Patent ID: 8813827

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 and forming an embryonic ingot having an external solid shell and an internal molten core; (b) 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; (c) providing direct cooling to the embryonic ingot by directing a supply of a first coolant liquid in a first amount onto an outer surface of the embryonic ingot emerging from said region where the metal is peripherally confined; (d) removing the first coolant liquid from the outer surface of the embryonic ingot at a first location along 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 first coolant; and (e) providing further direct cooling to said outer surface of the embryonic ingot following said removing of said first coolant liquid by applying a second coolant liquid to said outer surface at a second location, further along the ingot from the first location in said direction of advancement, where a cross section of the ingot perpendicular to the direction of advancement intersects a portion of said molten core, said second coolant liquid being applied in a second amount that is less than said first amount of said first coolant liquid, and that is effective to quench said embryonic ingot without preventing said temperatures of said core and shell from subsequently approaching a convergence temperature of 425° C. (797° F.) or higher for a period of time of at least 10 minutes following said quench.