| 摘要 |
PROBLEM TO BE SOLVED: To provide a pressure reducing method for a reduced pressure mold and its suction piping device with which even in the case the thickness of a forming film or casting film onto a lost foam patter is not made thick, the penetration of molten metal during pouring can be prevented and the exhausting capacity of generated gas in not lowered. SOLUTION: In the pressure reducing method during pouring the molten metal into the reduced pressure mold molded with a suction molding flask communicated with a vacuum source through the suction piping, the forming film or the lost foam pattern, a heat resistant granular filling material and a shut-off member, the gas in the suction molding flask is sucked in the highly sucking state at the initial stage of pouring the molten metal, and on and after the intermediate stage of pouring the molten metal, the suction in the ?suction molding flask is changed over into the lower sucking state than the sucking state at the initial stage of pouring the molten metal to pour the molten metal.
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