(1) chromite sand has good resistance to alkaline slag, does not react with iron oxide, etc.; therefore, in practical applications, chromium ore sand can avoid thermal chemical sticky sand;
(2) During the molten metal casting process, the solid phase sintering of the chromite sand itself prevents the penetration of the molten metal, thereby preventing mechanical sand sticking;
(3) The thermal conductivity of chrome ore is several times greater than that of silica sand, which can increase the cooling rate of castings. Therefore, chrome ore can play the role of external cold iron in practical applications;
(4) The most harmful impurity in chromite sand is carbonate (CaCO3·MgCO3). When it comes into contact with high-temperature metals, it decomposes CO2 and easily causes blowholes in castings; usually, the chromium ore containing carbonate passes 900° C-950°C high-temperature roasting to decompose the carbonate.
(5) The effect of the size of chromite sand on its refractoriness The size of chromite sand can significantly affect its refractoriness. In the past, it was believed that too coarse particle size would reduce the surface finish of castings. However, the sand molds made of chrome ore and the surface of sand cores are usually sprayed with a certain thickness of paint, so that the surface finish of castings is hardly affected.
In general, the suitable particle size of the sand mold used for the modeling of large steel castings is 40/70 mesh, and the particle size of the sand used for small and medium-sized parts is 50/100 mesh. There are also some special cases such as some small water pump industries, considering economic factors, replacing zirconia sand with chromite sand, the chromite sand purchased by these factories requires very fine, 70/140 mesh, even 100/200 mesh, etc.
