HOT-ROLLED STEEL SHEET, AND PRODUCTION METHOD THEREFOR

摘要

A hot rolled steel sheet consisting of, in mass%, C: 0.05% to 0.15%, Si: 0% to 0.2%, Al: 0.5% to 3.0%, Mn: 1.2% to 2.5%, P: 0.1% or less, S: 0.01% or less, N: 0.007% or less, Ti: 0.03% to 0.10%, Nb: 0.008% to 0.06%, V: 0% to 0.12%, one or more of Cr, Cu, Ni, and Mo: 0% to 2.0% in total, B: 0% to 0.005%, one or more of Ca, Mg, La, and Ce: 0% to 0.01% in total, total amount of Si and Al: 0.8 × (Mn-1)% or more, total amount of Ti and Nb: 0.04% to 0.14%, and the balance: Fe and impurities. In a structure of steel, a total area ratio of martensite and retained austenite is 3% to 20%, an area ratio of ferrite is 50% to 96%, and an area ratio of pearlite is 3% or less. In a superficial layer part, the thickness in a sheet thickness direction of a region in which a network-like oxide is present is less than 0.5 µm, and a maximum tensile strength is 720 MPa or more.