SSM

a case study with my teammates for our college project ( casting course ) about the semi-solid metal for Faculty of engineering ain shams university mechanical department

1. Manufacturing Technology II Part I: Casting

2. Semi-Solid Metal Casting (SSM)

3. Introduction

4. What is the SSM ?! ( SSM ) is a short standard for the semi-solid metal process Which is a manufacturing technique which involves casting and forming operations . Discovered at MIT in 1971 During study of hot tearing of steel during solidification regarded as an economical, high productivity process for manufacturing a broad variety of metal parts .

5. Semi-solid metal casting (SSM) is “ a near net shape ” “ industrial manufacturing technique. the initial production of the item is very close to the final (net) shape, reducing the need for surface finishing “ The process is used with non-ferrous metals , such as aluminium , copper and magnesium . There are four processes: thixocasting , rheocasting , thixomolding

6. Why SSM ? The conventional casting often contains internal structural defects that lead to poor mechanical properties. to improve the mechanical properties it is required to modify the dendritic microstructure of the alloys

7. Microstructure

8. Evolution to Non-dendritic Microstructure: Under Forced Convection Fragmentation of primary dendrites by Root melting of secondary dendritic arms Bending and shearing of secondary denritic arms Bending and root melting of secondary arms Fragments of primary dendrites grow into globular grains under forced convection

9. Partial melting and Iso -thermal holding Low temperature eutectic phase melts in semi-solid range Highly stressed grain boundaries favours wetting of grains with liquid Grain become globular to reduce curvature and liquid-solid interface energy

10. Characteristics of Slurry Sheared semi-solid slurry shows apparent viscosity similar to machine oil

11. SSM Processing exploits Solidification mechanism in the solid-liquid range i.e. nucleation and growth mechanisms Liquid Solid Liquid + Solid Composition, Time Conventional solidification Semi-solid Processing T

12. Solidification range Low melting point phase/eutectic phase Temperature Sensitivity of solid fraction Castability Potential for aging etc. Temperature Fraction Solid Processing Range Alloy Characteristics:

13. Other Mechanisms Grain refinement Spray forming and sintering Ultrasonic vibrations etc.

14. Different between Liquid Casting and SSM Microstructure: Liquid Casting SSM Casting

15. Techniques of SSM Processes:

16. Processing Techniques Techniques for feed stock Techniques for Finished Product

17. Semi-solid Metal Processing Techniques Techniques for non-dendritic Feedstock: Mechanical Stirring Megnatohydrodynamic (MHD) Stirring Stress Induced and melt Activated (SIMA) Process Spray Forming Liquidus Casting Ultrasonic treatment Grain refienment etc.

18. Mechanical Stirring Developed at MIT Stirring of liquid alloy while controlled cooling in the semi-solid range using auger, impeller or paddle Batch type or continuous process For Rheocasting and Thixocasting

19. Magneto hydrodynamic (MHD) Stirring Patented by Alumax Inc. Vigorous stirring by rotating magnetic field within the mould Normally for producing feedstock for thixocasting Disintegrated fine dendrites which convert to globular grains on partial melting Most widely used process

20. Stress Induced and Melt Activated (SIMA) Process Severe deformation of precursor results in residual stresses On heating recrystallization occurs On partial melting low melting point phase becomes liquid High residual stress favours wetting of grain boundaries Higher curvature and liquid-solid interface energy favours globular grain morphology Longer holding time favours coarsening and agglomeration which deteriorate semi- solidprocessability

21. Liquid's Casting Pouring of melt at near- liqudus temperature Higher rate of Nucleation favouring fine grain size On partial melting fine grains transform to globular grains Grain Refinement Promote heterogeneous nucleation Finer grain size Grains transform to globular on partial melting

22. Techniques for Net-shape Product : Rheocasting Thixoforming Thixomoulding Rheomoulding etc.

23. Rheocasting : Non-dendritic ally slurry obtained from shearing while cooling from liquid state Mechanical stirring MHD Stirring New Rheocasting (NRC)

24. Thixocasting : Partial melting of suitable feedstock Mechanical stirring MHD stirring SIMA process Spray forming Thixocasting Thixoforging

25. Thixomoulding : Simultaneous heating and shearing of solid feedstock in a chamber by rotating barrel Designed for Mg alloy Controlled atmosphere Similar to injection moulding

26. Rheomoulding : Vigorous Shearing of liquid alloy using screw type drive while cooling Similar to Injection moulding Suitable even for immiscible alloy formation and processing Twin Screw Rheomoulding (TSRM) process is an upgradation

27. Advantages & Disadvantages

28. Advantages: Energy efficient Production rate compete that for pressure die casting Smooth die filling with no air entrapment favouring product soundness Lower processing temperature Lower Impact to the die Reduced solidification shrinkage

29. Disadvantages: Relatively higher feedstock material cost Precise control of operating condition is required. Liquid segregation may occur as a result of non-uniform heating

30. Applications

31. Potential Applications: Replacement of permanent mould parts to eliminate machining and finishing Pressure tight parts such as master brake cylinders, fuel rails, air conditioner compressor housing etc. High strength parts such as engine mounts, tie rods etc. Wear resistant parts made from hypereutectic alloys such as compressor piston, brake drums, gear shift levers etc. Forged parts requiring excessive tooling

32. Brake master Cylinder Current Applications/Products : Hydraulic Brake Valve Automobile Wheels

33. Door Pillars for Audi Control arms for Steering Fiat Engine bracket

34. Process development Mechanism of formation of non-dendritic structure Alloy development Simulation studies of process Viable process for steel and Cast Iron Future Developments

35. The End

36. Any Questions?!

37. Presented By: Fatma Hesham Croix Akmal Ibrahim Kareem Hamdy Kareem Kamel El- gamal Karim Mohamed Ayman Kareem Mohey Yhyia