STEEL SHEET
A steel sheet includes: a predetermined chemical composition; and a steel structure containing, in are a fraction, 2% or more of ferrite and bainite, in which an average dislocation density in the ferrite and an average dislocation density in the bainite are both h3×10 12 m/m 3 to 1×10 14 m/m 3 , and an average grain diameter of the ferrite and the bainite is 5 μm or less.
1 - 6 . (canceled)
7 . A steel sheet, comprising:
a chemical composition represented by,
in mass %,
C: 0.05% to 0.40%,
Si: 0.05% to 3.0%,
Mn: 1.5% to 4.0%,
Al: 1.5% or less,
N: 0.02% or less,
P: 0.2% or less,
S: 0.01% or less,
Nb and Ti: 0.005% to 0.2% in total,
V and Ta: 0.0% to 0.3% in total,
Cr, Mo, Ni, Cu, and Sn: 0.0% to 1.0% in total,
B: 0.00% to 0.01%,
Ca: 0.000% to 0.005%,
Ce: 0.000% to 0.005%,
La: 0.000% to 0.005%, and
the balance: Fe and impurities; and
a steel structure containing, in area fraction, 2% or more in total of ferrite and bainite, wherein
an average dislocation density in the ferrite and an average dislocation density in the bainite are both 3×10 12 m/m 3 to 1×10 14 m/m 3 , and
an average grain diameter of the ferrite and the bainite is 5 μm or less.
8 . The steel sheet according to claim 7 , wherein
the steel structure contains, in area fraction, ferrite and bainite: 2% to 60% in total and martensite: 10% to 90%,
an area fraction of retained austenite in the steel structure is 15% or less, and
a ratio of an area fraction of the ferrite to an area fraction of the martensite is 0.03 to 1.00.
9 . The steel sheet according to claim 7 , wherein
in the chemical composition,
V and Ta: 0.01% to 0.3% in total is established.
10 . The steel sheet according to claim 8 , wherein
in the chemical composition,
V and Ta: 0.01% to 0.3% in total is established.
11 . The steel sheet according to claim 7 , wherein
in the chemical composition,
Cr, Mo, Ni, Cu, and Sn: 0.1% to 1.0% in total is established.
12 . The steel sheet according to claim 8 , wherein
in the chemical composition,
Cr, Mo, Ni, Cu, and Sn: 0.1% to 1.0% in total is established.
13 . The steel sheet according to claim 7 , wherein in the chemical composition,
B: 0.0003% to 0.01% is established.
14 . The steel sheet according to claim 8 , wherein
in the chemical composition,
B: 0.0003% to 0.01% is established.
15 . The steel sheet according to claim 7 , wherein
in the chemical composition,
Ca: 0.001% to 0.005%,
Ce: 0.001% to 0.005%,
La: 0.001% to 0.005%, or
an arbitrary combination of these is established.
16 . The steel sheet according to claim 8 , wherein
in the chemical composition,
Ca: 0.001% to 0.005%,
Ce: 0.001% to 0.005%,
La: 0.001% to 0.005%, or
an arbitrary combination of these is established.