PURPOSE: To prevent a blowhole defect by using a thoroughly dried stalk and pressurized gas to pour the melt of Al, etc. into a sand mold then controlling the descending speed of the molten metal to a specific value or below.
CONSTITUTION: A drag 12 and a cope 13 are both formed as a sand mold. The molten Al in a crucible 3 and a cavity 15 are connected via a sprue 14 and the stalk 20. The surface of the molten metal 4 is pressurized by the thoroughly dried gas, then the molten metal 4 is packed through the sprue 14 into the cavity 15 by passing through the stalk 20. The pressurization of the gas is then stopped and evacuation is executed. The pressure in the crucible 3 is released at 0.23kg/cm2/sec speed, etc. by which the unsolidified melt below the sprue 14 is controlled to ≤100mm/sec descending speed. The blowhole defect generated by the sand mold is prevented by the above-mentioned method.
SUZUKI TOSHIO
SHIMAMURA MASAHIRO
HARADA MASAYUKI
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