| 摘要 |
When the carbon content, silicon content and manganese content of this cold-rolled sheet are expressed as [C], [Si] and [Mn], respectively, in terms of unit mass%, a relationship of (5 × [Si] + [Mn])/[C] > 10 holds, and the metal structure contains ferrite at 40% to 90% and martensite at 10% to 60% by area ratio, and further contains one or more of perlite at 10% or less by area ratio, retained austenite at 5% or less by volume ratio, and bainite at 20% or less by area ratio. Furthermore, the hardness of the martensite, as measured by a nanoindenter, satisfies H20/H10 < 1.10 and σHM0 < 20, and TS × λ, which is represented by the product of the tensile strength (TS) and hole expansion rate (λ), is at least 50000 MPa∙%. |
