| 摘要 |
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,;0.05≦[% C]−(12/47.9)×[% Ti*]≦0.10 (1),;where;Ti*=[% Ti]−(47.9/14)×[% N]−(47.9/32.1)×[% S] (2). |
