Abstract: Vibration of an iron core is reduced to reduce transformer noise. An iron core for a transformer comprises a plurality of grain-oriented electrical steel sheets stacked together, wherein at least one of the plurality of grain-oriented electrical steel sheets: (1) has a region in which closure domains are formed in a direction crossing a rolling direction and a region in which no closure domains are formed; (2) has an area ratio R0 of 0.10% to 3.0%, the area ratio R0 being defined as a ratio of S0 to S; and (3) has an area ratio R1a of 50% or more, the area ratio R1a being defined as a ratio of S1a to S1.

Abstract: Vibration of an iron core is reduced to reduce transformer noise. An iron core for a transformer comprises a plurality of grain-oriented electrical steel sheets stacked together, wherein at least one of the plurality of grain-oriented electrical steel sheets: (1) has a region in which closure domains are formed in a direction crossing a rolling direction and a region in which no closure domains are formed; and (2) has an area ratio R of 0.10% to 30%, the area ratio R being an area ratio, to the whole grain-oriented electrical steel sheet, of a region in which a shrinkage amount at a maximum displacement point when excited in the rolling direction at a maximum magnetic flux density of 1.7 T and a frequency of 50 Hz is at least 2×10?7 less than a shrinkage amount in the region in which no closure domains are formed.

Abstract: Disclosed is a grain-oriented electrical steel sheet with extremely low iron loss by means of a magnetic domain refining technique. In a grain-oriented electrical steel sheet having a plurality of magnetic domains refined via a local strain introduction portion, when a direct-current external magnetic field is applied to the steel sheet in a rolling direction, for a magnetic flux leaked from the local strain introduction portion at a position 1.0 mm away from a surface of the steel sheet at a side of the local strain introduction portion, a value obtained by dividing an intensity level of a total leakage magnetic flux by an intensity level of a magnetic flux leaked due to causes other than strain is more than 1.2.

Abstract: Provided is a grain-oriented electrical steel sheet that can benefit from the iron loss improving effect by groove formation while effectively suppressing a decrease in magnetic flux density. A grain-oriented electrical steel sheet comprises predetermined linear grooves, wherein in each linear groove, a proportion of predetermined flat portions to an entire length of the linear groove is 30% or more and 90% or less, the number of flat portions each of which is continuous for a predetermined length is 10 or more per 100 cm2 surface area, and a ratio of ten-point average roughness Rzjis to average depth D is 0.1 or more and 1 or less.

Abstract: Provided is a grain-oriented electrical steel sheet comprising a magnetic flux density B8 of 1.92 T or more, wherein a ratio Wa/Wb of a film thickness Wa of a forsterite film on a strain-introduced surface to a film thickness Wb of a forsterite film on a non-strain-introduced surface is 0.5 or more, an average width of a magnetic domain discontinuous portion on the non-strain-introduced surface is 1.00 time or more of an average width of a magnetic domain discontinuous portion on the strain-introduced surface, the average width of the magnetic domain discontinuous portion on the non-strain-introduced surface is 400 ?m or less, and compressive stress exists in a rolling direction in a range from a surface of the steel sheet that is the strain-introduced surface to at least 2 ?m in a sheet thickness direction.

Abstract: Provided is a grain-oriented electrical steel sheet that combines low iron loss and low magnetostriction, together with an advantageous production method therefor. A grain-oriented electrical steel sheet comprises a linear strain portion extending in a direction intersecting a rolling direction of the grain-oriented electrical steel sheet, wherein the linear strain portion has a stress distribution in which a compressive stress region and a tensile stress region alternate in a longitudinal direction of the linear strain portion. The linear strain portion is formed by vibrating the grain-oriented electrical steel sheet in a sheet thickness direction, while irradiating a surface of the grain-oriented electrical steel sheet with an electron beam by repeatedly moving and detaining the electron beam in the direction intersecting the rolling direction of the grain-oriented electrical steel sheet.

Abstract: Provided is a wound core having a flat portion and corner portions adjacent to the flat portion, the flat portion including a lap portion, the corner portions including bent portions. A non-heat-resistant magnetic domain refined material is used for at least a part of the materials forming the wound core. Closure domains are formed in the non-heat-resistant magnetic domain refined material so as to extend in a direction intersecting a longitudinal direction of the non-heat-resistant magnetic domain refined material, an area of each of the closure domains in a cross section that is taken in the longitudinal direction being more than 7500 ?m2. In the lap portion, the ratio of the number of lap joint portions having a lap length of from 3.0 mm to 30 mm to the total number of lap joint portions is 50% or more.

Abstract: A grain-oriented electrical steel sheet with extremely excellent magnetic properties by removing an etching resist coating well to form narrow grooves on a metal strip surface even with low-output laser, while reducing thermal effects on the metal strip caused by laser irradiation, and a method for forming grooves on a metal strip surface, having forming an etching resist coating with 0 to 70 lightness L* on at least one side of the metal strip, irradiating laser with less than 1.5 kW output on the etching resist coating while scanning the laser in a direction that intersects a rolling direction of the metal strip to remove a portion of the etching resist coating irradiated by the laser, and etching a portion of the metal strip below the removed portion of the etching resist coating to form grooves, the lightness L* being a L* value in a CIELAB color space (CIE1976L*a*b* color space).

Abstract: A method for forming grooves on a surface of a metal strip, having applying a coating agent for etching resist coating formation to a roller; then, irradiating a laser on the roller while scanning the laser in an axial direction of the roller or in a direction inclined to the axial direction to remove a portion of the coating agent for etching resist coating formation irradiated by the laser; then, bringing the roller into contact with at least one side of the metal strip to transfer the coating agent for etching resist coating formation to the at least one side of the metal strip, with an unapplied area corresponding to the removed portion of the coating agent for etching resist coating formation.

Abstract: Provided is a method for manufacturing a grain-oriented electrical steel sheet to reduce iron loss by controlling the magnetic domain structure, in which the iron loss reduction effect can be maintained even when stress relief annealing is applied, and the magnetic flux density does not decrease after the magnetic domain control treatment. In the manufacturing method, on a surface of the grain oriented electrical steel sheet, a laser beam with a ring-shaped intensity distribution in which the intensity in a periphery is lower than that in a center is irradiated in a linear manner in a direction intersecting a rolling direction of the steel sheet.

Abstract: To provide a grain-oriented electrical steel sheet that can achieve both sufficiently low transformer core loss and sufficiently low noise. Disclosed is a grain-oriented electrical steel sheet having a tension coating on a surface thereof and subjected to magnetic domain refining treatment by generating linear closure domains extending in a direction within 30° of a transverse direction, in which an average interval L between adjacent closure domains is 15 mm or less, a depth ratio rd of a depth of the closure domains to a sheet thickness, calculated by a predetermined formula, is 35% or more, and a volume fraction rv of the closure domains, calculated by a predetermined formula, is 0.30% or more and 3.0% or less, and an area ratio rs of the closure domains, calculated by a predetermined formula, is 0.50% or more and 4.0% or less.

Abstract: To reduce variations in iron loss among materials subjected to magnetic domain refining by electron beam irradiation and to stably obtain good iron loss properties, disclosed is a method of producing a grain-oriented electrical steel sheet including performing magnetic domain refining treatment by irradiating with an electron beam, in a pressure reduced area, a surface of a grain-oriented electrical steel sheet after subjection to final annealing, the method further including: before the irradiating with the electron beam, delivering the grain-oriented electrical steel sheet wound in a coil shape and heating the delivered grain-oriented electrical steel sheet to 50° C. or higher; and then cooling the grain-oriented electrical steel sheet such that the grain-oriented electrical steel sheet has a temperature of lower than 50° C. at the time of entering the pressure reduced area.

Abstract: Provided is a grain-oriented electrical steel sheet which has been subjected to heat-resistant magnetic domain refining treatment and can effectively suppress carburizing and nitriding during stress relief annealing. The grain-oriented electrical steel sheet has a plurality of grooves on one side that extend linearly across the rolling direction and are lined up at intervals in the rolling direction, and has at least a forsterite film on a surface of the steel sheet, where an average thickness of the forsterite film formed on the floor of the grooves is 0.45 ?m or more, and a standard deviation a of the thickness is 0.34 ?m or less.

Abstract: To form linear grooves of desired groove width on a metal strip surface and provide a grain-oriented electrical steel sheet having excellent magnetic properties, a linear groove formation method comprises: forming a resist coating on at least one surface of a metal strip; thereafter irradiating the resist coating with a laser while scanning the laser in a direction crossing a rolling direction of the metal strip, to remove the resist coating in a part irradiated with the laser; and thereafter performing etching treatment to form a linear groove in a part of the metal strip in which the resist coating is removed, wherein the resist coating contains a predetermined amount of an inorganic compound, and on the surface of the metal strip, the laser has a predetermined elliptic beam shape.

Abstract: Provided is a linear groove formation pattern with which both an effect of reducing the building factor and a high magnetic flux density can be obtained. In a grain-oriented electrical steel sheet having a plurality of linear grooves extending in a direction crossing a rolling direction of the steel sheet on a surface of the steel sheet, a surface of the steel sheet between the linear grooves has a recessed defect that is recessed from the surface, a volume fraction of the recessed defect in the steel sheet is 0.0025 vol % or more and 0.01 vol % or less of a steel sheet without the recessed defect, and discontinuous portions that disrupt the extension of the linear grooves are provided at a frequency of 30 or more and 200 or less per square meter of the steel sheet.

Abstract: Provided is a grain-oriented electrical steel sheet having both low iron loss and good magnetostrictive properties, with which a transformer having excellent properties can be manufactured. The grain-oriented electrical steel sheet of the present disclosure has a linear strain region extending linearly in a direction intersecting the rolling direction, where the linear strain region has a region having compressive stress in the rolling direction, and a region adjacent in a rolling direction to the region having compressive stress has a region having tensile stress in the rolling direction.

Abstract: 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.

Abstract: Provided is a grain-oriented electrical steel sheet having better transformer iron loss property than conventional grain-oriented electrical steel sheets. A grain-oriented electrical steel sheet comprises: a steel substrate; a forsterite film on a surface of the steel substrate; and a Cr-depleted layer at a boundary between the steel substrate and the forsterite film, the Cr-depleted layer having a Cr concentration that is 0.70 times to 0.90 times a Cr concentration of the steel substrate.

Abstract: A grain-oriented electrical steel sheet for a stacked transformer core. The steel sheet having a sheet thickness t, where t and an iron loss deterioration ratio obtained by subjecting the steel sheet under elliptic magnetization satisfy the following relations: (i) when t?0.20 mm, the iron loss deterioration ratio is 85% or less; (ii) when 0.20 mm<t<0.27 mm, the iron loss deterioration ratio is 80% or less; and (iii) when 0.27 mm?t, the iron loss deterioration ratio is 75% or less. The iron loss deterioration ratio is calculated from ((WA?WB)/WB)×100, where WA is iron loss under 50 Hz elliptic magnetization of 1.7 T in a rolling direction and 1.0 T in a direction orthogonal to the rolling direction, and WB is iron loss under 50 Hz alternating magnetization of 1.7 T in the rolling direction.

Abstract: Provided is a grain-oriented electrical steel sheet that combines low iron loss and low magnetostriction, together with an advantageous production method therefor. A grain-oriented electrical steel sheet comprises a linear strain portion extending in a direction intersecting a rolling direction of the grain-oriented electrical steel sheet, wherein the linear strain portion has a stress distribution in which a compressive stress region and a tensile stress region alternate in a longitudinal direction of the linear strain portion. The linear strain portion is formed by vibrating the grain-oriented electrical steel sheet in a sheet thickness direction, while irradiating a surface of the grain-oriented electrical steel sheet with an electron beam by repeatedly moving and detaining the electron beam in the direction intersecting the rolling direction of the grain-oriented electrical steel sheet.