Abstract: A grain-oriented electrical steel sheet is subjected to magnetic domain refining treatment by irradiating a steel sheet surface with an electron beam having a beam diameter d of 0.40 mm or less, wherein a modulated irradiation line region is formed with repeating units connected to each other in the line region direction, a periodic distance of the repeating units in the modulated irradiation line region is ?×d mm to 2.5×d mm, a repeating interval of the modulated irradiation line region in the rolling direction is 4.0 mm to 12.5 mm, and intensity of the electron beam is not lower than an intensity with which long and narrow divided magnetic domains extending in the modulated irradiation line region direction are formed at least on an irradiated side, and not higher than an intensity with which coating damage does not occur and a plastic strain region is not formed on the irradiated side.

Abstract: A magnetic domain refining treatment is performed by dividing a surface of a steel sheet into a plurality of regions in a widthwise direction, disposing a laser irradiation apparatus or an electron beam irradiation apparatus in each of the regions, and forming beam-irradiated regions through beam irradiation, wherein beams are irradiated so that a nature of a juncture between beam-irradiated regions satisfies 0???0.3×a and ?1.2×a+0.02×w?0.5×??6.5????0.13×a?200×(1/w)+5.4 when TD spacing ? at the juncture between the beam-irradiated regions is ?3 to 0 mm, whereby a grain oriented electrical steel sheet having an excellent iron loss property is produced in a good productivity.

Abstract: Provided is a grain-oriented electrical steel sheet including: a forsterite base film formed on a surface of the steel sheet; and an insulating tension coating formed on the base film, in which when Ti intensity FX(Ti), Al intensity FX(Al), and Fe intensity FX(Fe) obtained through quantitative analysis by performing fluorescent X-ray analysis on the surface of the steel sheet satisfy FX(Ti)/FX(Al)?0.15 and FX(Ti)/FX(Fe)?0.004, the frequency of crystal boundaries of secondary recrystallized grains in the direction orthogonal to the rolling direction is 20 grain boundaries/100 mm or less, the mean thickness of the forsterite base film t(Fo) and the thickness of the insulating tension coating t(C) satisfies t(Fo)/t(C)?0.3, and magnetic domain refining treatment is performed by irradiation with a laser beam, plasma flame, or electron beam, a sufficient iron loss reducing effect is achieved in a range where coating detachment does not occur.

Abstract: A grain-oriented electrical steel sheet subjected to magnetic domain refining by linearly introducing strains in a direction intersecting a rolling direction of the steel sheet repeatedly with intervals in the rolling direction, wherein if a repeating interval of the strains in the rolling direction is d (mm) and, when the steel sheet is placed on a flat surface, a mean value of difference between a height from the flat surface in linear strain-introduced areas of a steel sheet surface and a height from the flat surface in intermediate points between adjacent linear strain-introduced areas is h (mm), then the ratio h/d of the h to the d is 0.0025 or more and 0.015 or less.

Abstract: An electron gun abnormality detecting device for detecting an abnormality in first and second electron guns of a magnetic domain refining device for an electrical steel sheet includes: a magnetooptic element configured to contact with and separate from an inspection region set to include a boundary between a magnetic domain discontinuity generated by irradiation of a surface of the electrical steel sheet with an electron beam by the first electron gun and a magnetic domain discontinuity generated by irradiation thereof with an electron beam by the second electron gun, and configured to detect a steel sheet magnetic domain structure in the inspection region as an optical property; a light source configured to irradiate the magnetooptic element with linearly polarized light; and a detector configured to detect polarized light rotated by the steel sheet magnetic domain structure transferred to the magnetooptic element.

Abstract: The location where forsterite is present is checked in a region from which light excited by an electron beam is emitted when a material containing forsterite is irradiated with an electron beam. The material is preferably a grain oriented electrical steel sheet having a forsterite layer. In addition, it is preferable that the accelerating voltage be 10 kV or more when an electron beam is radiated when the material is a grain oriented electrical steel sheet having a tension coating layer on the forsterite layer.

Abstract: The present invention provides a grain-oriented electrical steel sheet with reduced iron loss over a wide range of sheet thickness by providing a grain-oriented electrical steel sheet with an actually measured sheet thickness t (mm) that includes a closure domain region extending linearly in a direction from 60° to 120° with respect to the rolling direction on a surface of the steel sheet, the closure domain region being formed periodically at a spacing s (mm) in the rolling direction, such that h?74.9t+39.1 (0.26?t), h?897t?174.7 (t>0.26), (w×h)/(s×1000)??12.6t+7.9 (t>0.22), and (w×h)/(s×1000)??40.6t+14.1 (t?0.22), where h (?m) is the depth and w (?m) is the width of the closure domain region.

Abstract: According to the present invention, when irradiating the surface of a grain-oriented electrical steel sheet having a sheet thickness t with an electron beam in a direction intersecting a rolling direction, the irradiation energy E(t) of the electron beam is adjusted to satisfy Ewmin(0.23)×(1.61?2.83×t (mm))?E(t)?Ewmin(0.23)×(1.78?3.12×t (mm)) (Expression (1)) using the value of the irradiation energy Ewmin(0.23) that minimizes iron loss for material with a sheet thickness of 0.23 mm. The present invention thus allows for a grain-oriented electrical steel sheet with high productivity that can suppress a reduction in productivity caused by optical system adjustment operations or by shortening of line spacing.

Abstract: A steel sheet inspection device includes: a magnetooptic element that is able to detect, as an optical property, a magnetic domain structure of a steel sheet to be inspected; a light source that irradiates the magnetooptic element with linearly polarized light; a detector that detects the linearly polarized light with a polarization plane rotated according to the magnetic domain structure of the steel sheet transferred to the magnetooptic element; and a drive mechanism that drives at least the magnetooptic element so as to contact and separate the steel sheet and the magnetooptic element with and from each other.

Abstract: A grain-oriented electrical steel sheet exhibits reduced iron loss and reduced noise. The electrical steel sheet has magnetic domains refined by regions with a high lattice defect density being locally formed on the surface of or within the steel sheet, in which the regions with a high lattice defect density has a hardness, as measured by a micro Vickers hardness meter, equal to or lower than that of other regions.

Abstract: An electron gun abnormality detecting device for detecting an abnormality in first and second electron guns of a magnetic domain refining device for an electrical steel sheet includes: a magnetooptic element configured to contact with and separate from an inspection region set to include a boundary between a magnetic domain discontinuity generated by irradiation of a surface of the electrical steel sheet with an electron beam by the first electron gun and a magnetic domain discontinuity generated by irradiation thereof with an electron beam by the second electron gun, and configured to detect a steel sheet magnetic domain structure in the inspection region as an optical property; a light source configured to irradiate the magnetooptic element with linearly polarized light; and a detector configured to detect polarized light rotated by the steel sheet magnetic domain structure transferred to the magnetooptic element.

Abstract: According to the present invention, a grain-oriented electrical steel sheet for iron cores exhibiting excellent transformer iron loss properties in an excitation range from 1.5 T to 1.9 T is provided, in which a residual stress of 150 MPa or more is formed near strain regions, each extending 300 ?m or less in the rolling direction and 42 ?m or more in the sheet thickness direction, and the strain regions are formed periodically at intervals of 2 mm to 10 mm in the rolling direction, with reduced energy loss in transformers in operation.

Abstract: A grain-oriented electrical steel sheet, on which magnetic domain refining treatment by strain application has been performed, has an insulating coating with excellent insulation properties and corrosion resistance. The grain-oriented electrical steel sheet is obtained by irradiating a steel sheet with a high-energy beam to apply, to the steel sheet, linear strain extending in a direction that intersects a rolling direction of the steel sheet, and then re-forming an insulating coating on the steel sheet, in which in an irradiation mark region due to the high-energy beam, a ratio of an area containing defects on the insulating coating is 40% or less, a maximum width of the irradiation mark region in the rolling direction is 250 ?m or less, and a thickness of the insulating coating is 0.3 ?m or more and 2.0 ?m or less.

Abstract: Disclosed is a grain-oriented electrical steel sheet exhibiting low hysteresis loss and low coercive force, in which an increase in hysteresis loss due to laser irradiation or electron beam irradiation, which has been a conventional concern, is effectively inhibited. The grain-oriented electrical steel sheet has closure domain regions (X) formed to divide the magnetic domains in a rolling direction, from one end to the other in the width direction of the steel sheet, provided that Expression (1) is satisfied: ?(500t?80)×s+230?w??(500t?80)×s+330??Expression (1), where t represents a sheet thickness (mm); w represents a smaller one of the widths (?m) of the regions measured on the front and rear surfaces of the steel sheet, respectively, by using a Bitter method; and s represents an average number of the regions present within one crystal grain.

Abstract: A grain-oriented electrical steel sheet produces reduced noise when worked into a transformer, by setting length d of each plastic strain region in the widthwise direction of the steel sheet to 0.05 mm or more and 0.4 mm or less, and a ratio (?d/?w) of a total ?d of the length d to a total ?w of application interval w of each of the above plastic strain regions to 0.2 or more and 0.6 or less.

Abstract: A grain-oriented electrical steel sheet, on which magnetic domain refining treatment by strain application has been performed, has an insulating coating with excellent insulation properties and corrosion resistance. In a grain-oriented electrical steel sheet, linear strain having been applied thereto by irradiation with a high-energy beam, the linear strain extending in a direction that intersects a rolling direction of the steel sheet, an area ratio of irradiation marks within an irradiation region of the high-energy beam is 2% or more and 20% or less, an area ratio of protrusions with a diameter of 1.5 ?m or more within a surrounding portion of the irradiation mark is 60% or less, and an area ratio of exposed portions of steel substrate in the irradiation mark is 90% or less.

Abstract: The present invention proposes a method that can reduce the noise generated by a transformer core and the like when formed by laminations of a grain-oriented electrical steel sheet in which core loss has been reduced by a magnetic domain refinement process. In this steel sheet, linear distortion extending with an orientation in which an angle formed with a direction perpendicular to the rolling direction of the steel sheet is an angle of 30° or less is periodic in the direction of rolling of the steel sheet, core loss (W17/50) is 0.720 W/kg or less, and magnetic flux density (B8) is 1.930 T. The volume of the closure domain arising in the distortion part is 1.00-3.00% of the total magnetic domain volume within the steel sheet.

Abstract: A grain-oriented electrical steel sheet allows for manufacture of a transformer that exhibits, when the steel sheet is applied to an iron core thereof, extremely low iron loss and extremely low noise properties, makes highly efficient use of energy, and can be used in various environments. The grain-oriented electrical steel sheet has a strain distribution in regions where closure domains are formed, when observed in a cross section in the rolling direction, with a maximum tensile strain in a sheet thickness direction being 0.45% or less, and with a maximum tensile strain t (%) and a maximum compressive strain c (%) in the rolling direction satisfying Expression (1): t+0.06?t+c?0.35??(1).

Abstract: This device scans a high-energy beam in a direction traversing a feed path of a grain-oriented electrical steel sheet having subjected to final annealing so as to irradiate a surface of the steel sheet being passed through with the high-energy beam to thereby perform magnetic domain refinement, the device including an irradiation mechanism for scanning the high-energy beam in a direction orthogonal to the feed direction of the steel sheet, in which the irradiation mechanism has a function of having the scanning direction of the high-energy beam oriented diagonally, relative to the orthogonal direction, toward the feed direction at an angle determined based on a sheet passing speed of the steel sheet on the feed path.

Abstract: A grain-oriented electrical steel sheet to which electron beam irradiation is applied, has a film and a thickness of t (mm), wherein no rust is produced on a surface of the steel sheet after a humidity cabinet test lasting 48 hours at a temperature of 50° C. in an atmosphere of 98% humidity, and iron loss W17/50 after the electron beam irradiation is reduced by at least (?500 t2+200 t?6.5) % of the iron loss W17/50 before the electron beam irradiation and is (5 t2?2 t+1.065) W/kg or less.