Patent ID: 7516775

Claim:
A method of casting a metal ingot, comprising the steps of: (a) supplying molten metal from at least one source to a region where the molten metal is peripherally confined, thereby providing the molten metal with a peripheral portion; (b) cooling the peripheral portion of the metal, thereby forming an embryonic ingot having an external solid shell and an internal molten core; (c) advancing the embryonic ingot in a direction of advancement away from the region where the molten metal is peripherally confined while supplying additional molten metal to said region, thereby extending the molten core contained within the solid shell beyond said region; (d) cooling an outer surface of the embryonic ingot emerging from the region where the metal is peripherally confined by directing a supply of coolant liquid onto said outer surface; and (e) removing an effective amount of the coolant liquid from the outer surface of the embryonic ingot at a location on the outer surface of the ingot where a cross section of the ingot perpendicular to the direction of advancement intersects a portion of said molten core such that internal heat from the molten core reheats the solid shell adjacent to the molten core after removing said effective amount of coolant, thereby causing temperatures of said core and shell to each approach a convergence temperature of 425° C. or higher for a period of time of at least 10 minutes.