Probable Causes and Suggested Remedies of Various Casting Defects

Probable causes and suggested remedies of various casting defects such as blow holes, shrinkage, porosity, misruns, hot tears, mental penetration, cold shuts, cuts and washes, inclusions, fusion, drops, shot metal, shift, crushes, rat-tails, swells, hard spot, run out, fins and fash, spongings and warpage are given in the below table.

Various casting defects

Various casting defects. Image source: Green Mechanic

S.no
Name of Casting Defect
Probable Causes
Suggested Remedies
1 Blow holes
  1. Excessive moisture content in molding sand.
  2. Rust and moisture on chills
  3. Cores not sufficiently baked.
  4. Excessive use of organic binders.
  5. Molds not adequately vented.
  6. Molds not adequately vented.
  7. Molds rammed very hard.
  1. Control of moisture content.
  2. Use of rust free chills, chaplet and clean inserts.
  3. Bake cores properly.
  4. Ram the mold less hard.
  5. Provide adequate venting in mold and cores.
2 Shrinkage
  1. Faulty gating and risering system.
  2. Improper chilling.
  1. Ensure proper directional solidification by modifying gating, risering and chilling.
3 Porosity
  1. High pouring temperatures.
  2. Gas dissolved in metal charge.
  3. Less flux used.
  4. Molten metal not properly degassed.
  5. Slow solidification of casting.
  6. High moisture and low permeability.
  1. Regulate pouring temperature.
  2. Control metal composition.
  3. Increase flux proportions.
  4. Ensure effective degassing.
  5. Modify gating and risering.
  6. Reduce moisture and increase the permeability of mold.
4 Misruns
  1. Lack of fluidity ill molten metal.
  2. Faulty design.
  3. Faulty gating.
  1. Adjust proper pouring temperature.
  2. Modify design.
  3. Modify gating system.
5 Hot Tears
  1. Lack of collapsibility of core.
  2. Lack of collapsibility of mold.
  3. Faulty design.
  4. Hard ramming of mold.
  1. Improves collapsibility of core and mold.
  2. Modify casting design.
6 Mental penetration
  1. Large grain size and used.
  2. Soft ramming of mold.
  3. Molding sand or core has low strength.
  1. Use sand having finer grain size.
  2. Provide hard ramming.
  3. Suitably adjust pouring temperature.
7 Cold shuts
  1. Lack of fluidity in molten metal.
  2. Faulty design.
  3. Faulty gating.
  1. Adjust proper pouring metal.
  2. Modify design.
  3. Modify gating system.
8 Cuts and washes
  1. Low strength of mold and core.
  2. Lack of binders in facing and core stand.
  3. Faulty gating.
  1. Improve mold and core strength.
  2. Add more binders to facing and core sand.
  3. Improve gating.
9 Inclusions
  1. Faulty gating.
  2. Faulty pouring.
  3. Inferior molding or core sand.
  4. Soft ramming of mold.
  5. Rough handling of mold and core.
  1. Modify gating system.
  2. Improve pouring to minimize turbulence.
  3. Use of superior sand of good strength.
    Provide hard, ramming.
10 Fusion
  1. Low refractoriness in molding sand.
  2. Faulty gating.
  3. Too high pouring temperature of the metal.
  4. Pouring facing sand.
  1. Improve refractoriness of sand.
  2. Modify gating system.
  3. Use Lower pouring temperature.
  4. Improve the quality of facing sand.
11 Drops
  1. Low green strength in molding sand and core.
  2. Too soft ramming.
  3. Inadequate reinforcement of sand and core projections. 
  1. Increase green strength of sand mold.
  2. Provide harder ramming.
  3. Provide adequate reinforcement to sand projection and cope by using nails and gaggers.
12 Shot metal
  1. Too low pouring temperature.
  2. Excess sulphur contests in metal.
  3. Faulty gating.
  4. High moisture content in molding sand.
  1. Use proper pouring temperature.
  2. Reduce sulphur content.
  3. Modify gating of the system.
13 Shift
  1. Worn-out or bent clamping pins.
  2. Misalignments of two halves of pattern.
  3. Improper support of core.
  1. Repair or replace the pins, for removing the defect.
  2. Repair or replace dewels with cause misalignment.
  3. Provide adequate support to the core.
  4. Increases strength of both mold and core.
14 Crushes
  1. Defective core boxes producing over-sized cores.
  2. Worn out core prints on patterns producing undersized seals for cores in the mild.
  3. Careless assembly of cores in the mold.
  1. Repair or replace the pins, for removing the defect.
  2.  Repair or replace dowels with cause misalignment.
15 Rat-tails or buckles
  1. Continuous large flat surfaces on casting.
  2. Excessive mold hardness.
  3. Lack of combustible additives in molding sand.
  1. Break continuity of large flat grooves and depressions.
  2. Reduce mold hardness.
  3. Add combustible additives to sand.
16 Swells
  1. Too soft ramming of mold.
  2. Low strength of mold and core.
  3. Mold not properly supported.
  1. Provide hard ramming.
  2. Increase the strength of both mold and core.
17 Hard spot
  1. Faulty metal composition.
  2. Faulty casting design.
  1. Suitable charge metal composition.
  2. Modify casting design.
18 Run out, Fins and Fash
  1. Faulty molding.
  2. Defective molding boxes.
  1. Improving molding techniques.
  2. Change the defective molding boxes.
  3. Keep weights on mold boxes.
19 Spongings
  1. Availability of dirt and swarf held in molten metal.
  2. Improper skimming.
  3. Because of more impurities in molten metal.
  1. Remove dirt dwarf held in molten metal.
  2. Skimming should be perfect.
  3. Fewer impurities in molten metal should be there.
20 Warpage
  1. Continuous large flat surfaces on castings are indicating a poor design.
  2. No dimensional solidification of casting.
  1. Follow principle of sufficient directional solidification.
  2. Make good castings design.
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