Patent ID: 7025838
Filing Date: 2006-04-11
Classification: C21D,C22C,C23C

Abstract:
1. A method for making a ferritic stainless steel sheet, the method comprising the steps of: preparing a steel slab containing not more than about 0.1% C, not more than about 1.0% Si, not more than about 1.5% Mn, not more than about 0.06% P, not more than about 0.03% S, about 11% to about 23% Cr, not more than about 2.0% Ni, about 0.5% to about 3.0% Mo, not more than about 1.0% Al, not more than about 0.04% N, at least one of not more than about 0.8% Nb and not more than about 1.0% Ti, and the balance being iron (Fe) and unavoidable impurities, satisfying relationship (1): where C, N, Nb, and Ti in relationship (1) represent the C, N, Nb, and Ti contents by mass percent, respectively; heating the steel slab at a temperature in the range of about 1,000° C. to about 1,200° C.; hot-rough-rolling the steel slab at a rolling temperature of at least one pass of about 850° C. to about 1,100° C. by a reduction of about 35%/pass or more; hot-finish-rolling the slab at a rolling temperature of at least one pass of about 650° C. to about 900° C. by a reduction of about 20 to about 40%/pass to prepare a hot-rolled sheet; annealing the hot-rolled sheet at a temperature in the range of about 800° C. to about 1,100° C.; cold-rolling the resulting annealed sheet at least twice with intermediate annealing therebetween, said cold rolling being performed at a gross reduction of about 75% or more and a reduction ratio (reduction in the first cold rolling)/(reduction in the final cold rolling) in the range of about 0.7 to about 1.3; and finish annealing the cold-rolled sheet at a temperature in the range of about 850° C. to about 1,050° C.