Casting Defects and Remedies

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

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