ArcelorMittal S.A.
METHOD FOR MAKING A HIGH STRENGTH MULTIPHASE STEEL

Abstract:

A method for producing a cold rolled and hot dip coated steel sheet is provided. The method includes casting a steel into a slab, reheating, hot rolling, cooling, coiling, descaling and cold rolling the slab. The cold rolled steel sheet is annealed so a layer of iron oxide forms on the surface with an internal oxidation underneath. The sheet is then heated so the surface is oxidized and the layer of iron oxide is fully reduced to obtain an internally oxidized depth between 200 nm and 100 .mu.m which includes one or more of Si, Mn, Al, Ti containing oxides. The sheet is then hot dip coated and cooled.