| 摘要 |
PROBLEM TO BE SOLVED: To form a crown surface part with a good accuracy by forming a metal mold for forming the crown surface part of a piston out of porous material having a porosity of a specified value, in a metal mold for forming a cavity, and pressurizing molten metal filled in the cavity with pressure of a specified value, and carrying out casting. SOLUTION: A metal mold 21 is provided with upper and lower molds 22, 23, and a core 24, and a cavity 25 of a piston is formed in the metal mold 21. The upper mold 22 is shaped so as to form a crown surface part of the piston, and is sintered and molded in a porous shape to a density having a porosity of 3 to 30% using powder of die steel and stainless steel having heat resistance, and a pouring gate communicating with the inside of the cavity 25 is formed on a lower mold 23. After filling of molten metal 30 into the cavity 25 is completed, the sprue is sealed with a sealing device 38, and the molten metal 30 in the cavity 25 is pressurized with prescribed pressure selected in a range of 0.01 to 2.0 kg/cm2 according to a porosity. After casting is completed, mechanizing is applied on a part eliminated the crown surface part, in a piston taken out from the mold. |
