| 摘要 |
Provided are a high-strength hot-rolled steel sheet excellent in terms of punching workability and toughness and a method for manufacturing the steel sheet. Contained are 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 as a main phase in an amount of more than 90% in terms of area ratio and, optionally, one, two, or all of a ferrite phase, a martensite phase, and a retained austenite phase in an amount of less than 10% in total in terms of area ratio. The average grain diameter of the bainite phase is 2.5 µm or less, and the spacing between Fe-based carbides precipitated in bainitic ferrite grains in the bainite phase is 600 nm or less. |
