Abstract
In order to make the removal of plaster mold from casting, easy water soluble plaster molds containing MgSO4 were examined. The plaster containing 75∼84% CaSO4 and 16∼25% MgSO4 was easily shaped and showed considerably high transverse strength when dried. The plaster which contained some refractory fillers for foundry use, also showed increase in transverse strength by the addition of MgSO4, because of the bonding of the refractory materials with MgSO4. It was shown that molten aluminum poured into this plaster mold does not react with the mold, and castings with good surface smoothness are obtained. In the mixture of CaSO4, MgSO4 and H2O, the separation of MgSO4 takes place first and particles of CaSO4 are bonded with MgSO4⋅7H2O. Therefore this plaster is soluble in water.
