Hot-rolled steel sheet
A hot-rolled steel sheet includes a predetermined chemical composition, and a structure which includes, by area ratio, a ferrite in a range of 5% to 60% and a bainite in a range of 30% to 95%, in which in the structure, in a case where a boundary having an orientation difference of equal to or greater than 15° is defined as a grain boundary, and an area which is surrounded by the grain boundary and has an equivalent circle diameter of equal to or greater than 0.3 μm is defined as a grain, the ratio of the grains having an intragranular orientation difference in a range of 5° to 14° is, by area ratio, in a range of 20% to 100%.
1. A hot-rolled steel sheet comprising, as a chemical composition, by mass %,
C: 0.020% to 0.070%,
Si: 0.10% to 1.70%,
Mn: 0.60% to 2.50%,
Al: 0.01% to 1.00%,
Ti: 0.015% to 0.170%,
Nb: 0.005% to 0.050%,
Cr: 0% to 1.0%,
B: 0% to 0.10%,
Mo: 0% to 1.0%
Cu: 0% to 2.0%,
Ni: 0% to 2.0%,
Mg: 0% to 0.05%,
REM: 0% to 0.05%,
Ca: 0% to 0.05%,
Zr: 0% to 0.05%,
P: limited to equal to or less than 0.05%,
S: limited to equal to or less than 0.010%, and
N: limited to equal to or less than 0.0060%, with the remainder of Fe and impurities;
wherein a structure includes, by area ratio, a ferrite in a range of 5% to 60% and a bainite in a range of 30% to 95%, wherein a tensile strength of the steel is equal to or greater than 590 MPa, and a product of the tensile strength and a limit forming height in a saddle type stretch flange test is equal to or greater than 19500 mm·Mpa, and
wherein in the structure, in a case where a boundary having an orientation difference of equal to or greater than 15° is defined as a grain boundary, and an area which is surrounded by the grain boundary and has an equivalent circle diameter of equal to or greater than 0.3 μm is defined as a grain, an area ratio of grains having an intragranular orientation difference in a range of 5-14° to total amount of grains is 20% to 100%.
2. The hot-rolled steel sheet according to claim 1 ,
wherein the chemical composition contains, by mass %, one or more selected from
Cr: 0.05% to 1.0%, and
B: 0.0005% to 0.10%.
3. The hot-rolled steel sheet according to claim 1 ,
wherein the chemical composition contains, by mass %, one or more selected from
Mo: 0.01% to 1.0%,
Cu: 0.01% to 2.0%, and
Ni: 0.01% to 2.0%.
4. The hot-rolled steel sheet according to claim 1 ,
wherein the chemical composition contains, by mass %, one or more selected from
Ca: 0.0001% to 0.05%,
Mg: 0.0001% to 0.05%,
Zr: 0.0001% to 0.05%, and
REM: 0.0001% to 0.05%.