Method of lost foam casting of aluminum-silicon alloys
AssigneeBrunswick Corporation
InventorRaymond J. Donahue
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Abstract
An improved method of lost foam casting of aluminum silicon alloys utilizing a pattern formed of an expandable polymeric foam having a decomposition temperature less than 300.degree. C., and a heat of decomposition less than 600 Joules per gram. The foam pattern preferably has a heat of fusion less than 60 Joules per gram and a bulk density in the range of one to four pounds per cubic foot. The lost foam casting procedure has particular use when casting hypereutectic aluminum silicon alloys containing from 16 to 30% silicon, and eliminates the "liquid styrene" defect which occurs when casting such alloys in a lost foam process utilizing conventional polystyrene foam patterns. When casting hypoeutectic aluminum-silicon alloys containing from 5% to 8% silicon, the method eliminates the "fold" defect.
Claims12
A method of lost foam casting of aluminum-silicon alloys, comprising the steps of forming a pattern of expanded polymeric foam in the configuration of an article to be cast, said polymeric foam having a decomposition temperature less than 300.degree. C., a heat of fusion less than 60 Joules per gram, and a heat of decomposition less than 600 Joules per gram, placing the pattern in a mold, filling the mold and the cavities in the pattern with a free flowing generally inert particulate material, and introducing a molten aluminum-silicon alloy into contact with the pattern with the heat of the molten metal acting to liquefy and vaporize the pattern and the molten metal filling the void created by vaporization of the pattern to provide a cast part substantially identical in configuration to said pattern.
The method of casting an engine block for a marine internal combustion engine, comprising the steps of forming a pattern of expanded polyalkylene carbonate foam in the configuration of an engine block, placing the pattern in an outer mold, filling the mold and cavities in the pattern with unbonded free flowing sand, and introducing a molten hypereutectic aluminum silicon alloy comprising 16% to 30% by weight of silicon, 0.3% to 1.5% by weight of magnesium, up to 4.5% copper and the balance aluminum into contact with the pattern with the heat of said molten alloy acting to liquify and vaporize the pattern, said molten metal filling the void created by vaporization of the pattern to provide a cast engine block substantially identical in configuration to said pattern.
Dependencies are inferred from the claim text.