An electrical steel sheet (300) is formed such that centerlines of four magnetic poles (salient poles) of a rotor core (111) coincide with a direction of easy magnetization (ED1) or (ED2). In addition, the electrical steel sheets (300) are laminated such that the directions of easy magnetization (ED1) and (ED2) are aligned.

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.

Provides is a non-oriented electrical steel sheet suitable for use in a rotor of an IPM motor that has excellent magnetic flux density B.sub.50 and high-frequency iron loss properties, high tensile strength and fatigue strength, and little variation in tensile strength. The non-oriented electrical steel sheet has a predetermined steel sheet chemical composition and a microstructure in which a ratio of non-recrystallized microstructure is 5% or more and 70% or less and the number of inclusion having a diameter of 5 μm or more is not more than 5 counts/mm.sup.2.

An electric resistance welded steel pipe includes a base metal zone and an electric resistance welded zone. The base metal zone has a predetermined chemical composition and a microstructure including, by volume, ferrite: more than 30%, and bainite: 10% or more. The total volume fraction of the ferrite and the bainite is 70% or more and 95% or less. The balance being one or two or more phases selected from pearlite, martensite, and austenite. Further, when regions surrounded by boundaries between adjacent crystals having a misorientation of 15° or more are defined as crystal grains, the average size of the crystal grains is less than 7.0 μm, and the volume fraction of crystal grains having a size of 40.0 μm or more is 30% or less. A compressive residual stress generated in the inner and outer surfaces of the steel pipe in the axial direction is 250 MPa or less.

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.

The present invention relates to a soft high-silicon steel sheet, and more particularly, to a soft high-silicon steel sheet which has ductility even if the silicon content thereof is greater than 4%, and can thus be manufactured into a steel sheet having a high silicon content only by means of rolling without an additional siliconizing process. The soft high-silicon steel sheet may include a silicon content greater than 4 wt % and less than or equal to 7 wt % and 1 to 20% of chromium, or may include 5 to 7 wt % of Si+Al and 1 to 20 wt % of chromium.

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.

Provided is an oriented electrical steel sheet including: a forsterite film formed on one side or both sides of an oriented electrical steel sheet substrate; and a ceramic layer formed on an entire or partial region of the forsterite film. Provided is a manufacturing method for an oriented electrical steel sheet including: preparing an oriented electrical steel sheet having a forsterite film formed on one surface or both surfaces thereof; and forming a ceramic layer by spraying ceramic powder on the forsterite film.

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.