[Studies on the contract of the casting. (II) Influence of core inside the cast (author's transl)].

A alloy has its constant coefficient of casting shrinkage, but its value is changed by casting conditions. This time, we studied with effect of core which exist inside the cast. The results obtained were as follows: 1. The more the strength of core material increases, the smaller the coefficient of casting shrinkage becomes. 2. The smaller the thermal expansion coefficient of core material in solid state, the smaller the casting shrinkage. 3. In case of Silver-Palladium-Gold casting alloy, its actual casting shrinkage (y) has a multiple correlation with the compressive strength (x1) of core material in high temperature, and with the difference (x2) of the original casting shrinkage of the alloy from the casting shrinkage of core material, that is, y = -0.0023x1 + 0.0087x2 + 1.4927 4. Silver-Indium casting alloy is hard to be influenced by the quality of core material, for the alloy has a small shrinkage force.