MATERIAL FOR HIGH-STRENGTH STEEL SHEET, HOT ROLLE.

摘要

Provided is a high-strength steel sheet having tensile strength of at least 980MPa and a TS-El balance of at least 30,000MPa%, and further having excellent surface quality and formability by increasing the slag surface quality and internal qualities such as segregation during casting. The high-strength steel sheet comprises: a component composition including 0.08-0.30% of C, at most 2.0% of Si, greater than 3.0% and at most 10.0% of Mn, at most 0.05% of P, at most 0.01% of S, at most 1.5% of Al, 0.010-0.300% of Ti and 0.0020-0.0100% of N, all in a range that satisfies 1.1=(Ti+Mn1/2/400)/(0.01+5N)=6.0; and a structure including a residual austenite phase and a ferrite phase. The ratio ?Mn/Mn of the average Mn concentration (?Mn) of the residual austenite phase to the average Mn concentration (Mn) of the ferrite phase is at least 1.5.