shrinkage, casting

shrinkage, casting,

n a volume change (contraction) that occurs when molten metal solidifies after being cast into a pattern mold. It is compensated for in three ways: by using the indicated water:powder ratio for the refractory investment to gain the maximal setting expansion of which that investment is capable; by exposing the investment to moisture as the refractory investment sets, causing some hydroscopic expansion; and by properly heating the mold to achieve thermal expansion. The total expansion must equal the contraction of the metal being cast.