| 摘要 |
A method for manufacturing a high strength steel sheet having excellent formability suitable for the material of an automotive part is provided, where the tensile strength (TS) is 980 MPa or more and the total elongation (EL) is 25% or more. A steel slab having a chemical composition containing C: 0.03% to 0.35%, Si: 0.5% to 3.0%, Mn: 3.5% to 10.0%, P: 0.100% or less, S: 0.02% or less, and the remainder comprising Fe and incidental impurities on a percent by mass basis is hot-rolled, then a heat treatment is performed, in which an achieved temperature of Ac 1 to Ac 1 + 100°C is held for 3 minutes or more, subsequently, cold rolling is performed at a rolling reduction of 20% or more and, thereafter, annealing is performed, in which an achieved temperature of Ac 1 - 30°C to Ac 1 + 100°C is held for 1 minute or more. |
