| 摘要 |
PURPOSE:The coat which comprises kneading the specific ratios of silica powder, iron oxide powder and magnesia powder in water or alcohols and which does not cause seizure and metal penetration at all. CONSTITUTION:The coat for casting which comprises using silica powder 5- 40wt%, iron oxide powder 3-20wt% and the rest magnesia powder as base materials and kneading these in water or alcohol. In this coat layer, pyroxene [(Mg. Fe)O.SiO2] closely adheres around magnesia particles. It may be presumed that this refractory layer separates molten metal and molding sand, thereby preventing metal penetration and seizure. In the 2-element system of MgO-SiO2, MgO.SiO2 exists at SiO2 40wt% and when FeO is added, pyroxene is formed. Further when FeO increases, the melting point lowers from 1557 deg.C-1305 deg.C. Since the coat layer loses refractory characteristic when melts, the maximum amounts of siliceous stone and iron oxide are limited from the pouring temperatures 1300-1350 deg.C of cast iron and their minimum amounts from the minimum pyroxene amount in terms of strength. |
