METHOD FOR CASTING METAL

PURPOSE:To improve product quality by packing a granular back-up material into the spacing between the walls of a casting mold and outside flask, disposing an air passage to the aperture atop the outside flask and pouring a molten metal into the mold while evacuating the inside of a cavity to a vacuum. CONSTITUTION:The box-shaped outside flask 7 having a suction port 8 on the side face is provided and the granular backup material 10 consisting of metallic balls, etc., is laid to a uniform thickness on the base thereof. The air passage communicating with the layer of the back-up material 10 from the casting mold plane is then formed via a semi-cylindrical trough 14 and a vinyl sheet 15 atop the casting mold 11. Vacuum evacuation is executed from all of the base, side face and front face of the mold 11 when vacuum casting is executed by evacuating the air in the cavity 13 to a vacuum after the mold 11 is disposed in the flask 7. Generation of defects in the casting product formed in the cavity 13 is, therefore, prevented and the product quality is improved.