PURPOSE: To facilitate the forcedly cooling casting of a thick casting having the advantage of a chilling material as it is and making up the defect easily developing void by using foaming material of a metal having high m.p. and high sp. heat as the chilling material.

CONSTITUTION: The metal foaming material having high m.p. and high sp. heat or granular metal powder sintered material is used as the chilling material to the necessary position at the inner surface side of a sand mold contacting with molten metal to control cooling speed. By this method, the reduction of micro-shrinkage and the chilling effect, such as the fining of the crystal grain by quickening the cooling speed are actually utilized as it is, and the defect worsening gas venting by using the metal plate can be made up. As the foaming metal material strictly keeping the porous degree to the constant is difficult to stably manufactured, the sp.gr. of the manufactured foaming metal, etc., is measured and the equal heat capacity is obtd. by changing the plate thickness so as to become the same wt., and the effective speed can be controlled.