Chill (foundry)

A Chill is an object used in making metal castings.

Molten metal when poured into a sand mold will cool at a certain rate, depending upon the thickness of the casting. If it is noticed that a shrink porosity defect occurs at a certain location in a casting, a molder can place a chill in the mold at that location, so that the heat of the molten metal is removed faster at that location. This can eliminate the porosity.

Most sand molds are made of silica sand. A chill is commonly made of iron, which has a higher density, a higher thermal conductivity and a higher thermal capacity than silica sand. Thus, the heat in the molten metal is pulled from the metal faster than the other areas of the mold which contain sand.

Chills can be made of many materials, including iron, copper or bronze, aluminum, graphite, silicon carbide or other materials. The shape normally follows the contour of the pattern where the chill will be placed. Other sand materials with higher densities, thermal conductivity or thermal capacity can also be placed in the mold where the heat removal needs to be accelerated. When molding with silica sand, chromite sand or zircon sand can be used in certain locations in this manner.