Patent ID: 7250221

Claim:
A method of producing a clad metal ingot suitable for rolling to form a clad metal sheet, which method comprises the steps of: providing a solid core ingot having an upper rolling face and at least two undercut cavities extending inwardly into the ingot from said upper rolling face at mutually spaced positions; blocking all, or all-but-one, of said at least two cavities against molten metal entry to form one or more blocked cavities, and providing a casting core extending outwardly from said rolling face in alignment with each of said one or more blocked cavities, the or each casting core having a shape effective to produce an undercut void in a subsequently cast cladding layer; casting a molten metal on said upper rolling face around said casting core(s) to produce a composite ingot having a solid cladding layer cast on said upper rolling face of said core ingot, except where covered by said casting core(s); removing said casting core(s) to form one or more undercut voids in said cladding layer and unblocking said blocked cavity(ies), thereby interconnecting aligned void(s) and cavity(ies); and filling said aligned void(s) and cavity(ies) with a molten metal and allowing said metal to solidify to form at least one metal lug therein attaching said cladding layer to said core ingot.