Casting Defects and Remedies

Defect	Causes	Remedies
Blow holes	Excessive moisture in the sand Low permeability of sand Sand grains are too fine Sand is rammed too hard Insufficient venting	Maintain proper moisture content of the sand Use sand of proper grain size Avoid excessive ramming Provide sufficient vent holes
Mis-run and cold shut	Too thin sections and wall thickness Improper gating systems Damaged pattern Slow and intermediate pouring Poor fluidity of metal Improper alloy composition	Use hotter metals Inspect and replace patterns regularly Design proper gating and risers Use chills and padding
Drop	Low strength of the sand Soft ramming Insufficient reinforcement of hanging sections	Adopt proper moulding, gating, and melting techniques
Dirt	Improper handling of mould Presence of sand slag particles in molten metal	Proper handling of mould Adopt proper moulding, gating, and melting techniques Use of chills and padding
Shifts	Misalignment of pattern parts, due to worn or damaged patterns Misalignment of moulding box or flask equipment	Ensure proper alignment of the pattern and moulding boxes Correct mounting of pattern on pattern plates, etc.
Fins and flash	Incorrect assembly of moulds and cores Improper clamping of the mould Excessive rapping of the pattern Insufficient weight on the top part of the mould	Adopt proper moulding, gating, and melting techniques Ensure sufficient weight is placed on the top part of the mould
Swell	Improper ramming Low strength of the mould Pouring the metal too rapidly	Proper ramming of sand Ensure uniform flow of molten metal into the mould
Run-out	Defective moulding boxes Inadequate mould weights Excessive pouring pressure	Take corrective measures in respect of the above reasons
Warpage	Inadequate and improper gating, runners, and risers Continuous large flat surface on casting	Modify the casting design Ensure proper directional solidification
Hot tears (Hot Cracks)	Abrupt changes in section Poor design Incorrect pouring temperature	Avoid abrupt changes in section Use correct pouring temperature Ensure even rate of cooling