| 摘要 |
Provided are a high-strength hot-rolled steel sheet and a method for manufacturing the steel sheet. The steel sheet includes C: 0.060% or more and 0.140% or less, Si: 1.00% or less, Mn: 1.30% or more and 2.50% or less, P: 0.030% or less, S: 0.0050% or less, Al: 0.070% or less, N: 0.010% or less, Ti: 0.060% or more and 0.140% or less, Cr: 0.10% or more and 0.50% or less, B: 0.0002% or more and 0.0020% or less, and the balance being Fe and inevitable impurities, in which the relationship 5.0≦18C+Mn+1.3Cr+1500B≦6.0 is obtained. The microstructure includes a bainite phase in an amount of more than 90% one, two, or all of a ferrite phase, a martensite phase, and a retained austenite phase in an amount of less than 10%. |
| 主权项 |
1. A high-strength hot-rolled steel sheet having a chemical composition containing, by mass %, C: 0.060% or more and 0.140% or less, Si: 1.00% or less, Mn: 1.30% or more and 2.50% or less, P: 0.030% or less, S: 0.0050% or less, Al: 0.070% or less, N: 0.010% or less, Ti: 0.060% or more and 0.140% or less, Cr: 0.10% or more and 0.50% or less, B: 0.0002% or more and 0.0020% or less, and the balance being Fe and inevitable impurities, in which C, Mn, Cr, and B satisfy relational expression (1) below, and a microstructure Including a bainite phase as a main phase in an amount of more than 90% in terms of area ratio and one, two, or all of a ferrite phase, a martensite phase, and a retained austenite phase as second phases in an amount of less than 10% in total in terms of area ratio, wherein the average grain diameter of the bainite phase is 2.5 μm or less, wherein the spacing between Fe-based carbides precipitated in bainitic ferrite grains in the bainite phase is 600 nm or less, and wherein a tensile strength TS is 980 MPa or more:
5.0≦18C+Mn+1.3Cr+1500B≦6.0 (C,Mn,Cr, and B respectively denote the contents (mass %) of C,Mn,Cr, and B) (1). |
