| 摘要 |
A thin steel sheet that has a composition which contains, in terms of mass%, 0.06-0.12% C, 0.5-1.5% Si, 1.0-3.0% Mn, up to 0.05% P, up to 0.01% S, up to 0.5% Al, up to 0.01% N, and 0.02-0.20% Ti and which satisfies relationships (1) and (2), with the remainder comprising Fe and incidental impurities, and that comprises, in terms of areal proportion, at least 60% ferrite phase and 15-35% martensite phase, the sum of the ferrite phase and the martensite phase being 95% or more, the ferrite and the martensite having average grain diameters of 4.0 µm or smaller and 1.5 µm or smaller, respectively. The steel sheet has a tensile strength and a Young's modulus, as measured in the direction perpendicular to the rolling direction, of 780 MPa or higher and 240 GPa or higher, respectively, and has a strength-elongation balance of 16,500 MPa·% or more. 0.11<=[%C]-(12/47.9)×[%Ti*]<=0.15 (1) Ti*=[%Ti]-(47.9/14)×[%N]-(47.9/32.1)×[%S] (2) |
