Grain-oriented electrical steel sheet and its manufacturing method

Abstract

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 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 areal load ratio Smr1 separating the peaks and the core defined in JIS B 0681-2:2018 is 20% or less. The grain-oriented electrical steel sheet has excellent positioning ability. The Spk is preferably 0.05 μm or more. The Smr1 is preferably 5% or more.

Description

[Technical Field]

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

[0002] Grain-oriented electrical steel is a soft magnetic material used as the core of transformers, generators, etc. It has a crystal texture in which the <001> orientation, the axis of easy 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 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 include a steel sheet and an insulating coating disposed on both sides of the steel sheet (Patent Documents 1 and 2). The insulating coating not only applies tension to the steel sheet to reduce the iron loss of the grain-oriented electrical steel sheet, but also provides the grain-oriented electrical steel sheet with properties such as insulation, workability, and rust resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-158340 [Patent Document 2] Japanese Patent Application Publication No. 2018-90871 Summary of the Invention [Problem to be solved by the invention]

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

[0006] For this reason, emphasis is often placed on "lamination workability" in grain-oriented electrical steel sheets, and lamination workability is comprised of two properties: "sliding ability" and "positioning ability." The sliding property refers to the ease of fine-tuning the position of the grain-oriented electromagnetic steel sheet during the lamination process (the ease of continuing to slide the grain-oriented electromagnetic steel sheet once it has started to slide). On the other hand, positioning ability refers to the ease with which the grain-oriented electromagnetic steel sheets can be positioned during lamination (how easily the grain-oriented electromagnetic steel sheets will start to slip once they have come to a standstill).

[0007] Of the two characteristics that make up lamination workability, positioning ability in particular has a major impact on the productivity of the laminate. In other words, if the positioning ability of the grain-oriented electrical steel sheets is insufficient (the grain-oriented electrical steel sheets tend to shift position once they have been positioned and placed), work must be done to position them again and place them again, significantly reducing the productivity of the laminate.

[0008] Incidentally, Patent Documents 1 and 2 disclose a technique for improving the sliding property by adjusting the line roughness (arithmetic mean roughness Ra) of the surface of grain-oriented electrical steel sheet, but do not particularly mention positioning ability. Therefore, the present inventors produced grain-oriented electrical steel sheets based on the techniques disclosed in the cited documents 1 and 2, and evaluated their positioning capabilities, but found that all of them were insufficient. It was also found that there is no correlation between the line roughness (Ra) and positioning ability as described in the cited 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. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that the above object can be achieved by employing 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 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 areal load ratio Smr1 separating the peaks and the core as defined in JIS B 0681-2:2018 is 20% or less. [2] The grain-oriented electrical steel sheet according to [1] above, wherein the Spk is 0.05 μm or more. [3] The grain-oriented electrical steel sheet according to [1] or [2] above, wherein the 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 subjecting the steel sheet to friction two or more times using a friction body 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. [Effects of the Invention]

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

[0012] [Findings Obtained by the Inventors] The present 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 μm to several tens of μm and heights (distance in the sheet thickness direction) of several hundred nm to 1 μm. The shape of these protrusions is the determining factor for positioning ability.

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

[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 protrusions can be changed, and Spk and Smr1 can be controlled within appropriate ranges.

[0017] The present invention was made based on the above findings and further investigations. Next, a preferred embodiment 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 plate> The steel sheet included in the grain-oriented electrical steel sheet is, for example, a so-called secondary recrystallized sheet (finish annealed sheet) having a forsterite coating formed on the surface.

[0020] The chemical composition (steel composition) of the steel sheet contains, for example, 2.8 to 3.5% Si and 0.01 to 1.00% Mn, with the balance being Fe and unavoidable impurities. In addition, "%" in the component composition means "% by 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 chemical composition of the steel sheet may further contain at least one element selected from the group consisting of B: 0.05% or less, Ge: 0.10% or less, As: 0.10% or less, P: 0.10% or less, Te: 0.05% or less, Nb: 0.05% or less, Ti: 0.05% or less, and V: 0.05% or less. In this case, it is preferable that B: 0.01 to 0.02% or less, 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: 0.01 to 0.03%, and V: 0.01 to 0.03%.

[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 contains, 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, and further contains 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 (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 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, resulting in a reduced contact area on the surfaces of the grain-oriented electrical steel sheets and a reduced positioning ability. Therefore, from the viewpoint of obtaining good positioning, Spk on both surfaces 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 provided by the insulating coating. Therefore, from the viewpoint of obtaining good insulation properties, the Spk on both surfaces of the grain-oriented electrical steel sheet is preferably 0.05 μm or more.

[0028] <Smr1, the areal bearing ratio that separates the protruding peaks from the core> If Smr1 on both sides of the grain-oriented electrical steel sheet is too large, the area ratio of the flat portions (non-convex portions) decreases, which increases static friction, reduces the contact area between the flat portions (non-convex portions), and reduces positioning ability. Therefore, from the viewpoint of obtaining good positioning properties, 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 be concentrated on the minute protrusions described above when friction occurs between the already laminated grain-oriented electrical steel sheets and the newly laminated grain-oriented electrical steel sheets, which may cause the protrusions to peel off and reduce the insulation provided by the insulating coating. Therefore, from the viewpoint of obtaining good insulation properties, 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, multiple fields of view are imaged using a confocal laser microscope equipped with a 100x objective lens to obtain surface data for the test materials (steel sheet and grain-oriented electrical steel sheet with an insulating coating). When obtaining the image data, shape measurements are performed under the condition that the number of pixels per field of view (range of 145 μm width and 109 μm length) is 1024 x 768. The obtained image data is then trimmed and joined to obtain shape data for a 180 μm square range. When joining the image data, data compression may be performed. Noise is removed from the obtained shape data, and the surface texture parameters (Spk and Smr1) are determined within a 180 μm square area in accordance with JIS B 0681-2:2018. When determining the surface texture parameters, in order to perform an analysis that focuses on the shapes of the minute convexities mentioned above, a 25 μm L filter (high-pass filter) is applied to exclude various long-period structures such as waviness in 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 used as the Spk value for both surfaces of the grain-oriented electrical steel sheet. The same applies to Smr1.

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

[0033] The starting angle is calculated as follows. A small test piece (length 50 mm x width 30 mm) and a large test piece (length 300 mm x width 100 mm) 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 test pieces parallel to each other, and the plate surfaces of the large test piece and the small test piece are brought into contact with each other. Next, a weight is placed on the small test piece to apply a uniform load to the contact surface with the large test piece, and the mass of the weight is adjusted so that the total mass of the small test piece and the weight is 200 g. Then, one longitudinal end of the large test piece is raised while the other end is kept in contact with the horizontal surface. In this way, the small test piece and the large test piece with the weight on top are 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-of-slip angle is calculated and used as the start-of-slip angle of that grain-oriented electrical steel sheet. In the first and second measurements, the small test piece is placed and slid at different positions across the width of the large test piece, so that the sliding of the small test piece on the large test piece in the first measurement does not affect the second measurement.

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

[0035] The interlayer resistance is calculated as follows. In this embodiment, the interlaminar resistance is measured to evaluate the insulation properties, including the effect of friction between the stacked grain-oriented electrical steel sheets on the insulation properties of the insulating coating. Specifically, to simulate such a frictional state, the large test piece used for measuring the sliding angle described above is used as the test piece, and the surface area of ​​this test piece (large test piece) where the small test piece has slid once is used as the area to be evaluated for insulation. The interlaminar resistance of this evaluation area 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. On the other hand, 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 of manufacturing grain-oriented electrical steel sheets] Next, a method for manufacturing the grain-oriented electrical steel sheet of the present embodiment will be described. In summary, first, an insulating coating is 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. Then, the friction treatment is performed on the untreated sheet.

[0038] <Preparing the steel plate> First, the above-described steel plate 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 the surface as described above. The secondary recrystallized sheet is produced, for example, as follows.

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

[0040] <Insulating coating formation> Next, an insulating coating is formed on both sides of the steel sheet (for example, a secondary recrystallized sheet). The insulating coating is formed using an insulating coating treatment solution containing, for example, phosphate, colloidal silica, and metal oxide, and 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 and aluminum phosphate. As the phosphate, monophosphate (biphosphate) is easily available and is 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, relative to 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 metal oxides include TiO2, V2O5, CrO3, ZnO, ZrO2, and Nb2O3. 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, relative to 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 insulating film is formed by drying the coated substrate as required and then baking the coated substrate. Smoothing annealing may also be performed in conjunction with baking. 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] <Friction treatment> Next, the untreated plate is subjected to a 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 fibers solidified with resins such as urethane resins. The friction body may be a stationary pad or a rotating body. In friction treatment, for example, the untreated plate is conveyed between a pair of pads or rotors.

[0050] <Dynamic friction force per width> In the friction treatment, the dynamic friction force per width is controlled within an appropriate range. The kinetic friction force per width (unit: N / mm) is 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 board (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 dynamic friction force per width is, for example, 47.0 N / mm (4.8 kgf / mm). However, if the dynamic friction force per width is too large, Spk may become too small. Therefore, from the viewpoint of preventing Spk from becoming too small, the dynamic 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 (conveying speed) of the untreated plate when the friction body is stationary, and is the difference between the rotation speed of the outer periphery of the friction body and the moving speed (conveying 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 frictions is too large, 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 frictions is preferably 15 or less, and more preferably 10 or less. [Example]

[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] <Manufacturing of grain-oriented electrical steel sheets> A 100 kg vacuum steel ingot was used to obtain a secondary recrystallized steel plate having a forsterite coating on both the front and back surfaces according to the method described above. The chemical composition (steel composition) of the obtained steel plate is shown in Table 1 below. Next, an insulating coating treatment solution containing phosphate (monobasic magnesium phosphate), colloidal silica (Snowtex 30, manufactured by Nissan Chemical Industries, Ltd.), and metal oxide (CrO3) was applied to both sides of the obtained steel sheet (secondarily recrystallized sheet) 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 / m2). 2 The composition of the insulating coating formed is shown in Table 1 below. 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 the friction treatment was carried out. Next, the obtained untreated plate was subjected to friction treatment using a pair of pads (material: nylon fiber) as friction bodies under the conditions (dynamic friction force per width, relative speed, and number of frictions) shown in Table 1 below, to obtain a grain-oriented electrical steel plate (thickness: 0.23 mm).

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

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

[0063] [Table 1]

[0064] <Summary of evaluation results> As shown in Table 1 above, Nos. 1-1 to 1-13, which had Spk of 0.40 μm or less and Smr1 of 20% or less, all had a sliding angle of 10° or more, demonstrating excellent positioning ability.

[0065] Of 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 As a result, it was found that the insulating properties were also excellent. Specifically, the friction treatment conditions (dynamic friction force per width, relative speed, 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°, and the positioning ability was insufficient. Specifically, in No. 1-14, the dynamic friction force per width was less than 24.5 N / mm, and therefore the Spk was greater than 0.40 μm. In addition, in No. 1-15, the relative speed was less than 20 m / min, and therefore Smr1 was more than 20%. In addition, in No. 1-16, the number of times of rubbing was less than two, and therefore Spk was more than 0.40 μm and Smr1 was more than 20%.

[0067] [Test 2] <Manufacturing of grain-oriented electrical steel sheets> A steel plate (secondarily recrystallized plate) was obtained in the same manner as in Test 1. The chemical composition (steel composition) of the obtained steel plate is shown in Table 2 below. Next, in the same manner as in Test 1, an insulating coating treatment solution containing phosphate, colloidal silica (Snowtex 30, manufactured by Nissan Chemical Industries, Ltd.) and metal oxide was applied to both sides of the obtained steel sheet, and then baking was carried out to form an insulating coating (adhesion amount per side: 4 g / m 2 The composition of the insulating coating formed is shown in Table 2 below. The phosphates used were monobasic magnesium phosphate, monobasic aluminum phosphate, and monobasic calcium phosphate, and the metal oxides used were CrO3, TiO2, V2O5, and ZnO. 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 the friction treatment was carried out. Next, the obtained untreated sheet was subjected to a 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] [Table 2]

[0070] <Summary of evaluation results> As shown in Table 2 above, Nos. 2-1 to 2-24, which had Spk of 0.40 μm or less and Smr1 of 20% or less, all had a sliding angle of 10° or more, demonstrating excellent positioning ability.

Claims

1. A grain-oriented electrical steel sheet comprising a steel sheet and an insulating coating disposed on both sides of the steel sheet, A grain-oriented electrical steel sheet, wherein on both surfaces of the grain-oriented electrical steel sheet, a protruding peak height Spk defined in JIS B 0681-2:2018 is 0.40 μm or less, and a load area ratio Smr1 separating a protruding peak and a core 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, wherein the Smr1 is 5% or more.

4. A directional electromagnetic steel sheet as described in claim 2, wherein Smr1 is 5% or more.

5. A method for producing the grain-oriented electrical steel sheet according to any one of claims 1 to 4, a method for producing a grain-oriented electrical steel sheet, the method comprising: forming the insulating coating on both sides of the steel sheet; and then performing friction using a friction body at least twice under conditions in which the dynamic friction force per width is 24.5 N / mm or more and the relative speed is 20 m / min or more.

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