Grain-oriented electrical steel sheet

Description

/ 22 GRAIN-ORIENTED ELECTRICAL STEEL SHEET TECHNICAL FIELD

[001] The present invention relates to a grain-oriented electrical steel sheet.

[002] Priority is claimed in Japanese Patent Application No. 2022-186163, filed on November 22, 2022, the contents of which are incorporated herein by reference. FUNDAMENTALS OF THE TECHNIQUE

[003] Grain-oriented electrical steel sheets are a soft magnetic material and are mainly used as a transformer core material. Therefore, grain-oriented electrical steel sheets need to have magnetic properties such as high magnetization properties and low iron loss.

[004] Iron loss is the power loss due to thermal energy consumption that occurs when a core is excited by an AC magnetic field, and iron loss should be as low as possible from an energy saving perspective. The level of iron loss is affected by magnetic susceptibility, sheet thickness, coating voltage, amount of impurities, electrical resistivity, grain size, magnetic domain size, and the like. Even today, when various techniques have been developed regarding grain-oriented electrical steel sheets, research and development to reduce iron loss continues in order to increase energy efficiency.

[005] As one of the methods to reduce iron loss, a technique for forming a groove on a sheet metal surface has been proposed. For example, Patent Documents 1 and 2 describe a technique for forming a groove on a base metal surface by means of pressing, electrolytic engraving or similar methods. In this technique, a groove parallel to the width direction of a steel sheet is formed to Petition 870250040261, dated 05 / 16 / 2025, page 11 / 36 / 22 refine the magnetic domain width of 180° and, consequently, the eddy current loss that is part of the iron loss is reduced.

[006] However, a groove formed in a steel sheet by groove forming, such as in Patent Documents 1 and 2, has larger irregularities than the sheet surface and therefore hinders the movement of the domain wall. Iron loss includes eddy current loss and hysteresis loss. In the cases of Patent Documents 1 and 2, eddy current loss is reduced by groove forming, but hysteresis loss, which is part of the iron loss, is increased and therefore there is room for further improvements in iron loss. It is considered that the groove formed in the steel sheet by groove forming preferably has a refined magnetic domain width and small irregularities to avoid obstacles to the movement of the domain wall.

[007] With regard to the irregularity of a groove, for example, the Patent Document 3 describes a grain-oriented electrical steel sheet, including a steel sheet having a sheet surface in which a groove is formed that extends in a direction that crosses a rolling direction and has a groove depth direction in the sheet thickness direction, wherein, when the groove is viewed in a longitudinal groove cross-section, including the groove extension direction and the sheet thickness direction, a roughness curve forming a contour of a lower groove region of the groove has an arithmetic mean height Ra of 1 μm or more and 3 μm or less.

[008] Patent Document 4 describes a wound core comprising a grain-oriented electrical steel sheet having a sheet surface in which a groove is formed, for refining the magnetic domain resistant to annealing for stress relief, extending in a direction that intersects a rolling direction and has a direction of Petition 870250040261, dated 05 / 16 / 2025, page 12 / 36 / 22 groove depth in the sheet thickness direction, wherein, when the groove is viewed in the longitudinal cross-section of the groove including the groove extension direction and the sheet thickness direction, a roughness curve conforming to a contour of a lower groove region of the groove has an arithmetic mean height Ra of 1.1 μm or more and 2.7 μm or less. List of Citations Patent Documents

[009] Patent Document 1: Japanese Patent Application No. Examined, Second Publication No. S62-53579

[0010] Patent Document 2: Unexamined Japanese Patent Application, Second Publication No. S62-54873

[0011] Patent Document 3: International Publication PCT No. WO 2016-171124

[0012] Patent Document 4: Unexamined Japanese Patent Application, First Publication No. 2019-24039 SUMMARY OF THE INVENTION Technical Problem

[0013] In Patent Documents 3 and 4 described above, Ra of the lower groove region is controlled within a predetermined range. However, as a result of studies carried out by the present inventors, it has been verified that the hysteresis loss cannot necessarily be reduced, even if Ra is reduced.

[0014] Therefore, an objective of the present invention is to provide a grain-oriented electrical steel sheet having a groove in which a magnetic domain width of 180° is refined and a reduction in hysteresis loss is suppressed, thus having a low iron loss. Solution to the Problem

[0015] In order to clarify the shape of a groove that does not prevent Petition 870250040261, dated 05 / 16 / 2025, page 13 / 36 / 22, regarding the movement of the domain wall in a grain-oriented electrical steel sheet in which a groove is formed, the present inventors studied why the hysteresis loss is not reduced, even if Ra is small in a certain range or less. As a result, it was verified that, even if Ra is small, the hysteresis loss is not reduced in a case where the irregularity is pronounced.

[0016] The present invention was made based on the verifications described above. The essence of the present invention is as follows.

[0017] [1] An oriented grain electrical steel sheet according to an aspect of the present invention is an oriented grain electrical steel sheet including a base steel sheet having a surface in which a plurality of grooves are formed, extending in a direction of 60 to 120° with respect to a rolling direction in a range in the rolling direction of 2 to 10 mm, and in a lower portion of the grooves, Ra is 5.0 μm or less and an absolute value of Rsk is 2.0 or less along a direction of extension of the grooves.

[0018] [2] In the grain-oriented electrical steel sheet according to [1], on a lateral surface of the grooves, Ra is 5.0 μm or less along the direction of groove extension Advantageous Effects of the Invention

[0019] In accordance with the above-described aspect of the present invention, a grain-oriented electrical steel sheet having low iron loss can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [Figure 1] A view illustrating an example of a groove forming state of a grain-oriented electrical steel sheet according to the present embodiment.

[0021] [Figure 2] A view of a laser irradiation step for groove forming, viewed from an RD direction. Petition 870250040261, dated 05 / 16 / 2025, page 14 / 36 / 22

[0022] [Figure 3] A view of a laser irradiation step for groove forming, viewed from an ND direction. DESCRIPTION OF THE MODALITIES

[0023] A grain-oriented electrical steel sheet according to an embodiment of the present invention (grain-oriented electrical steel sheet according to the present embodiment) will be described. As illustrated in Figure 1, a grain-oriented electrical steel sheet 1 according to the present embodiment includes a base steel sheet (grain-oriented electrical steel sheet) 10 having a surface in which grooves 20 are formed. A plurality of grooves 20 are formed in a range PL in a rolling direction RD from 2 to 10 mm. Each groove 20 extends in a direction of 60 to 120° relative to the rolling direction RD (a direction of ±30° relative to TD).

[0024] In the grain-oriented electrical steel sheet 1 according to the present embodiment, in a lower portion of the groove 20, Ra is 5.0 μm or less, and an absolute value of Rsk is 2.0 or less along the groove extension direction.

[0025] Each one will be described below. <Chapa de Aço de Base>

[0026] The grain-oriented electrical steel sheet to be the base steel sheet is not limited and may be a known grain-oriented electrical steel sheet. For example, a grain-oriented electrical steel sheet manufactured by a known method (e.g., a grain-oriented electrical steel sheet that meets JIS C 2553:2019 or a proprietary standard product of each steel company) may be used. The grain-oriented electrical steel sheet may contain, for example, Si: 2.50 to 4.50%, Mn: 0.01 to 0.15%, C: 0.085% or less, acid-soluble Al: 0.065% or less, and N: 0.012% or less and, as required, Cr: 0.3% or less, Cu: 0.4% or less, P: 0.5% or less, Sn: 0.3% or less, Sb: 0.3% or less Petition 870250040261, dated 05 / 16 / 2025, page 15 / 36 / 22 less, Ni: 1% or less, S: 0.015% or less, Se: 0.015% or less, and Bi: 0.02% or less, as the chemical composition in % by mass. Grain-oriented electrical steel sheet may contain the chemical composition described above and the remainder being Fe and an impurity.

[0027] The thickness of the target base steel plate (grain-oriented electrical steel plate) is not limited and is, for example, from 0.15 to 0.23 mm from the point of view that the eddy current loss becomes smaller as the plate thickness becomes thinner. <ranhura> [Interval, Extension direction, Format]

[0028] As described above, in the grain-oriented electrical steel sheet 1, according to the present embodiment, the plurality of grooves 20, extending in a direction of 60 to 120° relative to the rolling direction, are formed substantially in parallel on the surface of the base steel sheet 10, in a range PL in the rolling direction RD of 2 to 10 mm. In the grain-oriented electrical steel sheet 1, according to the present embodiment, a refinement effect of the magnetic domain can be obtained by the grooves 20 formed on the surface of the base steel sheet (base metal) under the above conditions.

[0029] If the PL interval between the slots 20 (interval between adjacent slots) is less than 2 mm, the slots will considerably hinder the shaping of the magnetic flux. Meanwhile, if the PL interval is greater than 10 mm, the effect of improving magnetic properties by the slots will be greatly reduced. The PL interval is the distance from the center of one slot to the center of an adjacent slot.

[0030] If the extension direction of each groove 20 deviates from 60 to 120° relative to the rolling direction RD (becomes less than ±60° relative to the rolling direction, i.e., becomes almost parallel to the rolling direction RD), the magnetic domain refinement effect cannot be achieved. Petition 870250040261, dated 05 / 16 / 2025, page 16 / 36 / 22 sufficiently obtained. The extension direction is preferably close to 90° in relation to the rolling direction RD (parallel to the width direction TD).

[0031] The length of the groove 20 in the extension direction is not limited, and the groove 20 is preferably formed continuously throughout the width direction, from one end portion in the width direction of the steel sheet to the other end portion.

[0032] The shape (depth, width and the like) of slot 20 is not limited and, for example, the depth is from 10 to 40 μm and the width is from 10 to 200 μm, from the point of view of refining the magnetic domain width by 180°. [Ra and Rsk at the bottom]

[0033] The magnetic domain width of 180° is refined by shaping the groove 20 in a direction that crosses the rolling direction of the base steel sheet 10 and, consequently, the eddy current loss that is part of the iron loss is reduced.

[0034] Examples of methods for forming a groove in a base steel plate include laser irradiation and machining methods. However, in either of these methods, a groove formed in a base steel plate exhibits larger irregularities than the steel plate surface. Therefore, the formed groove hinders the movement of the domain wall, and hysteresis loss increases.

[0035] Therefore, in the grain-oriented electrical steel sheet 1 according to the present embodiment, in order to reduce the irregularity of a groove formed in the base steel sheet 10, the arithmetic mean roughness Ra of the lower portion of the groove is reduced. Specifically, Ra is defined as 5.0 μm or less. If Ra is greater than 5.0 μm, the movement of the domain wall will be significantly hindered.

[0036] Meanwhile, as a result of the examination carried out by the present inventors, it was verified that, even if Ra is 5.0 μm or less, the Petition 870250040261, dated 05 / 16 / 2025, p. 17 / 36 / 22 hysteresis loss will not be reduced as long as the irregularity is pronounced. Therefore, in the grain-oriented electrical steel sheet 1 according to the present embodiment, Ra is defined as 5.0 μm or less, and the absolute value of the asymmetry Rsk is defined as 2.0 or less in the lower portion of the groove 20. If the absolute value of Rsk is greater than 2.0, the effect of reducing hysteresis loss cannot be obtained. Ra and Rsk are preferably small.

[0037] In this embodiment, Ra and Rsk have the same definitions as the arithmetic mean roughness Ra and the skewness Rsk of the roughness curve specified in the JIS B 0601: 2013 standard, respectively.

[0038] The reason for controlling Ra and Rsk in the lower portion of the groove is that the irregularity of the lower portion of the groove affects iron loss more.

[0039] Ra and Rsk, in the lower portion of the groove, can be measured using a laser microscope (3D laser microscope using a confocal optical system through a pinhole).

[0040] Specifically, the surface roughness of the groove over a range of 1 mm or more in the extension direction is measured at five or more locations in the lower portion (at the deepest position) of the groove using a laser microscope. The average of the measurement values ​​at five or more locations is used to determine Ra and Rsk.

[0041] Ra and Rsk are determined based on the roughness profile obtained according to the definitions in the JIS B 0601: 2013 standard.

[0042] The depth D and width W of the groove can be measured using a laser microscope (3D laser microscope using a confocal optical system through a pinhole).

[0043] Specifically, the maximum depth d in a cross-section of a groove orthogonal to the groove extension direction is measured using a laser microscope at five or more locations distant from each other by Petition 870250040261, dated 05 / 16 / 2025, page 18 / 36 / 22 mm or more. The average value of the measurement values ​​d at five or more locations is considered the groove depth D. Similarly, the width w (groove opening portion) at a depth of 0.05 times the groove depth d in a groove cross-section orthogonal to the groove extension direction is measured using a laser microscope at five or more locations spaced 1 mm or more apart. The average value of the measurement values ​​w at five or more locations is considered the groove width W.

[0044] Ra of the lateral surface of the groove is not necessarily limited and, in the case of further reduction of iron loss, Ra of the lateral surface of the groove is preferably defined as 5.0 μm or less, while Ra and Rsk in the lower portion of the groove are defined in the above ranges.

[0045] As a general method of reducing the Ra of the lateral surface of the groove, shot blasting treatment is considered, but shot blasting treatment can increase the absolute value of Rsk in the lower portion of the groove to more than 2.0. Therefore, the Ra of the lateral surface of the groove can be set to a range of more than 5.0 μm in order to guarantee the predetermined Rsk.

[0046] The Ra of the lateral surface of the groove is measured using the following method.

[0047] The surface roughness of the groove in a range of 1 mm or more in the extension direction is measured at five or more locations at a point where the groove depth is 1 / 2 of the maximum depth d using a laser microscope. The average value of the measurement values ​​at five or more locations is considered as the Ra of the lateral surface of the groove.<Película de Vidro>

[0048] In the grain-oriented electrical steel sheet 1 according to the present embodiment, a glass film can be formed on the sheet of Petition 870250040261, dated 05 / 16 / 2025, page 19 / 36 / 22 base steel 10.

[0049] The glass film (also called the primary coating) is an inorganic coating containing magnesium silicate as a major component. The glass film is formed in the final annealing when an annealing separator including magnesia (MgO) applied to the surface of the base steel sheet reacts with a component on the surface of the base steel sheet. The glass film has a composition derived from the annealing separator and the component of the base steel sheet and has a microstructure that includes an Mg2SiO4 phase as a major phase (50% area or more) and an MgAl2O4 phase. In addition to these phases, a precipitate may be included in an amount of about 1% or less. <Revestimento Isolante>

[0050] In the grain-oriented electrical steel sheet 1 according to the present embodiment, an insulating coating can be formed directly onto the base steel sheet 10, or onto the glass film formed onto the base steel sheet 10.

[0051] The insulating coating imparts electrical insulation properties to the grain-oriented electrical steel sheet to reduce eddy current loss and thus improves the iron loss properties of the grain-oriented electrical steel sheet. In addition to the electrical insulation properties described above, various properties such as corrosion resistance, heat resistance and slip resistance can be obtained.

[0052] If an insulating coating is a voltage-transmitting insulating coating, the insulating coating will have the function of applying voltage to the grain-oriented electrical steel sheet. If a voltage is applied to the grain-oriented electrical steel sheet to facilitate the movement of the domain wall in the grain-oriented electrical steel sheet, the iron loss properties of the grain-oriented electrical steel sheet may be improved. Petition 870250040261, dated 05 / 16 / 2025, page 20 / 36 / 22

[0053] The voltage-transmitting insulating coating may be, for example, a known coating that is formed by applying a coating liquid containing a metallic phosphate and silica as main components onto the surface of the glass film and baking the coating liquid. <Método de Fabricação>

[0054] Next, a method for manufacturing grain-oriented electrical steel sheet according to the present embodiment will be described.

[0055] An effect of the grain-oriented electrical steel sheet according to the present embodiment can be obtained independently of the manufacturing method, provided that the grain-oriented electrical steel sheet has the characteristics described above, but a manufacturing method including the following step is preferable, since such a manufacturing method allows for stable manufacturing.

[0056] (I) A groove forming step to irradiate a surface of a steel sheet to be a base steel sheet with a laser beam to form a groove in the surface of the steel sheet.

[0057] Preferred conditions will be described later.

[0058] In the groove forming stage, a surface of a steel sheet that will be a base steel sheet (electrically oriented grain steel sheet) is irradiated with a laser beam to form a groove on the surface.

[0059] A grain-oriented electrical steel sheet is generally manufactured by means of a plate heating step, a hot rolling step, a hot band annealing step performed as needed, a cold rolling step, a decarburization annealing step, and a final annealing step. In the case of forming an insulating sheath, a grain-oriented electrical steel sheet is manufactured by means of an additive step, such as a step Petition 870250040261, dated 05 / 16 / 2025, page 21 / 36 / 22, regarding the shaping of insulating coatings. Furthermore, a nitriding treatment can be performed at one or more points after the decarburization annealing step and before the final annealing step, in the decarburization annealing step, and during the heating process in the final annealing step.

[0060] In the case of obtaining grain-oriented electrical steel sheet according to the present embodiment, the surface of the steel sheet is irradiated with a laser beam at any time after the cold rolling stage to form a groove.

[0061] A glass film is formed in the final annealing step. An insulating coating is formed in the insulating coating forming step. Therefore, if a state is established in which a glass film and an insulating coating are formed on the surface of a groove, irradiation with a laser beam (groove forming step) is preferably carried out before the final annealing step. If a state is defined in which an insulating coating is formed on the surface of a groove, irradiation with a laser beam is preferably carried out before the insulating coating forming step.

[0062] However, even if laser beam irradiation is performed after the insulating coating forming step, if an insulating coating is formed again in the groove after laser beam irradiation, a state can be defined in which an insulating coating is also formed on the groove surface.

[0063] The grain-oriented electrical steel sheet to be a base steel sheet can be a known grain-oriented electrical steel sheet and therefore known manufacturing conditions can be applied, except for conditions of irradiation with a laser beam.

[0064] For irradiation with a laser beam, a laser beam Petition 870250040261, dated 05 / 16 / 2025, page 22 / 36 / 22 emitted by a laser that serves as a light source is scanned by a scanning device in a direction of 60 to 120° relative to the rolling direction RD of the grain-oriented electrical steel sheet. The scanning is repeated while the grain-oriented electrical steel sheet is transported (passed) in the rolling direction and thus a plurality of substantially parallel grooves are formed at a predetermined interval in the rolling direction RD.

[0065] For groove forming, a laser irradiates a steel sheet under conditions of melting or evaporation of the steel sheet. For example, the laser irradiation conditions are preferably defined for a laser output of 200 to 3000 W, a condensed spot diameter of the laser beam (i.e., a diameter including 86% of the laser output, hereinafter abbreviated as 86% diameter) in the rolling direction of 10 to 1000 μm, a condensed spot diameter of the laser beam (86% diameter) in the sheet width direction of 10 to 1000 μm, and a laser scanning speed of 5 to 50 m / s.

[0066] Since the laser serves as a light source, for example, a CO2 laser can be used. A high-power laser commonly used in industry can be used, such as a YAG laser, a semiconductor laser, or a fiber laser.

[0067] It is believed that the reason why Ra and Rsk become large is because a portion melted from irradiation with a laser beam and solidified again. Therefore, in the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment, in order to reduce Ra and Rsk in the lower portion of the groove, the surface of the steel sheet is irradiated with a laser beam in a state in which the steel sheet is inclined at 5° or more relative to the horizontal in the width direction. In addition, an auxiliary gas is blown into the portion irradiated with a laser beam. Petition 870250040261, dated 05 / 16 / 2025, page 23 / 36 / 22

[0068] If an auxiliary gas is blown while the steel plate is inclined at 5° or more relative to the horizontal direction in the width direction (inclined so that φ1 becomes 5° or more in Figure 2), molten material generated by laser irradiation will be easily removed from the irradiated portion, and it will be less likely that molten and resolidified material will remain in the lower portion of the groove.

[0069] If the angle is less than 5°, the molten material will not be sufficiently removed, even when an auxiliary gas is blown in.

[0070] In the case where Ra of the lateral surface of the groove is also reduced, the inclination (φ 1) is preferably set to more than 20°.

[0071] Meanwhile, if the surface is irradiated with a laser beam in a state where the steel sheet is inclined at 3° or more relative to the horizontal in the rolling direction, the molten material within the groove cannot be sufficiently removed, and Ra and Rsk at the bottom of the groove will become large. Therefore, the inclination of the steel sheet in the rolling direction (φ2: not illustrated) is defined as less than 3°.

[0072] The type of auxiliary gas is not limited, and examples of auxiliary gas include air and inert gases. From the point of view of suppressing the formation of an oxide in the blast position, the auxiliary gas is preferably an inert gas.

[0073] The angle formed by the direction (blowing direction) in which the auxiliary gas is blown (Θ1 illustrated in Figure 2) and the normal direction of the steel plate is preferably from 20 to 85°. The angle formed by the direction in which the auxiliary gas is blown and the groove extension direction (θ2 illustrated in Figure 3) is preferably from 0 to 30°.

[0074] The auxiliary gas flow rate is preferably from 10 to 1000 liters per minute, and the blowing speed is preferably 10 m / s or more.

[0075] In the case of reducing only Ra of the lower portion and the lateral surface of the groove, a method such as a treatment of Petition 870250040261, dated 05 / 16 / 2025, page 24 / 36 / 22 shot blasting can be considered. However, if a shot blasting treatment is performed, a crack will be generated on the sheet surface and, if the crack remains, the height distribution in the lower portion of the groove will change very locally in the crack generation portion, resulting in an increase in the slope of the lower portion of the groove, i.e., Rsk.

[0076] In the present invention, to control Ra and Rsk simultaneously, the inclination angle of the steel plate and the blowing conditions of the auxiliary gas are controlled as described above.

[0077] In the irradiation of inclined grain-oriented electrical steel sheet with a laser beam, the focal position is preferably prevented from deviating from the surface of the steel sheet. For example, it is preferable that the scan be performed while moving parallel to the surface of the inclined steel sheet (the distance between the irradiation device and the steel sheet is kept constant), or an operation be performed while the focal distance is changed so that the focal position is on the surface of the sheet.

[0078] By performing the above method, the grain-oriented electrical steel sheet is obtained according to the present embodiment. Examples

[0079] A plate having a Si content of 3.25% by mass was subjected to hot rolling, hot band annealing and cold rolling to obtain a cold-rolled steel sheet having a thickness of 0.23 mm or 0.20 mm, and the cold-rolled steel sheet was irradiated with a laser beam to form a groove on the surface.

[0080] The conditions at the time of groove forming were shown in Table 1. Here, φ1 represents the inclination of the steel sheet relative to the horizontal direction in the width direction, φ2 represents the inclination of the steel sheet relative to the horizontal direction in the rolling direction, Θ1 Petition 870250040261, dated 05 / 16 / 2025, page 25 / 36 / 22 represents the angle formed by the normal direction of the steel sheet and the direction of the auxiliary gas blowing, and Θ2 represents the angle of the auxiliary gas blowing direction relative to the direction of groove extension. As different conditions from those shown in the table, the laser beam irradiation conditions were defined for a laser output of 1500 W, a condensed spot diameter of the laser beam in the lamination direction of 40 μm, and a condensed spot diameter of the laser beam in the sheet width direction of 40 μm. The auxiliary gas flow rate was set to 100 liters per minute, and the blowing speed was set to 50 m / s.

[0081] After groove forming, the steel sheet was subjected to decarburization annealing, final annealing and forming of an insulating coating, and thus each of the grain-oriented electrical steel sheets no. 1 to 6, 12 to 17, 21 to 24 and 26 to 29 was obtained.

[0082] In these grain-oriented electrical steel sheets, a glass film was formed on the base steel sheet and an insulating coating was formed on the glass film in the groove, similarly to the other portion.

[0083] In addition, a plate having a Si content of 3.25% was subjected to hot rolling, hot band annealing, cold rolling, decarburization annealing, final annealing and forming of an insulating coating to obtain a steel sheet having a thickness of 0.23 mm (steel sheet with insulating coating), and the steel sheet was irradiated with a laser beam to form a groove on the surface.

[0084] The conditions at the time of groove forming were as shown in Table 1 and, as different from the conditions shown in the table, the laser beam irradiation conditions were defined for a laser output of 1500 W, a condensed spot diameter of the laser beam in the rolling direction of 40 μm and a condensed spot diameter of the laser beam in the sheet width direction of 40 μm. The gas flow rate Petition 870250040261, dated 05 / 16 / 2025, page 26 / 36 / 22, the auxiliary flow rate was set to 100 liters per minute, and the blowing speed was set to 50 m / s.

[0085] After groove forming, an insulating coating was formed again. Thus, each of the grain-oriented electrical steel sheets numbered 7 to 11, 18 to 20, and 25 were obtained.

[0086] In these grain-oriented electrical steel sheets, a glass film was absent and an insulating coating was formed on the base steel sheet in the groove.

[0087] For the grain-oriented electrical steel sheets obtained (nos. 1 to 29), the groove depth and width, Ra and the absolute value of Rsk in the lower portion of the groove, and Ra of the lateral surface of the groove were measured using the methods described above.

[0088] Table 2 shows the results.

[0089] The magnetic property of each of the grain-oriented electrical steel sheets obtained was evaluated using the following method. Table 2 shows the results. [Magnetic Property Assessment]

[0090] A sample was collected from each test number that included the center width position of the grain-oriented electrical steel sheet, with a width of 60 mm and a length of 300 mm. The length direction of the sample was parallel to the rolling direction. Using this sample, the iron loss W17 / 50 (W / kg) at a frequency of 50 Hz and a maximum magnetic flux density of 1.7 T were measured by a single-sheet magnetic property test (SST test) according to JIS C 2556: 2015.

[0091] A sample having a sheet thickness of 0.23 mm and an iron loss of 0.750 W / kg or less was considered to have excellent magnetic properties (low iron loss). A sample having a sheet thickness of 0.20 mm and an iron loss of 0.700 W / kg or less was Petition 870250040261, dated 05 / 16 / 2025, page 27 / 36 / 22, considered to have excellent magnetic properties (low iron loss). [Table 1] No. Base steel sheet Groove forming stage Laser beam irradiation conditions Auxiliary gas Type Sheet thickness Slope φ1 in the sheet width direction Slope φ2 in the sheet rolling direction Interval in the rolling direction Scanning direction (relative to the rolling direction) Type Blow angle θ1 Blow direction θ2 - mm Degree Degree mm Degree - Degree Degree 1 Cold-rolled steel sheet 0.23 0 0 5 90 Ar 30 0 2 Cold-rolled steel sheet 0.23 10 0 5 90 Ar 10 50 3 Cold-rolled steel sheet 0.23 10 0 15 90 Ar 30 0 4 Cold-rolled steel sheet 0.23 10 0 5 30 Ar 30 0 5 Steel sheet Cold-rolled 0.23 0 0 5 90 Ar 10 40 6 Cold-rolled steel sheet 0.23 0 0 12 150 Ar 30 0 7 Steel sheet with an insulating coating 0.23 0 0 5 90 Ar 30 0 8 Steel sheet with an insulating coating 0.23 10 0 5 90 Ar 10 50 9 Steel sheet with an insulating coating 0.23 10 0 15 90 Ar 30 0 10 Steel sheet with an insulating coating 0,23 10 0 5 30 Ar 30 0 11 Steel sheet with an insulating coating 0.23 10 0 5 90 Ar 10 50 12 Cold-rolled steel sheet 0.23 10 0 5 90 Ar 30 0 13 Cold-rolled steel sheet 0.23 10 0 8 85 Ar 30 0 14 Cold-rolled steel sheet 0.23 20 0 5 95 Ar 30 0, Petition 870250040261, dated 05 / 16 / 2025, pages 28 / 36 / 22 No. Base steel sheet Groove forming stage Laser beam irradiation conditions Auxiliary gas Type Sheet thickness Slope φ1 in the sheet width direction Slope φ2 in the sheet rolling direction Interval in the rolling direction Scanning direction (relative to the rolling direction) Type Blow angle θ1 Blow direction θ2 - mm Degree Degree mm Degree - Degree Degree 15 Cold-rolled steel sheet 0.23 10 0 5 100 Ar 50 10 16 Cold-rolled steel sheet 0.23 5 0 5 90 Ar 30 0 17 Cold-rolled steel sheet 0.23 10 0 5 80 Nitrogen 30 0 18 Steel sheet with an insulating coating 0.23 10 0 5 90 Ar 30 0 19 Steel sheet with an insulating coating 0.23 5 0 5 90 Ar 30 0 20 Steel sheet with an insulating coating 0.23 10 0 5 90 Ar 50 10 21 Cold-rolled steel sheet 0.23 25 0 5 90 Ar 30 0 22 Cold-rolled steel sheet 0.23 30 0 5 90 Ar 30 0 23 Cold-rolled steel sheet 0.23 21 0 5 90 Ar 30 0 24 Cold-rolled steel sheet 0,23 25 0 5 90 Ar 30 0 25 Steel sheet with an insulating coating 0.23 30 0 5 90 Ar 50 10 26 Cold-rolled steel sheet 0.23 10 4 5 90 Ar 50 10 27 Cold-rolled steel sheet 0.20 10 0 5 90 Ar 30 0 28 Cold-rolled steel sheet 0.20 25 0 5 90 Ar 30 0 29 Cold-rolled steel sheet 0.20 0 0 5 90 Ar 30 0, Petition 870250040261, dated 05 / 16 / 2025, pages 29 / 36 / 22 [Table 2] No. Electrically Oriented Grain Steel Sheet Observation Groove Property Depth Width Ra at the bottom of the groove Absolute value of Rsk at the portion of the groove Ra of the lateral surface of the groove Iron loss μm μm μm - μm W / kg 1 22 44 4.8 2.5 5.1 0.758 Example Comparative 2 18 40 2.4 2.2 6.1 0.752 Example Comparative 3 23 45 3.7 2.0 5.4 0.761 Example Comparative 4 15 42 4.2 1.9 5.2 0.754 Example Comparative 5 19 43 5.2 3.0 6.0 0.760 Example Comparative 6 25 50 5.5 2.6 5.1 0.765 Example Comparative 7 25 55 4.5 2.4 5.4 0.755 Example Comparative 8 19 39 3.0 2.3 5.8 0.753 Example Comparative 9 25 44 3.8 1.8 6.1 0.760 Example Comparative 10 17 40 4.0 1.8 6.3 0.755 Example Comparative 11 22 44 5.2 1.8 6.5 0.753 Example Comparative 12 20 40 3.0 1.5 5.4 0.744 Example of the Invention 13 21 39 2.5 1.0 5.1 0.747 Example of the Invention 14 22 44 1.8 0.8 5.3 0.741 Example of Invention 15 20 45 3.2 1.8 5.7 0.745 Example of Invention 16 21 37 2.2 0.6 5.9 0.Example of Invention 17 18 39 2.6 1.2 5.1 0.746 Example of Invention 18 18 42 2.9 1.6 5.2 0.745 Example of Invention 19 23 45 2.7 1.5 6.0 0.744 Example of Invention 20 21 42 3.5 1.8 6.8 0.746 Example of Invention 21 25 50 3.4 1.2 4.1 0.720 Example of Invention 22 22 45 2.0 0.9 2.4 0.702 Example of Invention 23 19 44 1.1 0.5 1.3 0.694 Example of Invention 24 30 58 0.2 0.4 0.8 0.687 Example of the Invention 25 30 61 2.2 1.0 2.6 0.705 Example of the Invention Petition 870250040261, dated 05 / 16 / 2025, page 30 / 36 / 22 No. Electrically oriented grain steel sheet Observation Groove Property Depth Width Ra in the lower portion of the groove Absolute value of Rsk in the portion of the groove Ra of the lateral surface of the groove Iron loss μm μm μm - μm W / kg 26 20 41 5.1 2.4 5.2 0.754 Comparative Example 27 21 39 2.9 1.4 5.1 0.697 Example of the Invention 28 22 41 3.3 1.1 4.1 0.671 Example of the Invention 29 22 44 4.9 2.3 5.3 0.702 Comparative Example

[0092] As can be seen in Tables 1 and 2, excellent iron loss was obtained in Examples of the Invention 12 to 25, 27 and 28, in which the grain-oriented electrical steel sheet included a base steel sheet having a surface on which a plurality of grooves were formed, extending in a direction of 60 to 120° relative to the rolling direction in a range in the rolling direction of 2 to 10 mm, and the plurality of grooves had, in each groove, a lower portion in which Ra was 5.0 μm or less and the absolute value of Rsk was 2.0 or less along the direction of extension of the plurality of grooves.

[0093] Meanwhile, in Nos. 1, 2, 5, 7, 8, 11, 26 and 29, in which the inclination of the steel sheet, the angle of the auxiliary gas blowing and the direction of blowing were not defined for a preferred condition in the groove forming step, Ra and / or Rsk in the lower portion of the groove were outside the range of the present invention, and the iron loss was large.

[0094] Iron loss was also large in Nos. 3, 4, 9 and 10, in which the interval between the grooves and the direction of groove extension were outside the range of the present invention.

[0095] Also in No. 6, in which the inclination of the steel plate, the interval between the grooves and the direction of extension in the groove forming step were outside the range of the present invention, Ra and / or Rsk in the lower portion of the groove were outside the range of the present invention, and the iron loss was large. Petition 870250040261, dated 05 / 16 / 2025, page 31 / 36 / 22 INDUSTRIAL APPLICABILITY

[0096] According to the present invention, an electrically oriented grain steel sheet having low iron loss can be provided. Therefore, its industrial applicability is high. LIST OF REFERENCE SIGNS

[0097] 1 Grain-oriented electrical steel sheet Grain-oriented electrical steel sheet (base steel sheet) Slot Petition 870250040261, dated 05 / 16 / 2025, pages 32 / 36< / ranhura>

Claims

CLAIMS 1. Grain-oriented electrical steel sheet, characterized in that it comprises a base steel sheet having a surface on which a plurality of grooves are formed, the plurality of grooves extending in a direction of 60 to 120° relative to a rolling direction in a range in the rolling direction of 2 to 10 mm, wherein, in a lower portion of the grooves, Ra is 5.0 μm or less, and an absolute value of Rsk is 2.0 or less along a direction of extension of the grooves.

2. Grain-oriented electrical steel sheet according to claim 1, characterized in that, on a lateral surface of the grooves, Ra is 5.0 μm or less along the direction of groove extension. Petition 870250040261, dated 05 / 16 / 2025, pp. 33 / 36

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