Hot-rolled steel sheet for tailored rolled blank and tailored rolled blank

1. A tailored rolled blank in which a sheet thickness changes in a tapered shape in a rolling direction, comprising:

a thick-wall portion, and

a thin-wall portion that is thinner than the thick-wall portion;

wherein:

in the tailored rolled blank, a ratio of an average hardness H t max of a thickest wall portion at which the sheet thickness is thickest to an average hardness H t min of a thinnest wall portion at which the sheet thickness is thinnest is in a range of more than 1.0 to 1.5,

an average dislocation density of the thinnest wall portion is 1×10 14 m −2 or less, and

a number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is more than 2×10 17 per cm 3 .

2. The tailored rolled blank according to claim 1 ,

further comprising a galvanized layer on a surface thereof.

3. The tailored rolled blank according to claim 1 , wherein the tailored rolled blank is produced using a hot-rolled steel sheet comprising:

a chemical composition consisting of, in mass %,

C: 0.03 to 0.1%,

Si: 1.5% or less,

Mn: 1.0 to 2.5%,

P: 0.1% or less,

S: 0.02% or less,

Al: 0.01 to 1.2%,

N: 0.01% or less,

Ti: 0.015 to 0.15%,

Nb: 0 to 0.1%,

Cu: 0 to 1%,

Ni: 0 to 1%,

Mo: 0 to 0.2%,

V: 0 to 0.2%,

Cr: 0 to 1%,

W: 0 to 0.5%,

Mg: 0 to 0.005%,

Ca: 0 to 0.005%,

rare earth metal: 0 to 0.1%,

B: 0 to 0.005%, and

one or more types of element selected from a group consisting of Zr, Sn, Co and Zn in a total amount of 0 to 0.05%, with the balance being Fe and impurities, and satisfying Formula (1); and

a microstructure containing, in terms of area ratio, 20% or more of bainite, with 50% or more in terms of area ratio of the balance being ferrite;

wherein:

at a depth position that is equivalent to one-half of a sheet thickness from a surface of the hot-rolled steel sheet, an average value of pole densities of an orientation group {100}<011> to {223}<110> comprising crystal orientations {100}<011>, {116}<110>, {114}<110>, {113}<110>, {112}<110>, {335}<110> and {223}<110> is four or less and a pole density of a {332}<113> crystal orientation is 4.8 or less;

at a depth position that is equivalent to one-eighth of the sheet thickness from the surface of the hot-rolled steel sheet, a pole density of a {110}<001> crystal orientation is 2.5 or more;

a number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less among Ti carbo-nitrides in the hot-rolled steel sheet is 1.0×10 17 per cm 3 or less; and

a bake hardening amount is 15 MPa or more;

[Ti]−48/14×[N]−48/32×[S]≥0  (1),

where a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1).

4. The tailored rolled blank according to claim 3 , further comprising a galvanized layer on a surface thereof.