Casting is one of the oldest manufacturing process in which a liquid metal is poured into a cavity(mould) of desired shape. It is then allowed to solidify. The solidified part is also known as a casting, which is taken out of the mould to complete the process.

1. MUFFAKHAM JAH
COLLEGE OF ENGINEERING AND
TECHNOLOGY
Title : Casting Technique
Md Naseeruddin Shah
1604-11-736-072

2. Casting Technique

3. Contents
 History
 Need of casting
 Classification of casting
 Sand casting
 Special casting methods
 Casting defects
 Inspection of casting
 Reference

4. History
 Origins back to around 3,600 B.C
at Mesopotamia
 Bronze was melted and poured
into a mould.
 Good flow property of Iron at
1150 degree C have enabled the
casting of iron.

5. Need Of Casting
 Can produce a wide variety of metal components with
complex geometries.
 Castings of great size and weight can be produced.

6. Classification Of Casting Process
 Sand Casting
 Special Casting Methods
 Permanent Mould Casting
 Pressure Die Casting
 Centrifugal Casting
 Investment Casting

7. Equipments
 Cope and drag
 Sand
 Pattern
 Molten metal
Sand Casting

8. Governing Equations
 Bernoulli's principle : For an inviscid flow of a non-
conducting fluid, an increase in the speed of the fluid
occurs simultaneously with a decrease in pressure or a
decrease in the fluid's potential energy.
 Continuity Equation : Mass entering is equal to mass
leaving

9. Mould making :
Moulding sand consists of three basic elements
1) Silica sand particles (75-80%) : Used for producing
required strength of mould
2) Clay (15-20) : Used for producing bond between the
sand particles.
3) Water or sodium silicate (6-8%) : Used for initiating
the formation of bond between the sand particles

10. Properties of moulding sand
1) Porosity property : The ability of escaping the air or gases through the
moulding sand
2) Cohesiveness property : The ability to form bond between same
material particles.
3) Adhesiveness : The ability of bond formation of sand particles with
other materials
4) Refractoriness : The ability of withstanding higher temperature
without loosing its strength and hardness.
5) Collapsibility : The ability of breaking the mould with little amount of
force
6) Flowability : The ability of flowing of moulding sand into each and
every corner of the mould.

11. Pattern
Pattern is the replica of casting to be made.
Pattern size = casting size ± allowances
Allowances
1) Shrinkage allowance : Shrinkage of metal during cooling
2) Machining allowance : The extra material provided on the pattern
3) Draft allowance : Making the vertical surface of pattern into incline
4) Shake allowance : Provided to avoid the damages during removing of
pattern
5) Distortion allowance : Distortion of shape due to differential cooling

12. Gating System
It is the provision made for the molten metal to enter into the cavity
Elements of gating system
•Pouring basin
•Sprue
•Sprue base well
•Runner
•Ingate
•Mould

13. Special Casting Methods
Permanent Mould Casting
Casting is obtained by
pouring the molten
metal in permanent
metallic dies, as the
metal is not refractory
its use is limited to low
melting point metals like
aluminium, zinc,
magnesium, copper, lead
and its alloys.

14. Pressure Die Casting
• One die is fixed and another
movable, a nozzle is connected
to goose neck which is immersed
in molten bath.
• Metal is injected into the die
cavity by moving the plunger
down.
• After solidification the dies are
opened and casting is ejected

15. Centrifugal Casting
• Axis symmetrical castings
can be produced (cylindrical)
• Huge size casting can be
produced
• Core is not required
• Uniform distribution of
mass

16. Investment Casting

17. Casting Defects
1. Blow holes : It is smooth almost spherical bubble inside the
casting.
2. Shrinkage cavity : It is flat rough cavity formed due to improper
design of gating system.
3. Hot cracks : Smooth edged single cracks formed due to
differential contraction of the casting
4. Cold cracks : Sharp edged branched cracks formed due to
improper handling of castings
5. Misrun : It is incomplete casting resulting from incomplete filling
of mould
6. Cold shut : It is incomplete fusion of two streams of liquid metals
7. Runout : Leakage of molten metal from parting plane.
8. Mis match : It is due to improper matching of cope and drag
parts of the casting

18. Inspection of Casting
1. Visual Inspection : Common defects such as rough surface, shifts,
surface cracks can be detected by a visual inspection of casting
2. Pressure Test : The pressure test is conducted on a casting to be used
as a pressure vessel.
3. Magnetic Particle Inspection : It is practised to check for very small
voids and cracks at or just below the surface of a casting of a
ferromagnetic material.
4. Dye-Penetrant Test : This method is used to detect invisible surface
defects in a nonmagnetic casting. The casting is sprayed by a dye
containing a fluorescent material. The surface to be inspected is then
wiped,dried and viewed in dark.
5. Ultrasonic Inspection : An oscillator is used to send an ultrasonic signal
through the casting . The signal is transmitted through the casting and
any discontinuity will reflect the signal back.

19. References
• Production Technology by ACE
• http://www.custompartnet.com/wu/SandCasting
•http://thelibraryofmanufacturing.com/metalcasting
_basics.html
• http://www.castingstechnology.com/