| 摘要 |
PROBLEM TO BE SOLVED: To improve the coating suitability and corrosion resistance of end face of steel sheet after shearing, in an IF type cold rolled steel sheet and its surface treated steel sheet. SOLUTION: The cold rolled steel sheet has a composition consisting of, by mass, <=0.0080% C, <=0.10% Si, <=0.80% Mn, 0.010-0.025% S, <=0.05% P, <=0.1% Al, <=0.005% N, 0.02-0.15% Ti, and the balance essentially Fe and satisfying (Mn+0.1)×S=0.006 to 0.015% and (Ti/48)/(C/12+N/14)=0.8 to 4.0. The surface treated steel sheet is obtained by using this cold rolled steel sheet as a starting sheet and applying surface treatment to it. If necessary, either or both of <=0.05% Nb and 0.0003-0.0020% B can be incorporated into the composition.
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