The application and the requirement of silica sand in foundry industry

The mainly requirement of silica sand in casting is the original sand SiO2 content. Nature of the original sands contain some other minerals, such as feldspar, mica, iron oxide, and alkaline oxides, the presence of these minerals decreased the melting point of refractory material silica sand. It usually use sintering point instrument to test the sand in the mineral composition in high temperature melting point, such as 98% of SiO2 melting point is 600 ℃, 90% of SiO2 melting point is 1400 ℃. In principle with SiO2 is higher, the melting point will be higher, pouring makes molten iron oxide is small, the effect of casting surface chemical adhering sand is less, but contain high SiO2 sand expansion and phase change is very big, the sand is easy broken, poor reusability, besides could improve casting surface finish, harmful to the other casting quality and futile, such as easy to cause the casting sand, slag, crisp fall, deformation and crack. Sand broken sand binder dosage increased, and the casting surface integral dent and increase internal porosity and improve the original acquisition cost, therefore should be controlled w (Si), in order to meet the casting surface does not produce chemical adhering sand, using the appropriate additional measures, such as green sand and coal powder, resin sand with ferric oxide and refractoriness and other measures to improve coating.