Casting Defects

1.  Casting defects may be defined – Those
characteristics that create a deficiency or
imperfection to quality specifications
imposed by design and service
requirements.
 Reduces total output, increases the cost of
production.
 Even in modern foundries the rejection rate as
high up to 20% of the number of casting produced.

2. Casting Defects
Surface defects Internal defects
Incorrect chemical compo. Unsatisfactory mech.
properties

3.  Surface defects : May be visible on surface,
including incorrect shape & size, flashes, poor
surface finish.
Internal defects : These are present in interior of
cast. Can be revealed through NDT techniques.
Incorrect chemical composition – Formation of
undesirable microstructure.
Unsatisfactory mechanical properties – These
are due to low quality, poor percent of usage.

4.  SWELL
 FIN
 Gas HOLES
 SHRINKAGE CAVITY
 HOT TEAR
MISRUN AND COLD SHUT

5.  Swell - enlargement of the mould cavity by metal
pressures, results – localized or overall enlargement of
castings
Causes
 Insufficient ramming of the sand.
 Rapid pouring of molten metal.
 Also due to insufficient weighting of mould.
Remedies –
 Avoid rapid pouring.
 provide sufficient ram on sands.
 proper weighting of moulds.

6.  A thin projection of metal – not a part of cast.
Usually occur at the parting of mould or core
sections.
Causes –
 Incorrect assembly of cores and moulds,
 Improper clamping.
 Improper sealing.
Remedy –
 Reduces by proper clamping of cores and mould.

7. FINS OR FLASH

8. Gas Holes
Clean, smooth walled rounded holes of varying size
from pin heads to full section thickness, often
exposed during machining.
Causes
 Low pouring temperature.
 Gases blowing from the mould.
 Excessive turbulence during pouring.
 Moisture condensed on densors and chills.
Remedies
 Use correct pouring temperature and check with
pyrometer.

9. Continue…
 Increase permeability of sand and check grinding.
 Warm densors and chills.
 Modify gating to reduce turbulence, use sivex
filter.

10. Gas HOLE

11. Next Member
Waqar Sarwar

12. It is a void or depression in the casting caused
mainly by uncontrolled solidification.
Causes:
1. Pouring temperature is too high causing liquid
shrinkage.
2. Failure to supply liquid feed metal.
3. Pre mature solidification.
Remedies :
Apply principles of casting, reduce the
pouring temperature and provide adequate
risers, feeders, which supply the molten metal to
compensate the shrinkage.

13. Shrinkage cavity

14.  One of the main defects is hot tearing or hot
cracking, or hot shortness. Irrespective of the name,
this phenomenon represents the formation of an
“irreversible failure (crack) in the still
semisolid casting.”
 Cause:
The inadequate compensation of solidification
shrinkage by melt flow in the presence of thermal
stresses.
 Remedy
 Avoid excessive ramming.
 Controlled ramming should be done.

15. Hot Tears
ME 6222: Manufacturing Processes and Systems 7
Prof. J.S. Colton

16. Castings not fully form heaving lines or seam of
discontinuity or holes with rounded edges through
casting walls.
Causes:
 Incomplete fusion where two streams of metal
meat.
 Metal freezes before mold is filled.
 Die too cold.
Remedies:
 Increase pouring temperature.
 Increase die temperature or improve venting.
 Increase permeability of sand.

17. Casting Defects
ME 6222: Manufacturing Processes and Systems 6
Prof. J.S. Colton