Hot-rolled steel sheet
A hot-rolled steel sheet includes a predetermined chemical composition, and a structure which include, by area ratio, ferrite and bainite in a range of 80% to 98% in total, and martensite in a range of 2% to 10%, 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 10% to 60%.
1. A hot-rolled steel sheet comprising, as a chemical composition, by mass %,
C: 0.020% to 0.070%,
Mn: 0.60% to 2.00%,
Al: 0.10% to 1.00%,
Ti: 0.015% to 0.170%,
Nb: 0.005% to 0.050%,
Cr: 0% to 1.0%,
V: 0% to 0.300%,
Cu: 0% to 2.00%,
Ni: 0% to 2.00%,
Mo: 0% to 1.00%,
Mg: 0% to 0.0100%,
Ca: 0% to 0.0100%,
REM: 0% to 0.1000%,
B: 0% to 0.0100%,
Si: limited to equal to or less than 0.100%,
P: limited to equal to or less than 0.050%,
S: limited to equal to or less than 0.005%, and
N: limited to equal to or less than 0.0060%,
with the remainder of Fe and impurities; and
wherein a structure includes, by an area ratio, ferrite and bainite in a range of 80% to 98% in total, and martensite in a range of 2% to 10%, 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, the ratio of the grains having an intragranular orientation difference in a range of 5° to 14° is, by the area ratio, in a range of 10% to 60%.
2. The hot-rolled steel sheet according to claim 1 ,
wherein the chemical composition contains, by mass %, one or two or more of
V: 0.010% to 0.300%,
Cu: 0.01% to 1.20%,
Ni: 0.01% to 0.60%, and
Mo: 0.01% to 1.00%.
3. The hot-rolled steel sheet according to claim 1 or 2 ,
wherein the chemical composition contains, by mass %, one or two or more of
Mg: 0.0005% to 0.0100%,
Ca: 0.0005% to 0.0100%, and
REM: 0.0005% to 0.1000%.
4. The hot-rolled steel sheet according to claim 3 ,
wherein the chemical composition contains, by mass %, B: 0.0002% to 0.0020%.
5. The hot-rolled steel sheet according to claim 4 ,
wherein a tensile strength is equal to or greater than 540 MPa, and a product of the tensile strength and a maximum forming height in a saddle type stretch flange test is equal to or greater than 19500 mm·MPa.
6. The hot-rolled steel sheet according to claim 3 ,
wherein a tensile strength is equal to or greater than 540 MPa, and a product of the tensile strength and a maximum forming height in a saddle type stretch flange test is equal to or greater than 19500 mm·MPa.
7. The hot-rolled steel sheet according to claim 1 or 2 ,
wherein the chemical composition contains, by mass %, B: 0.0002% to 0.0020%.
8. The hot-rolled steel sheet according to claim 7 ,
wherein a tensile strength is equal to or greater than 540 MPa, and a product of the tensile strength and a maximum forming height in a saddle type stretch flange test is equal to or greater than 19500 mm·MPa.
9. The hot-rolled steel sheet according to claim 1 or 2 ,
wherein a tensile strength is equal to or greater than 540 MPa, and a product of the tensile strength and a maximum forming height in a saddle type stretch flange test is equal to or greater than 19500 mm·MPa.
10. A hot-rolled steel sheet comprising, as a chemical composition, by mass %,
C: 0.020% to 0.070%,
Mn: 0.60% to 2.00%,
Al: 0.10% to 1.00%,
Ti: 0.015% to 0.170%,
Nb: 0.005% to 0.050%,
Cr: 0% to 1.0%,
V: 0.010% to 0.300%,
Cu: 0.01% to 1.20%,
Ni: 0.01% to 0.60%,
Mo: 0.01% to 1.00%,
Mg: 0.0005% to 0.0100%,
Ca: 0.0005% to 0.0100%,
REM: 0.0005% to 0.1000%,
B: 0.0002% to 0.0020%,
Si: limited to equal to or less than 0.100%,
P: limited to equal to or less than 0.050%,
S: limited to equal to or less than 0.005%, and
N: limited to equal to or less than 0.0060%,
with the remainder of Fe and impurities; and
wherein a structure includes, by an area ratio, ferrite and bainite in a range of 80% to 98% in total, and martensite in a range of 2% to 10%, 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, the ratio of the grains having an intragranular orientation difference in a range of 5° to 14° is, by the area ratio, in a range of 10% to 60%.