| 摘要 |
<p>A thin steel sheet having sheet thickness ‰¤ 1.6 mm, but tensile strength ‰¥ 780 MPa and Young's modulus ‰¥ 240 GPa in transverse direction is provided, where the steel sheet has composition including, in mass%, C: 0.06-0.12 %, Si: 0.5-1.5 %, Mn: 1.0-3.0 %, P: 0.05 % or less, S: 0.01 % or less, Al: 0.5 % or less, N: 0.01 % or less, Ti: 0.02-0.20 %, and the balance being Fe and incidental impurities, where the composition satisfies relations of Formula (1) and (2), and microstructure such that ferrite phase has area ratio ‰¥ 60 % and martensite phase has area ratio of 15-35 %, ferrite and martensite phases are 95 % or more in total, average grain size of ferrite is ‰¤ 4.0 µm and that of martensite is ‰¤ 1.5 µm, 0.11 ‰¤ % C - 12 / 47.9 × % Ti * ‰¤ 0.15 , where Ti * = % Ti - 47.9 / 14 × % N - 47.9 / 32.1 × % S</p> |
