A hot-rolled steel sheet for a non-oriented electrical steel sheet containing, in mass %, components of C: 0.0010% to 0.0050%, Si: 1.90% to 3.50%, Al: 0.10% to 3.00%, Mn: 0.05% to 2.00%, P: 0.10% or less, S: 0.005% or less, N: 0.0040% or less and B: 0.0060% or less with a remainder consisting of Fe and impurities, in which, in a sheet width-direction end portion of the hot-rolled steel sheet for a non-oriented electrical steel sheet, a C concentration [atom %] in a crystal grain boundary is 3.0 or more times a P concentration [atom %], and the C concentration [atom %] in the crystal grain boundary of the hot-rolled steel sheet for a non-oriented electrical steel sheet is 3.5 or more times a C concentration in a crystal grain.

A grain oriented electrical steel sheet includes the texture aligned with Goss orientation. In the grain oriented electrical steel sheet, when (α.sub.1 β.sub.1 γ.sub.1) and (α.sub.2 β.sub.2 γ.sub.2) represent deviation angles of crystal orientations measured at two measurement points which are adjacent on the sheet surface and which have an interval of 1 mm, the boundary condition BA is defined as |γ.sub.2−γ.sub.1|≥0.5°, and the boundary condition BB is defined as [(α.sub.2−α.sub.1).sup.2+(β.sub.2−β.sub.1).sup.2+(γ.sub.2−γ.sub.1).sup.2].sup.1/2≥2.0°, the boundary which satisfies the boundary condition BA and which does not satisfy the boundary condition BB is included.

A non-oriented electrical steel sheet produced by hot-rolling a steel slab containing Si: 2.8 to 6.5 mass % and Zn: 0.0005 to 0.0050 mass % followed by cold rolling and finish annealing, a coating agent containing at least one element from Sn, Sb, P, S, Se, As, Te, B, Pb, and Bi is applied to the surface after annealing forming an insulation coating with nitriding-suppressing ability. Alternatively, an intermediate layer containing at least one element from Sn, Sb, P, S, Se, As, Te, B, Pb, and Bi and having a nitriding-suppressing ability forms on the steel sheet iron matrix after the annealing and forms an insulation coating, without above elements, on the intermediate layer thus obtaining a non-oriented electrical steel sheet wherein a high strength rotor core with and stator core with excellent magnetic is simultaneously obtained, and a motor core including a stator core and rotor core from the steel sheet.

In a production of a non-oriented electrical steel sheet by hot-rolling a steel slab containing Si: 2.8 to 6.5 mass % and Zn: 0.0005 to 0.0050 mass % followed by cold rolling and finish annealing, a coating agent containing at least one element selected from Sn, Sb, P, S, Se, As, Te, B, Pb, and Bi is applied to the steel sheet surface after the finish annealing to form an insulation coating with a nitriding-suppressing ability. Alternatively, an intermediate layer containing at least one element selected from Sn, Sb, P, S, Se, As, Te, B, Pb, and Bi and having a nitriding-suppressing ability is formed on the steel sheet iron matrix after the finish annealing and form an insulation coating not containing above elements is formed on the intermediate layer thus to obtain a non-oriented electrical steel sheet from which a rotor core with high strength and stator core with excellent magnetic properties after the stress-relief annealing can be obtained at the same time, and a motor core comprising a stator core and rotor core is produced from the steel sheet.

An annealing separator for an oriented electrical steel sheet includes: a first component including a Mg oxide or a Mg hydroxide; and a second component including one kind among oxides and hydroxides of a metal selected from Al, Ti, Cu, Cr, Ni, Ca, Zn, Na, K, Mo, In, Sb, Ba, Bi, and Mn, or two or more kinds thereof.

A preparation method of glassless grain-oriented silicon steel includes the following operations. During a decarburization annealing, a thickness of an oxide film on a surface of strip is 1.5-2.5 μm; an atomic weight ratio of Si element and Fe element in the oxide film satisfies: Si/(Si+Fe)≥0.76; during a high-temperature annealing, a cooling stage includes sequentially: cooling with an inner cover when a temperature drops from 1200° C. to 500° C.; wherein a protective gas is a mixed gas containing nitrogen and hydrogen, and a volume percentage of the hydrogen in the mixed gas is >3%; cooling with the inner cover when the temperature drops from 500° C. to 200° C.; wherein the protective gas is nitrogen; and cooling in air by removing the inner cover when the temperature is <200° C.

An annealing separator for an oriented electrical steel sheet including: a first component includes a Mg oxide or a Mg hydroxide; and a second component including one kind among oxides and hydroxides of a metal selected from Al, Ti, Cu, Cr, Ni, Ca, Zn, Na, K, Mo, In, Sb, Ba, Bi, and Mn, or two or more kinds thereof.

Provided is a method for manufacturing a grain-oriented electrical steel sheet. The method comprises: hot rolling a slab to obtain a hot rolled sheet; subjecting the hot rolled sheet to hot band annealing as necessary; subjecting the hot rolled sheet to cold rolling; subjecting the cold rolled sheet to decarburization annealing; applying an annealing separator having MgO as a main component onto a surface of the decarburization annealed sheet and subjecting the decarburization annealed sheet to final annealing to form the forsterite film; and applying an insulating coating treatment liquid onto the final annealed sheet and subjecting the final annealed sheet to flattening annealing to form a tension-applying insulating coating. A difference in total tensions between one and opposite surfaces of the sheet is less than 0.5 MPa. A difference in tensions between the forsterite films in one and opposite surfaces of the sheet is 0.5 MPa or more.

A non-oriented electrical steel sheet according to an embodiment of the present invention includes, in wt %, Si: 2.1 to 3.8%, Mn: 0.001 to 0.6%, Al: 0.001 to 0.6%, Bi: 0.0005 to 0.003%, and Ge: 0.0003 to 0.001%, and the balance of Fe and inevitable impurities.

In a double-oriented electrical steel sheet according to an embodiment of the present invention, the fraction of crystal grains having an orientation within 15° from {100}<001> is 50 to 75%, and the fraction of crystal grains having an orientation within 15° from {100}<380> is 50 to 75%.

The present invention relates to a non-oriented electrical steel sheet including 1.5 to 4.0 wt % of Si, 0.1 to 1.5 wt % of Al, 0.1 to 1.5 wt % of Mn, 0.005 wt % or less (excluding 0%) of C, 0.005 wt % or less (excluding 0%) of N, 0.005 wt % or less (excluding 0%) of Ti, 0.001 to 0.005 wt % of S, 0.1 wt % or less (excluding 0%) of P, 0.02 to 0.2 wt % of at least one of Sn and Sb, and a balance of Fe and other inevitable impurities; and satisfying the following Formulas 1, 2, and 3.
0.9≤[Al]+[Mn]≤2.1  [Formula 1]
0.2≤([Si]+[Al]+[Mn]/2)*([P]+[Sn]+[Sb])≤0.4  [Formula 2]
(Gs.sub.center−Gs.sub.surface)/(Gs.sub.center*t)≤0.5  [Formula 3] (In Formula 1 and Formula 2, [Al], [Mn], [Si], [P], [Sn], and [Sb] represent the content (weight %) of Al, Mn, Si, P, Sn, and Sb, respectively, and in Formula 3, t represents the thickness (mm) of the non-oriented electrical steel sheet, Gs.sub.surface represents the average grain size (μm) from 0 to t/4 or 3t/4 to t based on the thickness direction of the non-oriented steel sheet, Gs.sub.center represents the average grain size (μm) from more than t/4 to less than 3t/4 based on the thickness direction of the non-oriented steel sheet.)