HIGH-STRENGTH HOT-ROLLED STEEL SHEET HAVING EXCELLENT WORKABILITY, AND A METHOD FOR PRODUCING SAME

摘要

Provided are high-strength hot-rolled steel sheet having excellent workability in which a hole expansion ratio (?) of 125% or more can be reliably obtained and the TS is 490 MPa or more and less than 590 MPa, and a method for producing said high-strength hot-rolled steel sheet. A high-strength hot-rolled steel sheet having excellent workability and characterized by having: a composition containing, in mass %, 0.04 to 0.1% of C, 0.3 to 1.3% of Si, 0.8 to 1.8% of Mn, 0.3% or less of P, 0.005% or less of S, 0.005% or less of N, 0.005 to 0.1% of Al, at least one selected from among 0.002% or more and less than 0.03% of Ti, 0.002% or more and less than 0.03% of V, and 0.002% or more and less than 0.02% of Nb, and the remainder being Fe and unavoidable impurities; and a microstructure in which, in relation to the entire structure, the area ratio of a ferrite phase is 85% or more, the area ratio of a bainite phase is 10% or less, the area ratio of phases other than the ferrite phase and the bainite phase is 5% or less, and the area ratio of an acicular ferrite phase in relation to the entire ferrite phase is 30% or more and less than 80%.