| 摘要 |
PURPOSE:To efficiently execute the venting and to prevent development of the casting defect by forming venting gap having concentric circle state with a core between the outer mold body and the inner mold body as utilizing a difference of thermal expansion rate developed between the outer mold body and the inner mold body. CONSTITUTION:The outer mold body 22 is heated by molten metal in a cavity, and so expanded outward of the radius direction and in the other hand, as the inner mold body 23 is forcely cooled, its expansion rate is a little as compared with the outer mold body 22. As a result, at between a small diameter cylindrical part 22a of the outer mold body 22 and a small diameter part 23a of the inner mold body 23, the annular venting gap (g1) having the concentric circle state with the core 1 is formed. As the molten metal is filled up into the fiber reinforced body by pressurizing of the molten metal, a binder is decomposed by the molten metal, to generate gas and the gas is exhausted to outside through venting gap (g1), the first groove 321, gap (g2), the second groove 322, a large diameter part 17c and venting passway 19. As the gap (g1) is formed as annular state along circular arc at the upper end face of the strengthened fiber body, the venting is efficiently executed. Further, the remaining gas in the cavity and the fiber reinforced body and the gas, etc., contained in the molten metal are exhausted through the gap (g1).
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