HOT-ROLLED STEEL SHEET FOR COLD-ROLLED STEEL SHEET, HOT-ROLLED STEEL SHEET FOR HOT-DIPPED GALVANIZED STEEL SHEET, METHOD FOR PRODUCING HOT-ROLLED STEEL SHEET FOR COLD-ROLLED STEEL SHEET, AND METHOD FOR PRODUCING HOT-ROLLED STEEL SHEET FOR HOT-DIPPED

摘要

Provided are: a hot-rolled steel sheet which has a tensile strength (TS) of 540 MPa or more, excellent processability and excellent stability of material quality and which can be used for the production of a cold-rolled steel sheet and the production of a hot-dipped galvanized steel sheet; and a method for producing the hot-rolled steel sheet. The component composition of this hot-rolled steel sheet contains, in mass%, from 0.04% to 0.20% (inclusive) of C, from 0.7% to 2.3% (inclusive) of Si, from 0.8% to 2.8% (inclusive) of Mn, 0.1% or less of P, 0.01% or less of S, 0.1% or less of Al and 0.008% or less of N, with the balance made up of Fe and unavoidable impurities. The structure of this hot-rolled steel sheet contains ferrite and pearlite. The ferrite has an area ratio of 75% or more but less than 95% and an average crystal grain size from 5 µm to 25 µm (inclusive). The pearlite has an area ratio of 5% or more but less than 25%, an average crystal grain size of 2.0 µm or more, and a mean free path of 5 µm or more.