Grain-oriented electromagnetic steel sheet and method for manufacturing same

Abstract

Provided is a grain-oriented electromagnetic steel sheet comprising a steel sheet and an insulating coating disposed on both surfaces of the steel sheet, wherein, on both surfaces of the grain-oriented electromagnetic steel sheet, the peak height Spk defined in JIS B 0681-2:2018 is 0.40 μm or less, and the load area ratio Smr1 for separating a peak portion and a core portion as defined in JIS B 0681-2:2018 is 20% or less. The grain-oriented electromagnetic steel sheet has excellent positioning properties. The Spk is preferably 0.05 μm or more. The Smr1 is preferably 5% or more.

Description

Grain-oriented electrical steel sheet and its manufacturing method

[0001] The present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same.

[0002] Grain-oriented electrical steel sheets are soft magnetic materials used as iron cores for transformers, generators, etc. They have a crystal texture in which the <001> orientation, which is the easy axis of magnetization of iron, is highly aligned in the rolling direction of the steel sheet. This texture is formed during the manufacturing process of grain-oriented electrical steel sheets through a finishing annealing (secondary recrystallization annealing) process, which preferentially grows grains with the {110} <001> orientation, also known as the Goss orientation.

[0003] Such grain-oriented electrical steel sheets generally comprise a steel sheet and insulating coatings disposed on both sides of the steel sheet (see Patent Documents 1 and 2). The insulating coatings apply tension to the steel sheet to reduce the iron loss of the grain-oriented electrical steel sheet, and also impart properties such as insulation, workability, and rust resistance to the grain-oriented electrical steel sheet.

[0004] JP 6-158340 A JP 2018-90871 A

[0005] When assembling a product such as an iron core using grain-oriented electromagnetic steel sheets, an operation (stacking operation) is required in which a plurality of grain-oriented electromagnetic steel sheets are stacked one by one while being positioned to form a laminate.

[0006] For this reason, "lamination workability" is often emphasized for grain-oriented electrical steel sheets, and lamination workability is comprised of two properties: "sliding ability" and "positioning ability." Sliding ability refers to the ease of fine-tuning the position of grain-oriented electrical steel sheets during lamination (how easily grain-oriented electrical steel sheets can be kept sliding once they have started to slide). On the other hand, positioning ability refers to the ease of determining the position of grain-oriented electrical steel sheets during lamination (how difficult it is for grain-oriented electrical steel sheets to start sliding again once they have stopped).

[0007] Of the two properties that make up lamination workability, positioning ability in particular has a significant impact on the productivity of the laminate. That is, if the positioning ability of the grain-oriented electrical steel sheets is insufficient (the grain-oriented electrical steel sheets, once positioned and placed, tend to shift position), work must be done to position them again and place them again, which significantly reduces the productivity of the laminate.

[0008] Incidentally, Patent Documents 1 and 2 disclose techniques for improving the sliding properties by adjusting the line roughness (arithmetic mean roughness Ra) of the surface of a grain-oriented electrical steel sheet. However, there is no particular mention of positioning ability. Therefore, the present inventors manufactured grain-oriented electrical steel sheets based on the techniques disclosed in Patent Documents 1 and 2 and evaluated their positioning ability, but found that all of them were insufficient. Furthermore, it was also found that there is no correlation between the line roughness (Ra) and positioning ability described in Patent Documents 1 and 2.

[0009] The present invention has been made in view of the above points, and has an object to provide a grain-oriented electrical steel sheet that is excellent in positioning ability.

[0010] As a result of extensive research, the inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention. That is, the present invention provides the following [1] to [4]. [1] A grain-oriented electrical steel sheet comprising a steel sheet and an insulating coating disposed on both sides of the steel sheet, wherein, on both sides of the grain-oriented electrical steel sheet, a peak height Spk defined in JIS B 0681-2:2018 is 0.40 μm or less, and a material area ratio Smr1 separating the peaks and the core defined in JIS B 0681-2:2018 is 20% or less. [2] The grain-oriented electrical steel sheet according to [1] above, in which Spk is 0.05 μm or more. [3] The grain-oriented electrical steel sheet according to [1] or [2] above, in which Smr1 is 5% or more. [4] A method for producing the grain-oriented electrical steel sheet according to any one of [1] to [3] above, comprising forming the insulating coating on both sides of the steel sheet, and then using a friction body to perform friction two or more times under conditions of a dynamic friction force per width of 24.5 N / mm or more and a relative speed of 20 m / min or more.

[0011] According to the present invention, a grain-oriented electrical steel sheet with excellent positioning properties can be provided.

[0012] [Findings Obtained by the Inventors] The inventors have made the following findings.

[0013] The surface of the insulating coating of grain-oriented electrical steel sheet has many minute protrusions with diameters (distance in the sheet surface direction) of several micrometers to several tens of micrometers and heights (distance in the sheet thickness direction) of several hundred nanometers to 1 micrometer. The shape of these protrusions is the determining factor for positioning ability.

[0014] Because the convex portions are scattered on a plane (plate surface), the line roughness (such as the arithmetic mean roughness Ra) obtained by one-dimensionally measuring the irregularities may not fully reflect the shape of the convex portions. To obtain measurement results that fully reflect the shape of the convex portions, it is appropriate to measure an appropriate three-dimensional shape; perform processing (including filtering) on ​​the obtained measurement data at an appropriate cutoff wavelength to analyze the shape of the convex portions; and use the surface roughness calculated from the obtained processed data. Specifically, although the shape of each convex portion is different, the overall trend of the shape of the convex portions can be grasped by using the surface texture parameters "protruding peak height Spk" and "area load ratio Smr1 separating the protruding peak portion from the core portion" defined in JIS B 0681-2:2018.

[0015] By controlling the values ​​of both Spk and Smr1 within appropriate ranges, good positioning accuracy can be obtained.

[0016] By rubbing the surface of the grain-oriented electrical steel sheet under specific conditions, the shape of the convex portions can be changed, and Spk and Smr1 can be controlled within appropriate ranges.

[0017] The present invention has been made based on the above findings and further investigations. Next, preferred embodiments of the present invention will be described.

[0018] [Grain-oriented electrical steel sheet] A grain-oriented electrical steel sheet includes at least a steel sheet and an insulating coating disposed on both sides of the steel sheet. First, the steel sheet and the insulating coating will be described.

[0019] <Steel Sheet> The steel sheet included in the grain-oriented electrical steel sheet may be, for example, a so-called secondary recrystallized sheet (finish annealed sheet) having a forsterite coating formed on the surface.

[0020] The steel sheet has a chemical composition (steel composition) containing, for example, 2.8 to 3.5% Si and 0.01 to 1.00% Mn, with the balance being Fe and unavoidable impurities. Note that "%" in the chemical composition means "mass %" unless otherwise specified.

[0021] The chemical composition of the steel sheet may further contain at least one element selected from the group consisting of C: 0.005% or less, Al: 0.015% or less, N: 0.005% or less, Cu: 0.3% or less, Ni: 0.3% or less, Cr: 0.3% or less, Sb: 0.05% or less, Sn: 0.3% or less, Mo: 0.3% or less, and Bi: 0.05% or less. In this case, it is preferable that the contents are C: 0.001 to 0.002%, Al: 0.001 to 0.005%, N: 0.001 to 0.002%, Cu: 0.1 to 0.2%, Ni: 0.1 to 0.2%, Cr: 0.1 to 0.2%, Sb: 0.01 to 0.02%, Sn: 0.1 to 0.2%, Mo: 0.1 to 0.2%, and Bi: 0.01 to 0.02%.

[0022] The steel sheet may further contain at least one element selected from the group consisting of 0.05% or less B, 0.10% or less Ge, 0.10% or less As, 0.10% or less P, 0.05% or less Te, 0.05% or less Nb, 0.05% or less Ti, and 0.05% or less V. In this case, the steel sheet preferably contains 0.01 to 0.02% or less B, 0.01 to 0.03% Ge, 0.01 to 0.03% As, 0.01 to 0.03% P, 0.01 to 0.03% Te, 0.01 to 0.03% Nb, 0.01 to 0.03% Ti, and 0.01 to 0.03% V.

[0023] <Insulating Coating> The insulating coating is formed on the surface of the steel sheet (or the forsterite coating). The insulating coating has a component composition that includes, for example, 100 parts by mass of P, 80 to 250 parts by mass (preferably 100 to 150 parts by mass) of Si, and 20 to 200 parts by mass (preferably 40 to 160 parts by mass) of at least one element selected from the group consisting of Mg, Al, Ca, Ba, Sr, Ti, V, Cr, Zn, Zr, Nb, and Mo, as well as O (oxygen) and unavoidable impurities.

[0024] The insulating coating may contain 20% by volume or more of glass (such as phosphosilicate glass or borosilicate glass). Note that, since glass generally undergoes so-called crystallization (part of the glass may have a periodic crystalline structure), the insulating coating may contain less than 80% by volume of crystalline material.

[0025] The amount of the insulating coating applied (per side) is not particularly limited, and may be, for example, 1 to 12 g / m ２ is preferred, and 2 to 8 g / m ２ is more preferred.

[0026] <Protruding Peak Height Spk> If the Spk on both sides of the grain-oriented electrical steel sheet is too large, the microscopic contact areas between the insulating coatings of the laminated grain-oriented electrical steel sheets are limited to the apexes of the minute protrusions and their vicinity. As a result, the contact area on the surface of the grain-oriented electrical steel sheet is reduced, and positioning ability deteriorates. Therefore, from the viewpoint of obtaining good positioning ability, the Spk on both sides of the grain-oriented electrical steel sheet is 0.40 μm or less, preferably 0.30 μm or less, more preferably 0.20 μm or less, and even more preferably 0.15 μm or less.

[0027] On the other hand, the lower limit of Spk is, for example, 0.01 μm, and may be 0.03 μm. However, if Spk is too small, the contact area on the surface of the grain-oriented electrical steel sheet increases, which may reduce the insulation properties guaranteed by the insulating coating. Therefore, from the viewpoint of obtaining good insulation properties, Spk on both surfaces of the grain-oriented electrical steel sheet is preferably 0.05 μm or more.

[0028] <Smr1, the area ratio separating the peaks and the core> If Smr1 on both surfaces of the grain-oriented electrical steel sheet is too large, the area ratio of the flat portions (non-convex portions) decreases. As a result, the contact area between the flat portions (non-convex portions), which increases the static friction force, decreases, and positioning ability deteriorates. Therefore, from the viewpoint of obtaining good positioning ability, Smr1 on both surfaces of the grain-oriented electrical steel sheet is 20% or less, preferably 18% or less, and more preferably 15% or less.

[0029] On the other hand, the lower limit of Smr1 is, for example, 1%, and may be 3%. However, if Smr1 is too small, frictional force will concentrate on the minute protrusions described above when rubbing occurs between an already laminated grain-oriented electrical steel sheet and a newly laminated grain-oriented electrical steel sheet, which may cause these protrusions to peel off and reduce the insulation provided by the insulating coating. For this reason, from the viewpoint of obtaining good insulation, Smr1 on both surfaces of the grain-oriented electrical steel sheet is preferably 5% or more.

[0030] The surface texture parameters (Spk and Smr1) are determined as follows. First, a confocal laser microscope equipped with a 100x objective lens is used to obtain photographic data of multiple fields of view for the surface of the test material (steel sheet and grain-oriented electrical steel sheet with an insulating coating). When obtaining the photographic data, shape measurement is performed under the condition that the number of pixels per field of view (range of 145 μm width and 109 μm length) is 1024 × 768. The obtained photographic data is trimmed and joined to obtain shape data within a 180 μm square range. When joining the photographic data, data compression may be performed. Noise is removed from the obtained shape data, and the surface texture parameters (Spk and Smr1) within a 180 μm square range are determined in accordance with JIS B 0681-2:2018. When determining the surface texture parameters, in order to realize an analysis that focuses on the shapes of the minute convex portions described above, a 25 μm L filter (high-pass filter) is applied to exclude various long-period structures such as waviness of the steel plate from the shape data.

[0031] For one grain-oriented electrical steel sheet, the above-mentioned measurement is carried out in 10 randomly selected regions, and the arithmetic mean value of the Spk values ​​obtained in each region is calculated, and this is defined as the Spk value for both surfaces of the grain-oriented electrical steel sheet. The same applies to Smr1.

[0032] <Slip-out angle> The positioning ability of a grain-oriented electrical steel sheet is evaluated by the slip-out angle measured by the method described below. The larger the slip-out angle, the better the positioning ability. Specifically, the slip-out angle of the grain-oriented electrical steel sheet is preferably 10° or more, and more preferably 15° or more.

[0033] The sliding angle is determined as follows. A small test piece (50 mm long x 30 mm wide) and a large test piece (300 mm long x 100 mm wide) are cut out from one grain-oriented electrical steel sheet. The small test piece is placed on top of the large test piece placed on a horizontal surface, with the longitudinal directions of the small test piece parallel to each other, and the plate surfaces of the large and small test pieces are brought into contact with each other. Next, a weight is placed on the small test piece, and a load is applied evenly to the contact surface with the large test piece. At this time, the mass of the weight is adjusted so that the total mass of the small test piece and the weight is 200 g. Thereafter, one end of the large test piece in the longitudinal direction is raised while the other end remains in contact with the horizontal surface. In this way, the large test piece with the small test piece and the weight placed on it is tilted, and the minimum tilt angle (sliding angle) at which the small test piece begins to slide on the large test piece is measured. One large test piece and two small test pieces are cut out from one grain-oriented electrical steel sheet, and the above-mentioned measurement is carried out once using each of the two small test pieces. The average value of the start-up angle is calculated and used as the start-up angle of that grain-oriented electrical steel sheet. Note that in the first and second measurements, the small test pieces are placed and slid at different positions in the width direction on the large test piece. This prevents the sliding of the small test pieces on the large test piece in the first measurement from affecting the second measurement.

[0034] <Interlaminar Resistance> Grain-oriented electrical steel sheets are preferably excellent not only in positioning ability but also in insulation. The insulation of grain-oriented electrical steel sheets is evaluated by the interlaminar resistance measured by the method described below. The higher the interlaminar resistance, the better the insulation. Specifically, the interlaminar resistance of grain-oriented electrical steel sheets is, for example, 70 Ω cm ２ or more and 100 Ω cm ２ The above is preferable.

[0035] The interlaminar resistance is determined as follows. In this embodiment, the interlaminar resistance is measured to evaluate the insulation properties, taking into account the effect of friction between the stacked grain-oriented electrical steel sheets on the insulation properties of the insulating coating. Specifically, in order to simulate a state in which such friction occurs, the large test piece used in measuring the start-of-slip angle described above is used as the test piece, and the surface region of this test piece (large test piece) where the small test piece has slid once is used as the region to be evaluated for insulation properties. The interlaminar resistance of this evaluation region is measured in accordance with JIS C 2550:2000.

[0036] <Thickness> The thickness of the grain-oriented electrical steel sheet is not particularly limited, but from the viewpoint of manufacturability, it is preferably 0.10 mm or more, more preferably 0.15 mm or more, and even more preferably 0.20 mm or more, while the thickness of the grain-oriented electrical steel sheet is preferably 0.35 mm or less, more preferably 0.30 mm or less, and even more preferably 0.25 mm or less.

[0037] [Method for manufacturing grain-oriented electrical steel sheet] Next, a method for manufacturing the grain-oriented electrical steel sheet of the present embodiment will be described. Briefly, an insulating coating is first formed on both sides of a steel sheet to obtain a grain-oriented electrical steel sheet (hereinafter, for convenience, also referred to as an "untreated sheet") before the friction treatment described below is performed. The untreated sheet is then subjected to friction treatment.

[0038] <Preparation of Steel Sheet> First, the above-described steel sheet is prepared as a base material on which an insulating coating is to be formed. The steel sheet is, for example, a secondary recrystallized sheet (finish annealed sheet) having a forsterite coating formed on its surface, as described above. The secondary recrystallized sheet is produced, for example, as follows.

[0039] First, a steel slab having the above-described chemical composition (steel composition) is obtained from molten steel produced using a conventionally known refining process using a continuous casting method or an ingot casting-blooming rolling method. The steel slab is then hot-rolled to obtain a hot-rolled sheet. The hot-rolled sheet is then annealed as needed, and then cold-rolled once or twice or more times with intermediate annealing in between to obtain a cold-rolled sheet of the final thickness. Next, the cold-rolled sheet is subjected to primary recrystallization annealing and decarburization annealing, and then an annealing separator containing MgO as the main component is applied, followed by finish annealing (secondary recrystallization annealing) to form a forsterite coating. In this way, a secondary recrystallized sheet having a forsterite coating on its surface is obtained.

[0040] <Formation of Insulating Coating> Next, insulating coatings are formed on both sides of the steel sheet (e.g., secondary recrystallized sheet). To form the insulating coating, for example, an insulating coating treatment solution containing phosphate, colloidal silica, and metal oxide is used. The solvent for the insulating coating treatment solution is preferably water.

[0041] The phosphate preferably contains at least one element selected from the group consisting of Mg, Ca, Ba, Sr, Zn, and Al, and examples thereof include magnesium phosphate, calcium phosphate, aluminum phosphate, etc. As the phosphate, monophosphate (biphosphate) is easily available and is therefore preferred.

[0042] The content of colloidal silica is preferably 80 to 250 parts by mass, more preferably 100 to 150 parts by mass, calculated as Si, per 100 parts by mass of phosphate (calculated as P).

[0043] The metal oxide may be in the form of particles (powder), for example. The metal oxide preferably contains at least one element selected from the group consisting of Mg, Al, Ca, Ba, Sr, Ti, V, Cr, Zn, Zr, Nb, and Mo, and more preferably contains at least one element selected from the group consisting of Ti, V, Cr, Zn, Zr, and Nb. Specific examples of the metal oxide include TiO ２ , V ２ O ５ , CrO ３ , ZnO, ZrO ２ , Nb２ O ３ The content of the metal oxide is preferably 20 to 200 parts by mass, more preferably 40 to 160 parts by mass, calculated as the metal element, per 100 parts by mass of the phosphate (calculated as P).

[0044] A dispersant (such as a cationic surfactant) may be added to the insulating coating treatment solution as needed. The content of the dispersant is preferably 0.20 to 2.00 parts by mass, and more preferably 0.25 to 1.50 parts by mass, per 100 parts by mass of phosphate (P equivalent). When the dispersant is diluted with a solvent, the content of the dispersant means the amount excluding the solvent.

[0045] First, the insulating coating solution is applied to the surface of a steel sheet using, for example, a roll coater, and may be applied to the surface of the steel sheet while the steel sheet is being conveyed at a conveying speed of, for example, 180 m / min or more.

[0046] Thereafter, the coated film is dried as necessary and then baked to form an insulating coating. Planarization annealing, which also serves as baking, may be performed. The baking temperature is preferably 600 to 1000°C, more preferably 700 to 950°C, and even more preferably 800 to 900°C. The baking atmosphere is preferably an inert gas atmosphere such as a nitrogen gas atmosphere. The baking time is preferably 1 to 300 seconds, preferably 5 to 200 seconds, and more preferably 10 to 100 seconds.

[0047] In this way, a grain-oriented electrical steel sheet (untreated sheet) is obtained, which has insulating coatings formed on both sides of the steel sheet and has not yet been subjected to friction treatment.

[0048] <Rubbing Treatment> Next, the untreated plate is subjected to rubbing treatment, which is a treatment in which friction is applied to both the front and back sides of the untreated plate using a friction body.

[0049] <<Friction Body>> Examples of the material of the friction body include fibers such as nylon fibers, polyester fibers, and wool fibers; and those fibers solidified with resins such as urethane resins. The friction body may be a stationary pad or a rotating body. In the friction treatment, for example, the untreated plate is transported between a pair of pads or rotating bodies.

[0050] <<Dynamic friction force per width>> In the friction treatment, the dynamic friction force per width is controlled within an appropriate range. The dynamic friction force per width (unit: N / mm) is the dynamic friction force (unit: N / mm) calculated from the difference in tension of the untreated plate before and after the position where the untreated plate is rubbed. ２ ) by the width of the untreated plate (unit: mm).

[0051] If the dynamic friction force per width is too small, a small Spk cannot be obtained. Therefore, from the viewpoint of obtaining a small Spk, the dynamic friction force per width is 24.5 N / mm or more (2.5 kgf / mm or more), preferably 27.4 N / mm or more (2.8 kgf / mm or more), and more preferably 29.4 N / mm or more (3.0 kgf / mm or more).

[0052] On the other hand, the upper limit of the kinetic friction force per width is, for example, 47.0 N / mm (4.8 kgf / mm). However, if the kinetic friction force per width is too large, Spk may become too small. Therefore, from the viewpoint of preventing Spk from becoming too small, the kinetic friction force per width is preferably 43.1 N / mm or less (4.4 kgf / mm or less), and more preferably 39.2 N / mm or less (4.0 kgf / mm or less).

[0053] <<Relative Speed>> In the friction treatment, the relative speed between the untreated plate and the friction body is controlled within an appropriate range. The relative speed (unit: m / min) is, for example, the moving speed (transport speed) of the untreated plate when the friction body is stationary, or the difference between the rotation speed of the outer periphery of the friction body and the moving speed (transport speed) of the untreated plate when the friction body is a rotating body.

[0054] If the relative speed is too low, a small Smr1 cannot be obtained. Therefore, from the viewpoint of obtaining a small Smr1, the relative speed is 20 m / min or more, preferably 30 m / min or more, and more preferably 40 m / min or more.

[0055] On the other hand, the upper limit of the relative speed is, for example, 200 m / min. However, if the relative speed is too high, Smr1 may become too small. Therefore, from the viewpoint of preventing Smr1 from becoming too small, the relative speed is preferably 170 m / min or less, and more preferably 150 m / min or less.

[0056] <<Number of Frictions>> In the friction treatment, the surface of the untreated plate and the friction body are moved relative to each other while in contact with each other under the above-mentioned conditions (dynamic friction force per width and relative speed) (for example, the untreated plate is conveyed between a pair of stationary pads). In this way, the surface of the untreated plate is rubbed.

[0057] At this time, if the number of times of friction is too small, small Spk and Smr1 cannot be obtained. Therefore, from the viewpoint of obtaining small Spk and Smr1, the number of times of friction is 2 or more, preferably 3 or more, and more preferably 5 or more.

[0058] On the other hand, the upper limit of the number of friction times is, for example, 25 times, and may be 20 times. However, if the number of friction times is too high, Spk and Smr1 may become too small even if the dynamic friction force and relative velocity per width described above are within appropriate ranges. Therefore, from the viewpoint of preventing Spk and Smr1 from becoming too small, the number of friction times is preferably 15 times or less, and more preferably 10 times or less.

[0059] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples described below.

[0060] [Test 1] <Production of grain-oriented electrical steel sheet> Using a 100 kg vacuum steel ingot, a secondary recrystallized steel sheet having forsterite coatings on both surfaces was obtained as a steel sheet according to the method described above. The chemical composition (steel composition) of the obtained steel sheet is shown in Table 1 below. Next, phosphate (magnesium monophosphate), colloidal silica (Snowtex 30, manufactured by Nissan Chemical Industries, Ltd.), and metal oxide (CrO ３ ) was applied using a roll coater, and then baking was performed (baking temperature: 840°C, baking time: 20 seconds, baking atmosphere: nitrogen atmosphere) to form an insulating coating (adhesion amount per side: 4 g / m ２ ) was formed on the surface of the steel sheet. The component composition of the formed insulating coating is shown in Table 1 below. In this way, a grain-oriented electrical steel sheet (untreated sheet) was obtained, which had insulating coatings formed on both sides of the steel sheet and had not yet been subjected to friction treatment. Next, the untreated sheet was subjected to friction treatment using a pair of pads (material: nylon fiber) as friction bodies under the conditions (kinetic friction force per width, relative speed, and number of frictions) shown in Table 1 below, to obtain a grain-oriented electrical steel sheet (thickness: 0.23 mm).

[0061] <Evaluation> The surface texture parameters (Spk and Smr1) of both surfaces of the obtained grain-oriented electrical steel sheets were determined according to the method described above. The results are shown in Table 1 below. Specifically, a Keyence VK250 / 260 confocal laser microscope and a Keyence VK-H1XM multi-file analysis application were used. The upper and lower measurement limits and brightness were set automatically, and measurement conditions were set using the RPD (Real Peak Detection) method with a height interval of 0.08 μm. The RPD method is a method in which measurements are taken at specific height intervals and the true focal height is calculated from the reflected laser light intensity data obtained at each height. For noise removal in the analysis, DCL correction with a threshold value of 5000 and spike removal correction with a height cut level of 100 were used.

[0062] Furthermore, the obtained grain-oriented electrical steel sheets were measured for slip angle and interlaminar resistance according to the above-mentioned methods. The results are shown in Table 1 below. When the slip angle was 10° or more, the sheet was evaluated as having excellent positioning ability. When the interlaminar resistance was 100 Ω cm ２ When the value was equal to or greater than this, the insulating property was evaluated as excellent.

[0063]

[0064] <Summary of Evaluation Results> As shown in Table 1 above, all of No. 1-1 to No. 1-13, which had an Spk of 0.40 μm or less and an Smr1 of 20% or less, had a starting angle of 10° or more, and were found to have excellent positioning properties.

[0065] Among these, No. 1-1 to No. 1-4, No. 1-6 to No. 1-8, and No. 1-10 to No. 1-12 have an interlayer resistance of 100 Ω cm ２ Specifically, the friction treatment conditions (dynamic friction force per width, relative velocity, and number of frictions) were controlled within suitable ranges, and Spk and / or Smr1 were prevented from becoming too small.

[0066] In contrast, Nos. 1-14 to 1-16 had a sliding start angle of less than 10°, resulting in insufficient positioning. Specifically, No. 1-14 had a dynamic friction force per width of less than 24.5 N / mm, resulting in Spk exceeding 0.40 μm. Furthermore, No. 1-15 had a relative speed of less than 20 m / min, resulting in Smr1 exceeding 20%. Furthermore, No. 1-16 had a friction count of less than two, resulting in Spk exceeding 0.40 μm and Smr1 exceeding 20%.

[0067] [Test 2] <Production of grain-oriented electrical steel sheet> Steel sheets (secondarily recrystallized sheets) were obtained in the same manner as in Test 1. The chemical composition (steel composition) of the obtained steel sheets is shown in Table 2 below. Next, in the same manner as in Test 1, an insulating coating treatment liquid containing phosphate, colloidal silica (Snowtex 30, manufactured by Nissan Chemical Industries, Ltd.) and metal oxide was applied to both sides of the obtained steel sheets, and then baking was carried out to form insulating coatings (adhesion amount per side: 4 g / m ２ The composition of the insulating coating is shown in Table 2 below. The phosphates used were monobasic magnesium phosphate, monobasic aluminum phosphate, and monobasic calcium phosphate. The metal oxides used were CrO ３ , TiO ２ , V ２ O ５ , and ZnO were used. In this way, a grain-oriented electrical steel sheet (untreated sheet) was obtained, in which an insulating coating was formed on both sides of the steel sheet and before friction treatment was performed. Next, the obtained untreated sheet was subjected to friction treatment under the conditions shown in Table 2 below in the same manner as in Test 1, to obtain a grain-oriented electrical steel sheet (thickness: 0.23 mm).

[0068] <Evaluation> The surface texture parameters (Spk and Smr1), slip angle, and interlaminar resistance of the obtained grain-oriented electrical steel sheets were determined in the same manner as in Test 1. The results are shown in Table 2 below.

[0069]

[0070] <Summary of Evaluation Results> As shown in Table 2 above, all of No. 2-1 to No. 2-24, which had an Spk of 0.40 μm or less and an Smr1 of 20% or less, had a starting angle of 10° or more, and were found to have excellent positioning properties.

Claims

1. A grain-oriented electrical steel sheet comprising a steel sheet and an insulating coating disposed on both sides of the steel sheet, wherein the peak height Spk as defined in JIS B 0681-2:2018 is 0.40 μm or less on both sides of the grain-oriented electrical steel sheet, and the area load ratio Smr1 separating the peaks and core as defined in JIS B 0681-2:2018 is 20% or less.

2. The grain-oriented electrical steel sheet according to claim 1, wherein the Spk is 0.05 μm or more.

3. The grain-oriented electrical steel sheet according to claim 1 or 2, wherein the Smr1 is 5% or more.

4. A method for producing the grain-oriented electrical steel sheet according to any one of claims 1 to 3, comprising forming the insulating coating on both sides of the steel sheet, and then using a friction body to apply friction two or more times under conditions of a dynamic friction force per width of 24.5 N / mm or more and a relative speed of 20 m / min or more.

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