Provided is an electrical steel sheet comprising: a groove formed in a surface of a steel sheet, wherein the groove includes a bottom surface, a first side surface extending from the bottom surface, and a second side surface extending from the bottom surface in opposite to the first side surface, wherein the groove has a depth from the surface to the bottom surface, a width in a rolling direction of the steel sheet, and a length in a width direction of the steel sheet, and wherein the groove is formed through laser-irradiation and removal of melt produced by the laser-irradiation; an opening defined by the bottom surface, the first side surface and the second side surface; and a first solidification portion formed on the first side surface of the groove. The first solidification portion is formed by a solidification of part of the melt produced from the laser-irradiation.

Disclosed are a grain-oriented electrical steel sheet and a method of manufacturing the same. The method for manufacturing a grain-orientated electrical steel sheet according to an exemplary embodiment of the present invention includes: providing an electrical steel sheet before forming primary recrystallization or after forming the primary recrystallization; and forming a groove in a surface of the electrical steel sheet by radiating laser and simultaneously spraying gas onto the electrical steel sheet, in which energy density E.sub.d and a laser scanning speed V.sub.s of the radiated laser satisfy the following conditions,
1.0 J/mm.sup.2E.sub.d5.0 J/mm.sup.2,
0.0518 mm/secV.sub.s0.2 mm/sec.

In a laser processing apparatus for refining magnetic domains of a grain-oriented electromagnetic steel sheet by setting a laser beam to be focused on the grain-oriented electromagnetic steel sheet and scanned in a scanning direction, the laser beam focused on the grain-oriented electromagnetic steel sheet is linearly polarized light, and the angle between the linear polarization direction and the scanning direction is equal to or higher than 0 and lower than 45.

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.

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 00.3a and 1.2a+0.02w0.56.50.13a200(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.

A grain-oriented electrical steel sheet includes: a base steel sheet; a primary film formed on a surface of the base steel sheet; and a tension insulation coating formed on a surface of the primary film, in which a magnetic domain control is performed by irradiating the tension insulation coating with a laser from above. When a strip-like sample having a length of 300 mm in a direction parallel to a rolling direction of the grain-oriented electrical steel sheet and a length of 60 mm in a direction parallel to a transverse direction is extracted from the grain-oriented electrical steel sheet, a range from a surface of the tension insulation coating to a depth position of 5 m toward the base steel sheet side from an interface between the base steel sheet and the primary film is removed by pickling at least one surface of the sample, and a warpage amount of the sample is thereafter measured, the warpage amount satisfies predetermined conditions.

A method for refining a magnetic domain of a grain-oriented electrical steel strip is provided, including a steel strip supporting roll position adjusting step of controlling a position of the steel strip in a vertical direction while supporting the steel strip proceeding along a production line, a laser irradiating step of forming a groove on a surface of the steel strip by irradiating a laser beam onto the surface of the steel strip to melt the steel strip, and a detecting step of detecting a defect in the groove formed on the surface of the steel strip while the steel strip proceeds, so as to be able to detect whether the groove is defective by confirming a machining state of a magnetic domain refined groove formed on the surface of the steel strip in a working process.

A laser-scribed grain-oriented silicon steel resistant to stress-relief annealing and a manufacturing method therefor. Parallel linear grooves (20) are formed on one or both sides of grain-oriented silicon steel (10) by laser etching. The linear grooves (20) are perpendicular to, or at an angle to, the rolling direction of the steel plate. A maximum height of edge protrusions of the linear grooves (20) does not exceed 5 m, and a maximum height of spatters in etch-free regions between adjacent linear grooves (20) does not exceed 5 m, and the proportion of an area occupied by spatters in the vicinity of the linear grooves (20) does not exceed 5%. The steel has low manufacturing costs, and the etching effect of the finished steel is retained during a stress-relief annealing process. The steel is suitable for manufacturing of wound iron core transformers.

Disclosed is a grain-oriented electrical steel sheet including: closure domains, each containing a discontinuous region at a part thereof and extending at an angle within 30 with respect to a transverse direction of the steel sheet, wherein a closure domain overlapping portion in the discontinuous region on one surface of the steel sheet has a length in the transverse direction that is longer than a length in the transverse direction of the closure domain overlapping portion on the other surface of the steel sheet, and the length satisfies 0.55.0 and the length satisfies 0.20.8. Consequently, the iron loss and the deterioration of magnetostrictive properties are suppressed in discontinuous regions, which would be inevitably formed when magnetic domain refining treatment is performed using a plurality of irradiation devices.

In a grain-oriented electrical steel sheet, comprising magnetic domains refined by a plurality of linear grooves in a surface of a steel sheet, each of the linear grooves is provided on its floor with a plurality of recessed parts aligned in a direction in which the linear groove extends, at a predetermined interval p (m), and the recessed part is made to have a predetermined depth d (m). In this way, it is possible to provide a grain-oriented electrical steel sheet having further improved iron loss properties while having reduced magnetic flux density reduction.