Method of Expendable Pattern Casting Using Sand with Specific Thermal Properties

摘要

A method of producing a metal casting utilizing an expendable polymeric foam pattern along with unbonded sand having specific thermal properties. The pattern, formed of a material such as polystyrene, has a configuration corresponding to that of the article to be cast. The pattern is placed with an outer flask and unbonded sand surrounds the pattern as well as filling the cavities in the pattern. The sand has a linear expansion of less than 1% from 0.degree.C to 1600.degree.C, a particle size of 0.001 inch to 0.015 inch, and a heat diffusivity greater than 1500 J/m2/.degree.K/s1/2. A molten metal, such as a hypoeutectic or hypereutectic aluminum silicon alloy or a ferrous alloy, is fed into the mold in contact with the pattern causing the pattern to vaporize with the vapor being entrapped within the interstices of the sand while the molten metal fills the space initially occupied by the foam pattern to produce a cast article. The physical properties of the sand enable articles to be cast having more precise tolerances.