Reduction of gum emitted from shell mold during casting aluminum alloy

The amount of gum emitted from sepiolite-coated shell molds decreased with increasing amount of sepiolite during casting aluminum alloy. This reduction of gum resulted from the catalytic decomposition of the gum by sepiolite coated on the surface of the mold. When about 60 g/m2 sepiolite was coated on the mold, the amount of gum emitted was about 10 mg per mold. It was also observed to be effective in reducing gum by thinly coating the mold with inorganic porous materials such as activated carbons and alumina. The amount of the non-volatile in the gum emitted from sepiolite-coated shell mold was about 1/10 times that from the uncoated shell mold. The non-volatile consisted of high molecular fatty acids and esters, and these modified ingredients having high boiling point, or other higher molecular weight esters, acids, and ketones. The amount of gum attached to the metal mold plate during casting aluminum alloy at 1123 K using sepiolite-coated shell core was remarkably smaller than that using uncoated shell core.