| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength steel sheet exerting excellent deep drawability while securing strength of 980 MPa or more, and to provide a method for warm working the same. <P>SOLUTION: The high-strength steel sheet has a component composition containing, by mass, 0.02 to 0.3% C, 1 to 3% Si, 1.8 to 3% Mn, 0.1% or less P, 0.01% or less S, 0.001 to 0.1% Al, and 0.002 to 0.03% N, with the remainder being iron and impurities. The high-strength steel sheet has a structure containing, in terms of area ratio relative to the entire structure, each of the following phases: 50 to 85% bainitic-ferrite; 3% or more retained γ; 10 to 45% martensite and the retained γ; and 5 to 40% ferrite. The ratio (Mnγ<SB POS="POST">R</SB>/Mnav) of the Mn concentration (Mnγ<SB POS="POST">R</SB>) in the retained austenite to the average Mn concentration (Mnav) in the entire structure is 1.2 or more, based on the Mn concentration distribution obtained by means of EPMA line analysis. <P>COPYRIGHT: (C)2012,JPO&INPIT |
