Method for producing castings, casting apparatus, and gas-blowing nozzle used in casting apparatus
A method for producing a casting by pouring a metal melt by gravity into a gas-permeable casting mold having a cavity comprising at least a sprue, a runner and a product-forming cavity, comprises pouring a metal melt into a desired cavity portion including the product-forming cavity through the sprue, the melt being in a volume smaller than the volume of an entire cavity of the gas-permeable casting mold and substantially equal to the volume of the desired cavity portion; supplying a gas to the desired cavity portion through the sprue before the desired cavity portion is filled with the poured melt, so that the melt fills the desired cavity portion and solidifies; the gas being supplied from a gas-blowing nozzle fit into the sprue.
1. A method for producing a casting by pouring a metal melt by gravity into a gas-permeable casting mold having a cavity comprising at least a sprue, a runner and a product-forming cavity, comprising the steps of
pouring a metal melt into a desired cavity portion including said product-forming cavity through said sprue, said melt being in a volume smaller than the volume of an entire cavity of said gas-permeable casting mold and substantially equal to the volume of said desired cavity portion; and
supplying a gas to said desired cavity portion through said sprue before said desired cavity portion is filled with the poured melt, so that said melt fills said desired cavity portion and solidifies;
said gas being supplied from a gas-blowing nozzle fit into said sprue;
wherein:
the sprue has a cup portion having a tapered wall surface and an introducing hole portion extending downward from the cup portion and having a fitting portion having a tapered wall surface, and the gas-blowing nozzle has a side surface tapered at an angle which is substantially the same as that of the tapered wall surface of the fitting portion, wherein the gas-blowing nozzle is brought into contact with the tapered wall surface of the fitting portion for fitting, and wherein the gas-blowing nozzle has a gas-ejecting bore having an increasing diameter in a gas-supplying direction, wherein the gas-ejecting bore of the gas-blowing nozzle has a diameter continuously increasing from D 3 to D 2 in a gas-supplying direction in a range from a point upstream of a gas outlet end surface of the gas-blowing nozzle by distance L 2 to the gas outlet end surface, and with the sprue having a diameter D 1 after the fitting portion in a gas flow direction,
0.9×D1≤D2≤1.0×D1,
0.5×D2≤D3≤0.8×D2, and
1.1×D1≤L2≤1.2×D1.
2. The method for producing a casting according to claim 1 , wherein said gas-blowing nozzle is pushed in a gas-ejecting direction.
3. The method for producing a casting according to claim 1 , wherein the gas-blowing nozzle is rotated slidably on the tapered wall surface of the sprue.
4. A casting apparatus comprising
a gas-permeable casting mold having a cavity comprising at least a sprue into which a metal melt is poured, a runner constituting a flow path of said melt poured through said sprue, and a product-forming cavity to be filled with the melt supplied through said runner;
a gas-blowing nozzle for supplying a gas into a cavity of said gas-permeable casting mold through said sprue, such that a metal melt poured into said gas-permeable casting mold by gravity fills only a desired cavity portion including said product-forming cavity; and
a means for supplying said gas to said gas-blowing nozzle;
said gas-blowing nozzle having a portion fit into said sprue for supplying said gas to said cavity through said sprue;
wherein:
the sprue has a cup portion having a tapered wall surface and an introducing hole portion extending downward from the cup portion and having a fitting portion having a tapered wall surface, and the gas-blowing nozzle has a side surface tapered at an angle which is substantially the same as that of the tapered wall surface of the fitting portion, wherein the gas-blowing nozzle is brought into contact with the tapered wall surface of the fitting portion for fitting, and wherein the gas-blowing nozzle has a gas-ejecting bore having an increasing diameter in a gas-supplying direction, wherein the gas-ejecting bore of the gas-blowing nozzle has a diameter continuously increasing from D 3 to D 2 in a gas-supplying direction in a range from a point upstream of a gas outlet end surface of the gas-blowing nozzle by distance L 2 to the gas outlet end surface, and with the sprue having a diameter D 1 after the fitting portion in a gas flow direction,
0.9×D1≤D2≤1.0×D1,
0.5×D2≤D3≤0.8×D2, and
1.1×D1≤L2≤1.2×D1.
5. The casting apparatus according to claim 4 , which has a mechanism of pushing said gas-blowing nozzle in a gas-ejecting direction.