Patent ID: 7617864

Claim:
A method of direct chill casting an Al—Mg alloy that is susceptible to hot tearing during casting, which method comprises; melting an Al—Mg alloy that is susceptible to hot tearing during casting and delivering the molten metal to a first chamber of a co-casting apparatus to form a first body of molten metal; melting the same Al—Mg alloy and delivering the molten metal to a second chamber of a co-casting apparatus to form a second body of molten metal; casting a core ingot from said first body of molten metal, and co-casting a cladding layer from said second body of molten metal on at least one outer surface of said core ingot, said cladding layer being co-cast onto said core ingot at a position where said metal of the core ingot at said surface has not undergone complete solidification following casting; said thickness of said cladding layer relative to said core ingot being made effective to impart a finer microstructure to said cladding layer than to said core ingot, and to eliminate hot tears during casting.