Common Non-Ferrous Casting Problems and Their Causes


 

Shrinkage Cracks and Cavities

Sand Wash

Burning Into Sand

Gas Holes

Rough or Pitted Surface

Cold Shut

Scab

Weak or Discontinuous Structure

Tin or Lead Sweat

Wormy Surface

Core Blow

Burning Into Cores

Misrun

Solid Inclusions

 


 

Shrinkage Cracks and Cavities: Cracks or cavities formed by the metal pulling itself apart while cooling in the mold.

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Cold Shut: Lack of joining of metal where two streams meet, leaving a crack, or a weakness, which may result in a crack.

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Wormy Surface: Elongated depressions near the gate, like worm tracks, Often filled with zinc oxide. Sometimes shows a fracture.

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Sand Wash: Rough lumps of metal at some points of casting and rough holes at other points.

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Scab: A rough slightly raised surface on casting often with sand embedded.

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Core Blow: A smooth depression on inner surface of a cored casting or gas pocket above cored cavity.

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Burning Into Sand: Rough sandy appearances of outer part of casting with some sand embedded in the surface.

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Weak or Discontinuous Structure: Minute cavities or voids between large crystals. In bronze, badly discolored fractures, granular in appearance.

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Burning Into Cores: Rough appearance of inner part of casting with sand imbedded. Metal fins penetrating into core holding grains of sand.

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Gas Holes: Holes under or near surface of casting. Inside of gas cavities untarnished.

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Tin or Lead Sweat: Spots, lumps, or a thin layer of white metal on the surface of the casting.

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Misrun: An incompletely filled mold cavity. Lugs or corners not filled out.  A smoothly rounded hole through the wall of the casting.

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Rough or Pitted Surface: Rough surfaces on castings, some angular fairly deep pits but with no apparent sand wash or crush.

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Solid Inclusions: Pieces of non-metallic materials or separate particles of metal showing in the walls of the casting when fractured or machined.

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