Patent ID: 11248275

Abstract:
A warm-workable high-strength steel sheet having superior warm workability and residual ductility after warm working, and a method for manufacturing such steel sheets. The warm-workable high-strength steel sheet has a chemical composition including, in mass %, C: 0.05 to 0.20%, Si: not more than 3.0%, Mn: 3.5 to 8.0%, P: not more than 0.100%, S: not more than 0.02%, Al: 0.01 to 3.0% and N: not more than 0.010%, the balance being Fe and inevitable impurities. The steel sheet has a microstructure that includes, in area fractions, 10 to 60% retained austenite, 10 to 80% ferrite, 5 to 50% martensite and 0 to 5% bainite, the C content in the retained austenite being less than 0.40 mass %.