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Granularity Requirements

In “sand casting”, first put the lower half of the mold on a flat plate, put the sand box to fill the mold sand tightly and flatten, and after the lower mold is completed, turn the finished sand mold 180 degrees, put the upper half, sprinkle the parting agent, and place The upper sand box is filled with sand, compacted and flattened, the upper sand box is turned over 180 degrees, the upper and lower halves are taken out respectively, and the upper mold is turned over 180 degrees and the lower mold is combined. The sand mold is finished and waits for pouring. This set of craftsmanship is commonly known as “Furnishing”.

There are two requirements for the granularity:

  1. The sand on the 140 mesh sieve should be between 10-15%. Keeping more fine sand can reduce sand sticking on the surface of the casting. Moreover, the number of bonding bridges between sand particles will be increased, thereby reducing the brittleness of the molding sand and avoiding sand washing defects. In addition, it is beneficial to improve the temperature strength, dry strength and strength of the humidified layer after moisture migration of the molding sand.
  2. The sum of the 200 mesh sieve, 270 mesh sieve and the fine sand on the bottom plate should be as small as possible. Such fine sand has little effect on improving the surface quality of the casting, but it will make the mixed sand have a higher moisture content and reduce the air permeability of the molding sand. The sum of fine sand should generally be less than 4%