Patent ID: 9121079
Filing Date: 2015-09-01
Classification: B21B,C21D,C22C

Abstract:
1. A high-strength hot-rolled steel sheet containing: in mass %, C: 0.02% to 0.1%; Si: 0.001% to 3.0%; Mn: 0.5% to 3.0%; P: 0.1% or less; S: 0.01% or less; Al: 0.001% to 2.0%; N: 0.02% or less; Ti: 0.03% to 0.3%; and Nb: 0.001% to 0.06%, the steel sheet further containing at least one element selected from the group consisting of: Cu: 0.001 to 1.0%; Cr: 0.001 to 1.0%; Mo: 0.001 to 1.0%; Ni: 0.001 to 1.0%; and V: 0.01 to 0.2%, the balance being composed of Fe and inevitable impurities, a parameter Q expressed by Mathematical expression 1 below being 30.0 or more, a microstructure being made of a ferrite structure, a bainite structure, or a structure mixed with the ferrite structure and the bainite structure, an average grain size of grains included in the microstructure being 6 μm or less, an X-ray random intensity ratio of {211} plane on a rolled surface being 2.4 or less, and on a cross section with a sheet width direction set as a normal line, wherein [Ti] indicates the Ti content (mass %) and [S] indicates the S content (mass %).