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Metal Casting Technologies : June 2007
METAL Casting Technologies March 2007 53 NAME & DESCRIPTION OF DEFECT CAUSES Cold Shuts • Lack of fluidity in the metal resulting from These appear as lines, irregular in contour and extent, on the casting surface. either low metal pouring temperature or They seldom appear singly and are more prominent on cope or vertical surfaces. the presence of oxide films on the metal. Cuts or Washes • The result of erosion of the mold surface by Appear as irregular, rough area on the casting surface. Sand is embedded in the flowing molten metal. patches or firmly adheres to the metal surface. • Too low dry strength of the molding sand. • Low hot deformation of the sand. • In green sand, may be the result of low, or too high, moisture content. • Low green sand strength. • Light ramming of the molds resulting in low mold hardness of below 80 hardness. Dirt Spots • Slag or refractory material from the ladle. Small spots, ranging from round to irregular shapes, on the casting surface • Sand mold may be eroded in places. resulting from dirt entering the mold with the metal, eroded from the gate • Mold hardness is too low. or mold wall by the flowing metal. • Ladles not well maintained or poorly prepared. Drops • Reflected heat in slowly poured castings Irregularly shaped areas on the casting surface, especially on the cope side, acting on poorly prepared molds. looking like enlarged dirt spots, and are a result of portions of the mold falling • Low green deformation and low mold on the rising metal surface. hardness resulting in mold collapse. • Low sand green strength. • Too thick mold coatings. • Too slow pouring of the mold.