Shape and Crystal Structure of Common Artificial Sand
In terms of macro morphology, several kinds of artificial sand are similar to spheres with smooth surface. However, due to the different raw materials and production methods, the surface state and roundness of sand are different from each other from the micro aspect of surface morphology. It is pointed out that the micro bulges and cracks on the surface of raw sand are conducive to the adhesion of binder, to improve the strength.
From the perspective of chemical composition, the four kinds of artificial sand for casting belong to aluminosilicate refractories, and the mineral phase generally follows the principle of Al2O3-SiO2 binary phase diagram.
The artificial special sand has an approximate spherical particle shape, but the roundness of Fused Ceramic sand produced by melting and air crushing method is obviously better than that of special sand produced by other sintering methods. At the same time, due to its large bulk density and high surface hardness, Fused Ceramic sand has unique advantages as EPC filling sand.
Heat Storage Coefficient
About the concept of heat storage coefficient: the heat storage coefficient represents the cooling capacity of the material (the cooling capacity commonly used in casting). The greater the heat storage coefficient, the greater the solidification and cooling rate of the casting, the higher the compactness of the casting, and the lower the tendency of sand sticking. Zircon sand, chromite sand and Fused Ceramic sand have the characteristics of good chilling effect.
Performance of Common Artificial Sand
Fused ceramic sand, CB sand, lunar sand, and ceramiste sand, these four kinds of special artificial sand have high fire resistance and low thermal expansion rate, which can avoid the defects of casting veins caused by large thermal expansion of silica sand due to phase transformation. However, in the case of large stainless steel and carbon steel parts requiring higher fire resistance, higher fire resistance and smoother surface quality will achieve better casting effect. In addition, because there are many closed pores in sintering sand making, the thermal conductivity of molding sand is poor, and the mold collapsibility is not good when casting low melting point nonferrous alloys.
Except that the bulk density of Fused Ceramic sand is lower than that of chromite sand, some main thermophysical properties, such as thermal conductivity, thermal expansion rate and fire resistance, are similar to that of chromite sand. In terms of particle shape and crushing resistance, it is much better than chromite sand, but the price is only about 1/2 of chromite sand. The result of comprehensive analysis is that Fused Ceramic sand is an ideal substitute for chromite sand. At present, many large steel casting manufacturers have used Fused Ceramic sand to replace chromite sand as surface sand, especially developed "30 mesh + fine powder" Fused Ceramic sand as surface sand, and achieved greater economic benefits.