Differential pressure casting process

In a casting process which comprises;

• employing a split mold defining a cavity when closed and having in its lower portion a gate communicating with said cavity, and a stoke having an upper end connected to said gate and a lower end immersed in a bath of molten aluminum or its alloy in a holding furnace,
• increasing the pressure of said bath or decreasing the pressure of said cavity to introduce said molten aluminum or alloy into said cavity, and
• allowing said molten aluminum or alloy in said cavity to solidify to yield a cast product;
• the improvement wherein said mold is held at a temperature of 350.degree. to 430.degree. C. when said molten aluminum or alloy has a temperature higher than its melting point by 50.degree. to 80.degree. C. when introduced into said cavity.

In a casting process which comprises;

• employing a split mold defining a cavity when closed and having in its lower portion a gate communicating with said cavity, and a stoke having an upper end connected to said gate and a lower end immersed in a bath of molten metal or its alloy in a holding furnace,
• increasing the pressure of said bath or decreasing the pressure of said cavity to introduce said molten metal or alloy into said cavity,
• allowing said molten metal or alloy in said cavity to solidify to yield a cast product, and
• opening said mold to remove said product therefrom;
• the improvement wherein an inert gas is supplied into said stoke to effect the separation of said molten metal or alloy from said product, and the surface of said separated molten metal or alloy in said stoke is kept above that of said molten metal or alloy in said holding furnace when said product is cooled to solidify and removed from said mold.

In a casting process which comprises:

• employing a split mold defining a cavity when closed and having in its lower portion a gate communicating with said cavity and a stoke having an upper end connected to said gate and a lower end immersed in a bath of molten aluminum or its alloy in a holding furnace,
• increasing the pressure of said bath or decreasing the pressure of said cavity to introduce said molten aluminum or alloy into said cavity, and
• allowing said molten aluminum or alloy in said cavity to solidify to yield a cast product;
• the improvement wherein filling said stoke and said cavity with an inert gas before initial introduction of said molten aluminum or alloy into said cavity, maintaining molten aluminum or alloy in said stoke, and introducing inert gas in said stoke in contact with the surface of said molten aluminum or alloy before removal of cast product and each successive introduction of molten aluminum or alloy into said cavity.