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, 45 to 85% bainitic-ferrite, 3% or more retained γ, 10 to 50% martensite and the retained γ, and 5 to 45% ferrite, wherein: the C concentration of the retained γ is 0.6 to 1.2 mass%; the frequency ratio (X<SB POS="POST">KAM≤0.4°</SB>) when the KAM value is 0.4° or lower, relative to the entire frequency and the area ratio (V<SB POS="POST">α</SB>) of ferrite in a KAM value frequency distribution curve satisfy the relationship of X<SB POS="POST">KAM≤0.4°</SB>/V<SB POS="POST">α</SB>≥0.8; and the number of cementite particles having a circle equivalent diameter of 0.1 μm or more and present at the surface boundary of the ferrite and a hard second phase is three or less per 1 μm<SP POS="POST">2</SP>of the hard second phase. <P>COPYRIGHT: (C)2012,JPO&INPIT |