| 摘要 |
PURPOSE:To prevent the mold cracking and to reduce the cost by adding slag having the specific wt% of MgO, SiO2, Al2O3, FeO, CaO, etc., respectively to silica sand at prescribed adding range %, to compose a molding sand. CONSTITUTION:The molding sand for shell molding is formed by adding ferro- nickel ore smelting slag composing of 27-33% MgO, 48-58% SiO2, 1-3% Al2O3, 5-11% FeO, 4-6% CaO and remaining part of impurities to the silica sand at 15-70% adding ratio. This slag composition has almost the same coefficient of linear expansion as olivine sand's and so, it has almost the same coefficient of thermal expansion and is prevented from the mold cracking at the time of casting. And, as gas generating volume is reduced caused by slag composition, prevention of rough surface and carburization is effectively executed. Further, as the slag is gotten at low cost, the cost of the molding sand is remarkably reduced.
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