Method of lost foam casting of aluminum-silicon alloys

摘要

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 DEG 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.