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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What is semi solid metal casting?
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Metal shaping processes at varioustemperatures
What is semi solid metal casting?
Al
+ Si
+ L
L
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Metal shaping processes at varioustemperatures
What is semi solid metal casting?
Liquid casting
Al
+ L
L
+ Si
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Metal shaping processes at varioustemperatures
What is semi solid metal casting?
Forging, Rolling, Extrusion
Al
+ L
L
+ Si
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Metal shaping processes at varioustemperatures
What is semi solid metal casting?
Semi-solid casting(Semi-solid forging)
Al
+ L
L
+ Si
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Metal shaping processes at varioustemperatures
What is semi solid metal casting?
Semi-solid casting(Semi-solid forging)
Al
+ L
L
+ Si
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Metal shaping processes at varioustemperatures
What is semi solid metal casting?
Semi-solid casting(Semi-solid forging)
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
Overview / Historical background
1.5*103
2.1*106
Dendrites Globular grains
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Rheological behaviour of a semi-solidslurry with globular grains
Overview / Historical background
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Two main SSM processing routes
Overview / Historical background
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)
Advantages /Limitations
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
Advantages /Limitations
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
Advantages /Limitations
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
Advantages /Limitations
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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
Advantages /Limitations
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
Overview of some existing SSM casting processes
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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
Overview of some existing SSM casting processes
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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