An oriented electrical steel sheet according to an exemplary embodiment of the present invention includes C: 0.01% or less (excluding 0%), Si: 2.0%-4.0%, Mn: 0.01%-0.20%, acid soluble Al: 0.040% or less (excluding 0%), N: 0.008% (excluding 0%), S: 0.008% (excluding 0%), Se: 0.0001-0.008%, Cu: 0.002-0.1%, Ni: 0.005-0.1%, Cr: 0.005-0.1%, P: 0.005%-0.1% and Sn: 0.005%-0.20%, one or more among Sb: 0.0005%-0.10%, Ge: 0.0005%-0.10%, As: 0.0005%-0.10%, Pb: 0.0001%-0.10%, Bi: 0.0001%-0.10% and Mo: 0.001-0.1% as wt %, and consisting of the balance of Fe and other inevitable impurities, and after final secondary recrystallization, a magnetic flux density B8 is 1.92 Tesla or more.

This grain-oriented electrical steel sheet includes a base steel sheet, a forsterite-based primary film disposed on a surface of the base steel sheet, and a phosphate-based tension-imparting film containing no chromium, which is disposed on a surface of the primary film. In a case where a Ti content and a S content are respectively expressed as XTi and XS, by mass %, the forsterite-based primary film satisfies Expression (1) and Expression (2). A strain-introduced magnetic domain control is performed on the grain-oriented electrical steel sheet.

0.10≤XTi/XS≤10.00   Expression (1)

XTi+XS≥0.10 mass %.   Expression (2)

A soft magnetic material that is sheet-shaped or foil-shaped and has a high saturation magnetic flux density, contains iron, carbon, and nitrogen, and includes a martensite containing carbon and nitrogen, and γ-Fe, wherein the γ-Fe includes a nitrogen-containing phase. The soft magnetic material is produced by steps of heating an iron-based material that is sheet-shaped or foil-shaped, carburizing the iron-based material with a carburizing gas, dispersing a granular carbide in α-Fe in the iron-based material at a temperature equal to or lower than a eutectoid temperature, transforming the α-Fe into γ-Fe at a temperature higher than the eutectoid temperature, diffusing nitrogen into the γ-Fe using a nitrogen supply gas to form γ-Fe—N—C, and rapidly heating and then rapidly cooling the γ-Fe—N—C to transform the γ-Fe—N—C into a martensite. The result is a thermally stable soft magnetic material having a saturation magnetic flux density higher than that of pure iron.

Provided is a manufacturing method of a grain-oriented electrical steel sheet including preparing a hot-rolled sheet by hot-rolling a slab; removing some of scales formed on the hot-rolled sheet and leaving a scale layer having a thickness of 10 nm or more to prepare a hot-rolled sheet on which the scale layer remains; preparing a cold-rolled sheet by cold-rolling the hot-rolled sheet on which the scale layer remains; preparing the decarburization annealed cold-rolled sheet by decarburization annealing the cold-rolled sheet; coating an annealing separator on the decarburization annealed cold-rolled sheet to form a metal oxide layer; and final annealing the steel sheet on which the metal oxide layer is formed, wherein the annealing separator includes magnesium oxide (MgO) or magnesium hydroxide (MgOH) and fluoride.

A method for manufacturing a grain-oriented electrical steel sheet includes: a silicon steel material production process of producing a silicon steel material; a hot rolling process of obtaining a hot rolled sheet by subjecting the silicon steel material to hot rolling; a cold rolling process of obtaining a steel sheet having a final sheet thickness by subjecting the hot rolled sheet to a single cold rolling process or to multiple cold rolling processes having intermediate annealing performed between cold rolling processes; a decarburization annealing process of subjecting the steel sheet to decarburization annealing using a decarburization annealing furnace including a heating area and a soaking area; and a final annealing process of applying an annealing separator having alumina as a main component to the steel sheet and subjecting the steel sheet to final annealing, wherein, in the decarburization annealing process, when X represents the Cr content of the silicon steel material in terms of mass %, an oxidation degree P1 of an atmosphere gas in the heating area satisfies the following Expression 1 and an oxidation degree P2 of an atmosphere gas in the soaking area satisfies the following Expression 2:

0.18X−0.008≤P1≤0.25X+0.15≤0.20  (Expression 1); and

0.01≤P2≤0.15  (Expression 2).

Provided is a method for nitriding a grain-oriented electrical steel sheet which is very useful in obtaining excellent magnetic properties with no variation, that enables generating glow discharge between positive electrodes and negative electrodes disposed in a nitriding zone and irradiating the generated plasma to a strip to perform appropriate nitriding.

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 having: low high-frequency iron loss and high magnetic flux density; an inner layer and surface layers provided on both sides of the inner layer, the surface layers and the inner layer having specific chemical compositions; the thickness t of 0.01 mm to 0.35 mm; a multilayer ratio of ti to t of 0.10 to 0.70, t.sub.1 denoting a total thickness of the surface layers; a difference between [Si].sub.1 and [Si].sub.0 of 1.0 mass % to 4.5 mass % or less, [Si].sub.1 denoting a Si content in each of the surface layers and [Si].sub.0 denoting a Si content in the inner layer; and a difference between [Mn].sub.0 and [Mn].sub.1 of 0.01 mass % to 0.40 mass %, [Mn].sub.0 denoting a Mn content at a mid-thickness position t/2 and [Mn].sub.1 denoting an average Mn content in a region from a surface to a position at a depth of ( 1/10)t.

A grain-oriented electrical steel sheet includes: a base steel sheet; an intermediate layer arranged in contact with the base steel sheet; and an insulation coating arranged in contact with the intermediate layer to be an outermost surface, in which the insulation coating has a crystalline phosphide-containing layer containing a crystalline phosphide in an area in contact with the intermediate layer when viewing a cross section whose cutting direction is parallel to a thickness direction.

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.