Characteristics and remedy of sand inclusion defects in sand casting

Defect characteristics and detection methods

There are sand grains in the casting, which can appear in all parts of the casting. It is found after the casting is cleaned, visual inspection or X-ray fluoroscopy and machining

Causes of formation
  1. There is too much ash in the sand mold, or the mold is too tight or uneven, or the grain size of the molding sand is uneven, so that the surface layer of the mold expands unevenly during heating and the sand falls off
  2. Due to the poor ventilation of the mold or the excessive humidity of the molding sand, the air flow is increased, and a large gas back pressure is formed after the alloy liquid is poured, which makes the surface sand of the mold fall off
  3. The binding force of molding sand or core sand is too poor
  4. Sand is removed due to collision or vibration of the mold
Prevention methods and remedial measures
  1. Increase the proportion of new sand in molding sand or replace all new sand to reduce the ash content in molding sand
  2. Control the compactness of the mold to ensure that the compactness of all parts of the mold is even
  3. Use the sand with coarse particles to replace the sand with too small particles
  4. Adopt molding sand and core sand with small gas generation
  5. Strictly control the humidity of molding sand
  6. Multi tie vent or place outlet riser
  7. The binder with strong adhesion is selected to prepare molding sand and core sand
  8. It is forbidden to collide or shake the assembled mold. In case of collision or vibration, the mold shall be opened to check whether there is sand or crack, and the mold shall be reassembled after cleaning and repairing
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