2013-12-25 by seoer8Coated sand is usually aluminium distearate lubricant , it coated sand flowability , caking resistance, gas evolution , both the strength and toughness of the heat affected. Calcium stearate are uniformly distributed in the coated sand , in the core- temperature softening resin, and calcium stearate has melted to form interpenetrating network that increases the flexibility of the resin , increasing the deflection of the shell , causing the thermal toughness is increased. Improved lubricating properties of calcium stearate -coated sand flowability , so the degree of compaction of the sand core is increased , thereby increasing the strength of the cores . Calcium stearate -coated sand can improve the thermal cracking, thermal cracking of coated sand is mainly due to thermal expansion and thermal shock stress , increases the amount of calcium stearate , thermal cracking time gradually delayed reasons is higher than the melting point of the resin of calcium stearate , to increase its thermoplastic advantageously increase the sand core , whereby the thermal stress relaxation sand core . Calcium stearate coated sand was added in the amount although rarely , but the effect is very large, coated sand to prevent caking , improve mobility, improve resistance to shelling and mold release . Not only affect the quality of calcium stearate coated sand strength, high temperature performance of the coated sand is also crucial ten million can not be discounted . A certain amount of silica in the synthesis of calcium stearate may be a greater degree of calcium stearate -coated sand to improve the high temperature performance.