A non-oriented electrical steel strip or sheet having the following composition, in percent by weight: 3.2 to 3.4 of Si, 0.85 to 1.1 of Al, 0.07 to 0.18 of Mn, 0.01 to 0.04 of P, 0.0003 to 0.0030 of S, 0.0005 to 0.0020 of N, 0.0010 to 0.0050 of C, 0.0015 to 0.0040 of Ti, 0.01 to 0.008 of Cr, up to 0.05 in total of Nb+Mo+V, balance Fe and unavoidable impurities up to a total amount of 1.0% and having a specific electrical resistance at 50° C. of 0.62 to 0.65 μΩm. Also, a process for the production thereof and the use thereof in iron cores of rotating electric machines, in particular in electric motors, for example in electric vehicles or hybrid vehicles, and generators.

A non-oriented electrical steel sheet is produced by subjecting a steel slab containing, in mass %, C: not more than 0.0050%, Si: 1.0 to 6.5%, Mn: 0.05 to 2.0%, S: not more than 0.0050%, Al: not more than 0.01%, N: not more than 0.0050%, Ti: not more than 0.0030%, Nb: not more than 0.0030% and O: not more than 0.0050% to a hot rolling, a cold rolling and a finish annealing, the finish annealing conducted under conditions that a soaking temperature T (° C.) satisfies the following equation (1):

[00001]$\begin{array}{cc}\frac{\left(8000+400\times \mathrm{Si}\left(\mathrm{mass}\%\right)\right)}{\{\left(-\log \left(\mathrm{Al}\left(\mathrm{mass}\%\right)\times N\left(\mathrm{mass}\%\right)\right)+1.7+0.2\times \mathrm{Si}\left(\mathrm{mass}\%\right)\right\}}-273.15\le T\le 1200,& \left(1\right)\end{array}$

and an atmosphere in the finish annealing is a mixed gas composed of one or more selected from nitrogen, hydrogen and noble gas with a nitrogen content of not more than 50 vol % and a dew point of not higher than −20° C., whereby a non-oriented electrical steel sheet achieving a high magnetic flux density and a low iron loss is produced.

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 is produced by heating a steel slab containing, by mass %, C:0.02-0.10%, Si:2.0-5.0%, Mn:0.01-1.00%, sol. Al:0.01-0.04%, N:0.004-0.020% and S+Se:0.002-0.040% to a temperature of higher than 1280° C., and subjecting the sheet to a hot rolling, a hot-band annealing, a single cold rolling or two or more cold rollings having an intermediate annealing between each cold rolling and a primary recrystallization annealing combined with a decarburization annealing, applying an annealing separator onto a steel sheet surface, and subjecting the sheet to a finish annealing and a flattening annealing, a rapid cooling is conducted at an average cooling rate of not less than 200° C./s from 800° C. to 300° C. in the cooling process from a maximum achieving temperature in at least one annealing of the hot-band annealing and the intermediate annealing.

The present disclosure has as its object the provision of non-oriented electrical steel sheet excellent in magnetic properties which is free from any drop in magnetic flux density even after stress relief annealing and a method for manufacturing the same.

Non-oriented electrical steel sheet having a chemical composition containing C: 0.0030 mass % or less, Si: 2.0 mass % or more and 4.0 mass % or less, Al: 0.010 mass % or more and 3.0 mass % or less, Mn: 0.10 mass % or more and 2.4% mass or less, P: 0.0050 mass % or more and 0.20 mass % or less, S: 0.0030 mass % or less, and one or more elements selected from the group comprising Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd: total 0.00050 mass % or more and having a balance of Fe and unavoidable impurities, where, when designating a mass % of Si as [Si], a mass % of Al as [Al], and a mass % of Mn as [Mn], a parameter Q shown by the following formula (1) is 2.0 or more, a random intensity ratio of the {100} orientation is 2.4 or more, and an average grain size is 30 μm or less:

Q=[Si]+2[Al]−[Mn]  (1)

This electrical steel sheet contains, as a chemical composition, by mass %, C: 0.0035% or less, Si: 2.00% to 3.50%, Mn: 2.00% to 5.00%, P: 0.050% or less, S: 0.0070% or less, Al: 0.15% or less, N: 0.0030% or less, Ni: 0% to 1.00%, Cu: 0% to 0.10%, and a remainder: Fe and impurities, in which an X-ray random intensity ratio in a {100} <011> crystal orientation on a sheet surface is 15.0 to 50.0, and magnetic flux densities in 0°, 22.5°, and 45° directions from a rolling direction each satisfy [1.005×(B.sub.50 (0°)+B.sub.50 (45°))/2≥B.sub.50 (22.5°)].

A method for producing a non-oriented electrical steel sheet used as an iron core material for a motor or transformer and having excellent magnetic properties including subjecting a raw steel material including, by mass %, C: not more than 0.005%, Si: 1.0 to 5.0%, Mn: 0.04 to 3.0%, sol. Al: not more than 0.005%, P: not more than 0.2%, S: not more than 0.005%, N: not more than 0.005% and the remainder being Fe and impurities forming a hot-rolled sheet, subjecting the hot-rolled sheet to hot-band annealing and a single or two or more cold rollings including an intermediate annealing between each rolling forming a cold-rolled sheet having a final sheet thickness and subjecting the cold-rolled sheet to a finish annealing, wherein at least one pass in the final cold rolling at a friction coefficient μ of not less than 0.030 and a rolling reduction of not less than 15%.

Provided is a multilayer electrical steel sheet having both low high-frequency iron loss and high magnetic flux density. The multilayer electrical steel sheet has an inner layer and surface layers provided on both sides of the inner layer, in which each of the surface layers has a Si content of 2.5 mass % to 6.0 mass %, the inner layer has a Si content of 1.5 mass % to 5.0 mass %, and the multilayer electrical steel sheet has: ΔSi of 0.5 mass % or more; ΔAl of 0.05 mass % or less; Δλ.sub.1.0/400 of 1.0×10.sup.−6 or less; a sheet thickness t of 0.03 mm to 0.3 mm; and a ratio of a total thickness of the surface layers ti to t of from 0.10 to 0.70.

A method of manufacturing a grain oriented electrical steel sheet includes hot rolling a steel slab having a chemical composition including C: 0.002-0.10 mass %, Si: 2.5-5.0 mass %, Mn: 0.01-0.8 mass %, Al: 0.010-0.050 mass % and N: 0.003-0.020 mass % and the remainder being Fe and inevitable impurities to form a hot rolled sheet; subjecting the hot rolled sheet to one cold rolling or two or more cold rollings and interposing an intermediate annealing therebetween after hot band annealing or without hot band annealing to form a cold rolled sheet having a final thickness; subjecting the cold rolled sheet to a primary recrystallization annealing; applying an annealing separator to the surface of the steel sheet; and subjecting the sheet to a finish annealing and forming a tension coating.

Provided is a grain-oriented electrical steel sheet having a film that is effective for the magnetic properties of the steel sheet and particularly effective for iron loss reduction and has favorable adhesion. In a grain-oriented electrical steel sheet, an insulating film partially enters into a steel substrate to form an anchor part, a depth of the anchor part from the surface of the steel substrate is 3.5 μm or less, and a number of neck parts of 5 μm.sup.2 or less in area is 0.06/μm.sup.2 or less and a number of neck parts of 10 μm.sup.2 to 40 μm.sup.2 in area is 0.005/μm.sup.2 or more and 0.011/μm.sup.2 or less, where each neck part is a remaining part of the insulating film on the surface of the steel substrate when peeling the insulating film from the steel substrate in a bend test for the grain-oriented electrical steel sheet.