| 摘要 |
<p>The present invention provides a method for producing a high-strength cold-rolled steel sheet with low YP and excellent uniformity. A method for producing a high-strength cold-rolled steel sheet includes hot-rolling and cold-rolling steel having a composition which contains, by % by mass, over 0.01% to less than 0.08% of C, 0.2% or less of Si, 0.8% to less than 1.7% of Mn, 0.03% or less of P, 0.02% or less of S, 0.3% or less of sol. Al, 0.01% or less of N, and over 0.4% to 2% of Cr, and which satisfies 1.9 < [Mneq] < 3 and 0.34 ‰¤ [%Cr]/[%Mn], the balance being composed of iron and inevitable impurities; heating at an average heating rate of less than 3 °C/sec in a temperature range of 680°C to 740°C; annealing at an annealing temperature of over 740°C to less than 820°C; cooling at an average cooling rate of 2 to 30 °C/sec in a temperature range of the annealing temperature to 650°C; cooling at an average cooling rate of 10 °C/sec or more in the temperature range of 650°C to Tc°C represented by equation (1) below; and cooling at an average cooling rate of 0.2 to 10 °C/sec in the temperature range of Tc°C to 200°C. Tc = 410 - 40 × [%Mn] - 30 × [%Cr] ... (1) wherein [Mneq] represents the Mn equivalent shown by [Mneq] = [%Mn] + 1.3 × [%Cr] and [%Mn] and [%Cr] represent the contents of Mn and Cr, respectively.</p> |
