Steel sheet

1. A steel sheet comprising:

a chemical composition represented by, in mass %,

C: 0.05% to 0.40%,

Si: 2.6% to 6.00%,

Mn: 1.50% to 10.00%,

Acid-soluble Al: 0.01% to 1.00%,

P: 0.10% or less,

S: 0.01% or less,

N: 0.01% or less,

Ti: 0.0% to 0.2%,

Nb: 0.0% to 0.2%,

V: 0.0% to 0.2%,

Cr: 0.0% to 1.0%,

Mo: 0.0% to 1.0%,

Cu: 0.0% to 1.0%,

Ni: 0.0% to 1.0%,

Ca: 0.00% to 0.01%,

Mg: 0.00% to 0.01%,

REM: 0.00% to 0.01%,

Zr: 0.00% to 0.01%, and

the balance: Fe and impurities, and comprising

a steel microstructure represented by, in an area ratio,

ferrite: 5% to 80%,

a hard microstructure constituted of bainite, martensite or retained austenite or an arbitrary combination of the above: 20% to 95%, wherein at least 5% is retained austenite, and

a standard deviation of a line fraction of the hard microstructure on a line in a plane perpendicular to a thickness direction: 0.050 or less in a depth range where a depth from a surface when a thickness of a steel sheet is set as t is from 3t/8 to t/2.

2. The steel sheet according to claim 1 ,

wherein in the chemical composition, in mass %,

Ti: 0.003% to 0.2%,

Nb: 0.003% to 0.2%, or

V: 0.003% to 0.2%,

or an arbitrary combination of the above is established.

3. The steel sheet according to claim 1 ,

in the chemical composition, in mass %,

Cr: 0.005% to 1.0%,

Mo: 0.005% to 1.0%,

Cu: 0.005% to 1.0%, or

Ni: 0.005% to 1.0%,

or an arbitrary combination of the above is established.

4. The steel sheet according to claim 1 ,

wherein in the chemical composition, in mass %,

Ca: 0.0003% to 0.01%,

Mg: 0.0003% to 0.01%,

REM: 0.0003% to 0.01%, or

Zr: 0.0003% to 0.01%,

or an arbitrary combination of the above is established.