A chemical composition of a base metal of a non-oriented electrical steel sheet contains, by mass %, C: 0.0050% or less, Si: 3.8% to 5.0%, Mn: exceeding 0.2% and less than 2.0%, P: 0.030% or less, S: 0.0030% or less, Al: 0.005% or more and less than 0.050%, N: 0.0005% to 0.0030%, Ti: less than 0.0050%, Nb: less than 0.0050%, Zr: less than 0.0050%, V: less than 0.0050%, Cu: less than 0.20%, Ni: less than 0.50%, Sn: 0% to 0.10%, Sb: 0% to 0.10%, a remainder: Fe and impurities. [Si+0.5×Mn≥4.3] is satisfied and the average grain size of the base metal is in a range of 10 to 80 μm.

A non-oriented electrical steel sheet according to one embodiment of this invention includes a base metal steel sheet and a composite coating film composed of a Zn-containing phosphate and an organic resin, the composite coating film being formed on a surface of the base metal steel sheet. A molar ratio of Zn to all metal components in the composite coating film is 10 mol % or more, and after the non-oriented electrical steel sheet is boiled for 20 minutes in boiled distilled water, an amount of soluble Zn in the distilled water is 1.0 mg/m.sup.2 or more. The method for determining the amount of soluble Zn is in accordance with JIS K 0102: 2016 “Testing Methods for Industrial Wastewater”, 53.3 “ICP Emission Spectroscopy”.

The present disclosure relates to an iron (Fe)-based amorphous soft magnetic alloy and a method for manufacturing the soft magnetic alloy. According to the present disclosure, there is provided an Fe-based soft magnetic alloy including C and S meeting 1≥a+b≥6, wherein a is an atomic % content of C and b is an atomic % content of S, B meeting 4.5≥x≥13.0, wherein x is an atomic % content of B, Cu meeting 0.2≥y≥1.5, wherein y is an atomic % content of Cu, Al meeting 0.5≥z≥2, wherein z is an atomic % content of Al, and a remaining atomic % content of Fe and other inevitable impurities, wherein the Fe-based soft magnetic alloy includes a micro-structure, and wherein the micro-structure includes a crystalline phase with a mean crystalline grain size ranging from 15 nm to 50 nm in an amorphous base.

The present invention manufactures a steel sheet for a rotor core for an IPM motor, wherein the steel sheet has a magnetic flux density B.sub.8000 of 1.65 T or more as measured when magnetic field strength is 8000 A/m, and a residual magnetic flux density Br of 0.5 T or more as measured at that time, and optionally, a coercivity Hc of 100 A/m or more as measured after magnetization reaches 8000 A/m. By using the steel sheet manufactured according to the present invention for a rotor core of an IPM motor, it is possible to increase further an output torque in a high-speed rotational range and raise further the maximum rotational speed.

A method of production non grain-oriented Fe—Si steel sheet is provided. The method includes the steps of melting a steel composition that contains in weight percentage: C≦0.006, 2.0≦Si≦5.0, 0.1≦Al≦3.0, 0.1≦Mn≦3.0, N≦0.006, 0.04≦Sn≦0.2, S≦0.005, P≦0.2, Ti≦0.01, the balance being Fe and other inevitable impurities, casting said melt into a slab, reheating said slab, hot rolling said slab, coiling said hot rolled steel, optionally annealing the hot rolled steel, cold rolling, annealing and cooling the cold rolled steel down to room temperature.

A non-oriented electrical steel sheet according to an embodiment of the present invention includes, in wt %, C at 0.005% or less (excluding 0%), Si at 0.5 to 2.4%, Mn at 0.4 to 1.0%, S at 0.005% or less (excluding 0%), Al at 0.01% or less (excluding 0%), N at 0.005% or less (excluding 0%), Ti at 0.005% or less (excluding 0%), Cu at 0.001 to 0.02%, and the balance of Fe and inevitable impurities, and satisfies Formula 1 below, wherein a volume fraction of grains in which an angle formed by a {111} surface and a rolling surface of the steel sheet is 15° or less is 27% or more.

[Mn]/([Si]+150×[Al])≤0.35   [Formula 1]

(In Formula 1, [Mn], [Si], and [Al] are contents (wt %) of Mn, Si, and Al, respectively.)

A non-oriented electrical steel sheet having high magnetic flux density and a low iron loss at a high frequency is produced by subjecting a slab containing, in mass %, C: not more than 0.0050%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, P: not more than 0.10%, S: not more than 0.0050%, Al: 0.3 to 2.0%, N: not more than 0.0050% and Zn: 0.0005 to 0.0050% to a hot rolling, a hot-band annealing, a cold rolling and a finish annealing, a dew point in the hot-band annealing is set to 0 to 70 ° C. and an atmosphere of the finish annealing has a nitrogen content of not more than 30 vol % and a dew point of not higher than −20° C., and a ratio of the amount of nitrogen present as AlN in an entire sheet thickness to the amount of nitrogen present as AlN in a layer from one-side surface of steel sheet to a depth of 1/20 of sheet thickness is made to not less than 5.0.

Grain-oriented electrical steel sheet excellent in magnetic properties and excellent in adhesion of the primary coating to the steel sheet is provided. This is provided with a base metal steel sheet containing a predetermined chemical composition and a primary coating formed on a surface of the base metal steel sheet and containing Mg.sub.2SiO.sub.4 as a main constituent. A peak position of Al emission intensity obtained when performing elemental analysis by glow discharge optical emission spectrometry from a surface of the primary coating in a thickness direction of the grain-oriented electrical steel sheet is arranged within a range of 2.0 to 10.0 μm from the surface of the primary coating in the thickness direction. A number density of Al oxides of a size of 0.2 μm or more in terms of a circle equivalent diameter based on the area at the peak position of Al emission intensity is 0.032 to 0.20/μm.sup.2, and, in a 100 μm×100 μm distribution chart of Al oxides at the peak position of Al emission intensity obtained by glow discharge optical emission spectrometry, if dividing the distribution chart by 10 μm×10 μm grid section, a ratio of a number of grid sections not containing the Al oxides to the total number of grid sections in the distribution chart is 5% or less.

A method of producing a CoFe alloy strip is provided. The method comprises hot rolling a CoFe alloy to form a hot rolled strip, followed by quenching the strip from a temperature above 700° C. to a temperature of 200° C. The CoFe alloy comprises an order/disorder temperature T.sub.o/d and a ferritic/austenitic transformation temperature T.sub.α/γ, wherein T.sub.α/γ>T.sub.o/d. The method further comprises cold rolling the hot rolled strip, after cold rolling, continuous annealing the strip at a maximum temperature T.sub.1, wherein 500° C.<T.sub.1<T.sub.o/d, followed by cooling at a cooling rate R.sub.1 of at least 1 K/s in the temperature range of T.sub.1 to 500° C., and after continuous annealing, magnetic annealing the strip, or parts manufactured from the strip, at a temperature between 730° C. and T.sub.α/γ.

An embodiment of the present invention provides a non-oriented electrical steel sheet, including Si at 2.0 to 4.0 wt %, Al at 1.5 wt % or less (excluding 0 wt %), Mn at 1.5 wt % or less (excluding 0 wt %), Cr at 0.01 to 0.5 wt %, V at 0.0080 to 0.015 wt %, C at 0.015 wt % or less (excluding 0 wt %), N at 0.015 wt % or less (excluding 0 wt %), and the remainder including Fe and other impurities unavoidably added thereto.
0.004≤([C]+[N])≤0.022  [Equation 1] (In Equation 1, [C] and [N] represent a content (wt %) of C and N, respectively.)