| 摘要 |
PROBLEM TO BE SOLVED: To provide a method by which a high-strength cold-rolled steel sheet can be produced with good productivity, the high-strength cold-rolled steel sheet being improved in elongation (EL), stretch-flangeability (λ), bendability (R), and balance of these properties (TS×EL×λ/1000), being also excellent in composite workability as evaluated by an Erichsen test, and having a tensile strength of 980 MPa or more.SOLUTION: A steel product satisfying a prescribed constituent composition is held and soaked for fifty seconds or more at a temperature of the Acpoint or above, then cooled at an average cooling rate of 15°C/second or more to an optional temperature T satisfying the following expression (1) and held for 5-180 seconds in a temperature range satisfying the following expression (1), then heated to a temperature range satisfying the following expression (2) and held for 50 seconds or more in the temperature range, and then cooled. 300°C≤T1(°C)<400°C...(1). 400°C≤T2 (°C)≤540°C...(2). |
