KR101385742B1 - Method for refining magnetic domains in grain-oriented electrical steel sheet - Google Patents

Abstract

Disclosed is a method for miniaturization of a magnetic steel sheet of a directional steel sheet. According to the present invention, there is provided a method for refining the magnetic domain of a grain-oriented electrical steel sheet, the method comprising: providing an electrical steel sheet before or after the first annealing, applying a liquid organic material to the surface of the steel sheet to increase the laser absorption rate, and maintaining the liquid phase in a liquid state; Drying to form a film quality of the organic material; irradiating a continuous wave laser to the surface of the electrical steel sheet to form a groove by melting the surface portion of the steel sheet; and film quality of the organic material by scattering the melt when the groove is formed. In order to remove the spatter formed in the phase, the film quality of the organic material is removed by washing with water or mild pickling and drying.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of refining magnetic steel sheets for a directional electric steel sheet,

The present invention relates to miniaturization of magnetic domains of grain-oriented electrical steel sheet, and more particularly, after applying an organic substance to the surface of the steel sheet, forming a groove by laser irradiation, and then removing molten fly ash together with the organic substance to improve iron loss improvement. The present invention relates to a method for miniaturizing magnetic domains of electrical steel sheets.

Directional electric steel sheets are used as iron core materials of electric devices such as transformers. In order to reduce electric power loss of electric devices and increase efficiency, steel sheets having magnetic properties with high iron loss and high magnetic flux density are required.

Generally, a directional electric steel sheet refers to a material having a texture (also referred to as a "goss cluster texture") in which the {110} <001> direction is oriented in the rolling direction through hot rolling, cold rolling and annealing.

In such a directional electrical steel sheet, the {110} < 001 > direction is excellent in magnetic properties as the orientation degree of the iron in a direction in which magnetization is easy.

In order to improve the magnetic properties of oriented electrical steel sheets, a method of miniaturizing magnetic domains is used. The magnetic domain miniaturization method can be classified into temporary magnetic domain miniaturization and permanent magnetic domain miniaturization according to whether or not the magnetic domain miniaturization improvement effect is maintained by stress relief annealing. .

Temporary magnetic domain miniaturization is a domain micronization technique in which domains are refined by forming 90 ^o domains to minimize magnetic elastic energy generated by applying local compressive stress to the surface by thermal or mechanical energy. The technique of microminiaturization of the temporal magnetic domain is a laser magnetic domain refining method, a ball scratch method, a plasma or an ultrasonic wave magnetic domain refining method according to an energy source for making the domain finer.

The permanent magnetic microfabrication method which can maintain the iron loss improving effect even after the heat treatment can be classified into the etching method, the roll method and the laser method.

Etching method is difficult to control groove shape (groove width, groove depth) because the groove is formed on the surface of steel sheet by electrochemical corrosion reaction in acid solution in solution. ), It is difficult to guarantee the iron loss characteristics of the final product because it forms a groove, and it is not environmentally friendly because the acid solution is used.

Permanent magnetization method by roll process the projection shape on the roll to form grooves with a certain width and depth on the surface of the steel plate by the pressure method, and then recrystallize the bottom of the groove by annealing the steel plate after permanent magnetization process As a technique for miniaturization, the stability, reliability, and process of machining are complicated.

As a method of permanent magnetization by laser, a method of improving iron loss by forming a groove depth of 5 to 30 µm on the surface of a steel sheet after heat treatment by a Q-switch pulse or continuous wave laser is disclosed in Japanese Patent Laid-Open No. 2000-109961. .

In particular, during the formation of surface grooves accompanied by the melting of the steel sheet, spatters are generated around the grooves during the groove forming process, and spatters are generated on the surface of the steel sheet even after the base coating and the insulation coating. There is a problem of inferior characteristics and spot ratio.

The present invention has been made to solve the above problems, the organic material is applied to the surface of the grain-oriented electrical steel sheet and dried to form a groove by irradiating a continuous wave laser beam, spatter generated on the film quality of the organic material when the groove is formed The present invention relates to a method for miniaturizing magnetic domains of a grain-oriented electrical steel sheet by improving the iron loss improvement rate before and after heat treatment by removing the film quality of the organic material.

In order to achieve the above object, the method of refining the magnetic domain of a grain-oriented electrical steel sheet according to an embodiment of the present invention provides a electrical steel sheet before or after the first annealing, the liquid phase to increase the laser absorption on the surface of the electrical steel sheet Forming a film quality of the organic material by coating the organic material of the organic material or maintaining the liquid state, forming a groove by melting the surface portion of the steel sheet by irradiating a continuous wave laser on the surface of the electrical steel sheet, and forming the groove In order to remove the spatter formed on the film quality of the organic material by the scattering of the melt of the time, the film quality of the organic material is removed by washing or weak pickling and drying.

The organic material may be at least one selected from enamel, epoxy, surfactant, polyacryl, mineral oil and amide-based hydrophilic polymer.

The weak pickling may be performed by alcohol.

The thickness range of the film quality of the organic material may be 0.0002 to 5.0㎛.

The oscillation frequency of the continuous wave laser may be 100 Hz to 8.5 kHz.

The organic material may be dried in air at room temperature or in a drying furnace of 300 ° C. or less.

When the groove is formed by the continuous wave laser irradiation, the rolling direction groove diameter B _w of the electrical steel sheet may be 10 μm to 70 μm, and the width of the laser beam irradiated to the surface of the steel sheet may be spherical or elliptical in 60 μm. have.

When the groove is formed by the continuous wave laser irradiation, the steel sheet width direction groove length B _L is 10 µm to 100 µm, and the length of the laser beam irradiated to the surface of the steel sheet is 90 µm or less, or 150 µm or less. Can be.

In the continuous wave laser irradiation, the rolling direction irradiation distance (D _S ) may be 3 mm to 30 mm.

The grooves formed on the surface of the electric steel plate are formed to have mutually facing first side surfaces, second side surfaces and bottom surface, and the grooves formed on the first, second side surfaces and the bottom surface are melted The solidified portion formed by solidification of the non-product may be removed to expose at least one of the first and second side surfaces and the bottom surface.

The solidification portion formed on the first side surface or the second side surface may be formed so that the side distance C is defined as a distance from the boundary between the surface of the steel sheet and the solidification portion to the center of the bottom surface of the groove, Can occupy.

When the groove is formed, when the groove forming factor is defined as the depth D _G / lower half width W _{1 of} the groove, the groove forming factor may be 0.5 to 8.5, wherein the depth D of the groove is D _G ) is a distance from the surface of the steel sheet to the bottom surface, and the lower half width W ₁ is 1/2 of the length of the steel sheet width direction of the bottom surface.

According to the method for miniaturizing magnetic domains of a grain-oriented electrical steel sheet according to the present invention, after coating an organic substance which can increase the absorption rate of laser on the surface of the electrical steel sheet, the grooves are formed on the surface of the steel sheet by laser irradiation and melted and scattered when the grooves are formed. By removing the spatter along with water washing or light pickling of the organic matter, it is possible to reduce the iron loss of the steel sheet by maintaining the domain refining effect even after the first and second annealing.

In addition, the magnetic domain micronization method according to the present invention is applied at a high line speed of 15mpm or more by removing the organic matter formed with molten fly-bys by laser irradiation by water washing and weak pickling to prevent iron loss after heat treatment and deterioration of electrical insulation value can do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram of a method for miniaturization of a magnetic steel strip according to the present invention; FIG.
2 is a view schematically showing the laser irradiation in the direction perpendicular to the rolling direction on the surface of the grain-oriented electrical steel sheet according to the embodiment of the present invention.
Fig. 3 is a view showing the shape of the groove at the irradiated portion on the XY plane when irradiating the surface of the steel sheet with a laser. Fig.
4 is a cross-sectional view taken along the line AA ′ of the steel sheet shown in FIG. 2.
5 is an enlarged view of a solidification portion formed on the inner surface of the groove shown in FIG.
FIG. 6 is a view illustrating molten scatterers formed on an organic film quality when laser is irradiated onto a surface of a steel sheet in FIG. 2.
7 is a view showing a shape and a mode of a laser beam irradiated on the surface of a steel sheet when the magnetic steel sheet of the directional electric steel sheet according to the present invention is miniaturized.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, a method of refining the magnetic domain of a grain-oriented electrical steel sheet according to a preferred embodiment of the present invention will be described.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram of a method for miniaturization of a magnetic steel strip according to the present invention; FIG.

FIG. 2 is a diagram illustrating a radiation line of a laser irradiated at regular intervals perpendicular to the rolling direction of the electrical steel sheet on which an organic film is formed.

Fig. 3 is a view showing the shape of the groove at the laser irradiation site indicated by the dotted line in Fig. 2 on the XY plane when irradiating the surface of the steel sheet with the laser.

Referring to Figure 1, the method for refining the magnetic domain of the grain-oriented electrical steel sheet according to a preferred embodiment of the present invention comprises the steps of providing an electrical steel sheet 10 before or after the first annealing, the surface of the electrical steel sheet 10 Forming a film 20 of the organic material by applying a liquid organic material in order to increase the laser absorption rate or maintaining the liquid state, by irradiating a continuous wave laser on the surface of the electrical steel sheet 10 grooves by melting of the steel sheet surface portion Forming the grooves and removing the spatters 25 formed on the film quality 20 of the organic matter by scattering of the melt during formation of the grooves 30. The membrane 20 is removed by washing with water or weak pickling with alcohol or the like and drying.

The grain-oriented electrical steel sheet exhibits a GOSS texture in which the texture of the steel sheet is {110} <001> with respect to the rolling direction, and is a soft magnetic material having excellent magnetic properties in one direction or in the rolling direction. And it is used as iron core material of other electronic devices.

The organic material uses an organic polymer having a high specific heat so as to increase the laser absorptivity of the continuous wave (CW) laser irradiation on the surface of the steel sheet, and a material which can be easily removed by washing or weak pickling. Can be used. As the organic material, at least one selected from enamel, epoxy, surfactant, polyacryl, mineral oil, and amide-based hydrophilic polymer may be used. The organic polymer is used that can react with the molten fly product to form CO, CO ₂ at the interface between the base and the fly product.

Laser absorption rate (α) of the organic material applied to the surface of the electrical steel sheet 10 is as shown in the following equation (1).

…… (1)

... ... (One)

Where m is the mass of the medium, C _{p is the} average specific heat, U is the scan speed of the laser, s is the irradiation interval of the laser, P is the heat absorbed per unit area during laser irradiation, L is the latent heat of fusion, and T _m is the melting of the steel sheet. The temperature, T _o means any temperature raised by laser irradiation.

Since the laser absorption rate is proportional to the heat capacity and inversely proportional to reflectivity during laser irradiation, it is preferable to use an organic polymer having a high specific heat (500 to 4000 J / kg 占 폚).

In particular, when the thickness of the organic material applied to the surface of the steel sheet is less than 0.0002㎛ may cause partial exposure of the steel plate base layer, when the organic coating thickness is more than 5.0㎛ the coating is not formed uniformly the groove depth is irregular It is not desirable to appear.

Applying organic materials such as enamel, epoxy, surfactant, polyacryl, mineral oil and amide-based hydrophilic polymer on the surface of steel sheet before laser irradiation with a thickness of 0.0002 ~ 5.0μm It can be applied in a liquid state or dried, and the drying method can be dried in the air and can be dried in a drying furnace of less than 300 ℃ for accelerated drying.

On the other hand, when the oscillation frequency f _L of the laser beam is less than 100 Hz or more than 8.5 kHz, since the groove depth does not change at the same laser output, irradiation distance, and line speed, it is not applicable to a high speed line speed.

7 shows the shape of a continuous wave laser irradiated on a surface of a steel strip in order to form a groove on the surface of the steel strip, and shows a case where the shape of the laser is a sphere or an oval type .

The shape of the laser beam formed by the continuous wave laser has a single mode shape of spherical or oval type as shown in Fig.

FIG. 7 shows the shape of a spherical or elliptical laser and the Gaussian mode of each laser, which are all single modes.

FIG. 3 shows the two irradiation lines 15 of the steel sheet irradiated with the laser shown in FIG. 2 with respect to the XY plane. As the laser is irradiated, the surface is melted and the grooves 30 are formed by the removal of the molten by- As shown in FIG.

In FIG. 3, the first and second sides formed on both sides of the inside of the groove while the groove is formed are not shown.

The groove diameter (B _W ) in the rolling direction, the groove length (B _L ) in the width direction of the steel sheet, and the irradiation distance (D _S ) in the rolling direction of the laser beam are shown in Fig.

When the groove 30 is formed by the continuous wave laser irradiation, the rolling direction groove diameter B _W of the electrical steel sheet 10 is 10 µm to 70 µm, and the width of the laser beam irradiated to the surface of the steel sheet is within 60 µm. It is characterized by having a spherical or elliptic shape.

Here, when the rolling direction groove diameter (B _W ) is less than 10 μm, the iron loss is not improved after stress relief annealing heat treatment, and when the thickness is greater than 70 μm, the thermal effect of the continuous wave laser is large, and the iron loss is improved before heat treatment. It does not show any effect, and the magnetic flux density deterioration is large.

Further, in order to form the groove diameter Bw in the rolling direction, the width in the rolling direction of the laser beam irradiated on the surface of the electrical steel sheet is controlled within 60 占 퐉.

When the groove 30 is formed by the continuous wave laser irradiation, the steel plate width direction groove length B _L is 10 µm to 100 µm, and the length of the laser beam irradiated to the surface of the steel sheet is 90 µm or less, or 150 µm or less. It is characterized by the elliptic shape of.

Here, when the width direction groove length (B _L ) is less than 10μm, there is no improvement in iron loss before stress relief annealing heat treatment, and when it exceeds 100 μm, the magnetic flux density and iron loss deterioration are shown.

The formation factor (D _G / W ₁ ) of the fusion groove formed during continuous wave laser irradiation does not improve the iron loss at 0.5 or less, and the magnetic flux density and iron loss deterioration at 8.5 or more are undesirable.

In the continuous wave laser irradiation, the rolling direction irradiation distance D _s is 3 mm to 30 mm in order to minimize the influence of the heat affected portion by the continuous wave laser beam.

4 is a cross-sectional view along the AA ′ direction of the steel sheet illustrated in FIG. 2, and shows a solidification part 35 formed on the bottom surface of the groove 30 and the first and second side surfaces of the groove 30. .

The groove (30) formed on the surface of the electrical steel sheet is formed to have a first side facing each other, a second side and a bottom surface, and grooves (30) are formed on the first and second side surfaces and the bottom surface And an opening portion in which at least one surface of the first and second side surfaces and the bottom surface is exposed by removing a solidified portion formed by solidification of the molten non-product of the steel sheet in the process.

4 is a view showing that solidification portions 35 and 33 are formed on the first and second side surfaces and the bottom portion by laser irradiation.

The solidification portion 33 does not remain on the bottom surface from the left side of FIG. 4 and the solidification portion 35 is formed only on the first and second sides of the groove 30, Only the solidification portions 35 are formed on only one side of the second side of the groove 30 and only the grooves 30 are formed and the solidification portion is not left.

5 is an enlarged view of a solidification portion formed on the inner surface of the groove shown in FIG.

The solidification portion 35 formed on the first and second side surfaces of the groove 30 in the groove 30 formed on the surface of the steel sheet by the irradiation of the laser has the side distance C coincident with the surface of the steel sheet Is defined as a distance from the boundary of the groove to the center of the bottom surface of the groove (30), occupies 2% or more of the side distance.

When the groove 30 is formed, when the groove 30 forming factor is defined as the depth D _G / lower half width W _{1 of} the groove, the groove forming factor is 0.5 to 8.5.

Here, the groove depth (D _G ) constituting the forming factor of the groove (30) means the vertical distance from the surface of the steel sheet to the valley of the solidification portion formed on the bottom surface of the groove (30).

On the other hand, when there is no solidification portion on the bottom surface of the groove 30, it means a vertical distance from the surface of the steel sheet to the bottom surface of the groove 30. [

As shown in FIG. 4, the bottom half width W ₁ means half the length of the bottom surface in the width direction of the steel plate. The widthwise length of the bottom surface may be a straight line distance between the bottom surface and the boundary points formed by the first and second sides.

Hereinafter, a method of making a magnetic domain of a grain-oriented electrical steel sheet according to the present invention will be described in detail with reference to examples. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

&Lt; Example: Minorization of magnetic field of electric steel sheet by continuous wave laser irradiation &

2 is a view showing a continuous irradiation line 15 formed by a continuous wave laser after applying and drying the organic material on the surface of the grain-oriented electrical steel sheet 10.

The laser irradiation line 15 formed by the continuous wave laser was formed in parallel in the rolling width direction, and the irradiation line irradiated the laser on 3 to 10 divided lines in the width direction.

FIG. 3 is a view showing the shape of the groove 30 formed by the continuous wave laser in the range divided by the dotted line in FIG. The groove 30 formed by the continuous wave laser may have a molten re-solidification structure (solidification portion) on the lower side or a side surface, and may not show the re-enhancement structure (solidification portion).

The irradiation distance D _S of the group can be adjusted by adjusting the scanner speed in the laser optical system. Recoagulation tissue formation formed at least 2% recoagulation tissue in the groove inner side (first side, second side) length.

The shape of the laser beam formed by the continuous wave laser has a single beam shape of circular or oval shape as shown in FIG. 7.

FIG. 6 is a view showing the shape of a molten spatter formed on the organic film layer 20 on the surface of the steel sheet during laser irradiation in FIG. 2. The molten non-product is also referred to as spatter 25 (spatter).

The molten fly products are spherical and acicular in shape depending on the feed rate of the steel sheet and the conditions of the laser, and the depth of grooves by the organic material is increased after laser irradiation, and the molten scatter products on the surface of the steel sheet are removed during washing and weak pickling. In addition, in one embodiment according to the present invention, a brush may be used to more effectively remove the molten fly-products on the surface of the steel sheet, and the brush may be made of a polymer, a metal, or a mixture of a polymer and a metal. In addition, the weak pickling acid may be any of nitric acid and hydrochloric acid as long as it is an acid having a concentration capable of dissolving the organic material as well as alcohol.

Table 1 shows the change of the groove depth formed on the surface of the steel sheet having a thickness of 0.27mm by the continuous wave laser irradiation, the insulation value after the insulation coating, and the iron loss improvement rate after the organic material according to the present invention was applied and dried on the steel sheet surface.

Example 1 is a case of irradiating a continuous wave laser of 500Hz after applying polyamide, Example 2 is a case of irradiating a continuous wave laser of 8.5kHz after applying enamel, Example 3 is a polyamide coated Then, it is the case where 7kHz continuous wave laser was irradiated, and Example 4 shows the case where 7kHz continuous wave laser was irradiated with 3.0 mm of laser irradiation distances (Ds) after apply | coating polyamide.

On the other hand, Comparative Example 1 shows a case where a continuous wave laser of 7 kHz is irradiated without applying an organic substance to the surface of the electrical steel sheet, and Comparative Example 2 shows a case where discontinuous grooves are formed by irradiating a pulsed laser.

division Line
Speed
(m / min) B _W B _L D _S D _G / W ₁ D _G Laser
Joe's Dictionary SRA Iron loss
Improvement rate Electricity
Isolation I'm after mm Dimensionless ㎛ W17 / 50 % mA Example 1
(Polyamide
/ 500 Hz) 20 20 65 2.5 3.5 20 0.85 0.72 0.72 15.3 90 0.85 0.71 0.71 16.5 87 0.86 0.72 0.72 16.3 92 Example 2
(enamel
/8.5 kHz) 20 20 65 2.5 2.4 20 0.84 0.72 0.72 14.3 70 0.85 0.72 0.72 15.3 75 0.85 0.73 0.73 14.1 70 Example 3
(Polyamide
/ 7 kHz) 20 20 65 2.5 2.4 20 0.84 0.72 0.72 14.3 80 0.85 0.72 0.72 15.3 83 0.85 0.73 0.73 14.1 81 Example 4
(Polyamide
/ 7 kHz) 20 20 65 3.0 3.0 22 0.85 0.70 0.70 17.6 92 0.84 0.71 0.70 15.5 95 0.85 0.72 0.71 15.3 98 Comparative Example 1
(Unpainted
/ 7 kHz /
A continuous wave
laser) 20 20 65 2.5 2.4 17 0.85 0.76 0.76 10.6 280 0.84 0.76 0.76 9.5 360 0.85 0.75 0.75 11.8 460 Comparative Example 2
(Pulse laser /
Discontinuous groove) 10 20 40 2.5 2.4 7 0.85 0.79 0.79 7.1 330 0.84 0.77 0.77 8.3 310

As shown in Table 1, after forming the film quality of the organic material on the surface of the steel sheet, 85 ~ 95 ° with respect to the traveling direction of the steel sheet to accompany the melting and re-solidification of the steel sheet when forming the steel sheet surface grooves by laser irradiation Irradiation of the continuous wave laser beam at the angle of increased the groove formation depth and preventing the electrical insulation value inferior after the insulating coating, and improved the iron loss after heat treatment more than 13%.

The present invention is applied to the surface of the electrical steel sheet and then maintained in a liquid or (semi-dry) state, and the continuous wave laser irradiation increases the molten portion scattered and groove depth generated around the groove of the steel sheet surface by increasing the depth of the thin and thick directional electrical The present invention relates to an improvement in iron loss before and after heat treatment on steel sheets and to a micronized microstructure technology that can prevent the thermal insulation from inferior in electrical insulation values.

In other words, the present invention is applied to the surface of the electrical steel sheet (cold rolled plate, decarburized plate) and then dried to form a groove by laser irradiation to increase the depth of the groove and the thermal properties of the insulating properties of the surface of the steel sheet even at high line speeds Grooves can be formed, and after heat treatment, groove formation can maximize the miniaturization of magnetic domains and reduce the electrical insulation value inferiority.

Therefore, the magnetic domain refinement technology according to the present invention can be applied to thin and thick grain oriented electrical steel sheets even at high line speeds (15 mpm or more).

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

Claims (12)

A method of micro-finishing a directional electrical steel sheet,
Providing an electrical steel sheet before or after primary annealing;
Forming a film quality of the organic material by applying a liquid organic material to maintain a liquid state or drying the liquid to increase the laser absorption rate on the surface of the electrical steel sheet;
Forming a groove by melting the surface of the steel sheet by irradiating the surface of the steel sheet with a continuous wave laser; And
In order to remove the spatter formed on the film quality of the organic material by the scattering of the melt during the formation of the groove, the film quality of the organic electrical steel sheet comprising the step of removing and drying the film quality of the organic material by water washing or weak pickling. Magnetic domain micronization method. The method according to claim 1,
The organic material is magnetic domain of the grain-oriented electrical steel sheet, characterized in that at least one selected from enamel, epoxy, surfactant, polyacryl, mineral oil and amide-based hydrophilic polymer (Polymer) Micronization method. 3. The method of claim 2,
The weak pickling is a method of miniaturizing the magnetic domain of the grain-oriented electrical steel sheet, characterized in that the alcohol. 3. The method according to claim 1 or 2,
The thickness range of the film quality of the organic material is a method of miniaturizing the magnetic domain of the grain-oriented electrical steel sheet, characterized in that 0.0002 ~ 5.0㎛. 5. The method of claim 4,
The oscillation frequency of the continuous wave laser is 100Hz ~ 8.5kHz magnetic domain miniaturization method of the grain-oriented electrical steel sheet, characterized in that. 5. The method of claim 4,
Drying of the slurry of the organic material is a method for miniaturizing the magnetic domain of the grain-oriented electrical steel sheet, characterized in that in the air at room temperature or in a drying furnace of 300 ℃ or less. The method according to claim 6,
When the groove is formed by the continuous wave laser irradiation, the rolling direction groove diameter B _w of the electrical steel sheet is 10 µm to 70 µm, and the width of the laser beam irradiated to the surface of the steel sheet is spherical or elliptical within 60 µm. A method for miniaturizing magnetic domains of a grain-oriented electrical steel sheet. The method of claim 7, wherein
When the groove is formed by the continuous wave laser irradiation, the steel sheet width direction groove length B _L is 10 µm to 100 µm, and the length of the laser beam irradiated to the surface of the steel sheet is 90 µm or less, or 150 µm or less. Magnetic domain refinement method of a grain-oriented electrical steel sheet characterized in that the. The method of claim 7, wherein
Wherein the rolling direction irradiation distance (D _S ) in the continuous wave laser irradiation is 3 mm to 30 mm. The method of claim 7, wherein
The grooves formed on the surface of the electric steel plate
A first side surface, a second side surface and a bottom surface facing each other,
The solidified portion formed by solidification of the molten non-product of the steel sheet during the groove forming process on the first and second side surfaces and the bottom surface is removed to expose at least one surface of the first and second side surfaces and the bottom surface, Wherein said method comprises the steps of: 11. The method of claim 10,
The solidification portion formed on the first side surface or the second side surface,
When the side distance C is defined as the distance from the boundary between the surface of the steel sheet and the solidification portion to the center of the bottom surface of the groove,
Wherein the lateral distance occupies at least 2% of the lateral distance. 11. The method of claim 10,
When the groove is formed, when the groove forming factor is defined as the depth (D _G ) / lower half width (W ₁ ) of the groove, the groove forming factor is a method of refining the magnetic domain of the grain-oriented electrical steel sheet, characterized in that 0.5 to 8.5 .
Here, the depth D _G of the groove is a distance from the surface of the steel sheet to the bottom surface, and the bottom half width W ₁ is 1/2 of the length of the bottom surface in the steel sheet width direction.

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