Lost-Wax Method

a method for the production of shaped castings from metal alloys in a one-piece hot shell mold that does not evolve gases. The cavity of such a mold is generated through removal of the casting pattern by burning, melting, or dissolution.

In the lost-wax method, a pattern composition is pressed into a mold (usually a metal mold), forming the casting pattern and the gating. The pattern composition is removed, most frequently by melting it with hot water. The resulting shells are calcined at 800°-1000°C and then filled with metal.

The lost-wax method makes possible the casting of articles of complex shape weighing a few grams to several dozen kilograms. The castings have wall thicknesses of 0.5 mm or more, a surface roughness corresponding to the fourth to sixth classes of the Soviet standard, and higher dimensional precision than in other casting methods. These characteristics were the basis for the previous name of the method, “precision casting.” The dimensions of castings produced by the lost-wax process are very close to the dimensions of the finished part, which leads to a decrease in cost through reduction of mechanical treatment.

The lost-wax method is used to produce cast objets d’art, jewelry, and dental prostheses. One of the oldest casting methods, it has become widely used as a result of improvements in casting technology and studies of the properties of organosilicon compounds.

Casting by the lost-wax method is concentrated in the USSR in highly mechanized foundries, which produce up to 2,500 tons of finished castings per year. One of the achievements of Soviet industry is the creation of fully automated processes of lost-wax casting production.