| 摘要 |
Provided is a method for manufacturing a high strength steel sheet excellent in terms of formability having a TS of 980 MPa or more and a TS×EL of 24000 MPa·% or more. The method for manufacturing the high strength steel sheet having excellent formability comprises hot-rolling a steel slab having a chemical composition containing, by mass%, C: 0.03% or more and 0.35% or less, Si: 0.5% or more and 3.0% or less, Mn: 3.5% or more and 10.0% or less, P: 0.1% or less, S: 0.01% or less, N: 0.008% or less and the balance comprising Fe and inevitable impurities, coiling the hot-rolled steel sheet at a temperature range of the Ar 1 transformation point to the Ar 1 transformation point + (the Ar 3 transformation point - the Ar 1 transformation point) / 2, cooling the coiled steel sheet down to 200°C or lower, heating and holding the cooled steel sheet at a temperature range of the Ac 1 transformation point - 200°C to the Ac 1 transformation point for 30 minutes or more, pickling the heated steel sheet, cold-rolling the pickled steel sheet under the condition that the rolling reduction is 20% or more, and heating and holding the cold-rolled steel sheet at a temperature range of the Ac 1 transformation point to the Ac 1 transformation point + (the Ac 3 transformation point - the Ac 1 transformation point) / 2 for 30 seconds or more. |
