| 摘要 |
PURPOSE:To easily obtain a high tension cold rolled steel sheet having satisfactory workability and strength by cold rolling a steel consisting of specified amts. of C, Si, Mn, P, Al, Nb, N and Fe and by heat treating the resulting cold rolled steel sheet under prescribed conditions. CONSTITUTION:A steel consisting of, by weight, 0.02-0.15% C, <=0.1% Si, 0.9-3.5% Mn, 0.02-0.15% P, <=0.1% Al, 0.01-0.2% Nb, <=0.01% N and the balance Fe is manufactured by refining and cold rolled. The resulting cold rolled steel sheet is annealed by heating to the Ac1 transformation point - the recrystallization finish temp. and it is cooled at >=2 deg.C/sec cooling rate in the temp. range of 600-300 deg.C.
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