Patent ID: 6263950
Filing Date: 2001-07-24
Classification: B22C,Y10S

Abstract:
In a method of lost foam casting of metal including the principle steps of molding a foam pattern from polystirene beads expanded from raw polystirene beads that have a raw bead diameter from about 0.1 to about 0.6 millimeters and include a blowing agent, embedding said foam in a bed of loose foundry sand to form a loose sand mold about said pattern, and casting a molten metal into said sand mold to vaporize and replace said pattern in said mold, the improvement comprising, said blowing agent comprising at least about 40% by weight of a vaporizable compound having a diffusivity with respect to said pattern comparable to an alkane selected from the group consisting of isopentane, 2,2 dimethylpropane (neopentane), cyclopentane, 2,2 dimethylbutane, 2,3 dimethylbutane, hexane, cyclohexane, 2-methylpentane, and 3-methylpentane, and embedding said pattern in said foundry sand and casting said metal therein without first pretreating said pattern to stabilize it dimensionally.