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Sand Casting Materials Called Molding Materials
Jun 26, 2017

  Sand casting materials called molding materials, used in sand casting materials used to be known as type sand, used to make sand core molding material called core sand. Sand is usually formed from the original sand (sand or sand),Sand casting clay and water in a certain proportion, in which the clay is about 9%, the water is about 6%, the rest is the original sand. Sometimes add a small amount such as pulverized coal, vegetable oil, sawdust and other additions to improve the performance of sand and core sand.

  The quality of the sand and core sand directly affects the quality of the castings, and the bad quality of the moulding sand will make the castings produce pores, sand holes, sticky sands and sand clamps. Good sand should have the following properties:

  1) Breathable type

  High-temperature metal liquid poured into the mold, the type is filled with a lot of gas, these gases must be discharged smoothly in the mold, the type of sand this can let gas through the performance called breathability.Sand casting Otherwise, it will cause the castings to produce holes, insufficient watering and other defects. The permeability of the mould is influenced by the granularity of sand, clay content, water content and compaction degree of sand type. The finer the granularity of sand, the higher the content of clay and water, the higher the compaction degree of sand, the worse the permeability is.

  2) Strength

  The ability of the sand to resist external damage is called strength. Molding sand must have high enough strength to form, carry, and close the box without causing collapse, pouring will not destroy the mold surface. The strength of the sand is also not too high, otherwise it will be due to permeability, decline in the fall, so that castings have defects.

  3) Fire Resistance

  High-temperature metal liquid poured into the mold to produce a strong thermal effect, so the molding sand to resist high-temperature heat action is the ability of fire resistance. If the molding material is poor in fire resistance,Sand casting the castings are easy to produce sticky sand. The more SiO2 content in the sand, the larger the type sand particles, the better the fire resistance.

  4 plasticity

  The finger-shaped sand is deformed under the external force, and the ability of the shape can be completely maintained after removing the external force. Molding materials of good plasticity, easy to shape operation, made of sand shape accurate, clear outline.

  5) Concessions

  Castings in condensation, volume shrinkage, the type of sand should have a certain capacity to be compressed, called concessions. The yield of moulding sand is not good, the casting is easy to produce internal stress or crack.Sand casting The more compacted sand, the worse the yield. Adding sawdust and other things in the sand can improve the yield.