| 摘要 |
PROBLEM TO BE SOLVED: To make the baking hardenability and delayed aging properties of a steel sheet compatible and to secure stable bake hardening quantity by allowing it to have a specified compsn. contg. C, Si, Mn, P, S, Al, N, Ti and Nb, also allowing the contents of C, Nb, Ti and N to satisfy specified relation and moreover adding Mo thereto in a specified range. SOLUTION: This steel sheet contains, by weight, 0.0013 to 0.007% C, 0.001 to 0.08% Si, 0.01 to 0.9% Mn, 0.001 to 0.10% P, <=0.030% S, 0.001 to 0.1% Al and <=0.01% N. Then, the content of Ti is made to the range of 0.001 to 0.025% and Nb to the range of 0.001 to 0.040%, and the ranges are allowed to also satisfy k=C%-12/93×Nb%-12/48×(Ti%-48/14×N%)>=0.0008, where, in the case Ti%-48/14×N%<=0, they are zero. Moreover, Mo is added in such a manner that the Mo concn. satisfies 0.005<=Mo%<=0.25, and, also, 0.1×√k<=Mo%<=5×√k is satisfied.
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