8 - rapid s process - anders jarfors

8/11/2019 8 - Rapid S Process - Anders Jarfors

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Rapid S Process

Semi Solid Metal Casting

Prof. Anders E. W. JarforsDr. Magnus Wessn


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Content

What is semi solid metal casting?

Overview / Historical background

Advantages / Limitations in relation to liquid casting

processes

Overview of some existing SSM casting processes

The Rapid S process An innovation from JTH

Concluding remarks


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Metal shaping processes at varioustemperatures


Al

+ Si

+ L

L


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Liquid casting

Al

+ L

L

+ Si


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Forging, Rolling, Extrusion

Al

+ L

L

+ Si


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Semi-solid casting(Semi-solid forging)

Al

+ L

L

+ Si


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Al

+ L

L

+ Si


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Eutectic alloys

Pure metals

Al

+ L

L

+ Si


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Overview /

Historical background


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Couette viscometer trials at MIT 1972

Ref: D.B. Spencer, R. Mehrabian, M.C. Flemings,Metallurgical Transactions, Vol. 3, no. 7, 1972


1.5*103

2.1*106

Dendrites Globular grains


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Rheological behaviour of a semi-solidslurry with globular grains



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Two main SSM processing routes


Ref: T. Basner, SAE World Congress,Detroit, MI, USA, 6-9 March 2000,

paper no. 2000-01-0059


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Advantages / Limitations of SSM in

relation to liquid casting processes


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Ref: M. Shehata, E. Essadiqi and C. Loong,

MTH/ Canmet, Natural Resources Canada,

IMI/NRC, Industry Canada, Presentation at

Windsor Worksho , June 5, 2001

Interrupted shot experiments

1. Laminar filling - Less risk for air

entrapment

Advantages /Limitations


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Experiments using varying

- Solid fractions (0 50 %)

- Flow velocities (0.5 5 m/s)


1. Laminar filling - Less risk for air

entrapment

Ref: J.L. Jorstad, Q.Y. Pan, D Apelian,NADCA conf., Houston, Texas, 2007

Liquid

Fs = 0.5


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2. Reduced solidification shrinkage


Temperature

Volum

e

TLTS

Liquid

contraction

Solidification

contraction

Solid

contraction


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3. Semi-solid cast components can oftenbe heat treated

HPDC components are normally not heat treatable due to theexpansion of entrapped gas inside the components, which causes

surface blistering at elevated temperatures


Alloy Yield strength Tensile strength

Al-A356 ~120 MPa ~180 MPa

Al-A319 ~130 MPa ~230 MPa

Al-A356 T6 ~240 MPa ~280 MPa

Al-A319 - T6 ~380 MPa ~440 MPa


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4. Process benefits

Higher production rate

Less die soldering problem and less need

for lubrication

Less melt impact on the die inserts during cavity filling

Longer die life

Small holes (using small pins) and more complex geometries

can be cast directly to near net shape

Smaller HPDC machines can be used as less intensification

pressure is needed Lower environmental impact



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Drawbacks / Limitations1. Thick ingates are used in order to

obtain sufficient feeding from the

bisquit

Cutting / Sawing of ingates is

needed


2.Alloys with small solidification

ranges less suitable

3. Strict temperature control is needed in most processes

4. Metal flow needs to be optimized in order to avoid

cold flows / cold seams


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Overview of some existing

SSM casting processes


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NRC New Rheocasting process

Developed and commercialized byUBE Industries (Japan, ~1996)

Al-alloys



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SSR-process

Developed by a US/DoE funded consortium by WorchesterPolytechnic Institute, Massachussetts Institute of Technology

and Oak Ridge National Laboratories

Commercialized by Idra Prince /Bhler

Al-alloys

Graphite rod



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The Rapid S process

Developed at School of Engineering,

Jnkping University 2004

Spin off company RheoMetal is nowcommercialising the process


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The process is based on controlling the enthalpy instead ofthe temperature when controlling the solid fraction of the metalslurry. This is a fundamental difference from most other semi-solid forming processes.

Enthalpy Exchange Material (EEM)

Patented in Sweden, China and South Africa, Worldwide patents pending

The Rapid S ProcessInternal cooling

The Rapid S Process


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Heat balance during slurryformation

slurrySmeltSlurry

meltmeltmeltmeltmelt fHTTCpVQ )( 0

Energy released when melt cools down and partially solidifies

melt cooling partial solidification

)1()( 0 slurry

SeemeemSlurryeemeemeemeem fHTTCpVQ

Energy taken up during heating and partial melting of the EEM

EEM heating partial melting

The Rapid S Process


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Lab experiment AM60 alloy

The Rapid S Process


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Temperature evolution in melt/slurry (AM60)

230 240 250 260 270 280 290 300 310

618

620

622

624

626

628

630

Time (s)

Temperature(C)

Melting point of AM60 alloyLiquidus temperature

The Rapid S Process


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.

.

Temperature evolution in melt/slurry

The Rapid S Process


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Stenal Rheo1(left) Alloy 6082(right)

Temperature evolution in melt/slurry

The Rapid S Process


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Microstructure - A356 Al alloy

The Rapid S Process


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Implementation

The Rapid S Process

Jarfors, Kainer, Tan, YongCOSMOS, Vol. 5, No. 1

(2009) 2358


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Feature capability fo Rapid S withStenal Rheo 1

The Rapid S Process


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Porosity HPDC vs. Rapid S

Rapid S

HPDC

The Rapid S Process


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On-going research for Rapid S at JTH

Process stabilization for extended alloy range

Stenal Rheo 1 benchmark 6082 and similar low Si alloys for improved heat

conductivity

Heat treatment behaviour for low Si alloys

Mg-alloy capability

Process settings for standard casting alloys (AZ, AM

series and mechanical properties testing

Mg-MMC for improved thermal stability and wearresistance

Rapid S Process


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Concluding remarks


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Concluding remarks

Rapid S is established for

A356, Stenal Rheo 1 Superior shape capability

High internal soundness better than HPDC and

comparable to other SSM methods

Process stability developed to extend alloy

capability

Low Si alloys for thermal transfer

Light weight alloys including Mg alloys

Concluding remarks

8 - rapid s process - anders jarfors

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