PRESSURE REDUCING METHOD FOR MOLD, AND PRESSURE REDUCING DEVICE USED FOR THE PRESSURE REDUCING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a pressure reducing method for a mold where the formation of a thin metal film is suppressed upon casting, thus defects such as a gas defect, a foreign matter defect, a cold shut and a cold lap are prevented, and a satisfactory casting product can be obtained.;SOLUTION: The method for reducing pressure in a mold where a molten metal supply process is performed while evacuating the inside of the mold includes: a stage where, till the completion of the initial stage of molten metal supply in the molten metal supply process, the inside of the mold is evacuated under a prescribed first suction pressure close to the atmospheric pressure; and a stage where, from the point of time after the completion of the initial stage of the molten metal supply, the prescribed first suction pressure is changed to a prescribed second suction pressure lower than the above, so as to evacuate the inside of the mold.;COPYRIGHT: (C)2009,JPO&INPIT