PROBLEM TO BE SOLVED: To provide a blind riser structure or riser sleeve structure which can securely feed molten metal to a product portion.;SOLUTION: A void is formed in the riser even after pouring the molten metal and the expansion of the void is made easy or the suction of gas from a casting mold is made easy. If the air permeability of the casting mold is high, for example, air permeability at all or part of the top of the riser is made lower than that at the other parts, and the higher the pressure of the molten metal acting on the riser is, the lower the air permeability is made. Alternatively, a portion in the riser is sectioned with a porous material, or a substance which issues or generates gas is put into a portion in the riser, so that a void is formed in the riser. The substance to be used as the gas generating material is metal hydride, hydrogen absorbing alloy, hydroxide or oxide generating CO gas by reaction with carbon in the molten metal. A substance generating not only gas but heat is also included and used.;COPYRIGHT: (C)2010,JPO&INPIT
展开▼
