Cored wire for treating molten metal and method of manufacture

A cored wire comprising a reactive metal inner core and a sheath comprising a continuous lock seam for introducing a reactive metal into a bath of molten metal produced by:

• extruding said reactive metal into an elongated core wire having a generally cylindrical shape with a continuous flat surface;
• concurrently partially roll forming a sheath using a multi-step roll forming process, said sheath partially formed into a generally trough shaped member with peripheral edges having formed therein surfaces adapted to be mated and formed into a lock seam;
• inserting said core wire into said trough shaped portion of said partially formed sheath with said core wire positioned to accommodate a lock seam to be formed in said sheath;
• and
• finishing said cored wire by further roll forming steps to close said sheath around said core wire and forming a continuous lock seam in said sheath.