| 摘要 |
PURPOSE:To obtain a casting mold which is easy to mold, collapses easily when applied with water thereon and has excellent resistant to thermal impact and thermal stress by drying a molding consisting of hydrate of magnesium sulfate together with gypsum, a refractory material, etc. in two stages at a specific temp. CONSTITUTION:Hydrate of magnesium sulfate is mixed with gypsum in the amt. larger than the amt. of the gypsum, and a powder refractory material and water are added thereto. Further a granular refractory material such as silicon is mixed therewith to form a slurry, and the slurry is charged into a mold under reduced pressure. The gypsum is removed from the mold after it is allowed to solidify. The molding removed from the mold is subjected to primary drying in a drying oven kept at <=120 deg.C and after the primary drying, the molding is further subjected to secondary drying at >=200 deg.C. The fine crystal of magnesium sulfate is thus gathered in the surface layer part by flotation and the product having excellent dimensional accuracy and a good casting surface is obtained without application of coating on the core surface. |
