cast iron and steel

8/9/2019 Cast Iron and Steel

1/75

Cast Iron and Steel


2/75


3/75


4/75


5/75


6/75


7/75


8/75


9/75


10/75


11/75

Fe-C Fe-C-2% Si


12/75

2 wt. pct. Si


13/75

2.5 wt. pct. Si


14/75

C-Si Combinations


15/75

Gray Iron


16/75

Carbon Equivalent

C.E. = C + (Si + P) / 3

Properties related to C.E.

Mechanical

Hardness

Damping

Thermal conductivity


17/75

C.E. Effect


18/75

Other Important Elements

Mn, S

Mn 1.7 * S + 0.3

Cr

Promotes chill

Cu

Strength

Mo

Promotes pearlite

Ni

Sn

Strong pearlite former

P

From pig

Forms Steadite


19/75

P Effect on Eutectic Temperature


20/75

S Effect


21/75

Solidification

Two possibilities

C as cementite

Ledeburite

C as graphite

Flakes


22/75


23/75

Ledeburite


24/75

Types of Flake Graphite


25/75

Type A Flake Graphite


26/75


27/75

Type C and A Flake Graphite


28/75

Type D Flake Graphite


29/75

Type E Flake Graphite


30/75

Deep Etched Flake Graphite


31/75

Thermal Analysis

Look at cooling curve

Determine rough C, Si

Determine quality of melt/ladle


32/75

Thermal Analysis Plots


33/75

Cooling Curves


34/75

Melting Methods

Cupola

Continuous

Induction

Batch type


35/75

Cupola


36/75

Cupola Charging

Materials added in alternating layers Metals

Steel 25-90%

Scrap iron castings As available

Pig iron

As needed to dilute tramp in steel Alloys

FeMn, FeSi, etc.


37/75

Cupola Charging

Coke Carbon and heat source

8-16%

Flux

2-8% Limestone (CaO)

Soda ash (Na2CO3)

Increases slag fluidity

Fluorspar (CaF2) Maintains slag fluidity

Calcium carbide (CaC2)

Deox, raise C, raise T, adds to CaO


38/75

Induction Furnace


39/75

Induction Melting Materials

Pig Iron 4%C, 2.75%Si, 0.65%Mn, 0.02%S

Steel

0.3%C, 0.3%Si, 0.8%Mn

Returns

Alloying additions

FeSi

FeMn

Pyrite

Others


40/75


41/75

Inoculation Practice

Dry materials

Start tapping furnace into ladle then add

inoculants

Add to metal stream entering ladle

Provide good mixing

Pour quickly to prevent fade In mold

Prevent fade ladle inoculant


42/75

Classifications

UTS-Tensile bar size

25B

35A

40C 30S

Dimensions

A 0.88 x 6 B 1.2 x 9

C 2.0 x 10


43/75

Ductile Iron


44/75

C-Si Combinations


45/75

What is ductile iron?

Similar chemistry as gray iron

Add a nodulizer

Changes graphite flake into spherical nodule

Typically Mg

Significant change in mechanical properties


46/75


47/75

Preferred Chemistry Range


48/75

Composition

C, Si Primary elements

Mn Promotes pearlite

S Combines with Mg and R.E.

Mg Causes spheroids, lowers S, O

0.02-0.08%

Cu, Mo, Ni

Promote hardenability


49/75

Composition

Chunky

Ce, Ca, Si, Ni

Intercellular Flake

Bi, Cu, Al, Pb, Sb, Sn, As, Cd

Deleterious

Zr, Zn, Se, Ti, N, S, O


50/75

Classifications

UTS-YS-%Elongation

65-45-12

60-40-18

80-55-06

100-70-03

Tensile bar machined from Y-block Dimensions based on casting thickness


51/75


52/75

Nodularity


53/75

Nodule Size


54/75

Pearlite Content


55/75

Carbide


56/75

C Float


57/75

Magnesium Recovery

High affinity for S

Need base iron to be low in S or recovery will

suffer Can use Mg as a S remover


58/75

Mg Plunger


59/75

Sandwich Production Method

Started with open ladle

Slight improvement

Need fast tapping

Low recovery


60/75

Covered Ladle

Tundish

Improved Mg recovery

Need to tap fast

Can improve furtherwith refractory dam

Usually pour in different

ladle


61/75

Steel


62/75

C-Si Combinations


63/75


64/75


65/75

Materials

Need good control of the residual elements

Different grades available for most materials

Purer materials cost more

High C FeCr vs. Low C FeCr vs. Electrolytic Cr


66/75

Classifications

Steel vs. Stainless Steel

Chemistry

Mechanical properties


67/75

Steel WCB

Chemistry (max)

C: 0.3

Mn: 1.0

P: 0.04

S: 0.045 Si: 0.6

Cu: 0.3

Ni: 0.5

Cr: 0.5

Mo: 0.2

V: 0.03

Total Resid: 1.0

Mechanical props

Tensile: 70-95

Yield: 36

Elongation: 22% Reduction of Area: 35%

Pouring temp

2750 3000 F

1510 1650 C


68/75

Steel Melting

Dead melt

Minimize oxygen during melting

FeSi or FeMn additions to control O

Live melt

Purposely add taconite (Fe203)

Need to add deoxidizer at tap

CaSiBar, FeSi


69/75

Stainless CF8M

Chemisty

C: 0.08

Mn: 1.5

Si: 2.0 P, S: 0.04

Cr: 18.0-21.0

Ni: 9.0-12.0

Mo: 2.0-3.0 3#/1000 FeSe added for

green sand molding

Mechanical

Tensile: 70

Yield: 30

Elongation: 30%

Pouring temp

2900 3100 F

1590 1705 C


70/75

Molding Differences

Chemically bonded sand

Different chemicals needed that withstand higher

temperatures

Coating a must

Green Sand

Clay type


71/75

Clay Types

Southern Bentonite

Calcium

Found in southern US

Mississippi, Alabama Quick to develop green and

shear strength

Less mull time needed

Low mold shrinkage Good for non-ferrous

Mix for iron

Western Bentonite

Sodium

Found in western US

Wyoming, South Dakota Higher hot strength

Less flowable

More thermally durable

Used exclusively for steel


72/75

Charge Correction

Calculate weight of each element for

Aim

Prelim

Need to add to get to aim

Calculate addition of alloy for each element

Want to use cheapest materials that will not

cause other issues


73/75

Steel Charge Correction

1000#

C: 0.2%, Aim: 0.25

Mn: 0.45%, Aim: 0.85%

Shoot for 0.9% toaccount for recovery

Si: 0.15%, Aim: 0.25%

Final Si: 0.45%

Other elements: Min

Carbon 100% C

FeMn 75% Mn, 6.3% C

Electrolytic Mn 100%

Mn FeSi 75% Si


74/75

Steel Charge Correction 2

1000#

C: 0.23%, Aim: 0.25

Mn: 0.4%, Aim: 0.85%

Shoot for 0.9% toaccount for recovery

Si: 0.18%, Aim: 0.25%

Final Si: 0.45%

Other elements: Min

Carbon 100% C

FeMn 75% Mn, 6.3% C

Electrolytic Mn 100%

Mn FeSi 75% Si


75/75

Stainless Charge Correction

1000#

C: 0.04%, Aim: Min

Mn: 0.6%, Aim: 0.9%

Si: 0.45%, Aim: 1.0%

S: 0.015%, Aim: 0.03%

Ni: 8.75%, Aim:9.4%

Cr: 17.25%, Aim: 18.5% Mo: 1.9%, Aim: 2.1%

FeMn 75% Mn, 6.3% C

Electrolytic Mn 100% Mn

FeSi 75% Si

Pyrite 50% S

Ni

100% Ni FeMo 62.4% Mo

Pure Moly 100% Mo

High C FeCr 6.3% C, 65.6% Cr

Low C FeCr 0.035% C, 70% Cr

Electrolytic Cr 99.34% Cr

cast iron and steel

Documents