Casting Defects, Manufacturing Processes-2 (2141908)

1. Gandhinagar Institute
OF Technology(012)
Subject:- MP-2 (2141908)
Active Learning Assignment
Topic Name:- Casting Defects
Branch:- Mechanical B-1
Prepared By:- Jani Parth U.(150120119051)
Guided By:-Prof. Hitesh H. Patel

2. Content
i. Introduction
ii. Different type of casting defects
iii. Describe about casting defects
iv. Remedies for casting defects

3. i. INTRODUCTION
 Casting is a process of molten metal into a mould,
allowing it to cool and removing the metal from the
mould after solidify

4. Continue…
Production of casting involves
a large number of steps
including casting design,
pattern, making moulding,
melting , pouring , shake out ,
fettling ,inspection and
finishing.
Such unsatisfactory operations
result in a defective casting
which may be rejected at the
final stage .

5.  It is therefore necessary to understand the various defects that occur in
sand casting and the main factors that are responsible for their
occurrence.

6. ii. Different type of casting defects
1. Open blows , blow holes and pin hole porosity
2. Cracked casting
3. Bent and twisted casting
4. Fusion
5. Swell
6. Run out
7. Mismatch
8. Shrinkage faults
9. Metal penetration
10. Inclusions
11. Hot tears

7. 1. Open blows , Blow holes and Pin hole porosity
 Blow hole : They appear as cavities in a casting. When they
are visible on the upper surface of the casting, they are called
open blows. These blows are normally rounded and have
smooth walls.
 Pin hole porosity : This defect occurs in the casting the form
of pin hole porosity or gas porosity. These porosities are
caused by the gases absorbed by the molten metal. The gases
commonly absorbed and hydrogen, oxygen and nitrogen, the
later two forming oxides and nitrides respectively. It is mainly
hydrogen which is responsible for the pin hole porosity.

8. Remedies for open blow and blow holes remedies for pinhole porosity
1.moisture content 1.improved melting
2.providing proper venting 2.pouring methods
3.controlling binder 3.by prompting rapid rate
of solidification

9. 1. Cracked casting
 These are cracks caused by the inability of the casting to
cope up with internal stress resulting from solid shrinkage of
metal
 Immediately after solidification some metals have a low
strength and if stresses set up are high cracks develop in the
casting
• Remedies for cracked casting
1. Proper design of the casting
2. Avoiding joining of unequal sections,
3. Providing round corner fillets

11. 1. Bent or twisted casting
 When casting has wide variation in its sections, internal
stresses are often set up in wait due to differential cooling in
the thick and thin area.
 Remedy for bent or twisted casting
 provide suitable allowances on the pattern
 Controlling deformation by providing ribs
 Planning for uniforms cooling rate

13. 1. Metal penetration
If the sand grains used are very coarse or the metal pored has very high
temperature the metal is able to enter the spaces between sand grains to
some distance.
Such a sand becomes tightly wedged the metal and is difficult to remove.

14. 1. Fusion
 When the mould sand does not have enough refractoriness or the metal
is poured at very high temperature or the facing sand is of poor quality,
the sand may melt and fuse with casting surfaces
 This make it difficult to clean the castings and gives them a rough
glossy appearance
• Remedies for fusion
1. Using sand of enough refractoriness
2. Pouring at suitable temperature

15. 1. Run out
 Run out accurs when the molten metal leaks out of the mould during
pouring this is caused by defective moulding boxes fault clamping and
weighting and by casting too near the edge of the box
 Remedies
1. Modifying the moulding system
2. Selecting proper parting line
providing proper gating system

16. swell
 Swell is an enlargement or bulging of the casting surfaces resulting from
liquid metal pressure it accure due to poor ramming of the mould or not
properly reinforceing deep mould
 Remedies for swell
1. Proper ramming of the sand
2. And providing adequate support to the mould

17. mismatch
 Mismatch is caused by the cope and drag parts of the mould not
remaining in their proper position
 This is caused by loose box pin, inaccurate pattern dowel pins or
carelessness in placing the cope on the drag
 The deficiencies mentioned above must be attended to if mismatch is to
be avoided

18. SHRINCAGE FAULT
 Shrinkage fault are fault caused by improper directional direction
solidification , poor gating and risering and inadequate feeding
 Solidification leads to volumetric contraction which must be
compensated by feeding. If this compensation is inadequate either
surface shrinkage or internal shrinkage defects are produced making the
casting weaker
 Remedies for shrinkage fault
1.Providing proper gating system
2.Pouring a correct temperature and
3.Taking care of directional solidification

19. inclusions
 Inclusions are any foreign materials present in the cast metal. These
may be in the form of slag ,dirt, sand or nails
 Remedies
1. Using correct grade of moulding sand preventing any foreign items from
entering the mould

20. Hot tears
 Hot tears are ragged irregular internal or external cracks occurring
immediately after the metal has solidified
 Remedies
1. Improved casting design
2. Proper directional solidification
3. Uniform rate of cooling
4. Correct pouring temperature
5. Control of mould hardness