| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet and a plated steel sheet in which tensile strength effectively increases by press forming-heat treatment while maintaining excellent deep drawability in press forming. SOLUTION: The steel composition is controlled so as to contain <0.0050% C, 0.005 to 1.0% Si, 0.01 to 1.5% Mn, 0.005 to 0.050% Nb, 0.005 to 0.030% Al, 0.005 to 0.040% N, 0.0005 to 0.0015% B, <=0.1% P and <=0.01% S in the ranges satisfying the inequalities (1) and (2): N%>=0.0015+14/93.Nb%+14/27.Al%+14/11.B%...(l) and C%<=12/93.Nb%...(2) or further to contain one or more kinds selected from Cu, Ni and Mo, and the balance substantially Fe.
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