Non-oriented electrical steel sheet, manufacturing method of non-oriented electrical steel sheet, and manufacturing method of motor core

1. A non-oriented electrical steel sheet, comprising

a chemical composition represented by:

in mass %,

C: 0.0010% to 0.0050%;

Si: 2.5% to 4.0%;

Al: 0.0001% to 2.0%;

Mn: 0.1% to 3.0%;

P: 0.005% to 0.15%;

S: 0.0001% to 0.0030%;

Ti: 0.0005% to 0.0030%;

N: 0.0010% to 0.0030%;

Sn: 0.00% to 0.2%;

Sb: 0.00% to 0.2%;

Ni: 0.00% to 0.2%;

Cu: 0.00% to 0.2%;

Cr: 0.00% to 0.2%;

Ca: 0.0000% to 0.0025%;

REM: 0.0000% to 0.0050%; and

the balance: Fe and impurities, wherein

an average crystal grain diameter is 46 μm or less, and wherein

when an average value of Mn concentrations in a range from a surface of a base iron to a position where a depth from the surface of the base iron is 2 μm is set to [Mn 2 ], and an Mn concentration at a position where a depth from the surface of the base iron is 10 μm is set to [Mn 10 ], the base iron satisfies the following expression 1, and

wherein the [Mn10] substantially represents an average Mn concentration of the base iron,

0.1≤[Mn 2 ]/[Mn 10 ]≤0.9  (Expression 1).

2. The non-oriented electrical steel sheet according to claim 1 , wherein

the non-oriented electrical steel sheet contains one kind or more selected from a group consisting of:

Sn: 0.01% to 0.2%; and

Sb: 0.01% to 0.2%.

3. The non-oriented electrical steel sheet according to claim 1 , wherein

the non-oriented electrical steel sheet contains one kind or more selected from a group consisting of:

Ni: 0.01% to 0.2%;

Cu: 0.01% to 0.2%; and

Cr: 0.01% to 0.2%.

4. The non-oriented electrical steel sheet according to claim 1 , wherein

the non-oriented electrical steel sheet contains one kind or more selected from a group consisting of:

Ca: 0.0005% to 0.0025%; and

REM: 0.0005% to 0.0050%.

5. The non-oriented electrical steel sheet according to claim 1 , wherein:

an insulating coating film is provided to the surface of the base iron;

an adhesion amount of the insulating coating film is not less than 400 mg/m 2 nor more than 1200 mg/m 2 ; and

a divalent Fe content and a trivalent Fe content in the insulating coating film are not less than 10 mg/m 2 nor more than 250 mg/m 2 in total.

6. The non-oriented electrical steel sheet according to claim 1 , wherein the [Mn 10 ] substantially represents an average Mn concentration of the base iron,

0.1≤[Mn 2 ]/[Mn 10 ]≤0.9  (Expression 1).

7. A manufacturing method of a non-oriented electrical steel sheet, comprising:

performing hot rolling of a steel ingot to obtain a hot-rolled steel sheet;

performing hot-rolled sheet annealing of the hot-rolled steel sheet;

performing pickling after the hot-rolled sheet annealing;

performing cold rolling after the pickling to obtain a cold-rolled steel sheet; and

performing finish annealing of the cold-rolled steel sheet to obtain the non-oriented electrical steel sheet, wherein:

the hot-rolled sheet annealing is performed by setting a dew point to not less than −40° C. nor more than 60° C., setting an annealing temperature to not less than 900° C. nor more than 1100° C., and setting a soaking time to not less than 1 second nor more than 300 seconds, while leaving a scale generated during the hot rolling;

an annealing temperature is set to less than 900° C. in the finish annealing; and

the non-oriented electrical steel sheet comprises a chemical composition represented by:

in mass %,

C: 0.0010% to 0.0050%;

Si: 2.5% to 4.0%;

Al: 0.0001% to 2.0%;

Mn: 0.1% to 3.0%;

P: 0.005% to 0.15%;

S: 0.0001% to 0.0030%;

Ti: 0.0005% to 0.0030%;

N: 0.0010% to 0.0030%;

Sn: 0.00% to 0.2%;

Sb: 0.00% to 0.2%;

Ni: 0.00% to 0.2%;

Cu: 0.00% to 0.2%;

Cr: 0.00% to 0.2%;

Ca: 0.0000% to 0.0025%;

REM: 0.0000% to 0.0050%; and

the balance: Fe and impurities, wherein

an average crystal grain diameter is 46 μm or less, and wherein

when an average value of Mn concentrations in a range from a surface of a base iron to a position where a depth from the surface of the base iron is 2 μm is set to [Mn 2 ], a depth from the surface of the base iron is 5 μm is set to [Mn 5 ], and an Mn concentration at a position where a depth from the surface of the base iron is 10 μm is set to [Mn 10 ], the base iron after the pickling satisfies the following expressions, and

wherein the [Mn 10 ] substantially represents an average Mn concentration of the base iron,

0.1≤[Mn 2 ]/[Mn 10 ]≤0.9  (Expression 1)

0.1≤[Mn 5 ]/[Mn 10 ]≤0.9  (Expression 2).

8. The manufacturing method of the non-oriented electrical steel sheet according to claim 6 , further comprising

after the finish annealing, forming an insulating coating film on the surface of the base iron.

9. The manufacturing method of the non-oriented electrical steel sheet according to claim 7 , wherein

the steel ingot contains one kind or more selected from a group consisting of:

Sn: 0.01% to 0.2%; and

Sb: 0.01% to 0.2%.

10. The manufacturing method of the non-oriented electrical steel sheet according to claim 7 , wherein

the steel ingot contains one kind or more selected from a group consisting of:

Ni: 0.01% to 0.2%;

Cu: 0.01% to 0.2%; and

Cr: 0.01% to 0.2%.

11. The manufacturing method of the non-oriented electrical steel sheet according to claim 7 , wherein

the steel ingot contains one kind or more selected from a group consisting of:

Ca: 0.0005% to 0.0025%; and

REM: 0.0005% to 0.0050%.