| 摘要 |
PURPOSE:To develop covering sand for shell molds for Al alloys of superior collapsing properties after casting by using an aqueous soln. contg. methylol melamine and water-soluble org. compounds having hydroxyl groups as a binder. CONSTITUTION:As a binder for covering sand for shell molds for the purpose of shell mold casting of Al alloys, the one of the following composition is used without using any phenolic resin. Namely, while the aqueous soln. prepd. by mixing 10pts.wt. methylol melamine or alkylated methylol melamine and 5-100pts.wt. water-soluble org. compounds such as water-soluble cellulose derivatives, monosaccharides, polysaccharides, polyhydric alcohols and the like having hydroxyl groups and molding sand are being mixed, hot wind is blown to alloy water to evaporate, thereby covering the surfaces of the sand with the binder of the above-mentioned composition. At the time of molding shell molds, no malodors are produced and the collapsing properties of the molds after casting are excellent. |
