Introduction of Casting Processes

1. Introduction of Casting Processes

2. FLUID FLOW IN CASTING
 FOR THE SUCCESSFUL CASTING AND
CONTROL OF THE SOLIDIFICATION
PROCESS IT REQUIRES ADEQUATE
FLUID (MOLTEN METAL AND
ENTRAPPED GASES) FLOW IN THE
SYSTEM.

3. Open and Closed Mould

4. The Gating System
 A: pouring basin
 B: Weir
 C: Sprue
 D: Sprue well
 E: Runner
 F: Ingates
 G: Runner break up
 H: Blind
 J: Riser

5. Pattern geometry

6. Pouring basin

7. DESIGN OF SPURE

8. DESIGN OF SPURE
 RELATIONSHIP BETWEEN HEIGHT AND ANY CROSS
SECTIONAL AREA AT ANY POINT IN THE SPURE IS
GIVEN BY


 A1/A2 = (H2/H1)^(.5)

9. THE BASIC FUNCTION OF THE
GATING SYSTEM IN SAND
CASTING IS TO TRAP
CONTAMINANTS (SUCH AS
OXIDES AND OTHER
INCLUSIONS) IN THE MOLTEN
METAL BY HAVING THE
CONTAMINANTS ADHERE TO THE
WALLS OF GATING SYSTEM

10. DESIGN OF RUNNER

11. Location of Risers and Open and Closed
Risers
•Top riser has the
advantage of
additional pressure
head and smaller
feeding distance over
the side riser.
•Blind risers are
generally bigger in
size because of
additional area of
heat conduction.

12. Why Riser?
 The shrinkage occurs in three stages,
1. When temperature of liquid metal drops from pouring to
zero temperature
2. When the metal changes from liquid to solid state, and
3. When the temperature of solid phase drops from freezing
to room temperature
 The shrinkage for stage 3 is compensated by providing shrinkage
allowance on pattern, while the shrinkage during stages 1 and 2 are
compensated by providing risers.
 The riser should solidify in the last otherwise liquid metal will start
flowing from casting to riser. It should promote directional
solidification. The shape, size and location of the risers are
important considerations in casting design

13. TYPES OF GATE
 TOP GATE
 BOTTOM GATE
 PARTING GATE
 STEP GATE

14. TOP GATE

18. Use of chaplets to avoid shifting of cores
Possible chaplet design
and casting with core

19. Use of chills

20. The Gating System
1. Minimize turbulent flow so that absorption of
gases, oxidation of metal and erosion of mould
surfaces are less
2. Regulate the entry of molten metal into the mould
cavity
3. Ensure complete filling of mould cavity, and
4. Promote a temperature gradient within the casting
so that all sections irrespective of size and shape
could solidify properly

21. PERMEABILITY OF THE
WALLS
 PERMEABILITY OF THE WALLS IS
IMPORTANT BECAUSE OTHERWISE
LIQUID WILL PERMEATE THROUGH THE
WALLS AND FLOW RATE WILL
DECREASE AS THE FLUID WILL FLOW.

22. Cleaning and Finishing
1. Casting is taken out of the mould by shaking and the
Moulding sand is recycled often with suitable
additions.
2. The remaining sand, some of which may be embedded
in the casting, is removed by means of Shot blasting.
3. The excess material in the form of sprue, runners,
gates etc., along with the flashes formed due to flow of
molten metal into the gaps is broken manuaaly in case
of brittle casting or removed by sawing and grinding in
case of ductile grinding.
4. The entire casting is then cleaned by either shot
blasting or chemical pickling.
5. Sometimes castings are heat treated to achieve better
mechanical properties.