Production method of castings and gas-permeable casting mold
A method for producing a casting using a gas-permeable casting mold comprising a cavity composed of a production cavity and a flow path, the flow path comprising a sprue through which a gravity-poured melt flows downward, and a runner connecting the production cavity to the sprue, comprising gravity-pouring a metal melt in a volume smaller than that of the entire cavity and larger than that of the production cavity into the gas-permeable casting mold; supplying a gas through the sprue to push the metal melt in the flow path, thereby pushing the metal melt upward in the production cavity, so that the production cavity is filled with the metal melt; in a hypothetical equilibrium state in which a hypothetical liquid fills the production cavity by the supplied gas, setting the volume of the metal melt to be poured to be equal to the volume of the hypothetical liquid, such that the surface height hs of the hypothetical liquid remaining in the flow path after filling the production cavity, the height h 1 of the lowest ceiling portion of the runner, and the height h 2 of a point at which a ceiling of the runner is connected to the sprue, meet the relation of h 2 >hs>h 1.
1. A method for producing a casting using a gas-permeable casting mold comprising a cavity composed of a production cavity and a flow path, said flow path comprising a sprue through which a gravity-poured melt flows downward, and a runner connecting said production cavity to said sprue, comprising
gravity-pouring a metal melt in a volume smaller than that of the entire cavity and larger than that of said production cavity into said gas-permeable casting mold;
supplying a gas through said sprue to push said metal melt in said flow path, thereby pushing said metal melt upward in said production cavity, so that said production cavity is filled with said metal melt;
in a hypothetical equilibrium state in which a hypothetical liquid free from solidification, evaporation, expansion, shrinkage, intrusion into a casting mold, and the absorption and desorption of a gas fills said production cavity by the supplied gas, calculating the volume of said hypothetical liquid, such that the surface height hs of said hypothetical liquid remaining in said flow path after filling said production cavity, the height h 1 of the lowest ceiling portion of said runner, and the height h 2 of a point at which a ceiling of said runner is connected to said sprue, meet the relation of h 2 >hs>h 1 ; and the height ht of the highest bottom portion of said runner meet hs<ht; and
setting the volume of said metal melt to be poured to be equal to the volume of said hypothetical liquid.
2. The method for producing a casting according to claim 1 , wherein in an equilibrium state of a hypothetical liquid achieved by supplying said gas, the volume of said hypothetical liquid is calculated such that the volume of a metal melt to be poured is set to be equal to the volume of said hypothetical liquid.