Patent ID: 9617614
Date: 2017-04-11
CPC Classifications: B32B,C21D,C22C,C23C

Claim:
1. A method of manufacturing a high strength steel sheet having excellent formability comprising: preparing 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; hot-rolling the steel slab; subjecting the hot rolled steel sheet to a heat treatment in which an achieved temperature of Ac cold-rolling the steel sheet subjected to the heat treatment at a rolling reduction of 20% or more; and subjecting the cold rolled steel sheet to annealing in which an achieved temperature of Ac