5 and they have

CEASTM max values of 050 or 055 depending on the specific grade Grade WCB from

- 79 -

ASTM A216 is of particular interest because it was posited by the SFSA that the YS

requirements for this project could be attained through slight manipulation of chemistries

permitted in this standard

234 Key Findings from Previous Work

Previous work has found interesting differences between processing for HSLA

wrought steels and HSLA cast steels The key findings follow

bull It may be necessary to homogenize large casting sections for up to 6 hours at

temperatures ranging from 1740-2010 ˚F (950-1100 ˚C) to combat alloy

segregation Then an accelerated cooling is desired because it will yield a refined

ferrite grain structure73 The length of the homogenizing time and temperature in

general will dependent upon the casting size67

bull Austenitizing temperatures of greater than 1700 ˚F (930 ˚C) are required to

produce full strengthening of V-microalloys73

bull If an insufficient quench is performed coarse VCN will precipitate out during the

initial cooling Coarse VCN does not produce the high hardness that is seen with

finely dispersed precipitates However there is still a strengthening effect that is

seen when temperaging following a weak quench This implies that a temperaging

effect can be seen with thick casting sections as well 73

bull Rapid quench rates will produce the highest hardness however only a slight

decrease in hardness will be observed after temperaging because of the secondary

hardening effect This implies that the softening effect of martensite is more

dominant than the secondary hardening which is aging73

- 80 -

bull Non-heat-treated cast steels tend to have lower ductility compared to cast steel

subjected to heat treating Interestingly non-heat-treated steels have a higher yield

strength70

bull Minimal overaging in the temperaging process is acceptable and sometimes

desired to improve toughness at the expense of only a slight decrease in yield

strength67 Overaging is associated with decreasing the coherency of the

precipitates in the matrix54

bull Higher austenitizing temperatures will enable more precipitates to form during

temperaging because it increases the re-solution of microalloying elements while

in the austenite phase67 Austenitizing temperatures of 1740 ˚F (950 ˚C) were

proven sufficient for normalize and temper (NampT) cast steels the strength levels

of quench and tempered (QampT) cast steels were greatly increased by austenitizing

at 1920 ˚F (1050 ˚C)69

bull A typical NampT heat treatment can still precipitation harden during temperaging

however the resulting microstructure is less hard than a QampT67

bull According to early research with microalloying HSLA steels with niobium it will

increase strength more than vanadium when heat treating at high austenitizing

temperatures because it prevents austenite grains from coarsening However

coarsening of austenite grains was not observed by Voigt and Rassizadehghani in

1989 They proved this by austenitizing at high temperatures with and without

niobium and then performing the proper etch to display the prior-austenite

grains54

- 81 -

bull Intercritical heat treatments although not used in this body of work have yielded

promising results and high strength and toughness combinations in the past54

- 82 -

Chapter 3 Hypothesis and Statement of Work

31 Hypothesis

A 50 ksi (345 MPa) yield strength cast steel with a high weldability for structural

and military applications will be developed using high-strength-low-alloy (HSLA) steel

metallurgical techniques Finally the materialrsquos composition and properties can be

conveniently placed within an existing ASTM Standard for wrought or cast steels

allowing ready adoption of these cast steels for applications using cast-weld construction

techniques

32 Statement of Work

Weldable 50 ksi (350 MPa) yield strength cast steel composition and heat

treatment guidelines will be determined with four primary steps 1) examination of

composition heat treating and mechanical property data from the Steel Foundersrsquo

Society of Americarsquos (SFSA) database of cast C-Mn steels to identify fundamental

structure-property relationships 2) Thermocalc modeling will define stable phases in

equilibrium and determine solutionizing temperatures for a range of C-Mn steel alloys

with vanadium and niobium microalloying additions 3) heat treating and mechanical

testing of various compositions of steel will provide a validation of how alloys respond to

respective heat treatments 4) Finally rational composition and processing guidelines will

be developed so that future work can establish appropriate ASTM and AWS placement

for this alloy system

- 83 -

Chapter 4 Experimental Procedure

All samples in this study were standard ASTM keel block castings with two test

specimen legs donated by SFSA member foundries in the United States The keel blocks

used in this study had a thick body attached to two legs The keel block measured

approximately 60 in X 40 in X 40 in (1525 cm X 102 cm X 102 cm) and each leg

was approximately 60 in X 10 in X 20 in (1525 cm X 254 cm X 51 cm) The keel

block legs were halved lengthwise with a band saw such that the final dimensions of the

keel block legs used for heat treating were 60 in X 10 in X 10 in (1525 cm X 254 cm

X 254 cm) Thus each keel block could yield four keel block tensile test specimens All

times and temperatures for heat treating and tempers were obtained from the literature

notably from previous work completed by Voigt Rassizadehghani and the

SFSA154676973 Heat treating time was started when the temperature of the furnace

stabilized after loading the samples into the furnace

In all of the following sections keel blocks and keel block legs were heat treated

in a Thermo-Scientific Lindberg Blue M and the Brinell hardness tests were performed

with a NEWAGE Brinell NB3010 Additionally all mechanical testing conformed to

ASTM E8 Standard Test Method for Tension Testing of Metallic Materials

41 Heat Treating Modified C-Mn and Modified C-Mn-V

The initial alloys investigated in this study were reformulations of conventional

WCB C-Mn cast steel with and without vanadium ldquoModified C-Mnrdquo and ldquoModified C-

Mn-Vrdquo alloys were developed to obtain an understanding of C-Mn cast steel capabilities

and the effects of alloying a similar composition with small amounts of vanadium Keel

- 84 -

block legs were removed from the Modified C-Mn and Modified C-Mn-V keel blocks

and halved lengthwise on a band saw Both the keel block and keel blocks legs which

become test bar specimens were austenitized to 1750 ˚F (955 ˚C) for 10 hr Half of each

alloy were subjected to a normalizing air cool and the other half were water quenched

Subsequent tempering that followed both normalizing and quenching was performed at

1150 ˚F (621 ˚C) for 25 hr for keel blocks and at 1150 ˚F (621 ˚C) for 20 hr for keel

block legs Heat treated keel block legs were subjected to tensile tests for both the

Modified C-Mn and Modified C-Mn-V

42 Tempering Study

An investigation into the temperaging response of the vanadium alloyed material

in particular was necessary to develop heat treating guidelines Modified C-Mn and

Modified C-Mn-V were used to compare a plain WCB type steel to one that should

experience a temperaging response respectively Keel block legs of Modified C-Mn and

Modified C-Mn-V were cut from the keel blocks and austenitized to 1750 ˚F (955 ˚C) for

20 hr Keel block legs were either normalized in an air cool or water quenched Then the

keel block legs were sliced into approximately 025 in (~6 mm) thick sections for

subsequent tempering such that different times and temperatures can be easily studied

for each alloy

bull A sample for each composition in the normalized and quenched conditions was

subjected to a specific temperature for either 10 hr or 40 hr These temperatures

ranged from 900 ˚F to 1200 ˚F (482 ˚C to 649 ˚C) in 50˚F (28 ˚C) increments

resulting in 56 total samples The furnace used for these small samples was a

Barnstead Thermolyne 47900

- 85 -

bull Each sample was then Rockwell hardness tested to develop an understanding of

temperaging for these alloys The machine used was a NEWAGE Rockwell

Digital ME-2

43 Special Heat-Treating Options

431 Thick-Section Study Part I (Keel Block)

Heat treating has to be more controlled with HSLA steels than conventional steels

due to the microalloys and the secondary hardening72 A concern was that thicker sections

of castings could not be quenched quickly enough to produce a supersaturated solution of

microalloys without having them fall out of solution prior to tempering Keel blocks of

Modified C-Mn and Modified C-Mn-V were heat treated as described in Chapter 41

Then they were cut at frac14 thickness and the cut faces were Brinell hardness tested

bull A range of 12-14 Brinell Hardness indentations were performed on each samplersquos

face to obtain a hardness profile from the edge to the center of these 40 in (102

cm) sections

432 Thick-Section Study Part II (Normalizing Cooling Rate Effect)

Commonly in real world casting scenarios castings are not uniform in shape and

size such as a keel block leg This poses kinetic and thermal property issues associated

with cooling rates Theoretically a thin section of casting could form a completely

different microstructure than a thick section on the same casting cooled with the same

cooling media This was investigated with keel blocks of Modified C-Mn and Modified

C-Mn-V that were cut differently than for previous heat-treating studies A keel block for

each alloy had one of its legs removed from the keel block body This resulted in two

- 86 -

keel block legs of the dimensions used previously 60 in X 10 in X 10 in (1525 cm X

254 cm X 254 cm) and two identical to it still attached to the keel block body Each

keel block with legs attached and its separated legs were austenitized to 1750 ˚F (955 ˚C)

for 2 hr and then subjected to a normalized air cool

bull Upon completion of the heat treating the keel block legs still attached to the keel

blocks were removed and all keel block legs were subsequently tensile tested

433 Double Normalize

For some microalloyed steel alloys a double normalize heat treatment is

commonly used to improve mechanical properties such as increased ductility with a

relatively small strength penalty75 A keel block and keel block legs from Modified C-Mn

and Modified C-Mn-V were subjected to a double normalizing heat treatment The first

austenitizing was at 1750 ˚F (955 ˚C) for 05 hr followed by an air cool The second

austenitizing was at 1600 ˚F (871 ˚C) for 20 hr followed by another air cool

bull Upon completion of the heat treating these keel block legs were then subjected to

tensile testing

44 Heat Treating of Factorial Design Alloys

To obtain a better understanding of composition limits for carbon manganese

and vanadium Alloys C D E and F with variations in carbon manganese and

vanadium contents were created This enabled analysis into the influence that alloys

upon one-another and how effective one alloy is with and without others present Keel

block legs were removed from Alloys C D E and Frsquos keel blocks and halved lengthwise

on a band saw Both the keel block legs and keel blocks were austenitized to 1750 ˚F

- 87 -

(955 ˚C) for 10 hr Subsequent tempering that followed both normalizing and quenching

was performed at 1150 ˚F (621 ˚C) for 25 hr for keel blocks at 1150 ˚F (621 ˚C) for 20

hr for keel block legs

bull Heat treated keel block legs were subjected to tensile tests for Alloys C D E and

F

45 Metallography of Samples

Samples prepared for metallography include Alloys A-F NampT and QampT Alloys

A and B double normalize and thick section normalized No metallography was

performed on tempering study 0250 in (~6 mm) thick wafers The samples prepared

were sliced sections of tensile test bar ends These were hot-pressed in Allied High-Tech

Products Inc Phenolic mounting powder using a ldquoTech Press 2rdquo manufactured by Allied

High-Tech Products Inc Samples were ground using automated grinding set to 150

RPMs with a pressing force of 18 N Each sample was ground for 30 s at each of the

following grits 240 320 400 and 600 (grinding with the 600-grit pad was performed

twice for a better surface finish)

Next the samples were polished using 1 μm diamond slurry polish for 5 min

followed by a subsequent polish using a 025 μm diamond slurry polish for 3 min After

each grinding and polishing step the samples were rinsed with distilled water The last

step of preparation was to etch both steel alloys using a 2 nital mix This mixture was 2

mL of nitric acid and 98 mL of methanol Upon etching the samples were rinsed with

ethanol

- 88 -

bull Optical microscopy was used to analyze the microstructures of all the steel

samples The microscope used was a Zeiss Axiovert 10 Inverted Microscope

- 89 -

Chapter 5 Results and Discussions

The United States has failed to dedicate the same effort to developing both HSLA

cast and wrought steels compared to Europe and Asia The largest body of work

currently is that created by the Steel Foundersrsquo Society of America (SFSA) and Voigt et

al The following work was conducted as a continuation of previous work done as well as

a new attempt at integrating 50 ksi (345 MPa) yield strength HSLA cast steels into

existing HSLA wrought standards

51 SFSA Database for Conventional C-Mn (WCB) Steel

The SFSA has compiled a database of over 20000 C-Mn cast steel chemistries

and mechanical properties data from participating steel casting foundries in the United

States This spreadsheet consisted of WCB (ASTM A216) conventional C-Mn cast steel

that was either normalized NampT or QampT The data was analyzed to determine whether

or not it is possible to reach 50 ksi (345 MPa) with conventional C-Mn steel

compositions without microalloying with vanadium and niobium The data was cleaned

and the resulting spreadsheet contained approximately 2500 data entries It should be

noted that ASTM A216 grade WCB is for conventional C-Mn cast steel with a minimum

36 ksi (248 MPa) YS and a maximum CEASTM 050 wt CEASTM The CEASTM does not

consider the effects of silicon which the CEAWS D11 does Additionally as with most

ASTM standards for steel ASTM A216 grade WCB is based more on mechanical

properties than composition Albeit there are composition limits in this standard their

allowable ranges are rather large

- 90 -

The spreadsheet was organized by heat treatments performed on the cast steel test

bars normalized NampT and QampT Scatter plots were made from these data to determine

if correlations between YS composition and CEAWS D11 (weldability) could be detected

Figures 43-45 show the trends between YS and CEAWS D11 (not CEASTM) carbon content

and manganese content respectively

Figure 43 Scatterplot of YS vs CE for all heat treatments (normalize NampT and QampT) According to the

spreadsheet there is a broad range of weldabilities that produce a YS of 50 ksi (345 MPa)

Figure 43 suggests that high YS values of over 50 ksi (345 MPa) are possibly but

not when a CEAWS D11 le 045 wt CE is maintained ASTM A215 grade WCB specifies

that a CEASTM le 050 wt CE be maintained this plot helps to show the decrease in

weldability when silicon is accounted for because there are copious samples that now

exceed the 050 wt CEAWS D11

- 91 -

Figure 44 YS vs Carbon Content This scatterplot is color coded to detect trends in heat treatment related

to YS There is negligible correlation The highest R2 value in this data set is 004 which gives a positive

correlation for increasing carbon content providing a higher YS in the QampT condition However a R2 value

this low should not be considered statistically significant

Figure 45 YS vs Manganese Content This scatterplot is color coded to detect trends in heat treatment

related to YS There is slightly better correlation with YS as a function of manganese content than as a

function of carbon content However the best correlation observed is an R2 value of 01 for a positive

correlation of QampT improving YS with increasing manganese content Likewise this should not be

considered statistically significant

- 92 -

Figures 43-45 do not suggest a statistically significant trend in YS as a function of

composition for any type of heat treatment Therefore to make possible trends of

chemical composition and mechanical properties more apparent the database was split

into two groups of high-strength-high-weldability and low-strength-low-weldability

Then the composition of materials with these extremes in mechanical properties and

weldability were compared in Table 2

Table 2 SFSA Spreadsheet Analysis of Mechanical Property Extremes to Detect Trends

in Composition

Designation Range C wt Mn wt V wt Si wt

High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451

Despite the significant difference in mechanical properties the compositions

show little variance There is only a 0017 wt C difference between the YS less than or

equal to 45 ksi (3102 MPa) and a YS greater than or equal to 55 ksi (3792 MPa) The

difference in manganese and silicon is greater however this is still a small difference

These composition variations are smaller than most allowable composition ranges as

would be seen with an ASTM standard Even after these extrema of the spreadsheet data

have been analyzed there is no strong correlation between mechanical properties

weldability and composition

The correlation between normalize NampT and QampT heat treatments and YS CE

ranges is shown in Table 3 It should be noted that 55 ksi (3792 MPa) was chosen as the

upper range instead of 50 ksi (345 MPa) because 50 ksi (345 MPa) is the bare minimum

YS requirement This strength level must be achieved consistently so perturbations in the

YS distribution curve must be taken into account

- 93 -

Table 3 Percentage of Heat Treatments per Designation for the SFSA Spreadsheet

Designation Range Overall Normalize

NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047

For the entire spreadsheet only 041 of all cast steels obtained 55 ksi (345 MPa)

while maintaining a maximum 042 CEAWS D11 Surprisingly a majority of these were

normalize heat treatment instead of QampT A possible contribution to this result is that the

normalized heat-treated steel samples in this spreadsheet greatly outnumbered the NampT

and QampT heat treated samples There were 1318 normalized samples 347 NampT samples

and only 51 QampT samples The difference in number of samples can also be observed in

Figures 46-48 which display YS as a function of normalized NampT and QampT heat

treatments respectively Tables 4-6 are paired with them as well

Figure 46 All normalized heat treatments and how their YS is a function of weldability The correlation is

poor for plain normalized There is not an increase in YS with increasing the CE but rather a slightly

negative trend

- 94 -

Table 4 Average Chemistries per Designation in the Normalized Condition Data Set


High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421

Figure 46 and Table 4 display normalized heat treatment data obtained from the

SFSA spreadsheet Figure 46 is a scatterplot of YS as a function of weldability (CEAWS

D11) and there is no statistically significant correlation between an increase in alloying

content leading to an increase in YS Table 4 displays the average chemical composition

for each respective designation In this case there is only a 0035 wt C difference over

a 10 ksi (689 MPa) YS change

Figure 47 NampT heat treatments with YS as a function of weldability The correlation suggests that

increasing CE in this condition will decrease YS

- 95 -

Table 5 Average Chemistries for Property Ranges of the NampT Data Set


High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484

Figure 47 and Table 5 display NampT heat treatment data obtained from the SFSA

spreadsheet Figure 47 is a scatterplot of YS as a function of weldability (CEAWS D11) and

there is no statistically significant correlation between an increase in alloying content

leading to an increase in YS Table 5 displays the average chemical composition for each

respective designation In this case there were not any data points that met the high-

strength-low-CE designation

Figure 48 QampT heat treatments and their YS as a function of weldability The correlation is the best out of

normalize and NampT however there is a negative trend suggesting that increasing CE will decrease YS

- 96 -

Table 6 Average Chemistries for Property Ranges of the QampT Data Set


High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

Figure 48 and Table 6 display QampT heat treatment data obtained from the SFSA


there is only a slight statistically significant correlation between an increase in alloying

content and increasing YS This negative trend in the R2 of 01 suggests that there is a

slight correlation between increasing alloying elements and a decrease in YS Table 6

displays the average chemical composition for each respective designation In this case

there is a 0044 wt C difference over a 10 ksi (689 MPa) YS change

Finally the last analysis completed on this spreadsheet was dividing it up into

quartiles based on YS and then analyzing the average and standard deviation in chemical

composition for the top and bottom quartile The results are displayed in Table 7 The

middle 50 percent of data were ignored because the extreme differences in mechanical

properties from the database should better expose any existing chemical-property

relationships of WCB conventional C-Mn cast steels

Table 7 Weight Percent Addition of Primary Alloying Elements with Respective Total

Top Quartile and Bottom Quartile Average and Standard Deviation

YS Ave C Mn Si V CMn CEAWS D11 YS (MPA)

Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -

The results displayed in Table 7 support the previous analyses of the spreadsheet

The WCB conventional cast steel spreadsheet compiled by the SFSA suggests results that

do not make sense metallurgically It is highly improbable that an increase in carbon

content andor manganese content would not make a cast steel stronger There should be

positive correlations in YS with increasing carbon content and manganese content

however this was not observed The positive correlations that did exist had very small R2

values that were not statistically significant the largest being 01 for YS as a function of

manganese content as observed in Figure 45 In Table 7 the difference between the

average wt C for the top quartile of YS and the average wt C for the bottom

quartile of YS is only 0006 wt C This is because the overall ranges in composition in

this database was not large Table 8 is a summary table depicting the total percentages of

the spreadsheet that achieved certain strengths and weldability values

Table 8 Database Summary Table Depicting Percentages of Samples within YS and

Weldability Ranges

Designation Range Overall

Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047

The spreadsheet data suggests lack of composition correlation with mechanical

properties and variation in spectrometry and mechanical testing This was not a

controlled study that was conducted by the SFSA There were nine foundries that

participated in data collection each using their own spectrometer to provide a chemistry

analysis It would only take a slight variation between foundries data collection validity

for the values of this spreadsheet to be drastically different Additionally there was no

- 98 -

control of the mechanical testing It is unknown where each foundry sent their tensile test

bars for mechanical testing or if they were tested on-site by each foundry Nonetheless

more reputable data would have been obtained if all tensile test bars were sent to one

mechanical testing facility that would perform the mechanical test as well as retrieve an

official chemistry analysis Nonetheless since only 041 of samples in the entire

database reached YS and weldability requirements it can be concluded that conventional

C-Mn cast steels cannot achieve 50 ksi (345 MPa) YS and CEAWS D11 le 045 CE

consistently enough to be used Therefore microalloying is needed

52 Modified C-Mn and Modified C-Mn-V

The initial two heats of material were designed to build off of previous work done

in the literature ldquoModified C-Mnrdquo is a reformulated version of conventional WCB C-Mn

cast steel ldquoModified C-Mn-Vrdquo is has less carbon content but more manganese and there

is a modest vanadium addition These alloys were meant to contrast a plain C-Mn cast

steel with a similar cast steel microalloyed with vanadium and slightly more manganese

The complete spectrometer readout is displayed in Table 9 and the CEAWS D11 and

CEASTM values are given in Table 10 Both CE values were computed with the data in

Table 8 not the ldquotarget carbonrdquo shown in Table 11

- 99 -

Table 9 Complete Spectrometer Readout for Compositions of Modified C-Mn and

Modified C-Mn-V

Element Modified C-Mn (wt addition) Modified C-Mn-V (wt addition)

C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA

Table 10 Summary of Carbon Equivalent Values for Modified C-Mn and Modified C-

Mn-V

Alloy CEASTM CEAWS D11 CEAWS Primary CEAWS Residual

Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008

Table 11 Target Carbon Weight Percent vs Multiple Spectrometer Readings from

Multiple Foundries for Modified C-Mn (ldquoAlloy Ardquo) and Modified C-Mn-V (ldquoAlloy Brdquo)

Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159

Table 11 displays inconsistent chemistry measurements for carbon content

between foundries and measurement methods This severely compromises a foundryrsquos

ability to accurately meet chemistry targets For example the target carbon composition

for Modified C-Mn is 020 wt C and according to all spectrometers used and the

LECO there is a up to a 059 wt C difference between all measures This could have

profound effects associated with inconsistencies Customers could be receiving steel that

- 100 -

both themselves and the casting foundry believe to be in spec when the actual chemistry

is significantly different This also has direct ramifications with the CE errors due

inaccurate carbon content reporting This could cause weld defects due to lack of

preheating when the CE calculated for that specific steel determined that no preheat was

needed Ultimately this reinforces the theory that variance in spectrometers between

foundries is probably one of the major contributing factors to such large scatter in the

spreadsheet data from the SFSA

53 Thermocalc CALPHAD Modeling

Due to the microalloy additions of vanadium a full austenitic transformation must

occur during austenitizing heat treatments such that all VC VN and VCN are

solutionized This will increase the propensity for fine dispersed precipitation of VC VN

and VCN during subsequent temperaging If a fully cohesive austenite phase it not

formed ie not all microalloying additions are solutionized then there will be unwanted

growth during cooling of non-quenched heat treatments as well as in all subsequent

tempers This produces overly large VC VN and VCN that will not have the same

strengthening effects in the ferrite matrix of fine dispersed precipitates This is because

many fine-dispersed precipitates have a greater surface area interaction with the matrix

than fewer larger precipitates57 Figures 49-51 are outputs from Thermo-Calc Software

TCFE SteelsFe-alloys database version 8 which show phase fraction as a function of

temperature for the Modified C-Mn chemistry Modified C-Mn-V chemistry and the

Modified C-Mn-V with 003 wt Nb respectively76 A niobium addition is modeled

such that an understanding can be developed for the difference in solutionizing

temperature between itself and vanadium

- 101 -

Figure 49 Phase fraction as a function of temperature for Modified C-Mn All carbides and other present

phases solutionize completely by 1531 ˚F (833 ˚C)

Figure 50 Phase fraction as a function of temperature for Modified C-Mn-V All carbides and other

present phases solutionize by 2003 ˚F (1095 ˚C)

- 102 -

Figure 51 Phase Fraction as a function of temperature for Modified C-Mn-V with a 003 wt Nb

addition All carbides and other present phases solutionize by 2187 ˚F (1197 ˚C)

Fully homogenous austenite occurs at 1531 ˚F (833 ˚C) for Modified C-Mn 2003

˚F (1095 ˚C) for Modified C-Mn-V and 2187 ˚F (1197 ˚C) for Modified C-Mn-V with a

003 wt Nb addition The results for Modified C-Mn-V were not expected because it is

repeated throughout the literature that the solutionizing temperature for vanadium is

approximately 1740 ˚F (950 ˚C)1 Admittedly these Thermo-Calc models were created

after all heat treating was completed because literature is so adamant about the

solutionizing temperatures of vanadium which is why austenitizing of the Modified C-

Mn-V samples was performed at 1750 ˚F (955 ˚C) This creates controversy because if

Thermo-Calc is correct the austenitizing temperature of 1750 ˚F (955 ˚C) was not

adequate to fully solutionize the vanadium which could lead to oversized precipitates

It should be noted that there are limitations to the commercial databases used in

Thermo-Calc when full systems of alloying elements are modeled because of the program

has difficulty calculating the free energies of non-Fe elements Miscibility gaps can

siphon vanadium away from carbides and form different FCC sublattices These are

- 103 -

depicted in Figures 49-51 To create more accurate Thermo-Calc models a specific

database for all present elements would be needed Even when ldquoartifactrdquo phases are not

displayed graphically Thermo-Calc still calculates their existence even though it is not

visible on the graph Therefore the other phases that are depicted behave the same

whether ldquoartifactsrdquo are visible or not The major problem with this database when

modeling microalloying additions with vanadium is that it does not recognize the

introduction of nitrogen into the carbide which is a crucial component

54 Tempering Study

A tempering investigation was conducted to observe temperaging effects of the

microalloying elements present in Modified C-Mn-V versus Modified C-Mn which did

not contain vanadium These graphs should serve as heat treating guidelines for foundries

and metallurgists The curve drawn between the data points are suggestions rather than

ldquofitted curvesrdquo The Keel block legs from Modified C-Mn and Modified C-Mn-V were

austenitized to 1750 ˚F (955 ˚C) for 20 hr and then normalized in an air cool or water

quenched Subsequent 10 hr or 40 hr tempers were performed with temperatures

ranging from 900 ˚F to 1200 ˚F (482 ˚C to 649 ˚C) in 50˚F (28 ˚C) increments as seen in

Figures 52-61 More specifically Figures 52-57 show the effect of the tempering times

and temperatures for each Modified C-Mn and Modified C-Mn-V Figures 57-61 show a

comparison between the Modified C-Mn and Modified C-Mn-V so that effects of

vanadium during tempering can be more clearly seen

bull The hardness readings shown in each figure is the average hardness from multiple

readings on each sample

bull The reading at 00 hr is the initial hardness before any tempering is performed

- 104 -

Figure 52 Modified C-Mn NampT showing HRB at 1 hr and 4 hr for various temperatures There is no

temperaging response observed however a negligible increase in hardness happened for 1000 ˚F (538 ˚C)

at 1 hr

Figure 53 Modified C-Mn QampT showing HRB at 1 hr and 4 hr tempering times for different

temperatures There was dramatic softening especially with the 1200 ˚F temperature at 4 hr due to

standard tempering mechanisms

- 105 -

Figure 54 Modified C-Mn-V NampT showing HRB at 1 hr and 4 hr for various temperatures Initially at 1

hr standard tempering softening occurs at all temperatures The most effective being 1100 ˚F (593 ˚C)

Then precipitation aging occurs before 4 hr and a hardness increase is observed

Figure 55 Modified C-Mn-V QampT This is less straightforward than the NampT heat treatment however

similar results are obtained There was a drastic softening at 1 hr and a subsequent increased hardness due

to aging by 4 hr for 900 ˚F (482 ˚C) There was only a slight temperaging response for 1000 ˚F (538 ˚C)

and the 1200 ˚F (649 ˚C) temperature only softened after 1 hr

- 106 -

Figure 56 Modified C-Mn where both NampT and QampT are placed on the same HRB scale such that a direct

comparison can be appreciated of the effects of a normalize and quench can have on starting hardness

values for the same material and their subsequent tempering responses

Figure 57 Modified C-Mn-V displaying both NampT and QampT on the same HRB scale enabling direct

comparison between the two heat treatments and their subsequent temper(aging) responses

- 107 -

Figure 58 Modified C-Mn and Modified C-Mn-V This serves to analyze the presence of vanadium when

subjected to NampT Modified C-Mn-V experienced a hardness increase from 1 hr to 4 hr when tempered at

1000 ˚F and 1100 ˚F (538 ˚C and 593 ˚C) The other results did not indicate temperaging


subjected to QampT Modified C-Mn-V experienced a hardness increase from 1 hr to 4 hr when tempered at

900 ˚F (482 ˚C) The other results did not indicate sufficient temperaging

- 108 -

Figure 60 Modified C-Mn and Modified C-Mn-V in the NampT condition 1000 ˚F (538 ˚C) proves to be the

temperature where the temperaging response is predominantly initiated A different sample was used for

each temperature and that these lines do not indicate a temperaging response for Modified C-Mn

Figure 61 Modified C-Mn and Modified C-Mn-V in the QampT condition 1000 ˚F (538 ˚C) proves to be the

temperature where the temperaging response is predominantly initiated for Modified C-Mn-V at 1 hr

temper time Modified C-Mn-V for 4 hr temper time behaves anomalously A different sample was used

for each temperature and that these lines do not indicate a temperaging response for Modified C-Mn at 4 hr

temper time

- 109 -

This tempering study showed that ldquotemperagingrdquo effects are simultaneous

martensite softening and precipitation strengthening produced when microalloying with

vanadium It is hopeful that these tempering graphs can serve as suggestions for foundry

heat treating applications of cast steels containing vanadium As expected a temperaging

response was not observed in Modified C-Mn due to its lack of vanadium however not

all Modified C-Mn-V tempering samples showed a complete temperaging response

depending on the tempering temperature chosen It is customary to not exceed 100 HRB

such that HRC is used after this hardness point however all measurements were

completed using HRB so all hardness values could be compared using the same scale

The validity of this study needs to be explored with a future tempering study at

more tempering times and temperatures than used in this study Additionally fitted

curves should be applied such that a more accurate times and temperatures can be

approximated for optimum temperaging

55 Initial Round of Heat Treating

Modified C-Mn and Modified C-Mn-V were subjected to NampT and QampT heat

treatments to establish benchmarks for behavior of conventional WCB C-Mn cast steel

alloys with and without vanadium additions

551 Analysis of Modified C-Mn

Modified C-Mn alloy is a reformulation of a conventional WCB C-Mn alloy

containing no vanadium Table 12 displays mechanical property data for Modified C-Mn

after both NampT and QampT heat treatments were performed Table 13 displays the averages

of the mechanical properties from Table 12

- 110 -

Table 12 Mechanical Property Data for NampT and QampT Modified C-Mn with YS and TS

in ksi

Heat

Treatment YS (MPa) TS (MPa) EL RA HB

NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216

Table 13 Average of Mechanical Property Data for Modified C-Mn with YS and TS in

ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211

The results displayed in Tables 12 and 13 show that there is an average difference

in YS of 288 ksi (1986 MPa) between NampT condition and the stronger QampT condition

The QampT condition also has an average hardness of 64 HB over the NampT condition but

a 51 EL decrease

It is expected that there is a YS and hardness increase from the NampT condition to

the QampT condition in the Modified C-MN alloy The full quench of a steel produces

martensite which is the hardest microstructure possible in steels According to the

tempering studies full hardness of the Modified C-Mn alloy in the QampT condition

produces a Brinell hardness of approximately 240 HB Then during tempering of the

keel blocks legs at 1150 ˚F (621 ˚C) for 20 hr the rapid diffusion and coarsening of

cementite softened the matrix to 211 HB This was a pure softening effect as no

secondary hardening effects were seen due to the lack of vanadium and other

microalloying elements50 The microstructures of Modified C-Mn in the NampT condition

and QampT condition are in Figures 62 and 63 respectively

- 111 -

Figure 62 Modified C-Mn in the NampT condition

Figure 63 Modified C-Mn in the QampT Condition

- 112 -

Figures 62 and 63 show different microstructures of Modified C-Mn that are

induced by different heat-treating conditions Figure 62 indicates proeutectoid ferrite

(white) and pearlite (dark) According to Table 9 the carbon content of Modified C-Mn

is 018 wt C This composition places the alloy in the hypoeutectoid two-phase

cooling region far left of the eutectoid at 077 wt C which provides ample time for

proeutectoid ferrite nucleation and growth as seen in Figure 9 The slower cooling rates

of a NampT provide time for diffusion and nucleation and growth to enable this

microstructure The fast cooling of a quench does not allow for any diffusion to occur

Figure 63 is characteristic of a tempered martensite microstructure The dark regions are

cementite and the lighter areas are ferrite Tempering provided enough thermal energy for

some diffusion to occur and the laths of martensite are not visible

552 Analysis Modified C-Mn-V

Modified C-Mn-V alloy is a reformulation of a conventional WCB C-Mn alloy

with the addition of vanadium Tables 14 displays the mechanical property data for

Modified C-Mn-V after both NampT and QampT heat treatments were performed Table 15

displays the averages of the mechanical properties from Table 14

Table 14 Mechanical Property Data for NampT and QampT Modified C-Mn-V with YS and

TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -

Table 15 Average of Mechanical Property Data for Modified C-Mn-V with YS and TS

in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231




an 86 EL decrease There is an increase in YS from Modified C-Mn to Modified C-

Mn-V for both the NampT and QampT condition 128 ksi (883 MPa) and 23 ksi (1586

MPa) respectively

It is logical that strength levels for the vanadium containing Modified C-Mn-V

alloy are higher than for the Modified C-Mn alloy Additionally there is a 390 ksi (2689

MPa) YS increase from the NampT condition to the QampT condition in Modified C-Mn-V

compared to a 288 ksi (1986 MPa) strength increase from the NampT condition to the

QampT condition in the Modified C-Mn alloy This difference suggests that a secondary

hardening event occurred during the QampT heat treating of the Modified C-Mn-V If

temperaging did not occur it would be expected that the difference in strength between

the NampT condition and QampT conditions would be similar to what is observed in

Modified C-Mn The microstructures of Modified C-Mn-V in the NampT condition and the

QampT condition are in Figures 64 and 65 respectively

- 114 -

Figure 64 Modified C-Mn-V in the NampT condition

Figure 65 Modified C-Mn-V in the QampT condition

- 115 -

Figure 64 has micro-specs (precipitates) that are evident throughout the

proeutectoid ferrite matrix This dispersion is not seen as well QampT condition in Figure

65 due to the amount of tempered martensite which obscures the view These

precipitates are not visible in the vanadium-free Modified C-Mn alloy in Figures 62 and

63 Due to the uniform nature of the precipitates displayed in Figure 64 it can be

concluded that a normalizing cool is sufficient to retain the precipitates in solution until

below the critical transformation temperature such that they do not de-solutionize during

initial cooling If a finite amount of precipitates would have de-solutionized during the

initial air cool then there would be large precipitates visible with the fine precipitates

because the larger precipitates would have grown during initial cooling

553 SEM Analysis of Modified C-Mn and Modified C-Mn-V

Analysis of microstructures with a Scanning Electron Microscope (SEM) was also

performed on the Modified C-Mn and Modified C-Mn-V alloys to compare the

microalloying effects of vanadium at a more microscopic level This was in response to

the precipitates that are visible in Figure 64 and an attempt to verify the existence of VN

VC andor VCN precipitates in addition to comparing the relative size of the precipitates

to determine if some de-solutionized The precipitates that de-solutionized during the

normalizing air cool would be larger than those aged into the matrix Figures 66-68

display Modified C-Mn in the NampT condition Modified C-Mn-V in the NampT condition

at 5000X and 10000X respectively

- 116 -

Figure 66 SEM image of Modified C-Mn in the NampT condition There are no precipitates in this alloy due

to the lack of microalloying additions

Figure 67 SEM image of Modified C-Mn-V in the NampT condition

- 117 -

Figure 68 SEM image of Modified C-Mn-V in the NampT condition at a higher magnification than Figure

67 The Precipitates of vanadium are more defined in this image

There are no precipitates or dispersoids visible in the SEM micrograph of

Modified C-Mn in the NampT condition in Figure 66 However in the SEM micrographs in

Figures 67 and 68 there are precipitates present Figure 68 which is 10000X

magnification shows these precipitates better than Figure 67 Most of the precipitates in

the image appear to be uniform in size however there are a few larger precipitates This

size difference was not visible with just optical microscopy Therefore it can now be

postulated that a small finite number of precipitates de-solutionized during normalizing

air cool but it is a small percentage Thus the air cool is still adequate for a subsequent

temper to induce aging and not over-age precipitates

Electron Dispersion Spectroscopy (EDS) was also performed on these samples to

determine the composition of the precipitates However a proper balance in eV could not

- 118 -

be found such that the beam either over-penetrated the sample and was reading the

composition of the matrix or it was not strong enough to read the sample This is due to

the nm magnitude of the precipitates It is suggested that a surface technique such as X-

Ray Photoelectron Spectroscopy (XPS) be performed so that over-penetration does not

occur and a quantitative analysis of the composition can be acquired


There needs to be more metallurgical control in heat treating of microalloyed

HSLA steels than with conventional steels to ensure that a proper temperaging response

is observed72 An open question is the heat treatment response of heavy section castings

that will have slower cooling rates for NampT and QampT heat treatments


This thick-section study involves subjecting the keel block bodies of both

Modified C-Mn and Modified C-Mn-V to NampT and QampT to better understand the

cooling rate effect of large section size Table 16 displays the results of a Brinell

Hardness testing profile across the 40 in (102 cm) face of keel blocks Table 17 also

displays the Brinell Hardness results but with an interpretation of the hardness at the

edge and center for each keel block

- 119 -

Table 16 Brinell Hardness of Heavy Section Samples of Modified C-Mn (ldquoAlloy Ardquo)

and Modified C-Mn-V (ldquoAlloy Brdquo) Across 40 in (102 cm) Face After NampT and QampT

Heat Treatments Each ldquoIndentationrdquo Value is Represented as the Hardness Profile

Developed Across the Face

Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments

Sample and (HT) Midway Hardness (HB) Edge Hardness (HB)

Alloy A (NampT) 147 147

Alloy A (QampT) 172 180

Alloy B (NampT) 156 172

Alloy B (QampT) 216 234

The Brinell Hardness profiles across the 40 in (102 cm) faces of the keel blocks

determined that the edge hardness was greater for both conditions of Modified C-Mn-V

and the QampT condition of Modified C-Mn The NampT condition of Modified C-Mn did

not develop a profile

Cooling gradients are to be expected in thick-casting sizes due to the specific heat

capacity of the material Therefore the steel should be harder in areas near the edge of

the material where a faster cooling rate is observed than at the center where the material

- 120 -

is more insulated from severe quenches The results in Table 17 do not make sense for

the NampT condition of Modified C-Mn The QampT condition and both conditions of

Modified C-Mn-V have the expected profile

Additionally when the HRB values from the tempering study are converted to

HB values and applied to this data the results also are not consistent For example the

HB conversion value for the normalized condition of Modified C-Mn-V before a temper

is 180 HB (taken from tempering study) The hardest HB value in the thick-section data

is 182 for the same alloy after NampT Therefore the following are possible 1) incorrect

conversions from HRB to Brinell 2) a temperaging response increased the hardness in

the thick section meaning that the effects of age hardening overpowered the temper on a

slow cool which is very unlikely 3) the data is compromised and should be repeated


Commonly in real-life situations metal castings are complex in shape and do not

experience uniform cooling rates The kinetic and thermal property issues associated with

this will be addressed It is important to understand how the microstructure of one-section

of casting could be significantly different than another section of the same casting

because of cooling rates To study this effect keel block legs were normalized with and

without the keel blocks still attached for both Modified C-Mn and Modified C-Mn-V

these results are displayed in Tables 18 and 20 respectively Tables 19 and 21 are

summary tables displaying the averages of the mechanical properties from Tables 18 and

20

- 121 -

Table 18 Mechanical Property Data for Thin Section Attached to Keel Block for

Modified C-Mn (ldquoAlloy Ardquo) and Modified C-Mn-V (ldquoAlloy Brdquo) with YS and TS in ksi

Alloy YS (MPa) TS (MPa) EL RA HB

A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152

Table 19 Average of the Mechanical Property Data for Thin Section Attached to Keel

Block for Modified C-Mn (ldquoAlloy Ardquo) and Modified C-Mn-V (ldquoAlloy Brdquo) with YS and

TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153

Table 20 Mechanical Property Data for Thin Section Separated from Keel Block for



A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168

Table 21 Average of the Mechanical Property Data for Thin Section Separated from

Keel Block for Modified C-Mn (ldquoAlloy Ardquo) and Modified C-Mn-V (ldquoAlloy Brdquo) with YS

and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167

The data from Part II of the thick-section study investigated the cooling rate

effects of a thin-section attached to a thick-section versus a thin-section cooling

autonomously This was conducted for both Modified C-Mn and Modified C-Mn-V The

data suggests that faster cooling rates are observed when the thin-section is autonomous

versus when the thin-section is attached to a thick-section (keel block) Faster cooling

rates yield finer grain structures which are consistently found to increase strength

Consequently the YS values for both alloys are higher in Table 21 when the thin-section

- 122 -

cooled autonomously To analyze the difference in grain structure between cooling rates

Figures 69-72 display micrographs of Modified C-Mn and Modified C-Mn-V attached to

the keel block and cooled autonomously respectively

Figure 69 Modified C-Mn attached to the keel block

- 123 -

Figure 70 Modified C-Mn-V attached to keel block

Figure 71 Modified C-Mn normalized autonomously from keel block

- 124 -

Figure 72 Modified C-Mn-V normalized autonomously from keel block

There is an obvious difference in grain size between samples that were cooled

while attached to the keel block (Figures 69 and 70) and ones that were cooled

autonomously (Figures 71 and 72)


Double normalizing heat treatments have been reported to increase toughness and

ductility while sacrificing relatively little strength75 Therefore it became a heat treatment

of interest Modified C-Mn and Modified C-Mn-V were both subjected to the double

normalizing heat treatment There was no temper that followed either normalization heat

treatment Table 22 displays the mechanical properties of Modified C-Mn and Modified

C-Mn-V after a double normalize The averages are in Table 23

- 125 -

Table 22 Mechanical Property Data for Double Normalize Heat Treatment with



A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162

Table 23 Average of Mechanical Property Data for Double Normalize Heat Treatment

with Modified C-Mn (ldquoAlloy Ardquo) and Modified C-Mn-V (ldquoAlloy Brdquo) with YS and TS in

ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164

The double normalizing heat treatment mechanical properties are best-compared

to the mechanical properties obtained by the single normalizing heat treatment of a keel

block leg in Table 21 The average YS for Modified C-Mn and Modified C-Mn-V in

single normalizing condition is 473 ksi (3258 MPa) and 543 ksi (3744 MPa)

respectively These are both slightly weaker than the YS values produced with a double

normalizing heat treatment for Modified C-Mn and Modified C-Mn-V 498 ksi (3437

MPa) and 554 ksi (3821 MPa) respectively Equally important was the EL increase

that was observed with the double normalizing heat treatment compared to the single

normalizing heat treatment These results are conducive with literature To analyze the

grain refinement that occurred Figures 73 and 74 are images of double normalized

condition Modified C-Mn and Modified C-Mn-V respectively

- 126 -

Figure 73 Modified C-Mn double normalize

Figure 74 Modified C-Mn-V double normalize

- 127 -

Figures 73 and 74 are micrographs of the double normalized condition of

Modified C-Mn and Modified C-Mn-V respectively


The Modified C-Mn and Modified C-Mn-V used in previous experiments had

chemical composition data from multiple sources that was not consistent Additionally

they did not meet the YS and CEAWS D11 requirement Therefore more compositional data

needed testing and validation Factorial design alloys were also produced to better

develop compositional understandings and how much variance is allowed in composition

to still maintain strength Table 24 displays the 4 new alloys (C-F) and their designations

Table 25 shows the compositional targets for Alloys C-F and the actual spectrometer

compositions are shown in Table 26 Then the data from Table 26 was used to calculate

the CE values for these alloys and this data is displayed in Table 27 Finally carbon

content comparisons were made with spectrometer data from multiple foundries and the

results are shown in Table 28

Table 24 Alloy Name and Designation for Factorial Design Alloys

Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V

Table 25 Alloy C-F Compositional Targets for Carbon Manganese Vanadium and

Silicon

Alloy C wt Mn wt V wt Si wt

C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -

Table 26 Actual Chemical Compositions for Alloys C-F as Determined by

Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA

Table 27 Summary of Carbon Equivalent Values for Alloys C-F


C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004

Table 28 Target Carbon Wt vs Multiple Spectrometer Readings from Multiple

Foundries for Alloys C-F

Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182

Alloys C-F faced similar compositional difficulties that Modified C-Mn and

Modified C-Mn-V did The actual compositions do not match the target compositions

- 129 -

571 Analysis of Alloy C-F

Alloys C-F were subjected to NampT and QampT heat treatments and their

mechanical property data is dispersed in Tables 29-36

Table 29 Mechanical Property Data for Alloy C NampT and QampT YS and TS in ksi

Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222

Table 30 Average of Mechanical Property Data for Alloy C with YS and TS in ksi

Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219

Table 31 Mechanical Property Data for Alloy D NampT and QampT YS and TS in ksi

Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240

Table 32 Average of Mechanical Property Data for Alloy D with YS and TS in ksi

Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240

Table 33 Mechanical Property Data for Alloy E NampT and QampT YS and TS in ksi

Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -

Table 34 Average of Mechanical Property Data for Alloy E with YS and TS in ksi

Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234

Table 35 Mechanical Property Data for Alloy F NampT and QampT YS and TS in ksi

Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247

Table 36 Average of Mechanical Property Data for Alloy F with YS and TS in ksi

Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253

Alloys C and E are the only two alloys that have an acceptable CE value (lt045

wt CE) including Modified C-Mn and Modified C-Mn-V In the QampT condition

Alloy C has adequate YS with 807 ksi (5561 MPa) Alloy E in both NampT and QampT

conditions exceeds the 50 ksi threshold with 511 ksi (3523 MPa) and 882 ksi (6078

MPa) respectively This can be attributed to their low carbon contents which helps to

limit CE moderate amounts of manganese and high vanadium contents An observation

of the micrographs for Alloys C-F in both the NampT and QampT conditions can be made

with Figures 74-82

- 131 -

Figure 75 Alloy C in the NampT condition

Figure 76 Alloy C in the QampT condition

- 132 -

Figure 77 Alloy D in the NampT condition

Figure 78 Alloy D in the QampT condition

- 133 -

Figure 79 Alloy E in the NampT condition

Figure 80 Alloy E in the QampT condition

- 134 -

Figure 81 Alloy F in the NampT condition

Figure 82 Alloy F in the QampT condition

- 135 -

There does not appear to be any significant difference between the QampT condition

micrographs amongst Alloys D-F The main difference to note between the alloys is the

grain refinement observed with Alloy E in the NampT condition which is noticeably more

than in the other alloyrsquos NampT conditions Additionally there appears to be more

precipitates dispersed throughout the ferrite comparatively Consequently Alloy E is the

only Alloy to reach both the YS and CEAWS D11 requirement

58 Weldability and Carbon Equivalent Analysis

There is a need for an understanding of allowable compositional variance ie

how much can the composition of certain alloying elements deviate and still reach

required strength levels Furthermore this becomes important for standards where there

are large allowable composition windows which is common since most steel casting

standards are based on mechanical properties This analysis was completed using the

Factorial Design alloys (Alloys C-F) Figures 83-88 are graphs that have ISO-YS lines as

a function of carbon content (Y-Axis) and manganese content (X-Axis) Figures 83-85

are for the NampT condition for 00 wt V 008 wt V and 012 wt V

respectively Figures 86-88 are for the QampT condition for 00 wt V 008 wt V

and 012 wt V respectively Therefore if a metallurgist wants to maintain a certain

YS for a certain wt V then they just have to alloy the wt C and wt Mn

according to the X and Y axis on the graphs The regression equations used for NampT and

QampT are shown in Equations 9 and 10 respectively

119884119878 = 51547 + (42064 times 119862) + (284495 times 119872119899) + (999979 times 119881) Eq 9

119884119878 = minus157501 + (1548821 times 119862) + (543727 times 119872119899) + (2631891 times 119881) Eq 10

- 136 -

Figure 83 NampT with no vanadium content

Figure 84 NampT with 008 wt V

- 137 -


Figure 86 QampT with no vanadium content

- 138 -

Figure 87 QampT with 008 wt V


- 139 -

The graphs display ISO-YS lines such that if the composition of the alloy waivers

in between two YS lines which are a function of carbon content and manganese content

then the YS of the alloy with that specific heat treatment and vanadium content will fall

between the two lines The correlation (R2 value) for the accuracy of the regression

equations are 08662 and 09879 for NampT and QampT respectively

59 ASTM Considerations

The final goal of this project involves integration of the developed alloy (most

likely some slight variation of Alloy E) into an existing ASTM Standard Table 37

provides suggestions of possible ASTM Standards both for wrought and cast grades

where a 50 ksi (345 MPa) YS cast steel could be integrated

Table 37 ASTM Specification Summary

ASTM Form TS-YS-EL (2rdquo)-

CVN

CE Cmax Mnmax

A487 Steel cast pressure (W) 85-55-22-Yes No 030 100

A242 HSLA Structural (W) 70-50-21-No No 015 100

A500 Cold-Formed Welded Tube

(W)

62-50-21-No No 023 135

A529 High-Strength C-Mn (W) 65-50-21-No 055 027 135

A709 Structural Bridge Multiple

Grade (W)

65-50-21-Yes No 023 135

A913 HSLA QST Grade 50 (W) 65-50-21-No 038 012 160

A992 Structural Steel Shapes (W) 65-50-21-No 045 023 160

A1043 Structural Build Grade 50

(W)

65-50-21-Yes 045 020 160

A148 Carbon Steel (C) 80-50-22-No No NA NA

A216 WCB (C) 70-36-22-No 050 030 100

A217 High-P High-T (C) 105-50-18-No No 021 080

A356 Low Alloy Grade 8 (C) 80-50-18-No No 020 090

A958 Steel Multiple Grades (C) 80-50-22-No No

consult original standard for more information

(W) for Wrought

(C) for Cast

- 140 -

Table 37 just serves to display possibilities This is groundwork that can help

assist in future deliberations regarding the matter It should also be noted that the goal is

to integrate the alloy into both an ASTM Standard and the AWS D11 Structural Welding

Code for Steel Integration of the developed alloy into an ASTM Standard and AWS

D11 Structural Welding Code is a highly political decision that is not taken lightly

There will be many composition tests welding tests mechanical tests and deliberations

to emerge

- 141 -

Chapter 6 Summary Conclusion and Future Work

61 Summary

This research was conducted to develop a 50 ksi (345 MPa) Yield Strength (YS)

cast steel alloy using common alloying elements complete with heat treating guidelines

such that any foundry in the United States can produce this alloy and consistently achieve

the strength requirements Interest for this research spawned from industry and the

militaryrsquos transition from 36 ksi (248 MPa) highly weldable HSLA wrought steels to 50

ksi (345 MPa) HSLA wrought steels in recent decades Alloys investigated were

restricted to a carbon equivalent (CEAWS D11) of le 045 wt CE to ensure that optimum

weldability is maintained Introductory work was completed for implementation of this

alloy into an existing ASTM Standard for wrought or cast steels and certification of this

alloy into the AWS D11 Structural Welding Code for steel Implementation of the high

weldability 50 ksi (345 MPa) cast steel into these standards and codes will enable the full

potential of the developed cast steel to be realized It will enable complex shapes of 50

ksi (345 MPa) cast steel to be cast into the final form and welded into place to expedite

construction processes

The research began with analysis of a conventional C-Mn cast steel (ASTM A216

WCB grade specific cast steel) database that was compiled by the Steel Foundersrsquo

Society of America (SFSA) to determine whether or not it was possible to reach the

desired properties and CE requirements with conventional cast steels The database

consisted of mechanical property data composition and heat treatment for conventional

C-Mn cast steels produced by a multitude of foundries across North America

- 142 -

The database analysis found that only 041 of the cast steels reached YS and

CE requirements This suggested that it is not possible to obtain the required YS while

maintaining the CE requirements with conventional C-Mn cast steel Additional findings

of the database analysis implied much variance in spectrometer data between foundries

because there was no significant correlation between increasing alloying content and an

increasing YS regardless of heat treatment

The second stage of research was conducted to compare and contrast the

microalloying effects of vanadium in Modified C-Mn and Modified C-Mn-V cast steels

that had compositions based on previous literature work1 The compositions were

modeled using Thermo-Calc to verify austenitizing temperatures for complete

solutionizing of VCN These alloys were subjected to NampT and QampT heat treatments a

tempering study and special heat treatments that included thick-section analysis

normalizing cooling rate study and double normalizing The tempering study analyzed

hardness values of normalized or quenched wafers that were subjected to tempering times

of either 10 hr or 40 hr for various times These values were then plotted to obtain

tempering curves however these curves were not true ldquofitted curvesrdquo but merely

suggestions The thick-section analysis was completed with keel blocks to see the effects

of cooling rates because it was postulated that thick-sections may not cool fast enough for

vanadium to stay in solution Keel blocks were subjected to NampT and QampT heat

treatments and were subsequently sliced at frac14 thickness Brinell hardness testing was then

perform across the freshly exposed keel block faces to develop hardness profiles The

normalizing cooling rate study was done to mimic real-world cooling of complex casting

shapes which may not cool uniformly One of the two keel block legs was removed from

- 143 -

a keel block and its mate remained on the keel block Then both the autonomous keel

block leg and the one still attached to the keel block were normalized The difference in

cooling rates divulged different properties These samples were not tempered Finally a

double normalizing heat treatment was performed because it is commonly done in

industry to HSLA cast steels to improve ductility with only a slight strength penalty75

bull Thermocalc modeling predicted that the full austenitizing temperatures for the full

solutionizing of Modified C-Mn and Modified C-Mn-V to be 1531 ˚F (833 ˚C)

and 2003 ˚F (1095 ˚C) respectively This is a contradiction with literature which

suggests that vanadium fully solutionizes at approximately 1740 ˚F (950 ˚C)1

bull Optical microscopy was performed on both samples and there was precipitation

hardening observed in the Modified C-Mn-V alloy for both NampT and QampT

conditions

bull The targeted chemistry for both alloys was not achieved by the casting foundry

this resulted in high CE for both alloys 048 and 051 wt CE for Modified C-

Mn and Modified C-Mn-V respectively

bull There was also substantial variance in spectrometer readings between foundries

bull The resulting average YS of the NampT condition for the Modified C-Mn and

Modified C-Mn-V alloys were 466 ksi (3210 MPa) and 594 ksi (4092 MPa)

respectively Likewise the average YS of the QampT condition were 754 ksi (5195

MPa) and 984 ksi (6781 MPa) respectively

bull The tempering study found temperaging effects in the vanadium containing alloy

There was an initial softening at 10 hr due to tempering of martensite The

kinetics for aging take time to initiate and hardness increased on some samples at

- 144 -

40 hr Some C-Mn-V samples especially higher temperature samples did not

display an aging response at hour 40 however this was probably due to

overaging Therefore it can be posited that C-Mn-V samples exposed to higher

temperatures probably hit peak-age in between 10 and 40 hr

bull The thick-section study produced hardness profiles as expected (higher hardness

at the edge than at the center) in all samples except the Modified C-Mn in the

NampT condition Testing of this sample in particular should be repeated to verify

the results However the Brinell hardness of the Modified C-Mn thick-section in

the NampT condition identically matched its tensile test bar in the NampT condition

for hardness 147 HB

bull Other findings of the thick-section study were that the edge hardness values for

Modified C-Mn in the QampT condition were 180 HB compared to its tensile test

bar in the QampT condition which were 211 HB This can be attributed to slower

cooling rates for the keel block It allowed precipitates to de-solutionize during

the initial cooling from the austenite phase Both the NampT and QampT conditions of

Modified C-Mn-V had higher hardness at the edges of the keel blocks than their

respective tensile test bars average hardness 172 HB compared to 169 HB for the

NampT condition and 234 HB compared to 231 HB for QampT condition However

these results have a negligible difference This proves thicker sections can be

quenched rapidly enough to prevent precipitates from de-solutionizing

bull The normalizing cooling rate study found that test bars cooled autonomously had

a more refined grain structure and higher average YS values and higher average

hardness values Modified C-Mn had a YS of 448 ksi (3085 MPa) and hardness

- 145 -

of 148 HB attached to the keel block and a YS of 473 (3258 MPa) and a

hardness of 149 HB when cooled separately Modified C-Mn-v had a YS of 520

ksi (3585 MPa) and hardness of 153 HB attached to the keel block and a YS of

543 (3744 MPa) and a hardness of 167 HB when cooled separately

bull The double normalizing study found that average EL is increased for both

Modified C-Mn and Modified C-Mn-V when compared to NampT and QampT

conditions For Modified C-Mn in the NampT and QampT conditions the average EL

was 29 and 24 respectively while in the double normalized condition

the average EL was 328 For Modified C-Mn-V in the NampT and QampT

conditions the average EL was 29 and 30 respectively while in the

double normalized condition the average EL was 314

bull The double normalizing study also found that there was an increase in YS and EL

when compared to the single normalizing heat treatment that the autonomous

tensile test bars were subjected to in the normalizing cooling rate study The

average double normalizing YS values are 498 ksi (3437 MPa) and 554 ksi

(3821 MPa) for Modified C-Mn and Modified C-Mn-V respectively This is due

to a more refined grain structure that is present in the double normalizing

condition

The third stage of research was conducted to determine the compositional range

allowable to still maintain YS values Alloys C-F were created to further analyze this All

samples were subjected to NampT and QampT heat treatments to the same processing

parameters as seen with Modified C-Mn and Modified C-Mn-V

- 146 -

bull Only Alloy C and Alloy E reached the CEAWS D11 requirement with 039 wt

CE and 044 wt CE respectively

bull The YS values for Alloys C-F in the NampT condition are 450 ksi (3099 MPa)

520 ksi (3585 MPa) 511 ksi (3523 MPa) 550 ksi (3794 MPa)

bull The YS values for Alloys C-F in the QampT condition are 807 ksi (5561 MPa)

956 ksi (6588 MPa) 882 ksi (6078 MPa) and 1037 ksi (7146 MPa)

respectively

bull Alloy C met both the CE requirement and YS requirement in its QampT condition

with 807 ksi (5561 MPa)

bull Alloy E met both the CE requirement and YS for both NampT and QampT conditions

with 511 ksi (3523 MPa) and 882 ksi (6078 MPa) respectively

bull Optical microscopy was performed on all samples and it was determined that

precipitation hardening occurred in both NampT and QampT conditions for Alloys C-

F

bull The compositions of Alloys C-F were not on target Therefore a full factorial

design could not be completed however this further bolsters the fact that it is

difficult for foundries to produce compositions accurately Additionally when the

spectrometer data was compared between foundries there was also a large

variance as seen with Modified C-Mn and Modified C-Mn-V

bull Alloy E has the optimum composition to achieve high weldability and 50 ksi (345

MPa) YS with the following composition 012 wt C 104 wt Mn 025 wt

Si 036 wt Cr 006 wt Ni 003 wt Mo 006 wt Cu and 011 wt

- 147 -

V Therefore this is the composition that should be investigated for its

inception into an ASTM Standard or AWS welding code

62 Conclusion

In conclusion this research was conducted to develop a 50 ksi (345 MPa) Yield

Strength (YS) cast steel with a carbon equivalent (CEAWS D11) of le 045 wt CE to

ensure that optimum weldability is maintained without preheating This is in response to

industry and the military transitioning from 36 ksi (248 MPa) highly weldable HSLA

wrought steels to 50 ksi (345 MPa) HSLA wrought steels in recent decades It is desired

that complex shapes of 50 ksi (345 MPa) cast steel be cast into the final form and welded

into place to expedite construction processes Thus the reason for a high weldability

Additionally only common alloying elements are used to ensure that every steel foundry

in America has the capabilities to cast it To accomplish this an initial understanding of

conventional C-Mn cast steel capabilities needed to be developed A database of over

20000 conventional C-Mn cast steel (ASTM A216 WCB grade specific cast steel)

compositions and mechanical properties was compiled by the Steel Foundersrsquo Society of

America (SFSA) It was analyzed to determine the limitations of conventional C-Mn cast

steel Ie if these can meet YS and CE requirements or if microalloying additions would

be needed The database analysis found that only 041 of the cast steels reached YS

and CE requirements thus microalloying was needed to achieve YS and CE

requirements

There was a need to develop a basic understanding of the microalloying effects of

vanadium when compared to a similar compositional sample without vanadium This was

accomplished with Modified C-Mn and Modified C-Mn-V cast steel samples that were

- 148 -

based upon compositions from previous literature work1 These alloys were subjected to

NampT and QampT heat treatments (austenitizing at 1750 ˚F (955 ˚C) for 2 hr) a tempering

study and special heat treatments that included thick-section analysis normalizing

cooling rate study and double normalizing Optical microscopy was performed on both

samples and there was precipitation hardening observed in the Modified C-Mn-V alloy

for both NampT and QampT conditions The targeted chemistry for both alloys was not

achieved by the casting foundry this resulted in high CE for both alloys 048 and 051

wt CE for Modified C-Mn and Modified C-Mn-V respectively Further work

continued because these alloys did not meet YS and CE requirements Thermocalc

modeling of these alloys was completed to understand at what temperature the system

would fully solutionize It predicted the solutionizing temperatures of Modified C-Mn

and Modified C-Mn-V to be 1531 ˚F (833 ˚C) and 2003 ˚F (1095 ˚C) respectively This

suggests that the vanadium in the Modified C-Mn-V would not have been fully

solutionized This is however a contradiction with literature which suggests that

vanadium fully solutionizes at approximately 1740 ˚F (950 ˚C) Future work should

investigate this disagreement

Next Alloys C-F were developed with a focus on how much variation in



requirements with 039 and 044 wt CE respectively Alloy C earned a YS of 81 ksi




- 149 -


wt Cr 006 wt Ni 003 wt Mo 006 wt Cu and 011 wt V Therefore

this is the composition that should be investigated further for future implementation into

ASTM Standards and AWS Structural Welding Codes

63 Future Work

Future work must revisit the following to either validate the existing work or to

develop the theory more comprehensively

bull Tempering Study with larger samples of Modified C-Mn and Modified C-Mn-V

to see if results are repeatable Then curves should be ldquofittedrdquo to obtain true

tempering profiles

bull Hardness Profiles for the thick-section study to see if the results are repeatable

and to compare how the hardness values compare to the ones produced in the

tempering study

bull Perform optical microscopy on the thick-section castings

bull Reinvestigate Thermo-Calc models with a specific database for HSLA steels

Future work must continue in the following areas that were either beyond the

scope of this project or not permitted with time and funding allotted

bull Double normalize and temper study with Modified C-Mn and Modified C-Mn-V

to compare these results with the existing double normalizing heat treatment

results

bull Complete more investigations with variations of Alloy E

- 150 -

Appendix A

Figure 89 Comparing and contrasting a conventional cast steel microstructure with a microalloyed HSLA

cast steel microstructure1

- 151 -

Figure 90 As-Cast microstructure of HSLA steels vs normalized microstructure for HSLA cast steel1

- 152 -

Figure 91 Original estimate for vanadium content to obtain 50 ksi (345 MPa) YS as a function of carbon

content and manganese content

Figure 92 Original attempt at creating a 50 ksi (345 MPa) surface as a function of carbon content and

manganese content

- 153 -

Appendix B

Table 38 Summary of Carbon Equivalent Values for Alloys A and B

Alloy CEAWS D11 CEIIW CET PCM CEAWS Primary

A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426

Table 40 Original Quartile Analysis for Database

C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References

(1) Voigt Robert C Blair M and Rassizadehghani J Properties and Processing of

High-Strength Low-Alloy (HSLA) Cast Steels 1994

(2) Beddoes J Bibby M J ldquoSolidification and Casting Processesrdquo In Principles of

Metal Manufacturing Processes Elsevier Butterworth Heinemann Amsterdam

Netherlands 2003 pp 18ndash75

(3) Pakker E R Zackay V F Materials Science of Modern Steels Prog Solid State

Chem 1975 9 (C) 105ndash138

(4) Krauss G ldquoHistory and Primary Steel Processingrdquo In Steels-Processing

Structure and Performance Second Edition ASM International Materials Park

OH 2016 pp 9ndash16

(5) Beddoes J Bibby M J ldquoMetal Processing and Manufacturingrdquo In Principles of



(6) Australian-Foundry-Association ldquoMelting Technologyrdquo In Cleaner Production

Manual for the Queensland Foundry Industry 1999 p Chapter 3

(7) Hurtuk D J ldquoSteel Ingot Castingrdquo In ASM Handbook Vol 15 Casting ASM

International Materials Park OH 2018 pp 911ndash917

(8) Jorstad J L Technologies J L J ldquoShape Casting ProcessesmdashAn Introductionrdquo

In ASM Handbook Vol 15 Casting ASM International Materials Park OH

2018 pp 485ndash487

(9) ASM-International ldquoGreen Sand Moldingrdquo In ASM Handbook Vol 15 Casting

ASM International Materials Park OH 2018 pp 549ndash566

(10) What-When-How Sand Castings httpwhat-when-howcommaterialsparts-and-

finishessand-castings

(11) ECS-Staff Guide to Casting and Molding Processes 2006

(12) ASM-International ldquoPermanent Mold Castingrdquo In ASM Handbook Vol 15

Casting ASM International Materials Park OH 2018 Vol 1 pp 689ndash699

(13) AFS US Casting Sales Reach 331 Billion Modern Casting 2019 pp 27ndash29

(14) Krauss G ldquoPearlite Ferrite and Cementiterdquo In Steels-Processing Structure and

Performance Second Edition ASM International Materials Park OH 2016 pp

39ndash62

(15) Callister-Jr W D Rethwisch D G ldquoPhase Diagramsrdquo In Fundamentals of

Material Science and Engineering An Integrated Approach John Wiley amp Sons

INC Hoboken New Jersey 2012 pp 359ndash420

(16) Krauss G ldquoPhases and Structuresrdquo In Steels-Processing Structure and


15ndash32

- 155 -

(17) Okamoto H The C-Fe (Carbon-Iron) System J Phase Equilibria 1992 13 (5)

543ndash565

(18) Krauss G ldquoNormalizing Annealing and Spheroidizing Treatments

FerritePearlite and Spherical Carbides In Steels-Processing Structure and


277ndash291

(19) Krauss G ldquoHardness and Hardenabilityrdquo In Steels-Processing Structure and


297ndash325

(20) Brooks C R ldquoHardenabilityrdquo In Principles of the Heat Treatment of Plain

Carbon and Low Alloy Steels ASM International Materials Park OH 1999 pp

43ndash86

(21) Tuttle R Understanding the Mechanism of Grain Refinement in Plain Carbon

Steels Int J Met 2013 7 (4) 7ndash16

(22) Krauss G ldquoDeformation Strengthening and Fracture of Ferritic Microstructuresrdquo

In Steels-Processing Structure and Performance Second Edition ASM


(23) Gladman T ldquoMicrostructure-Property Relationshipsrdquo In The Physical Metallurgy

of Microalloyed Steels The Institute of Materials London England 1997 pp 19ndash

79

(24) Balluffi R W Allen S M Carter W C ldquoMorphological Evolution Due to

Capillary and Applied Forces Diffusional Creep and Sinteringrdquo In Kinetics of

Materials John Wiley amp Sons INC Hoboken New Jersey 2005 pp 387ndash418

(25) Krauss G ldquoAustenite in Steelrdquo In Steels-Processing Structure and Performance

Second Edition ASM International Materials Park OH 2016 pp 133ndash162

(26) Smith R M Chandra T Dunne D P Ferrite Grain Refinement in HSLA Steels

Strength Mater Alloy 1983 1 235ndash240

(27) Brooks C R ldquoStructural Steelsrdquo In Principles of the Heat Treatment of Plain


263ndash306

(28) Duckworth W E Thermomechanical Treatment of Metals J Met 1966 No

August 915ndash922

(29) Kula E B Radcliffe V Thermomechanical Treatment of Steel J Met 1963 52

(7) 96ndash97

(30) Callister-Jr W D Rethwisch D G ldquoPhase Transformationsrdquo In Fundamentals

of Material Science and Engineering An Integrated Approach John Wiley amp

Sons INC Hoboken New Jersey 2012 pp 421ndash482

(31) Balluffi R W Allen S M Carter W C ldquoNucleationrdquo In Kinetics of Materials

John Wiley amp Sons INC Hoboken New Jersey 2005 pp 459ndash500

(32) Kingery W D Bowen H K Uhlmann D ldquoPhase-Transformations Glass

- 156 -

Formation and Glass-Ceramicsrdquo In Introduction to Ceramics Second Edition

John Wiley amp Sons INC New York New York 1976 pp 320ndash380

(33) Perepezko J H Madison W ldquoNucleation Kinetics and Grain Refinementrdquo In

ASM Handbook Vol 15 Casting ASM International Materials Park OH 2018

Vol 15 pp 276ndash287

(34) Kurz W Fe E P ldquoPlane Front Solidificationrdquo In ASM Handbook Vol 15

Casting ASM International Materials Park OH 2018 pp 293ndash298

(35) Krauss G ldquoPrimary Processing Effects on Steel Microstructure and Propertiesrdquo In

Steels-Processing Structure and Performance Second Edition ASM


(36) Trivedi R Sunseri E ldquoNon-Plane Front Solidificationrdquo In ASM Handbook Vol

15 Casting ASM International Materials Park OH 2008 pp 299ndash306

(37) Edwards L Endean M ldquoManufacturing with Materialsrdquo Butterworth

Heinemann Oxford United Kingdom 1990

(38) Beckermann C ldquoMacrosegregationrdquo In ASM Handbook Vol 15 Casting ASM


(39) Dantzig J A ldquoTransport Phenomena During Solidificationrdquo In ASM Handbook

Vol 15 Casting ASM International Materials Park OH 2018 pp 70ndash74

(40) Brody H D ldquoMicrosegregationrdquo In ASM Handbook Vol 15 Casting ASM


(41) Han Q ldquoShrinkage Porosity and Gas Porosityrdquo In ASM Handbook Vol 15


(42) Brooks C R ldquoAustentization of Steelsrdquo In Principles of the Heat Treatment of

Plain Carbon and Low Alloy Steels ASM International Materials Park OH 1999

pp 205ndash234

(43) Chaudhury S K Honeywell-Int ldquoHomogenizationrdquo In ASM Handbook Vol 15


(44) Brooks C R ldquoAnnealing Normalizing Martempering and Austemperingrdquo In

Principles of the Heat Treatment of Plain Carbon and Low Alloy Steels ASM


(45) Krauss G ldquoMartensite In Steels-Processing Structure and Performance


(46) Krauss G ldquoIsothermal and Continuous Cooling Transformation Diagramsrdquo In



(47) Brooks C R ldquoThe Iron-Carbon Phase Diagram and Time-Temperature-

Transformation (TTT) Diagramsrdquo In Principles of the Heat Treatment of Plain


3ndash41

(48) Brooks C R ldquoQuenching of Steelsrdquo In Principles of the Heat Treatment of Plain

- 157 -


87ndash126

(49) Chaudhury S K Honeywell-Int ldquoHeat Treatmentrdquo In ASM Handbook Vol 15


(50) Krauss G ldquoTempering of Steelrdquo In Steels-Processing Structure and


373ndash403

(51) Brooks C R ldquoTemperingrdquo In Principles of the Heat Treatment of Plain Carbon

and Low Alloy Steels ASM International Materials Park OH 1999 pp 127ndash204

(52) Krauss G ldquoLow-Carbon Steelsrdquo In Steels-Processing Structure and


233ndash275

(53) Zackay V F Thermomechanical Processing Mater Sci Eng 1976 25 247ndash261

(54) Voigt R C Rassizadehghani J Properties and Processing of HSLA Cast Steels

1989

(55) Lippold J C ldquoIntroductionrdquo In Welding Metallurgy and Weldability John Wiley

amp Sons INC Hoboken New Jersey 2015 pp 1ndash8

(56) Lippold J C ldquoHydrogen-Induced Crackingrdquo In Welding Metallurgy and

Weldability John Wiley amp Sons INC Hoboken New Jersey 2015 pp 213ndash262

(57) Lagneborg R Siwecki T Zajac S Hutchinson B The Role of Vanadium in

Microalloyed Steels Scand J Metall 1999 28 (October) 186ndash241

(58) Purtscher PT Cheng Y-W Structure-Property Relationships in Microalloyed

Ferrite-Pearlite Steels Phase 1 Literature Review Research Plan and Initial

Results Gov Res Announc Index 1993 1ndash59

(59) Deardo A J Niobium in Modern Steels Int Mater Rev 2003 48 (6) 371ndash402

(60) Sage A M The Use of Vanadium in Low Alloy Structural Steels In Specialty

Steels and Hard Materials Proceedings of the International Conference on Recent

Developments in Specialty Steels and Hard Materials (Materials Development

rsquo82) held in Pretoria South Africa 8-12 November 1982 Pergamon Press Ltd

1983 pp 111ndash125

(61) Ohtani H Hillert M A Thermodynamic Assessment of the Fe-N-V System

Calphad 1991 15 (1) 25ndash39

(62) Liu Z Thermodynamic Calculations of Carbonitrides in Microalloyed Steels Scr

Mater 2004 50 601ndash606

(63) ASM-International ldquoHigh-Strength Structural and High-Strength Low-Alloy

Steelsrdquo In ASM Handbook Vol 1 Properties and Selection Irons Steels and

High-Performance Alloys ASM International Materials Park OH 1990 Vol 1

pp 389ndash423

(64) Wright P H ldquoHigh-Strength Low-Alloy Steel Forgingsrdquo In ASM Handbook Vol

1 Properties and Selection Irons Steels and High-Performance Alloys ASM

- 158 -

International Materials Park OH 1990 Vol 1 pp 358ndash362

(65) Jack D H Jack K H Invited Review  Carbides and Nitrides in Steel Mater

Sci Eng 1973 11 1ndash27

(66) Baker T N Processes Microstructure and Properties of Vanadium Microalloyed

Steels Mater Sci Technol 2009 25 (9) 1083ndash1107

(67) Voigt Robert C Rassizadehhghani J Initial Investigation of Microalloyed Cast

Steel 1987

(68) Naylor D J Review of International Activity on Microalloyed Engineering Steels

Ironmak Steelmak 1989 16 (4) 246ndash252

(69) Voigt R C Rassizadehghani J Gattu R K The Development of High Strength

Low Alloy (HSLA) Cast Steels 1988

(70) Voigt R C Tu C-H Rosmait R L Development of As-Cast Steels 1990

(71) Dutcher D E Production and Properties of Microalloyed Steel Castings 1987

(72) Jackson W J The Use of Vanadium in Steel Castings A Review of the Literature

1978

(73) Voigt R C Blair M Rassizadehhghani J High Stength Low Alloy Cast Steels

1990

(74) Collie-Welding Carbon Equivalent Calculators

httpwwwcollieweldingcomcecalculatorsphp (accessed Oct 15 2019)

(75) Panneer Selvi S Sakthivel T Parameswaran P Laha K Effect of

Normalization Heat Treatment on Creep and Tensile Properties of Modified 9Crndash

1Mo Steel Trans Indian Inst Met 2016 69 (2) 261ndash269

(76) Thermo-Calc Thermo-Calc Software TCFE SteelsFe-Alloys Database Version 8

2016

II

The thesis of Cody Daniel Snyder was reviewed and approved by the following

Robert C Voigt

Professor and Graduate Program Coordinator of Industrial Engineering

Thesis Advisor

Allison M Beese

Associate Professor of Materials Science and Engineering

Jingjing Li

Associate Professor of Industrial Engineering

Amy C Robinson

Associate Teaching Professor of Materials Science and Engineering

Special Signatory

John C Mauro

Professor of Materials Science and Engineering

Associate Head for Graduate Education of Materials Science and Engineering

Signatures are on file in the Graduate School

III

Abstract























IV





V

Table of Contents

List of Figures IX

List of Tables XIII



















133 Pearlite - 18 -










VI

































VII

































VIII














61 Summary - 141 -



Appendix A - 150 -

Appendix B - 153 -

References - 154 -

IX

List of Figures

FIGURE PAGE



























X































XI































XII







XIII

List of Tables

TABLE PAGE



























XIV















XV

List of Equations

EQUATION PAGE











XVI

Acknowledgements





















11 Project Overview





















- 2 -






















- 3 -
























- 4 -























- 5 -




















ferrous metals56




- 6 -













- 7 -




12222 Ingot Casting










- 8 -

12223 Shape Casting


















- 9 -





ways to cure sand8












- 10 -
























- 11 -
















- 12 -












the metal faster9




- 13 -
























- 14 -


shake-out process9









finished9













- 15 -


















- 16 -

















- 17 -























- 18 -




133 Pearlite











- 19 -














- 20 -













- 21 -






















- 22 -
















- 23 -












- 24 -
























- 25 -
























- 26 -








suffice26








120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1







- 27 -


















- 28 -
























- 29 -




















- 30 -




a new slip plane3











- 31 -

151 Cast Metal























- 32 -

152 Wrought Metal










transition2229











- 33 -





















new growth3132

- 34 -

















∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -





nuclei30













- 36 -




temperature30











favorable303132



- 37 -






120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3







- 38 -



















- 39 -



















- 40 -
























- 41 -













1641 Chill Zone



- 42 -













from the center

1642 Columnar Zone





- 43 -
























- 44 -









most defects2

171 Macroporosity












- 45 -













- 46 -















liquid238

- 47 -




173 Microporosity










pouring metal2

- 48 -




microsegregation2












175 Gas Porosity




- 49 -








of the melt241






- 50 -















- 51 -






metastable form2542








- 52 -









181 Homogenization














- 53 -



182 Full Anneal









183 Process Anneal












- 54 -

184 Normalization






















- 55 -



















- 56 -

1852 Martensite






















- 57 -

















- 58 -




to happen45










- 59 -




can be expected45














- 60 -

186 Spheroidizing













occur1844









- 61 -




















1101 Weldability



- 62 -




weldability










- 63 -























- 64 -








22 HSLA Steels
















- 65 -




HSLA steels




















- 66 -
















recrystallization57








- 67 -














- 68 -





grain pinning63

- 69 -




















- 70 -




nitrogen57







VN60




- 71 -


precipitates60
















higher57




nuclei57

- 72 -


















- 73 -
















- 74 -









23 HSLA Cast Steels










154676970





- 75 -











Wt 012-050 03-06 09-15 04-06 007-015











- 76 -








231 Temperaging















- 77 -




119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4












119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -





electrodes


required
















- 79 -























- 80 -



strength70










at 1920 ˚F (1050 ˚C)69









grains54

- 81 -



- 82 -


31 Hypothesis






techniques













- 83 -























- 84 -









42 Tempering Study









for each alloy






- 85 -



Digital ME-2











cm) sections









- 86 -















tensile testing








- 87 -





F
















ethanol

- 88 -



- 89 -






















- 90 -













- 91 -










- 92 -








in Composition


High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451














- 93 -



NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047











negative trend

- 94 -



High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421









- 95 -



High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484









- 96 -



High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

















Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -














Weldability Ranges


Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047







- 98 -


















- 99 -


Modified C-Mn-V


C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA


Mn-V


Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159







- 100 -
























- 101 -





- 102 -

















- 103 -








54 Tempering Study
















- 104 -



at 1 hr




- 105 -








- 106 -






- 107 -







- 108 -








temper time

- 109 -























- 110 -


in ksi

Heat


NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216


ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211




a 51 EL decrease











- 111 -



- 112 -


















TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -


in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231






MPa) respectively











- 114 -



- 115 -





















- 116 -




- 117 -














- 118 -


















- 119 -





Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments













- 120 -





















20

- 121 -




A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152



TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153




A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168



and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167








- 122 -





- 123 -



- 124 -












- 125 -




A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162



ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164












- 126 -



- 127 -
















Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V


Silicon


C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -


Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA



C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182



- 129 -





Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222


Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219


Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240


Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240


Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -


Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234


Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247


Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253








with Figures 74-82

- 131 -



- 132 -



- 133 -



- 134 -



- 135 -























- 136 -



- 137 -



- 138 -



- 139 -













CVN

CE Cmax Mnmax




(W)

62-50-21-No No 023 135



Grade (W)

65-50-21-Yes No 023 135




(W)

65-50-21-Yes 045 020 160


A216 WCB (C) 70-36-22-No 050 030 100





(W) for Wrought

(C) for Cast

- 140 -







to emerge

- 141 -


61 Summary





















- 142 -
























- 143 -












conditions












- 144 -










for hardness 147 HB














- 145 -


















condition





- 146 -







respectively







F









- 147 -



62 Conclusion

















requirements




- 148 -
























- 149 -





63 Future Work





tempering profiles



tempering study







results


- 150 -

Appendix A



- 151 -


- 152 -




manganese content

- 153 -

Appendix B



A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426


C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References







Chem 1975 9 (C) 105ndash138



OH 2016 pp 9ndash16










2018 pp 485ndash487











39ndash62






15ndash32

- 155 -


543ndash565




277ndash291



297ndash325



43ndash86








79










263ndash306


August 915ndash922


(7) 96ndash97







- 156 -

























pp 205ndash234














3ndash41


- 157 -


87ndash126





373ndash403





233ndash275



1989















1983 pp 111ndash125








pp 389ndash423



- 158 -







Steel 1987








1978


1990







2016

III

Abstract























IV





V

Table of Contents

List of Figures IX

List of Tables XIII



















133 Pearlite - 18 -










VI

































VII

































VIII














61 Summary - 141 -



Appendix A - 150 -

Appendix B - 153 -

References - 154 -

IX

List of Figures

FIGURE PAGE



























X































XI































XII







XIII

List of Tables

TABLE PAGE



























XIV















XV

List of Equations

EQUATION PAGE











XVI

Acknowledgements





















11 Project Overview





















- 2 -






















- 3 -
























- 4 -























- 5 -




















ferrous metals56




- 6 -













- 7 -




12222 Ingot Casting










- 8 -

12223 Shape Casting


















- 9 -





ways to cure sand8












- 10 -
























- 11 -
















- 12 -












the metal faster9




- 13 -
























- 14 -


shake-out process9









finished9













- 15 -


















- 16 -

















- 17 -























- 18 -




133 Pearlite











- 19 -














- 20 -













- 21 -






















- 22 -
















- 23 -












- 24 -
























- 25 -
























- 26 -








suffice26








120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1







- 27 -


















- 28 -
























- 29 -




















- 30 -




a new slip plane3











- 31 -

151 Cast Metal























- 32 -

152 Wrought Metal










transition2229











- 33 -





















new growth3132

- 34 -

















∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -





nuclei30













- 36 -




temperature30











favorable303132



- 37 -






120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3







- 38 -



















- 39 -



















- 40 -
























- 41 -













1641 Chill Zone



- 42 -













from the center

1642 Columnar Zone





- 43 -
























- 44 -









most defects2

171 Macroporosity












- 45 -













- 46 -















liquid238

- 47 -




173 Microporosity










pouring metal2

- 48 -




microsegregation2












175 Gas Porosity




- 49 -








of the melt241






- 50 -















- 51 -






metastable form2542








- 52 -









181 Homogenization














- 53 -



182 Full Anneal









183 Process Anneal












- 54 -

184 Normalization






















- 55 -



















- 56 -

1852 Martensite






















- 57 -

















- 58 -




to happen45










- 59 -




can be expected45














- 60 -

186 Spheroidizing













occur1844









- 61 -




















1101 Weldability



- 62 -




weldability










- 63 -























- 64 -








22 HSLA Steels
















- 65 -




HSLA steels




















- 66 -
















recrystallization57








- 67 -














- 68 -





grain pinning63

- 69 -




















- 70 -




nitrogen57







VN60




- 71 -


precipitates60
















higher57




nuclei57

- 72 -


















- 73 -
















- 74 -









23 HSLA Cast Steels










154676970





- 75 -











Wt 012-050 03-06 09-15 04-06 007-015











- 76 -








231 Temperaging















- 77 -




119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4












119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -





electrodes


required
















- 79 -























- 80 -



strength70










at 1920 ˚F (1050 ˚C)69









grains54

- 81 -



- 82 -


31 Hypothesis






techniques













- 83 -























- 84 -









42 Tempering Study









for each alloy






- 85 -



Digital ME-2











cm) sections









- 86 -















tensile testing








- 87 -





F
















ethanol

- 88 -



- 89 -






















- 90 -













- 91 -










- 92 -








in Composition


High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451














- 93 -



NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047











negative trend

- 94 -



High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421









- 95 -



High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484









- 96 -



High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

















Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -














Weldability Ranges


Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047







- 98 -


















- 99 -


Modified C-Mn-V


C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA


Mn-V


Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159







- 100 -
























- 101 -





- 102 -

















- 103 -








54 Tempering Study
















- 104 -



at 1 hr




- 105 -








- 106 -






- 107 -







- 108 -








temper time

- 109 -























- 110 -


in ksi

Heat


NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216


ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211




a 51 EL decrease











- 111 -



- 112 -


















TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -


in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231






MPa) respectively











- 114 -



- 115 -





















- 116 -




- 117 -














- 118 -


















- 119 -





Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments













- 120 -





















20

- 121 -




A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152



TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153




A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168



and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167








- 122 -





- 123 -



- 124 -












- 125 -




A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162



ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164












- 126 -



- 127 -
















Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V


Silicon


C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -


Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA



C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182



- 129 -





Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222


Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219


Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240


Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240


Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -


Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234


Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247


Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253








with Figures 74-82

- 131 -



- 132 -



- 133 -



- 134 -



- 135 -























- 136 -



- 137 -



- 138 -



- 139 -













CVN

CE Cmax Mnmax




(W)

62-50-21-No No 023 135



Grade (W)

65-50-21-Yes No 023 135




(W)

65-50-21-Yes 045 020 160


A216 WCB (C) 70-36-22-No 050 030 100





(W) for Wrought

(C) for Cast

- 140 -







to emerge

- 141 -


61 Summary





















- 142 -
























- 143 -












conditions












- 144 -










for hardness 147 HB














- 145 -


















condition





- 146 -







respectively







F









- 147 -



62 Conclusion

















requirements




- 148 -
























- 149 -





63 Future Work





tempering profiles



tempering study







results


- 150 -

Appendix A



- 151 -


- 152 -




manganese content

- 153 -

Appendix B



A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426


C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References







Chem 1975 9 (C) 105ndash138



OH 2016 pp 9ndash16










2018 pp 485ndash487











39ndash62






15ndash32

- 155 -


543ndash565




277ndash291



297ndash325



43ndash86








79










263ndash306


August 915ndash922


(7) 96ndash97







- 156 -

























pp 205ndash234














3ndash41


- 157 -


87ndash126





373ndash403





233ndash275



1989















1983 pp 111ndash125








pp 389ndash423



- 158 -







Steel 1987








1978


1990







2016

IV





V

Table of Contents

List of Figures IX

List of Tables XIII



















133 Pearlite - 18 -










VI

































VII

































VIII














61 Summary - 141 -



Appendix A - 150 -

Appendix B - 153 -

References - 154 -

IX

List of Figures

FIGURE PAGE



























X































XI































XII







XIII

List of Tables

TABLE PAGE



























XIV















XV

List of Equations

EQUATION PAGE











XVI

Acknowledgements





















11 Project Overview





















- 2 -






















- 3 -
























- 4 -























- 5 -




















ferrous metals56




- 6 -













- 7 -




12222 Ingot Casting










- 8 -

12223 Shape Casting


















- 9 -





ways to cure sand8












- 10 -
























- 11 -
















- 12 -












the metal faster9




- 13 -
























- 14 -


shake-out process9









finished9













- 15 -


















- 16 -

















- 17 -























- 18 -




133 Pearlite











- 19 -














- 20 -













- 21 -






















- 22 -
















- 23 -












- 24 -
























- 25 -
























- 26 -








suffice26








120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1







- 27 -


















- 28 -
























- 29 -




















- 30 -




a new slip plane3











- 31 -

151 Cast Metal























- 32 -

152 Wrought Metal










transition2229











- 33 -





















new growth3132

- 34 -

















∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -





nuclei30













- 36 -




temperature30











favorable303132



- 37 -






120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3







- 38 -



















- 39 -



















- 40 -
























- 41 -













1641 Chill Zone



- 42 -













from the center

1642 Columnar Zone





- 43 -
























- 44 -









most defects2

171 Macroporosity












- 45 -













- 46 -















liquid238

- 47 -




173 Microporosity










pouring metal2

- 48 -




microsegregation2












175 Gas Porosity




- 49 -








of the melt241






- 50 -















- 51 -






metastable form2542








- 52 -









181 Homogenization














- 53 -



182 Full Anneal









183 Process Anneal












- 54 -

184 Normalization






















- 55 -



















- 56 -

1852 Martensite






















- 57 -

















- 58 -




to happen45










- 59 -




can be expected45














- 60 -

186 Spheroidizing













occur1844









- 61 -




















1101 Weldability



- 62 -




weldability










- 63 -























- 64 -








22 HSLA Steels
















- 65 -




HSLA steels




















- 66 -
















recrystallization57








- 67 -














- 68 -





grain pinning63

- 69 -




















- 70 -




nitrogen57







VN60




- 71 -


precipitates60
















higher57




nuclei57

- 72 -


















- 73 -
















- 74 -









23 HSLA Cast Steels










154676970





- 75 -











Wt 012-050 03-06 09-15 04-06 007-015











- 76 -








231 Temperaging















- 77 -




119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4












119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -





electrodes


required
















- 79 -























- 80 -



strength70










at 1920 ˚F (1050 ˚C)69









grains54

- 81 -



- 82 -


31 Hypothesis






techniques













- 83 -























- 84 -









42 Tempering Study









for each alloy






- 85 -



Digital ME-2











cm) sections









- 86 -















tensile testing








- 87 -





F
















ethanol

- 88 -



- 89 -






















- 90 -













- 91 -










- 92 -








in Composition


High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451














- 93 -



NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047











negative trend

- 94 -



High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421









- 95 -



High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484









- 96 -



High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

















Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -














Weldability Ranges


Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047







- 98 -


















- 99 -


Modified C-Mn-V


C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA


Mn-V


Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159







- 100 -
























- 101 -





- 102 -

















- 103 -








54 Tempering Study
















- 104 -



at 1 hr




- 105 -








- 106 -






- 107 -







- 108 -








temper time

- 109 -























- 110 -


in ksi

Heat


NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216


ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211




a 51 EL decrease











- 111 -



- 112 -


















TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -


in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231






MPa) respectively











- 114 -



- 115 -





















- 116 -




- 117 -














- 118 -


















- 119 -





Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments













- 120 -





















20

- 121 -




A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152



TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153




A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168



and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167








- 122 -





- 123 -



- 124 -












- 125 -




A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162



ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164












- 126 -



- 127 -
















Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V


Silicon


C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -


Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA



C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182



- 129 -





Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222


Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219


Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240


Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240


Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -


Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234


Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247


Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253








with Figures 74-82

- 131 -



- 132 -



- 133 -



- 134 -



- 135 -























- 136 -



- 137 -



- 138 -



- 139 -













CVN

CE Cmax Mnmax




(W)

62-50-21-No No 023 135



Grade (W)

65-50-21-Yes No 023 135




(W)

65-50-21-Yes 045 020 160


A216 WCB (C) 70-36-22-No 050 030 100





(W) for Wrought

(C) for Cast

- 140 -







to emerge

- 141 -


61 Summary





















- 142 -
























- 143 -












conditions












- 144 -










for hardness 147 HB














- 145 -


















condition





- 146 -







respectively







F









- 147 -



62 Conclusion

















requirements




- 148 -
























- 149 -





63 Future Work





tempering profiles



tempering study







results


- 150 -

Appendix A



- 151 -


- 152 -




manganese content

- 153 -

Appendix B



A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426


C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References







Chem 1975 9 (C) 105ndash138



OH 2016 pp 9ndash16










2018 pp 485ndash487











39ndash62






15ndash32

- 155 -


543ndash565




277ndash291



297ndash325



43ndash86








79










263ndash306


August 915ndash922


(7) 96ndash97







- 156 -

























pp 205ndash234














3ndash41


- 157 -


87ndash126





373ndash403





233ndash275



1989















1983 pp 111ndash125








pp 389ndash423



- 158 -







Steel 1987








1978


1990







2016

V

Table of Contents

List of Figures IX

List of Tables XIII



















133 Pearlite - 18 -










VI

































VII

































VIII














61 Summary - 141 -



Appendix A - 150 -

Appendix B - 153 -

References - 154 -

IX

List of Figures

FIGURE PAGE



























X































XI































XII







XIII

List of Tables

TABLE PAGE



























XIV















XV

List of Equations

EQUATION PAGE











XVI

Acknowledgements





















11 Project Overview





















- 2 -






















- 3 -
























- 4 -























- 5 -




















ferrous metals56




- 6 -













- 7 -




12222 Ingot Casting










- 8 -

12223 Shape Casting


















- 9 -





ways to cure sand8












- 10 -
























- 11 -
















- 12 -












the metal faster9




- 13 -
























- 14 -


shake-out process9









finished9













- 15 -


















- 16 -

















- 17 -























- 18 -




133 Pearlite











- 19 -














- 20 -













- 21 -






















- 22 -
















- 23 -












- 24 -
























- 25 -
























- 26 -








suffice26








120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1







- 27 -


















- 28 -
























- 29 -




















- 30 -




a new slip plane3











- 31 -

151 Cast Metal























- 32 -

152 Wrought Metal










transition2229











- 33 -





















new growth3132

- 34 -

















∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -





nuclei30













- 36 -




temperature30











favorable303132



- 37 -






120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3







- 38 -



















- 39 -



















- 40 -
























- 41 -













1641 Chill Zone



- 42 -













from the center

1642 Columnar Zone





- 43 -
























- 44 -









most defects2

171 Macroporosity












- 45 -













- 46 -















liquid238

- 47 -




173 Microporosity










pouring metal2

- 48 -




microsegregation2












175 Gas Porosity




- 49 -








of the melt241






- 50 -















- 51 -






metastable form2542








- 52 -









181 Homogenization














- 53 -



182 Full Anneal









183 Process Anneal












- 54 -

184 Normalization






















- 55 -



















- 56 -

1852 Martensite






















- 57 -

















- 58 -




to happen45










- 59 -




can be expected45














- 60 -

186 Spheroidizing













occur1844









- 61 -




















1101 Weldability



- 62 -




weldability










- 63 -























- 64 -








22 HSLA Steels
















- 65 -




HSLA steels




















- 66 -
















recrystallization57








- 67 -














- 68 -





grain pinning63

- 69 -




















- 70 -




nitrogen57







VN60




- 71 -


precipitates60
















higher57




nuclei57

- 72 -


















- 73 -
















- 74 -









23 HSLA Cast Steels










154676970





- 75 -











Wt 012-050 03-06 09-15 04-06 007-015











- 76 -








231 Temperaging















- 77 -




119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4












119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -





electrodes


required
















- 79 -























- 80 -



strength70










at 1920 ˚F (1050 ˚C)69









grains54

- 81 -



- 82 -


31 Hypothesis






techniques













- 83 -























- 84 -









42 Tempering Study









for each alloy






- 85 -



Digital ME-2











cm) sections









- 86 -















tensile testing








- 87 -





F
















ethanol

- 88 -



- 89 -






















- 90 -













- 91 -










- 92 -








in Composition


High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451














- 93 -



NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047











negative trend

- 94 -



High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421









- 95 -



High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484









- 96 -



High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

















Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -














Weldability Ranges


Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047







- 98 -


















- 99 -


Modified C-Mn-V


C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA


Mn-V


Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159







- 100 -
























- 101 -





- 102 -

















- 103 -








54 Tempering Study
















- 104 -



at 1 hr




- 105 -








- 106 -






- 107 -







- 108 -








temper time

- 109 -























- 110 -


in ksi

Heat


NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216


ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211




a 51 EL decrease











- 111 -



- 112 -


















TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -


in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231






MPa) respectively











- 114 -



- 115 -





















- 116 -




- 117 -














- 118 -


















- 119 -





Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments













- 120 -





















20

- 121 -




A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152



TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153




A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168



and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167








- 122 -





- 123 -



- 124 -












- 125 -




A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162



ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164












- 126 -



- 127 -
















Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V


Silicon


C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -


Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA



C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182



- 129 -





Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222


Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219


Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240


Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240


Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -


Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234


Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247


Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253








with Figures 74-82

- 131 -



- 132 -



- 133 -



- 134 -



- 135 -























- 136 -



- 137 -



- 138 -



- 139 -













CVN

CE Cmax Mnmax




(W)

62-50-21-No No 023 135



Grade (W)

65-50-21-Yes No 023 135




(W)

65-50-21-Yes 045 020 160


A216 WCB (C) 70-36-22-No 050 030 100





(W) for Wrought

(C) for Cast

- 140 -







to emerge

- 141 -


61 Summary





















- 142 -
























- 143 -












conditions












- 144 -










for hardness 147 HB














- 145 -


















condition





- 146 -







respectively







F









- 147 -



62 Conclusion

















requirements




- 148 -
























- 149 -





63 Future Work





tempering profiles



tempering study







results


- 150 -

Appendix A



- 151 -


- 152 -




manganese content

- 153 -

Appendix B



A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426


C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References







Chem 1975 9 (C) 105ndash138



OH 2016 pp 9ndash16










2018 pp 485ndash487











39ndash62






15ndash32

- 155 -


543ndash565




277ndash291



297ndash325



43ndash86








79










263ndash306


August 915ndash922


(7) 96ndash97







- 156 -

























pp 205ndash234














3ndash41


- 157 -


87ndash126





373ndash403





233ndash275



1989















1983 pp 111ndash125








pp 389ndash423



- 158 -







Steel 1987








1978


1990







2016

VI

































VII

































VIII














61 Summary - 141 -



Appendix A - 150 -

Appendix B - 153 -

References - 154 -

IX

List of Figures

FIGURE PAGE



























X































XI































XII







XIII

List of Tables

TABLE PAGE



























XIV















XV

List of Equations

EQUATION PAGE











XVI

Acknowledgements





















11 Project Overview





















- 2 -






















- 3 -
























- 4 -























- 5 -




















ferrous metals56




- 6 -













- 7 -




12222 Ingot Casting










- 8 -

12223 Shape Casting


















- 9 -





ways to cure sand8












- 10 -
























- 11 -
















- 12 -












the metal faster9




- 13 -
























- 14 -


shake-out process9









finished9













- 15 -


















- 16 -

















- 17 -























- 18 -




133 Pearlite











- 19 -














- 20 -













- 21 -






















- 22 -
















- 23 -












- 24 -
























- 25 -
























- 26 -








suffice26








120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1







- 27 -


















- 28 -
























- 29 -




















- 30 -




a new slip plane3











- 31 -

151 Cast Metal























- 32 -

152 Wrought Metal










transition2229











- 33 -





















new growth3132

- 34 -

















∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -





nuclei30













- 36 -




temperature30











favorable303132



- 37 -






120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3







- 38 -



















- 39 -



















- 40 -
























- 41 -













1641 Chill Zone



- 42 -













from the center

1642 Columnar Zone





- 43 -
























- 44 -









most defects2

171 Macroporosity












- 45 -













- 46 -















liquid238

- 47 -




173 Microporosity










pouring metal2

- 48 -




microsegregation2












175 Gas Porosity




- 49 -








of the melt241






- 50 -















- 51 -






metastable form2542








- 52 -









181 Homogenization














- 53 -



182 Full Anneal









183 Process Anneal












- 54 -

184 Normalization






















- 55 -



















- 56 -

1852 Martensite






















- 57 -

















- 58 -




to happen45










- 59 -




can be expected45














- 60 -

186 Spheroidizing













occur1844









- 61 -




















1101 Weldability



- 62 -




weldability










- 63 -























- 64 -








22 HSLA Steels
















- 65 -




HSLA steels




















- 66 -
















recrystallization57








- 67 -














- 68 -





grain pinning63

- 69 -




















- 70 -




nitrogen57







VN60




- 71 -


precipitates60
















higher57




nuclei57

- 72 -


















- 73 -
















- 74 -









23 HSLA Cast Steels










154676970





- 75 -











Wt 012-050 03-06 09-15 04-06 007-015











- 76 -








231 Temperaging















- 77 -




119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4












119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -





electrodes


required
















- 79 -























- 80 -



strength70










at 1920 ˚F (1050 ˚C)69









grains54

- 81 -



- 82 -


31 Hypothesis






techniques













- 83 -























- 84 -









42 Tempering Study









for each alloy






- 85 -



Digital ME-2











cm) sections









- 86 -















tensile testing








- 87 -





F
















ethanol

- 88 -



- 89 -






















- 90 -













- 91 -










- 92 -








in Composition


High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451














- 93 -



NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047











negative trend

- 94 -



High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421









- 95 -



High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484









- 96 -



High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

















Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -














Weldability Ranges


Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047







- 98 -


















- 99 -


Modified C-Mn-V


C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA


Mn-V


Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159







- 100 -
























- 101 -





- 102 -

















- 103 -








54 Tempering Study
















- 104 -



at 1 hr




- 105 -








- 106 -






- 107 -







- 108 -








temper time

- 109 -























- 110 -


in ksi

Heat


NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216


ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211




a 51 EL decrease











- 111 -



- 112 -


















TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -


in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231






MPa) respectively











- 114 -



- 115 -





















- 116 -




- 117 -














- 118 -


















- 119 -





Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments













- 120 -





















20

- 121 -




A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152



TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153




A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168



and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167








- 122 -





- 123 -



- 124 -












- 125 -




A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162



ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164












- 126 -



- 127 -
















Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V


Silicon


C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -


Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA



C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182



- 129 -





Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222


Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219


Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240


Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240


Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -


Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234


Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247


Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253








with Figures 74-82

- 131 -



- 132 -



- 133 -



- 134 -



- 135 -























- 136 -



- 137 -



- 138 -



- 139 -













CVN

CE Cmax Mnmax




(W)

62-50-21-No No 023 135



Grade (W)

65-50-21-Yes No 023 135




(W)

65-50-21-Yes 045 020 160


A216 WCB (C) 70-36-22-No 050 030 100





(W) for Wrought

(C) for Cast

- 140 -







to emerge

- 141 -


61 Summary





















- 142 -
























- 143 -












conditions












- 144 -










for hardness 147 HB














- 145 -


















condition





- 146 -







respectively







F









- 147 -



62 Conclusion

















requirements




- 148 -
























- 149 -





63 Future Work





tempering profiles



tempering study







results


- 150 -

Appendix A



- 151 -


- 152 -




manganese content

- 153 -

Appendix B



A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426


C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References







Chem 1975 9 (C) 105ndash138



OH 2016 pp 9ndash16










2018 pp 485ndash487











39ndash62






15ndash32

- 155 -


543ndash565




277ndash291



297ndash325



43ndash86








79










263ndash306


August 915ndash922


(7) 96ndash97







- 156 -

























pp 205ndash234














3ndash41


- 157 -


87ndash126





373ndash403





233ndash275



1989















1983 pp 111ndash125








pp 389ndash423



- 158 -







Steel 1987








1978


1990







2016

VII

































VIII














61 Summary - 141 -



Appendix A - 150 -

Appendix B - 153 -

References - 154 -

IX

List of Figures

FIGURE PAGE



























X































XI































XII







XIII

List of Tables

TABLE PAGE



























XIV















XV

List of Equations

EQUATION PAGE











XVI

Acknowledgements





















11 Project Overview





















- 2 -






















- 3 -
























- 4 -























- 5 -




















ferrous metals56




- 6 -













- 7 -




12222 Ingot Casting










- 8 -

12223 Shape Casting


















- 9 -





ways to cure sand8












- 10 -
























- 11 -
















- 12 -












the metal faster9




- 13 -
























- 14 -


shake-out process9









finished9













- 15 -


















- 16 -

















- 17 -























- 18 -




133 Pearlite











- 19 -














- 20 -













- 21 -






















- 22 -
















- 23 -












- 24 -
























- 25 -
























- 26 -








suffice26








120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1







- 27 -


















- 28 -
























- 29 -




















- 30 -




a new slip plane3











- 31 -

151 Cast Metal























- 32 -

152 Wrought Metal










transition2229











- 33 -





















new growth3132

- 34 -

















∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -





nuclei30













- 36 -




temperature30











favorable303132



- 37 -






120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3







- 38 -



















- 39 -



















- 40 -
























- 41 -













1641 Chill Zone



- 42 -













from the center

1642 Columnar Zone





- 43 -
























- 44 -









most defects2

171 Macroporosity












- 45 -













- 46 -















liquid238

- 47 -




173 Microporosity










pouring metal2

- 48 -




microsegregation2












175 Gas Porosity




- 49 -








of the melt241






- 50 -















- 51 -






metastable form2542








- 52 -









181 Homogenization














- 53 -



182 Full Anneal









183 Process Anneal












- 54 -

184 Normalization






















- 55 -



















- 56 -

1852 Martensite






















- 57 -

















- 58 -




to happen45










- 59 -




can be expected45














- 60 -

186 Spheroidizing













occur1844









- 61 -




















1101 Weldability



- 62 -




weldability










- 63 -























- 64 -








22 HSLA Steels
















- 65 -




HSLA steels




















- 66 -
















recrystallization57








- 67 -














- 68 -





grain pinning63

- 69 -




















- 70 -




nitrogen57







VN60




- 71 -


precipitates60
















higher57




nuclei57

- 72 -


















- 73 -
















- 74 -









23 HSLA Cast Steels










154676970





- 75 -











Wt 012-050 03-06 09-15 04-06 007-015











- 76 -








231 Temperaging















- 77 -




119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4












119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -





electrodes


required
















- 79 -























- 80 -



strength70










at 1920 ˚F (1050 ˚C)69









grains54

- 81 -



- 82 -


31 Hypothesis






techniques













- 83 -























- 84 -









42 Tempering Study









for each alloy






- 85 -



Digital ME-2











cm) sections









- 86 -















tensile testing








- 87 -





F
















ethanol

- 88 -



- 89 -






















- 90 -













- 91 -










- 92 -








in Composition


High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451














- 93 -



NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047











negative trend

- 94 -



High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421









- 95 -



High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484









- 96 -



High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

















Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -














Weldability Ranges


Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047







- 98 -


















- 99 -


Modified C-Mn-V


C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA


Mn-V


Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159







- 100 -
























- 101 -





- 102 -

















- 103 -








54 Tempering Study
















- 104 -



at 1 hr




- 105 -








- 106 -






- 107 -







- 108 -








temper time

- 109 -























- 110 -


in ksi

Heat


NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216


ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211




a 51 EL decrease











- 111 -



- 112 -


















TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -


in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231






MPa) respectively











- 114 -



- 115 -





















- 116 -




- 117 -














- 118 -


















- 119 -





Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments













- 120 -





















20

- 121 -




A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152



TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153




A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168



and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167








- 122 -





- 123 -



- 124 -












- 125 -




A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162



ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164












- 126 -



- 127 -
















Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V


Silicon


C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -


Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA



C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182



- 129 -





Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222


Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219


Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240


Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240


Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -


Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234


Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247


Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253








with Figures 74-82

- 131 -



- 132 -



- 133 -



- 134 -



- 135 -























- 136 -



- 137 -



- 138 -



- 139 -













CVN

CE Cmax Mnmax




(W)

62-50-21-No No 023 135



Grade (W)

65-50-21-Yes No 023 135




(W)

65-50-21-Yes 045 020 160


A216 WCB (C) 70-36-22-No 050 030 100





(W) for Wrought

(C) for Cast

- 140 -







to emerge

- 141 -


61 Summary





















- 142 -
























- 143 -












conditions












- 144 -










for hardness 147 HB














- 145 -


















condition





- 146 -







respectively







F









- 147 -



62 Conclusion

















requirements




- 148 -
























- 149 -





63 Future Work





tempering profiles



tempering study







results


- 150 -

Appendix A



- 151 -


- 152 -




manganese content

- 153 -

Appendix B



A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426


C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References







Chem 1975 9 (C) 105ndash138



OH 2016 pp 9ndash16










2018 pp 485ndash487











39ndash62






15ndash32

- 155 -


543ndash565




277ndash291



297ndash325



43ndash86








79










263ndash306


August 915ndash922


(7) 96ndash97







- 156 -

























pp 205ndash234














3ndash41


- 157 -


87ndash126





373ndash403





233ndash275



1989















1983 pp 111ndash125








pp 389ndash423



- 158 -







Steel 1987








1978


1990







2016

VIII














61 Summary - 141 -



Appendix A - 150 -

Appendix B - 153 -

References - 154 -

IX

List of Figures

FIGURE PAGE



























X































XI































XII







XIII

List of Tables

TABLE PAGE



























XIV















XV

List of Equations

EQUATION PAGE











XVI

Acknowledgements





















11 Project Overview





















- 2 -






















- 3 -
























- 4 -























- 5 -




















ferrous metals56




- 6 -













- 7 -




12222 Ingot Casting










- 8 -

12223 Shape Casting


















- 9 -





ways to cure sand8












- 10 -
























- 11 -
















- 12 -












the metal faster9




- 13 -
























- 14 -


shake-out process9









finished9













- 15 -


















- 16 -

















- 17 -























- 18 -




133 Pearlite











- 19 -














- 20 -













- 21 -






















- 22 -
















- 23 -












- 24 -
























- 25 -
























- 26 -








suffice26








120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1







- 27 -


















- 28 -
























- 29 -




















- 30 -




a new slip plane3











- 31 -

151 Cast Metal























- 32 -

152 Wrought Metal










transition2229











- 33 -





















new growth3132

- 34 -

















∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -





nuclei30













- 36 -




temperature30











favorable303132



- 37 -






120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3







- 38 -



















- 39 -



















- 40 -
























- 41 -













1641 Chill Zone



- 42 -













from the center

1642 Columnar Zone





- 43 -
























- 44 -









most defects2

171 Macroporosity












- 45 -













- 46 -















liquid238

- 47 -




173 Microporosity










pouring metal2

- 48 -




microsegregation2












175 Gas Porosity




- 49 -








of the melt241






- 50 -















- 51 -






metastable form2542








- 52 -









181 Homogenization














- 53 -



182 Full Anneal









183 Process Anneal












- 54 -

184 Normalization






















- 55 -



















- 56 -

1852 Martensite






















- 57 -

















- 58 -




to happen45










- 59 -




can be expected45














- 60 -

186 Spheroidizing













occur1844









- 61 -




















1101 Weldability



- 62 -




weldability










- 63 -























- 64 -








22 HSLA Steels
















- 65 -




HSLA steels




















- 66 -
















recrystallization57








- 67 -














- 68 -





grain pinning63

- 69 -




















- 70 -




nitrogen57







VN60




- 71 -


precipitates60
















higher57




nuclei57

- 72 -


















- 73 -
















- 74 -









23 HSLA Cast Steels










154676970





- 75 -











Wt 012-050 03-06 09-15 04-06 007-015











- 76 -








231 Temperaging















- 77 -




119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4












119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -





electrodes


required
















- 79 -























- 80 -



strength70










at 1920 ˚F (1050 ˚C)69









grains54

- 81 -



- 82 -


31 Hypothesis






techniques













- 83 -























- 84 -









42 Tempering Study









for each alloy






- 85 -



Digital ME-2











cm) sections









- 86 -















tensile testing








- 87 -





F
















ethanol

- 88 -



- 89 -






















- 90 -













- 91 -










- 92 -








in Composition


High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451














- 93 -



NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047











negative trend

- 94 -



High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421









- 95 -



High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484









- 96 -



High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

















Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -














Weldability Ranges


Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047







- 98 -


















- 99 -


Modified C-Mn-V


C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA


Mn-V


Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159







- 100 -
























- 101 -





- 102 -

















- 103 -








54 Tempering Study
















- 104 -



at 1 hr




- 105 -








- 106 -






- 107 -







- 108 -








temper time

- 109 -























- 110 -


in ksi

Heat


NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216


ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211




a 51 EL decrease











- 111 -



- 112 -


















TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -


in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231






MPa) respectively











- 114 -



- 115 -





















- 116 -




- 117 -














- 118 -


















- 119 -





Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments













- 120 -





















20

- 121 -




A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152



TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153




A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168



and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167








- 122 -





- 123 -



- 124 -












- 125 -




A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162



ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164












- 126 -



- 127 -
















Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V


Silicon


C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -


Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA



C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182



- 129 -





Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222


Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219


Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240


Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240


Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -


Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234


Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247


Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253








with Figures 74-82

- 131 -



- 132 -



- 133 -



- 134 -



- 135 -























- 136 -



- 137 -



- 138 -



- 139 -













CVN

CE Cmax Mnmax




(W)

62-50-21-No No 023 135



Grade (W)

65-50-21-Yes No 023 135




(W)

65-50-21-Yes 045 020 160


A216 WCB (C) 70-36-22-No 050 030 100





(W) for Wrought

(C) for Cast

- 140 -







to emerge

- 141 -


61 Summary





















- 142 -
























- 143 -












conditions












- 144 -










for hardness 147 HB














- 145 -


















condition





- 146 -







respectively







F









- 147 -



62 Conclusion

















requirements




- 148 -
























- 149 -





63 Future Work





tempering profiles



tempering study







results


- 150 -

Appendix A



- 151 -


- 152 -




manganese content

- 153 -

Appendix B



A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426


C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References







Chem 1975 9 (C) 105ndash138



OH 2016 pp 9ndash16










2018 pp 485ndash487











39ndash62






15ndash32

- 155 -


543ndash565




277ndash291



297ndash325



43ndash86








79










263ndash306


August 915ndash922


(7) 96ndash97







- 156 -

























pp 205ndash234














3ndash41


- 157 -


87ndash126





373ndash403





233ndash275



1989















1983 pp 111ndash125








pp 389ndash423



- 158 -







Steel 1987








1978


1990







2016

IX

List of Figures

FIGURE PAGE



























X































XI































XII







XIII

List of Tables

TABLE PAGE



























XIV















XV

List of Equations

EQUATION PAGE











XVI

Acknowledgements





















11 Project Overview





















- 2 -






















- 3 -
























- 4 -























- 5 -




















ferrous metals56




- 6 -













- 7 -




12222 Ingot Casting










- 8 -

12223 Shape Casting


















- 9 -





ways to cure sand8












- 10 -
























- 11 -
















- 12 -












the metal faster9




- 13 -
























- 14 -


shake-out process9









finished9













- 15 -


















- 16 -

















- 17 -























- 18 -




133 Pearlite











- 19 -














- 20 -













- 21 -






















- 22 -
















- 23 -












- 24 -
























- 25 -
























- 26 -








suffice26








120590119884 = 120590119894 + 119870119910119889minus1

2 Eq 1







- 27 -


















- 28 -
























- 29 -




















- 30 -




a new slip plane3











- 31 -

151 Cast Metal























- 32 -

152 Wrought Metal










transition2229











- 33 -





















new growth3132

- 34 -

















∆119866 =4

31205871199033∆119866119907 + 41205871199032120574 Eq 2

- 35 -





nuclei30













- 36 -




temperature30











favorable303132



- 37 -






120574119868119871 = 120574119878119868 + 120574119878119871119888119900119904(120579) Eq 3







- 38 -



















- 39 -



















- 40 -
























- 41 -













1641 Chill Zone



- 42 -













from the center

1642 Columnar Zone





- 43 -
























- 44 -









most defects2

171 Macroporosity












- 45 -













- 46 -















liquid238

- 47 -




173 Microporosity










pouring metal2

- 48 -




microsegregation2












175 Gas Porosity




- 49 -








of the melt241






- 50 -















- 51 -






metastable form2542








- 52 -









181 Homogenization














- 53 -



182 Full Anneal









183 Process Anneal












- 54 -

184 Normalization






















- 55 -



















- 56 -

1852 Martensite






















- 57 -

















- 58 -




to happen45










- 59 -




can be expected45














- 60 -

186 Spheroidizing













occur1844









- 61 -




















1101 Weldability



- 62 -




weldability










- 63 -























- 64 -








22 HSLA Steels
















- 65 -




HSLA steels




















- 66 -
















recrystallization57








- 67 -














- 68 -





grain pinning63

- 69 -




















- 70 -




nitrogen57







VN60




- 71 -


precipitates60
















higher57




nuclei57

- 72 -


















- 73 -
















- 74 -









23 HSLA Cast Steels










154676970





- 75 -











Wt 012-050 03-06 09-15 04-06 007-015











- 76 -








231 Temperaging















- 77 -




119862119864119860119882119878 11986311 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 4












119862119864119860119878119879119872 = 119862 +119872119899

6+

119862119903+119872119900+119881

5+

119873119894+119862119906

15 Eq 5

119862119864119879 = 119862 +119872119899+119872119900

10+

119862119903+119862119906

20+

119873119894

40 Eq 6

119862119864119860119878119879119872 119860529 = 119862 +119872119899+119878119894

6+

119862119903+119872119900+119881+119873119887

5+

119873119894+119862119906

15 Eq 7

119875119862119872 = 119862 +119878119894

30+

119862119903+119862119906+119872119899

20+

119873119894

60+

119872119900

15+

119881

10+ 5119861 Eq 8

- 78 -





electrodes


required
















- 79 -























- 80 -



strength70










at 1920 ˚F (1050 ˚C)69









grains54

- 81 -



- 82 -


31 Hypothesis






techniques













- 83 -























- 84 -









42 Tempering Study









for each alloy






- 85 -



Digital ME-2











cm) sections









- 86 -















tensile testing








- 87 -





F
















ethanol

- 88 -



- 89 -






















- 90 -













- 91 -










- 92 -








in Composition


High Strength

Low CE

ge 55 ksi le

042 CE 0214 0687 00002 0384

Low Strength

High CE

le 45 ksi ge

045 CE 0231 0816 0006 0451














- 93 -



NampT QampT

High Strength

Low CE

ge 55 ksi le

042 CE 041 035 0 005

Low Strength

High CE

le 45 ksi ge

045 CE 91 43 42 047











negative trend

- 94 -



High Strength

Low CE

ge 55 ksi le

042 CE 0218 0669 00002 0392

Low Strength

High CE

le 45 ksi ge

045 CE 0243 0667 0004 0421









- 95 -



High Strength

Low CE

ge 55 ksi le

042 CE 0 0 0 0

Low Strength

High CE

le 45 ksi ge

045 CE 0218 0975 0006 0484









- 96 -



High Strength

Low CE

ge 55 ksi le

042 CE

0195 0795 0 0333

Low Strength

High CE

le 45 ksi ge

045 CE

0239 0740 0012 0427

















Total Ave 023

plusmn 002

075

plusmn 014

043

plusmn 006

0003

plusmn 0004

030

plusmn 016

046

plusmn 005

49 (339)

plusmn 39 (27)

Top 25 023

plusmn 002

074

plusmn 010

042

plusmn 006

0002

plusmn 0004

032

plusmn 023

046

plusmn 004

54 (369)

plusmn 11 (78)

Bottom 25 023

plusmn 002

081

plusmn 020

044

plusmn 007

0005

plusmn 0004

028

plusmn 009

048

plusmn 005

44 (304)

plusmn 32 (219)

- 97 -














Weldability Ranges


Normalize

NampT

QampT

High Strength Low

CE

ge 55 ksi le 042

CE 041 035 0 005

Low Strength High

CE

le 45 ksi ge 045

CE 91 43 42 047







- 98 -


















- 99 -


Modified C-Mn-V


C 0180 0153

Mn 117 123

P 0010 0017

S 0003 0003

Si 035 043

Cr 017 024

Ni 006 006

Mo 0020 002

Cu 0060 007

Al 0055 0057

W 0002 0002

V 0002 0097

Nb 0001 0006

Zr 0028 0023

N 0012 NA


Mn-V


Modified C-Mn 042 048 043 005

Modified C-Mn-V 044 051 043 008



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

LECO

Carbon

A 020 0180 0141 0196 0171

B 015 0153 0106 0166 0159







- 100 -
























- 101 -





- 102 -

















- 103 -








54 Tempering Study
















- 104 -



at 1 hr




- 105 -








- 106 -






- 107 -







- 108 -








temper time

- 109 -























- 110 -


in ksi

Heat


NampT 458 (3158) 768 (5295) 289 620 150

NampT 473 (3261) 773 (5330) 289 625 144

QampT 727 (5012) 939 (6474) 250 638 205

QampT 780 (5378) 968 (6674) 226 600 216


ksi

Heat


NampT 466 (3210) 771 (53130 289 623 147

QampT 754 (5195) 954 (6574) 238 619 211




a 51 EL decrease











- 111 -



- 112 -


















TS in ksi

Heat


NampT 590 (4068) 859 (5923) 289 587 172

NampT 597 (4116) 856 (5902) 289 636 165

QampT 976 (6729) 1142 (7874) 196 496 231

QampT 991 (6833) 1156 (7970) 211 576 231

- 113 -


in ksi

Heat


NampT 594 (4092) 858 (5913) 289 612 169

QampT 984 (6781) 1149 (7922) 2035 536 231






MPa) respectively











- 114 -



- 115 -





















- 116 -




- 117 -














- 118 -


















- 119 -





Indentation

Number

Alloy A

(NampT)

Hardness

Alloy A

(QampT)

Hardness

Alloy B

(NampT)

Hardness

Alloy B

(QampT)

Hardness

1 136 189 169 260

2 153 182 182 215

3 153 183 173 214

4 141 169 162 211

5 141 167 164 219

6 153 168 155 217

7 150 179 150 218

8 131 168 165 218

9 159 171 164 219

10 153 178 151 224

11 149 185 166 228

12 153 179 172 229

13 NA 184 168 242

14 NA 176 NA NA



Heat Treatments













- 120 -





















20

- 121 -




A 453 (3123) 769 (5302) 282 518 146

A 442 (3047) 770 (5309) 266 520 150

B 518 (3571) 805 (5550) 274 426 153

B 522 (3599 806 (5557) 250 388 152



TS in ksi


A 448 (3085) 770 (5306) 274 519 148

B 520 (3585) 8055 (5554) 262 407 153




A 475 (3275) 784 (5405) 304 552 150

A 470 (3240) 782 (5392) 289 603 148

B 544 (3751) 829 (5716 234 458 166

B 542 (3737) 832 (5736) 274 516 168



and TS in ksi


A 473 (3258) 783 (5399) 297 578 149

B 543 (3744) 831 (5726) 254 487 167








- 122 -





- 123 -



- 124 -












- 125 -




A 493 (3399) 794 (5474) 312 646 153

A 508 (3503) 795 (5481) 352 680 150

A 498 (3434) 793 (5468) 312 652 153

A 493 (3413) 801 (5523) 336 678 156

B 557 (3840) 835 (5757) 304 634 165

B 551 (3799) 834 (5750) 312 645 162

B 560 (3861) 835 (5757 320 643 165

B 549 (3785) 829 (5716) 320 629 162



ksi


A 498 (3437) 796 (5487) 328 664 153

B 554 (3821) 833 (5745) 314 638 164












- 126 -



- 127 -
















Alloy Designation

C Lo-CLo-MnLo-V

D Hi-CLo-MnHi-V

E Lo-CHi-MnHi-V

F Hi-CHi-MnLo-V


Silicon


C 013 10 007 lt 04

D 017 10 011 lt 04

E 013 14 011 lt 04

F 017 14 007 lt 04

- 128 -


Spectrometry

Element Alloy C (wt

addition)

Alloy D (wt

addition)

Alloy E (wt

addition)

Alloy F (wt

addition)

C 014 017 012 0159

Mn 088 098 104 135

P 0007 001 0008 0008

S 0005 0005 0002 0004

Si 025 033 025 041

Cr 015 017 036 019

Ni 003 008 006 007

Mo 001 002 003 0018

Cu 006 007 006 009

Al NA NA NA NA

W NA NA NA NA

V 010 012 011 0075

Nb NA NA NA NA

Zr NA NA NA NA

N NA NA NA NA



C 035 039 033 006

D 041 046 039 007

E 040 044 034 010

F 045 049 043 004



Alloy Target

Carbon

Spectrometer

1 Carbon

Spectrometer

2 Carbon

Spectrometer

3 Carbon

Leco

Carbon

C 013 0140 0167 0149 0184

D 017 0170 0188 0180 0190

E 013 0120 0139 0134 0167

F 017 0159 0172 0165 0182



- 129 -





Heat


NampT 435 (2999) 664 (4578) 336 655 130

NampT 464 (3199) 676 (4661) 328 655 137

QampT 828 (5709) 990 (6826) 242 603 216

QampT 785 (5412) 961 (6626) 234 606 222


Heat


NampT 450 (3099) 670 (4620) 332 655 134

QampT 807 (5561) 976 (6726 238 605 219


Heat


NampT 520 (3585) 751 (5178) 297 589 156

NampT 520 (3585) 753 (5192) 312 620 156

QampT 964 (6647) 1117 (7701) 203 525 240

QampT 947 (6529) 1103 (7605) 203 525 240


Heat


NampT 520 (3585) 752 (5185) 305 605 156

QampT 956 (6588) 1110 (7653) 203 525 240


Heat


NampT 501 (3454) 717 (4944) 320 666 141

NampT 521 (3592) 724 (4992) 336 675 141

QampT 905 (6240) 1061 (7315) 219 583 240

QampT 858 (5916) 1020 (7033) 203 581 228

- 130 -


Heat


NampT 511 (3523) 721 (4968) 328 671 141

QampT 882 (6078) 1041 (7174) 211 582 234


Heat


NampT 543 (3754) 802 (5530) 336 689 159

NampT 556 (3833) 807 (5564) 304 661 162

QampT 1013 (6984) 1142 (7873) 1795 561 258

QampT 1060 (7308) 1167 (8046) 1955 589 247


Heat


NampT 550 (3794) 805 (5547) 320 675 161

QampT 1037 (7146) 1155 (7960) 188 575 253








with Figures 74-82

- 131 -



- 132 -



- 133 -



- 134 -



- 135 -























- 136 -



- 137 -



- 138 -



- 139 -













CVN

CE Cmax Mnmax




(W)

62-50-21-No No 023 135



Grade (W)

65-50-21-Yes No 023 135




(W)

65-50-21-Yes 045 020 160


A216 WCB (C) 70-36-22-No 050 030 100





(W) for Wrought

(C) for Cast

- 140 -







to emerge

- 141 -


61 Summary





















- 142 -
























- 143 -












conditions












- 144 -










for hardness 147 HB














- 145 -


















condition





- 146 -







respectively







F









- 147 -



62 Conclusion

















requirements




- 148 -
























- 149 -





63 Future Work





tempering profiles



tempering study







results


- 150 -

Appendix A



- 151 -


- 152 -




manganese content

- 153 -

Appendix B



A (C-Mn) 048 0421 0312 0264 043

B (C-Mn-V) 051 0438 0295 0256 043



C 0386 0345 024 0214 0328

D 046 0405 0284 0257 0388

E 0443 0401 025 0215 0335

F 0493 0451 0312 0259 0426


C Mn Si V CMn CEAWS

D11 YS (MPA)

Total Ave 0229 0753 0425 0003 0304 046 49230 (339429)

Ave Top

025 YS 0232 0735 0420 0002 0316 046 53574 (369380)

Ave Bottom

025 YS 0226 0812 0441 0005 0278 048 44022 (303521)

Total Std

Dev 0022 0138 0065 0004 0162 0048 3917 (27007)

Std Dev

Top 025 YS 0022 0099 0063 0004 0225 0042 1137 (7839)

Std Dev

Bottom 025

YS

0018 0197 0067 0004 0091 0049 3182 (21939)

- 154 -

References







Chem 1975 9 (C) 105ndash138



OH 2016 pp 9ndash16










2018 pp 485ndash487











39ndash62






15ndash32

- 155 -


543ndash565




277ndash291



297ndash325



43ndash86








79










263ndash306


August 915ndash922


(7) 96ndash97







- 156 -

























pp 205ndash234














3ndash41


- 157 -


87ndash126





373ndash403





233ndash275



1989















1983 pp 111ndash125








pp 389ndash423



- 158 -







Steel 1987








1978


1990







2016

development of a cast 50 ksi (345 mpa) yield strength …

Documents