Hot-rolled steel sheet for tailored rolled blanks, tailored rolled blanks, and production methods thereof

摘要

A hot-rolled steel sheet for tailored rolled blanks having high tensile strength and excellent cold formability is provided. This hot-rolled steel sheet contains C, Si, Mn, P, S, Al, N, and Ti by mass%, and the balance consists of Fe and impurities, with a chemical composition that satisfies the formula (1) and an area ratio. And 20% or more of bainite, and the remaining 50% or more by area ratio has a microstructure composed of ferrite. In the hot-rolled steel sheet, the average value of the pole density of the {100} 011 to {223} 110 orientation group is 4 or less, and the pole density of the crystal orientation of {332} 113 is 4 .8 or less. In the surface layer of the hot-rolled steel sheet, the pole density of the crystal orientation of {110} 001 is 2.5 or more. Further, among the Ti carbonitrides in the hot-rolled steel sheet, the number density of fine Ti carbonitrides having a particle size of 10 nm or less is 1.0 × 10 17 pieces / cm 3 or less, and the bake hardening amount is 15 MPa or more. [Ti] −48 / 14 × [N] −48 / 32 × [S] ≧ 0 (1)