A method for manufacturing a motor core includes a step of manufacturing a motor core by performing melt-cutting on an electrical steel sheet using heat input from a surface, the electrical steel sheet having an average thermal conductivity in depth positions from the surface to one-third depth of a sheet thickness lower than a thermal conductivity in a middle position in a sheet thickness direction by 30% or greater.

A double oriented electrical steel sheet according to an embodiment of the present invention includes: in wt %, Si at 2.0 to 4.0 wt %, Al at 0.01 to 0.04 wt %, S at 0.0004 to 0.002 at %, Mn at 0.05 to 0.3 wt %, N at 0.008 wt % or less (excluding 0 wt %), C at 0.005 wt % or less (excluding 0 wt %), P at 0.005 to 0.15 wt %, Ca at 0.0001 to 0.005 wt %, Mg at 0.0001 to 0.005 wt %, and the balance including Fe and other impurities unavoidably added thereto.

A non-oriented electrical steel sheet with an average magnetostriction λ.sub.p-p at 400 Hz and 1.0 T of not more than 4.5×10.sup.−6, and area ratio of recrystallized grains at a section in rolling direction of steel sheet of 40 to 95% and an average grain size of 10 to 40 μm is obtained by subjecting a steel slab containing, in mass %, C: not more than 0.005%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, Al: not more than 3.0%, P: not more than 0.20%, S: not more than 0.005%, N: not more than 0.005%, Ti: not more than 0.003%, V: not more than 0.005% and Nb: not more than 0.005% and satisfying Si-2Al-Mn≥0 to hot rolling, hot-band annealing, cold rolling and finish annealing under adequate cold rolling and finish annealing conditions, and a motor core is manufactured by such a steel sheet.

This electrical steel sheet contains, as a chemical composition, by mass %, C: 0.0035% or less, Si: 2.00% to 3.50%, Mn: 2.00% to 5.00%, P: 0.050% or less, S: 0.0070% or less, Al: 0.15% or less, N: 0.0030% or less, Ni: 0% to 1.00%, Cu: 0% to 0.10%, and a remainder: Fe and impurities, in which an X-ray random intensity ratio in a {100} <011> crystal orientation on a sheet surface is 15.0 to 50.0, and magnetic flux densities in 0°, 22.5°, and 45° directions from a rolling direction each satisfy [1.005×(B.sub.50 (0°)+B.sub.50 (45°))/2≥B.sub.50 (22.5°)].

A non oriented electrical steel sheet consists of a silicon steel sheet and an insulation coating. The silicon steel sheet includes an internally oxidized layer containing SiO.sub.2 in a surface thereof, an average thickness of the internally oxidized layer is 0.10 to 5.0 μm, and a vickers hardness in the internally oxidized layer is 1.15 to 1.5 times as compared with a vickers hardness in a thickness central area.

Proposed is a non-oriented electrical steel sheet being low in iron loss and excellent in tensile strength and fatigue strength, which has a chemical composition comprising C: not more than 0.005 mass %, Si: 3 to 5 mass %, Mn: not more than 5 mass %, P: not more than 0.1 mass %, S: not more than 0.01 mass %, Al: not more than 3 mass %, N: not more than 0.005 mass %, Zn: 0.0005 mass % to 0.003 mass %, and the remainder being Fe and inevitable impurities, an average crystal grain size being not more than 40 μm, the number of the inclusions having a diameter of not less than 5 μm being not more than 5/mm.sup.2, a tensile strength being not less than 600 MPa, and the fatigue strength being not less than 450 MPa.

A non oriented electrical steel sheet consists of a silicon steel sheet and an insulation coating. The silicon steel sheet contains Si, Al, and Mn as chemical composition, and an alignment degree to {5 5 7}<7 14 5> orientation in a central area along a thickness direction of the silicon steel sheet is 12 to 35.

A method for producing a coated magnetic powder in which particle surfaces of a soft magnetic powder are coated with a silicone resin includes a preparation step of preparing a silicone emulsion by mixing a silicone resin with water containing a surfactant and dispersing the silicone resin in the water, an application step of applying the silicone emulsion onto particle surfaces of a soft magnetic powder, and a drying step of drying the soft magnetic powder after the silicone emulsion is applied.

A non-oriented electrical steel sheet with an average magnetostriction λ.sub.p-p at 400 Hz and 1.0 T of not more than 4.5×10.sup.−6, and area ratio of recrystallized grains at a section in rolling direction of steel sheet of 40 to 95% and an average grain size of 10 to 40 μm is obtained by subjecting a steel slab containing, in mass %, C: not more than 0.005%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, Al: not more than 3.0%, P: not more than 0.20%, S: not more than 0.005%, N: not more than 0.005%, Ti: not more than 0.003%, V: not more than 0.005% and Nb: not more than 0.005% and satisfying Si-2Al—Mn≥0 to hot rolling, hot-band annealing, cold rolling and finish annealing under adequate cold rolling and finish annealing conditions, and a motor core is manufactured by such a steel sheet.

A grain-oriented electrical steel sheet of the present invention has a base steel sheet, an amorphous oxide layer formed on the base steel sheet, and a tension-insulation coating formed on the amorphous oxide layer, in which the base steel sheet contains, as a chemical composition, by mass %, C: 0.085% or less, Si: 0.80 to 7.00%, Mn: 1.50% or less, acid-soluble Al: 0.065% or less, S: 0.013% or less, Cu: 0 to 0.80%, N: 0 to 0.012%, P: 0 to 0.50%, Ni: 0 to 1.00%, Sn: 0 to 0.30%, and Sb: 0 to 0.30%, a remainder is Fe and an impurity, a surface glossiness Gs20(A) in a direction parallel to a rolling direction is 2.0 to 70, and a surface glossiness Gs20(B) in a direction perpendicular to the rolling direction is 2.0 to 70.