Patent ID: 6763876
Filing Date: 2004-07-20
Classification: B22C,B22D

Abstract:
A method of lost foam casting, comprising the steps of positioning a polymeric foam pattern corresponding in configuration to an article to be cast in a flask, connecting the pattern to a polymeric foam gating system located in the flask, introducing a finely divided inert material in the flask to surround the pattern and the gating system and fill internal cavities in the pattern, placing the flask and the pattern in an outer pressure vessel, positioning a pouring cup in the pressure vessel and connecting said pouring cup with said gating system, pouring a molten metal into the pouring cup, the heat of said molten metal acting to decompose the gating system and pattern with the molten metal filling the void created by decomposition of the polymeric foam material and the products of decomposition passing into the interstices of the finely divided material, sealing the pressure vessel with the pouring cup retained within said vessel, applying an external pressure in the range of 5 to 60 atmospheres to the molten metal in the pouring cup and to the finely divided material in the flask after sealing the vessel and before the molten metal has fully decomposed the pattern, maintaining said pressure on said molten metal until said molten metal fully decomposes the pattern, and continuing said pressure during solidification of said molten metal to produce a cast article corresponding in configuration to the pattern.