| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength steel sheet that has a strength of at least 980 MPa class, has excellent formability at room temperature, and exhibits an effect of reducing a forming load at a warm temperature, and a method of warm-forming the same. <P>SOLUTION: The high-strength steel sheet includes a component composition comprising, in mass%, C: 0.02 to 0.3%, Si: 1 to 3%, Mn: 1.8 to 3%, P: not more than 0.1%, S: not more than 0.01%, Al: 0.001 to 0.1%, and N: 0.002 to 0.03% with the balance being iron and impurities; and has a structure including respective phases comprising, in an area ratio relative to the entire structure, bainitic ferrite: 50 to 85%, retained γ: at least 3%, the sum of martensite and the retained γ: 10 to 45%, and ferrite: 5 to 40%, wherein the concentration of C (Cγ<SB POS="POST">R</SB>) in the retained austenite is 0.3 to 1.2 mass%, a part or the whole of N in the component composition is solid solution N, and the amount of the solid solution N is 30 to 100 ppm. <P>COPYRIGHT: (C)2013,JPO&INPIT |
