High-strength hot-rolled steel sheet excellent in bending resistance and a method of manufacturing the same

摘要

PROBLEM TO BE SOLVED: To provide a high strength hot rolled steel sheet having both excellent strength and workability (bendability in particular), and a method for producing the same.;SOLUTION: The high strength hot rolled steel sheet having a tensile strength of 980 MPa or higher and also having excellent bendability has a composition comprising, by mass, 0.06 to 0.1% of C, 0.05% or lower of Si, 0.1 to 1.2% of Mn, 0.03% or lower of P, 0.005% or lower of S, 0.08% or lower of Al, 0.0035 to 0.0090% of N, 0.14 to 0.25% of Ti and 0.01 to 0.15% of V, and the balance Fe with inevitable impurities, and a structure in which the area ratio of a ferrite phase is 95% or higher, the average crystal grain size of the ferrite phase is 5 μm or lower, the average crystal grain size of carbides in the crystal grains in the ferrite phase is 6 nm or lower, the X-ray random intensity in the [001]110orientation of the sheet face in the central part of the sheet thickness is 7.5 or higher, the average X-ray random intensity ratio in the [111]112to [111]110orientation group is 3.0 or lower, TiN is included as precipitates, the average grain size of the TiN is 5 μm or lower and its precipitation quantity is 0.01% or higher by mass%.;COPYRIGHT: (C)2014,JPO&INPIT