| 摘要 |
Producing a high-strength cold-rolled steel sheet with low YP and excellent uniformity by hot-rolling and cold-rolling steel containing, by % by mass, 0.01 to 0.08 C, 0.2 or less Si, 0.8 to 1.7 Mn, 0.03 or less P, 0.02 or less S, 0.3 or less sol. A1, 0.01 or less N, and 0.4 to 2 Cr, and where 1.9 < [Mneq] < 3 and 0.34 <= [%Cr] / [%Mn]. The steel is heated at less than 3 °C/sec to 680 to 740°C, annealed at 740 to 820°C, cooled at 2 to 30 °C/sec to 650°C; cooled at 10 °C/sec or more to 650 to Tc°C and cooled at 0.2 to 10 °C/sec to Tc°C to 200°C. Tc = 410 - 40 x [%Mn] - 30 [%Cr] and [Mneq] is [%Mn] + 1.3 x [%Cr].
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