A grain-oriented electrical steel sheet includes: a silicon steel sheet including Si and Mn; a glass film arranged on a surface of the silicon steel sheet; and an insulation coating arranged on a surface of the glass film, wherein the glass film includes a Mn-containing oxide.

A method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises: a step for hot-rolling a slab to produce a hot-rolled sheet; a step for cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; a step for subjecting the cold-rolled sheet to primary recrystallization annealing; and a step for subjecting the primary recrystallization annealing-completed cold-rolled sheet to secondary recrystallization annealing, wherein the primary recrystallization annealing step includes a preceding step and a subsequent step, and the amount (A) of nitriding gas introduced in the preceding step with respect to the total amount (B) of nitriding gas introduced in the primary recrystallization annealing step satisfies expression 1 below.
0.05≤[A]/[B]≤[t]  [Expression 1] (In expression 1, the amount of nitriding gas introduced is in units of Nm.sup.3/hr, and [t] represents the thickness (mm) of a cold-rolled sheet.)

A non-oriented electrical steel sheet according to an exemplary embodiment of the present invention includes, by weight, Si: 2.0 to 3.5%, Al: 0.3 to 2.5%, Mn: 0.3 to 3.5%, Sn: 0.0030 to 0.2%, Sb: 0.0030 to 0.15%, P: 0.0040 to 0.18%, individually or in a total amount of 0.0005 to 0.03% of at least one of Ga and Ge, and a remainder including Fe and unavoidable impurities, and satisfies Equation 1 below.
0.05≤([Sn]+[Sb])/[P]≤25  [Equation 1] ([Sn], [Sb], and [P] respectively represent the content (% by weight) of Sn, Sb, and P.)

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 double-oriented electrical steel sheet according to an example of the present invention comprises, by weight 2.0 to 4.0 wt % of Si, 0.01 to 0.04 wt % of Al, 0.0004 to 0.02 wt % of S, 0.05 to 0.3 wt % of Mn, at most 0.01 wt % (exclusive of 0 wt %) of N, at most 0.005 wt % (exclusive of 0 wt %) of C, 0.005 to 0.15 wt % of P, 0.001 to 0.005 wt % of Ti, and 0.0001 to 0.005 wt % of Mg, with the balance being Fe and other inevitable impurities, wherein the area fraction of crystal grains having an orientation within 15° from {100}<001> is 60 to 99%, and the area fraction of crystal grains having an orientation within 15° from {100}<025> is 1 to 30%.

A hot-rolled steel sheet for a non-oriented electrical steel sheet according to one aspect of the present invention contains, by mass %, C: 0.0050% or less, Si: 0.5% or more and 3.5% or less, Mn: 0.1% or more and 1.5% or less, Al: 0.1% or more and 1.5% or less, Cu: 0.01% or more and 0.10% or less, Sn: 0.01% or more and 0.20% or less, and a remainder including Fe and impurities, in which the hot-rolled steel sheet has a Cu concentration peak value of 0.12% or more in a range from a surface thereof to a depth of 10 μm.

A method for manufacturing a grain-oriented electrical steel sheet according to an aspect of the present invention includes a step of obtaining a hot-rolled steel sheet by carrying out hot rolling on a slab containing a predetermined component composition with a remainder including Fe and impurities, a step of obtaining a hot-rolled annealed sheet by carrying out hot-rolled sheet annealing as necessary, a step of carrying out pickling to obtain a pickled sheet, a step of carrying out cold rolling to obtain a cold-rolled steel sheet, a step of carrying out primary recrystallization annealing, a step of applying an annealing separating agent including MgO to a surface and then carrying out final annealing to obtain a final-annealed sheet, and a step of applying an insulating coating and then carrying out flattening annealing.

Grain-oriented electrical steel sheet excellent in magnetic properties and excellent in adhesion of a primary coating to the steel sheet is provided. The grain-oriented electrical steel sheet is provided with a base steel sheet having a chemical composition containing C: 0.005% or less, Si: 2.5 to 4.5%, Mn: 0.050 to 1.000%, a total of S and Se: 0.005% or less, sol. Al: 0.005% or less, and N: 0.005% or less and having a balance of Fe and impurities and a primary coating having Mg.sub.2 SiO.sub.4 as a main constituent formed on a surface of the base steel sheet. A peak position of Al emission intensity obtained when conducting elemental analysis by glow discharge spectrometry from a surface of the primary coating in a thickness direction is present in a range of 2.0 to 12.0 .Math.m from a surface of the primary coating to the thickness direction. A sum of perimeters of the Al oxides at the peak position of Al emission intensity is 0.20 to 1.00 .Math.m/.Math.m.sup.2, and a number density of Al oxides is 0.02 to 0.20 /.Math.m.sup.2.

A grain oriented electrical steel sheet includes: a base steel sheet; a lower layer which is arranged in contact with the base steel sheet; and an insulation coating which is arranged in contact with the lower layer and which includes a phosphate and a colloidal silica as main components. The base steel sheet includes the predetermined chemical composition and includes a B compound whose major axis length is 1 to 20 μm and whose number density is 1×10 to 1×10.sup.6 pieces/mm.sup.3. The lower layer is a glass film which includes a forsterite as main component or an intermediate layer includes a silicon oxide as main component.

A grain oriented electrical steel sheet includes: a base steel sheet; a glass film which is arranged in contact with the base steel sheet; and an insulation coating which is arranged in contact with the glass film and which includes a phosphate and a colloidal silica as main components. The base steel sheet includes the predetermined chemical composition. A BN whose average particle size is 50 to 300 nm is included at a predetermined number density in a region which is from an interface between the glass film and the insulation coating till 5 μm toward the base steel sheet in a depth direction. A B emission intensity obtained inside the glass film is more than a B emission intensity obtained inside the base steel sheet, when a B emission intensity is measured from a surface of the insulation coating by a glow discharge emission spectroscopy.