Steel sheet
A steel sheet includes a predetermined chemical composition and a metal structure represented by, in area fraction, ferrite: 30% to 50%, granular bainite: 5% to 20%, martensite: 30% to 55%, bainite: less than 35%, and retained austenite and pearlite: 10% or less in total. Preferably, of the steel sheet, a tensile strength is 1180 MPa or more, elongation is 10% or more, and a hole expansion value is 20% or more. Further preferably, a VDA bending angle in the case where a thickness is set to t (mm) is “7.69t 2 −38.4t+109” or more.
1. A cold-rolled steel sheet comprising:
a chemical composition represented by, in mass %,
C: 0.09% to 0.15%,
Si: 0.2% to 2.5%,
Al: 0.01% to 1.00%,
Mn: 1.0% to 3.0%,
P: 0.02% or less,
S: 0.01% or less,
N: 0.007% or less,
O: 0.006% or less,
Cr: 0.00% to 1.00%,
Mo: 0.00% to 1.00%,
B: 0.0000% to 0.010%,
Nb: 0.000% to 0.30%,
Ti: 0.000% to 0.30%,
Ni: 0.00% to 1.00%,
Cu: 0.00% to 1.00%,
V: 0.000% to 0.50%,
Mg: 0.0000% to 0.04%,
REM: 0.0000% to 0.04%, and
the balance: Fe and impurities; and
a metal structure represented by, in area fraction,
ferrite: 30% to 50%,
granular bainite: 5% to 20%,
martensite: 30% to 55%,
bainite: less than 35%, and
retained austenite and pearlite: 10% or less in total,
wherein
a tensile strength is 1180 MPa or more.
2. The cold-rolled steel sheet according to claim 1 , wherein
elongation is 10% or more, and
a hole expansion value is 20% or more.
3. The cold-rolled steel sheet according to claim 1 , wherein
a VDA bending angle in the case where a thickness is set to t (mm) is “7.69t 2 −38.4t+109” or more.
4. The cold-rolled steel sheet according to claim 2 , wherein
a VDA bending angle in the case where a thickness is set to t (mm) is “7.69t 2 −38.4t+109” or more.
5. The cold-rolled steel sheet according to claim 1 , further comprising:
a hot-dip galvanizing layer on a surface thereof.
6. The cold-rolled steel sheet according to claim 2 , further comprising:
a hot-dip galvanizing layer on a surface thereof.
7. The cold-rolled steel sheet according to claim 3 , further comprising:
a hot-dip galvanizing layer on a surface thereof.
8. The cold-rolled steel sheet according to claim 4 , further comprising:
a hot-dip galvanizing layer on a surface thereof.
9. The cold-rolled steel sheet according to claim 1 , further comprising:
an alloyed hot-dip galvanizing layer on a surface thereof.
10. The cold-rolled steel sheet according to claim 2 , further comprising:
an alloyed hot-dip galvanizing layer on a surface thereof.
11. The cold-rolled steel sheet according to claim 3 , further comprising:
an alloyed hot-dip galvanizing layer on a surface thereof.
12. The cold-rolled steel sheet according to claim 4 , further comprising:
an alloyed hot-dip galvanizing layer on a surface thereof.