Non-oriented magnetic steel sheet and method of manufacturing the same

1. A non-oriented magnetic steel sheet, comprising:

a chemical composition represented by, in mass %:

Si: 3.0% to 3.6%;

Al: 0.50% to 1.25%;

Mn: 0.5% to 1.5%;

Sb or Sn or both of them: [Sb]+[Sn]/2 is 0.0025% to 0.05% where [Sb] denotes an Sb content and [Sn] denotes an Sn content;

P: 0.010% to 0.150%;

Ni: 0.010% to 0.200%;

C: 0.0010% to 0.0040%;

N: 0.0030% or less;

S: 0.0020% or less;

Ti: 0.0030% or less;

Cu: 0.0500% or less;

Cr: 0.0500% or less;

Mo: 0.0500% or less;

Bi: 0.0050% or less;

Pb: 0.0050% or less;

V: 0.0050% or less;

B: 0.0050% or less; and

balance: Fe and impurities, and

magnetic properties represented by, where t denotes a thickness (mm) of the non-oriented magnetic steel sheet:

a magnetic flux density B50: “0.2×t+1.52” T or more;

a magnetic flux density difference ΔB50: 0.08 T or less;

core loss W10/50: 0.95 W/kg or less; and

core loss W10/400: “20×t+7.5” W/kg or less,

wherein

the thickness is 0.15 mm to 0.30 mm, and

a ratio of a number of intergranular carbides precipitated in grains relative to a sum of the number of the intergranular carbides and a number of grain boundary carbides precipitated on grain boundaries is 0.50 or less.

2. The non-oriented magnetic steel sheet according to claim 1 , wherein in the chemical composition,

P: 0.015% to 0.100%,

Ni: 0.020% to 0.100%, or

C: 0.0020% to 0.0030%, or

any combination thereof is satisfied.

3. A method of manufacturing a non-oriented magnetic steel sheet, comprising:

hot-rolling of a steel material to obtain a hot-rolled steel sheet;

cold-rolling of the hot-rolled steel sheet to obtain a cold-rolled steel sheet;

first annealing of the hot-rolled steel sheet before the cold-rolling is completed; and

second annealing of the cold-rolled steel sheet,

wherein the first annealing includes:

retaining the hot-rolled steel sheet in a first temperature range from 850° C. to 1100° C. for 10 seconds to 120 seconds, and

after the retaining, cooling the hot-rolled steel sheet at a rate of 5° C./s to 50° C./s in a temperature zone from 850° C. to 600° C.,

wherein the second annealing includes:

retaining the cold-rolled steel sheet in a second temperature range from 900° C. to 1100° C. for 10 seconds to 240 seconds, and

after the retaining, cooling the cold-rolled steel sheet at a rate of 10° C./s 15° C./s to 40° C./s in a temperature zone from 900° C. to 300° C., and

wherein the steel material comprises a chemical composition represented by, in mass %,

Si: 3.0% to 3.6%;

Al: 0.50% to 1.25%;

Mn: 0.5% to 1.5%;

Sb or Sn or both of them: [Sb]+[Sn]/2 is 0.0025% to 0.05% where [Sb] denotes an Sb content and [Sn] denotes an Sn content;

P: 0.010% to 0.150%;

Ni: 0.010% to 0.200%;

C: 0.0010% to 0.0040%;

N: 0.0030% or less;

S: 0.0020% or less;

Ti: 0.0030% or less;

Cu: 0.0500% or less;

Cr: 0.0500% or less;

Mo: 0.0500% or less;

Bi: 0.0050% or less;

Pb: 0.0050% or less;

V: 0.0050% or less;

B: 0.0050% or less; and

balance: Fe and impurities.

4. The method of manufacturing the non-oriented magnetic steel sheet according to claim 3 , wherein hot-rolled sheet annealing is performed as the first annealing before the cold-rolling.

5. The method of manufacturing the non-oriented magnetic steel sheet according to claim 3 , further comprising hot-rolled sheet annealing before the cold-rolling, wherein an intermediate annealing is performed as the first annealing during the cold-rolling.

6. The method of manufacturing the non-oriented magnetic steel sheet according to claim 3 , wherein in the chemical composition,

P: 0.015% to 0.100%,

Ni: 0.020% to 0.100%, or

C: 0.0020% to 0.0030%, or

any combination thereof is satisfied.

7. The method of manufacturing the non-oriented magnetic steel sheet according to claim 3 , wherein a thickness of the cold-rolled steel sheet is 0.15 mm to 0.30 mm.