| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet capable of effectively suppressing the occurrence of pocket wave which is a matter of concern at the time of roll forming, and its manufacturing technique. SOLUTION: A steel, having a composition consisting of, by weight, <=0.1% C, <=0.5% Si, <=1.0% Mn, <=0.15% P, <=0.02% S, <=0.10% Al, <=0.01% N, <=0.2% Ti, <=0.2% Nb, <=0.2% V, <=0.01% B, and the balance Fe with inevitable impurities, is used. A sheet bar of this steel is finish rolled under the condition of <=35% draft per pass and >=60% total draft in the temperature region between the Ar3 transformation point and (Ar3 transformation point -100 deg.C). After this finish rolling is finished at >=(Ar3 transformation point -100 deg.C), cold rolling is performed and the resultant steel sheet is annealed. By this procedure, r-value in a direction perpendicular to rolling direction is regulated to <=0.7.
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