Casting of metals and alloys

1. Casting of Metals and Alloys
in 2000 and Beyond

2. Introduction
Casting is a manufacturing process by which a liquid
material is usually poured into a mold, which contains a
hollow cavity of the desired shape, and then allowed to
solidify.
Advantages of casting
1.Lowest cost method for manufacturing complex parts
2.Reduces part count, weight, machining
3.Reduces manufacturing space and inventory

3. Vacancies in the market
1.Shortage of Skilled Technicians and competition
because of globalization
2.Requirement of more capable computer programs.
3.Much of development in metal casting driven by
“solidification simulation packages.”

4. Benefits of Computer Simulation Packages
1. Automotive and aircraft industries
2. High degree of accuracy
3. Predict the cast structure depending on cast
parameters
4. Static and dynamic properties of the component
can be predicted and compared with designer’s
requirement
5. Identify Casting Defects and
so Non Destructive
6.Evaluation is done.
7.Reduce life cycle costs of
casting
8.Minimized machining

5. Metal Shaping Routes
Final properties of a casting greatly influenced by casting
and moulding process alone .
Major contribution to casting industry new developments
given by Automotive industry.
For e.g.
1.Aluminum Suspension parts used in steering as it’s first
production application
2.Dashboard in Plymouth Prowler is die cast
Mg alloy
Car Steering Suspension partsPlymouth Prowler

6. Squeeze casting, also known as liquid metal forging,
is a combination of casting and forging process.
• Both ferrous and non-ferrous materials can be
produced using this method.
• Slow Ingate velocities with minimal turbulence and
slow application(50-100mm/min) of high pressures
(35-105 MPa)
• Low porosity
• High integrity
• Heat treatable
• Two types
Direct –application of pressure to the piston, which
contacts the molten metal.
Indirect –the melt is forced from a system of runners to
the mould cavity gate.

7. Lost-foam casting (LFC) or Evaporative-pattern casting
process i.e.
Similar to investment casting except foam is used for the
pattern instead of wax.
1.Advantage of the low boiling point of foam by removing
the need to melt the wax out of the
mold.
2.Applications: Making truck,
pipe, and automotive high volume
components
Commonly cast metals include
• cast irons,
• aluminium alloys.
• steels, and nickel alloys;
• less frequently stainless steels
• and copper alloys are also cast.

8. Shell Moulding
Shell mold casting or shell molding is a metal casting
process in manufacturing industry in which the mold
is a thin hardened shell of sand and thermosetting
resin binder, backed up by some other material. Shell
mold casting is particularly suitable for steel castings
The sand mixture is poured or blown over the hot
casting pattern. Reaction of the thermosetting
resin with the hot metal pattern, a thin shell forms
on the surface of the pattern.

9. The excess "loose" sand is then removed, leaving the shell
and pattern.
The shell and pattern are then placed in an oven for a short
period of time, (minutes),.
the hardened shell is separated from the casting pattern by
way of ejector pins Two of these hardened shells, each
representing half the mold for the casting, are assembled
together either by gluing or clamping.

11. Counter Gravity Casting
Production Parts
Cast Stainless Steel Exhaust
Cast Steel Contoured
Camshaft, Brake Rotor,
Primary Pump Body, Crank
Case for Air compressors,
Bearing case for Industrial
machinery

12. Differential pressure sand
casting:
• Alternative to conventional
gravity casting.
• Create differential pressure
by evacuating the mould
cavity, in contrast to most
processes,
• Relatively Simple
• Can be used for small batch
melting operations Ex. Light
alloys aerospace foundries.

13. Flaskless vertically parted green sand moulding
In flaskless moulding, no flask is used for supporting the
moulding sand; the mould itself is made sufficiently strong to
bear the liquid metal pressure.
Two types:1.Vertical Parting Flaskless Moulding (DISAMATIC)
2.Horizontal Parting Flaskless Moulding
(Website: www.ijrdet.com (ISSN 2347 - 6435 (Online) Volume 2, Issue 4, April 2014) )
Fig: Vertical Parting Flaskless Moulding (DISAMATIC)

14. Advantages of Flaskless Moulding
• It does not use flasks, which avoids a need of
their transporting, storing and maintaining.
• No repair expenditure on flasks
• By adopting aeration sand filling technology,
energy saving and noise reduction have been
achieved
• Stable pattern draw is secured by automatic
pattern spray
• Minimize turbulence and porosity in casting

15. Freeze Cast Process(FCP):
By subjecting an aqueous slurry to a directional temperature
gradient crystals will nucleate on one side of the slurry
Steps:
1. Making a solid master pattern by traditional machining and
materials, or by any one of the state of the art pattern
generating methods such as
• stereo lithography,
• laminated object manufacturing(LOM),
• selective laser sintering(SLS)
2. Making rubber moulds using silicon rubber or urethane
polysulfide, which are available in liquid form, from the master
pattern.
3. Pouring water containing additives into rubber mould and
freeze the water
4. Stripping the ice pattern
5. Repeated stripping of the ice pattern into refrigerated ethyl
(alcohol) silicate slurry

16. 6. Exposing the shell containing ice pattern to slow
heating pouring out water and then firing of shell.
7. Pouring of molten metal into the shell solidify to get
final casting.

17. Metals and alloys like gray iron, ductile iron, steel,
aluminium and copper.
Significance:
• Near net shape castings,
• fast pattern making,
• pattern is not burned out
Not Suitable for large casting, flat parts with thin walls.

18. Semisolid Processing
Thixomolding is one step process for making
near net shape castings
E.g.
• Mostly Magnesium and Zinc alloy parts.
• Electronics and communication,
• Automotive shift cams, throttle bodies,
etc.
Notebook computer cases
Digital camera bodies
Hand held power tools

19. Hot Isostatic Pressing (HIP)
Components are subjected to the simultaneous
application of heat and high pressure in an inert gas
medium.
Pressure by gas makes it Isostatic and uniform and
leading to plastic state collapses any left voids.
Use as precision castings.
Complex shapes can be formed without expensive
tooling.

20. Plasma Cupola
Plasma Cupola Pilot Plant
at General Motors
• First used for the production
of Cast iron engine blocks.
• Cost effective melting in
difficult to melt raw materials
such as
• Loose cast iron borings and
production of world class
automotive castings
Melting and Melt Treatments

22. Mg Heating
• Humid conditions must be avoided and mixing
gases must contain less than 0.1 %moisture.
• SF6 base gases and SO2 – air mixtures are used
as oxide barrier for melting Mg and its alloys but
are very harmful for environment even in ppm

23. Ultrasonic degassing of Al melt
• Water vapour and Al2O3 reacts and H2 evolves causing
microstructure degradation and embrittlement
• So Ultrasonic (cavitational) degassing more effective
than fluxes/argon/vacuum degassing in lowering the
hydrogen content of Al melt.
• 10% increase in tensile strength
(UTS) and 80% more % elongation
attained with combined vacuum
and ultrasonic treatment.
• Produce non dendritic
microstructure& very low H2
content Ultrasonic vibration
Al Melt

24. Running, Gating and Risering
• Designed to introduce clean, dross- free, tranquil
metal into the mould cavity and continue to feed
liquid metal to casting as it solidifies.
• Gating system should ensure non-turbulent pouring
at lowest velocity
• Distance between sprue and ingates should be
maximized to allow time for dross to float out and
trapped at top surface of the runner bar.
• American Foundrymen’s Society, USA found a
software simulation package called ‘AFS 3D’ solid
model system that provides data related to casting
quality without manufacturing the casting.
• Finite Difference Method (FDM) used to find energy
during pouring, including mixing and turbulence
during mixing.

26. Tooling
Computer Tomography (CT) for reverse engineering
and Rapid proto typing (RP) techniques are used for
producing patterns for tools.
Rapid pattern making gives the foundry new
possibilities for the fast production of metal prototypes
and series parts.
Rapid tooling for sand casting can be made using
1. Computer numerically Controlled (CNC) machining
of non-ferrous pattern materials
2. By using patterns created directly in rapid prototyping
machines.

27. Development and usage of New Alloys and materials
Todays Need
• Cost effective in global economy
• Integrated approach incorporating materials science
• Process technology
• Design and Performance of the product is must.
For e.g.. Use of New high grade H13 tool steel for shot
sleeves and other die components of aluminium pressure die
casting machine has yielded a 10-20 % enhanced die life and
huge savings.
• Protein based ,water soluble binder for sand casting has been
developed as also environment friendly.
• Used or unused cores can be placed in a water bath and the
resin can be reclaimed.
• Lower cost Aluminium metal matrix composites (AMMC)
expanded its market potential e.g. in automobiles parts like
brake rotors, drums, calipers and pads back plated, Cylinder
liners, Steering links, Clutch Plates, Structural Oil Pans,
Brackets, Suspension arms, etc.

28. Reuse, Recycling And Eco friendliness
• Increasing pressure to improve its environmental
performance to meet sustainable development
• Reuse of foundry by-products
• Cryogenic sand reclamation could be a potential route of
the future (liquid N2 is used to reduce sand temperature
to as low as -80° C which separates sand from other
valuable constituents)
• Recycled aluminium for making automotive Al castings in
US was around 63% in 1999.
• Process control, major tool for waste reduction generally
a little or no capital cost and quality improvement.
• Foundries are most polluting industry

29. Conclusion
Foundries of tomorrow have to explore
1. Near net shape process
2. Concept of cast-to-fill and HIP-to-density for critical
components
3. Consortium/ co-operative approach towards R&D
4. Beneficial reuse options
5. Use newer tools such as computer simulation,
expert system, neural net work, etc.
6. Reduction of production cost by better control
7. Converting into an ecofriendly industry.

30. References
• Casting of Metals and Alloys in 2000 and Beyond
R.M Pillai, B.C. Pai and K.G. Satyanarayana
Regional Research Laboratory, Council of Scientific and Industrial Research, Thiruvananthapuram-695019