METHOD FOR PREVENTING SURFACE CRACKING OF CONTINUOUS CAST SLAB UNDER LARGE REDUCTION OF HOT ROLLED WIDTH

摘要

PROBLEM TO BE SOLVED: To provide a method for preventing a surface cracking of a continuous cast slab containing Al, N that occurs when a hot rolled width is largely reduced.;SOLUTION: In the method that molten steel containing Al, N is continuous-casted into a cast slab and, by heating the slab, the hot rolled width or the hot rolled width/ thickness of the slab is reduced, a target composition of Al, N is determined in advance, and also a target cooling depth from the surface of the slab that reaches a temperature of Ar1 point is determined in advance from a target heat temperature, from a target width draft that is defined by a reduction amount of the width and by the width of the slab before the reduction, and from a target ratio of the thicknesses of the slab before and after the reduction of the thickness of the slab so that a thickness of not less than 10 mm is secured for a sound layer thickness of the surface layer of the slab after the hot rolled width is reduced. The surface cracking of the continuous cast slab that occurs when the hot rolled width is largely reduced is prevented by cooling the slab so that a resulting cooling depth shall be deeper than that of the target cooling depth, or by controlling the heat temperature of the slab or by controlling the draft of the width of the slab.;COPYRIGHT: (C)2002,JPO