| 摘要 |
PROBLEM TO BE SOLVED: To produce a cold rolled steel sheet excellent in baking hardenability and cold aging resistance and to provide a method for producing the same. SOLUTION: This cold rolled steel sheet has a composition containing, by weight, 0.0010 to 0.0035% C, <=0.05% Si, 0.17 to 0.80% Mn, 0.01 to 0.08% P, 0.003 to 0.02% S, 0.03 to 0.1% SolAl, 0.003 to 0.02% Nb, also <=93/12 [C%] and <=0.0015% N also so as to satisfy C+N<=0.0035% and C/N>=1, and the balance Fe with inevitable impurities. The steel sheet is produced by performing hot rolling and cold rolling, next raising the temperature at the average temperature rising rate of 20 deg.C/sec or more, subsequently holding the steel sheet at 800 to 870 deg.C, then performing cooling at the average cooling rate of 5 to 20 deg.C/sec to 600 deg.C or less, furthermore cooling the steel sheet to 100 deg.C or less and thereafter performing skinpass rolling at a rolling ratio of 1.0 to 2.0%.
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