Grain-oriented electrical steel sheet and method for manufacturing the same

Abstract

This grain-oriented electromagnetic steel sheet comprises a base steel sheet and an insulating coating film disposed directly on the base steel sheet. When this grain-oriented electromagnetic steel sheet is cut along a direction parallel with the sheet thickness direction and perpendicular to the sheet width direction and the cut surface is examined, the average determined Fe content Ibase of an inner-layer region of the base steel sheet and the average determined Fe content Icoating of an inner-layer region of the insulating coating film satisfy 0.010≤Icoating / Ibase≤0.50.

Description

【Technical Field】 【0001】 The present invention relates to a grain-oriented electrical steel sheet. In particular, the present invention relates to a grain-oriented electrical steel sheet having excellent film adhesion without relying on a forsterite film and a method for producing the same. This application claims priority based on Japanese Patent Application No. 2022-070072 filed in Japan on April 21, 2022, and incorporates the content thereof herein. 【Background Art】 【0002】 Grain-oriented electrical steel sheets are mainly used in transformers. Since a transformer is continuously excited and generates energy losses over a long period from installation until disposal, the energy loss when magnetized with alternating current, that is, the iron loss, is a major index determining the performance of the transformer. 【0003】 To reduce the iron loss of grain-oriented electrical steel sheets, many methods have been proposed so far. For example, regarding the steel sheet structure, a method of increasing the accumulation in the {110}<001> orientation called the Goss orientation, regarding the steel sheet, a method of increasing the content of solid solution elements such as Si that increase the electrical resistance, a method of reducing the sheet thickness of the steel sheet, and the like. 【0004】 Also, it is known that applying tension to the steel sheet is an effective method for reducing iron loss. Therefore, usually, a film is formed on the surface of the grain-oriented electrical steel sheet for the purpose of reducing iron loss. This film reduces the iron loss of the single steel sheet by applying tension to the grain-oriented electrical steel sheet. This film further reduces the iron loss as an iron core by ensuring electrical insulation between the steel sheets when the grain-oriented electrical steel sheets are laminated and used. 【0005】 In the case of coated grain-oriented electrical steel sheets, a forsterite coating, which is an oxide film containing Mg, is formed on the surface of the base steel sheet, and an insulating coating is further formed on the surface of the forsterite coating. In other words, in this case, the coating on the base steel sheet includes the forsterite coating and the insulating coating. Each of the forsterite coating and the insulating coating performs both insulating functions and tension-applying functions to the base steel sheet. 【0006】 The forsterite coating is formed during a finish annealing process that induces secondary recrystallization of the steel sheet. This process involves a reaction between an annealing separator, primarily composed of magnesia (MgO), and silicon oxide (SiO2) formed on the base steel sheet during decarburization annealing. The reaction occurs during a heat treatment at 900-1200°C for 20 hours or more. 【0007】 The insulating coating is formed by applying a coating solution containing, for example, phosphate and colloidal silica to a steel sheet after finish annealing, and then baking and drying it at 350°C to 1150°C for 5 seconds or more. 【0008】 For these coatings to perform their functions of insulation and tensioning the base steel sheet, a high degree of adhesion between the coating and the base steel sheet is necessary. 【0009】 Conventionally, the above-mentioned adhesion has been ensured primarily by the anchoring effect caused by the irregularities at the interface between the base steel sheet and the forsterite coating. However, in recent years, it has become clear that these interface irregularities hinder the movement of magnetic domain walls when grain-oriented electrical steel sheets are magnetized, thus hindering the reduction of iron loss. 【0010】 Therefore, in order to further reduce iron loss, techniques for forming an insulating coating on a smooth surface of the base steel sheet without the presence of a forsterite coating on the base steel sheet have been proposed, for example, in Patent Documents 1 to 3. 【0011】 The technology disclosed in Patent Document 1 involves removing the formed forsterite film by pickling or the like, and then smoothing the surface of the base steel sheet by chemical polishing or electropolishing. The technology disclosed in Patent Document 2 involves using an annealing separating agent containing alumina (Al2O3) to suppress the formation of the forsterite film itself and smooth the surface of the base steel sheet. The technology disclosed in Patent Document 3 involves using an annealing separating agent containing bismuth chloride to suppress the formation of the forsterite film itself and smooth the surface of the base steel sheet. 【0012】 While these technologies can smooth the surface of the base steel sheet, they have the challenge of difficulty in achieving good adhesion of the insulating coating after its formation. If the coating does not adhere well, it becomes difficult to apply tension to the base steel sheet and to ensure electrical insulation between the laminated steel sheets. 【0013】 Therefore, techniques for smoothing the surface of the base steel sheet and then improving the adhesion of the coating have been proposed, for example, in Patent Documents 4 to 6. 【0014】 The technology disclosed in Patent Document 4 involves performing finish annealing using an annealing separation agent containing alumina, followed by oxide film formation annealing to control thermal history and oxygen partial pressure, and then forming an insulating coating. In Patent Document 4, an intermediate oxide film layer of externally oxidized SiO2 is formed on the base steel sheet, and an insulating coating is formed on the intermediate oxide film layer. Patent Document 4 attempts to improve coating adhesion by solid-solving elements such as Mn in this intermediate oxide film layer. 【0015】 The technology disclosed in Patent Document 5 involves performing finish annealing using an annealing separation agent containing bismuth chloride, followed by pickling, then heat treatment to control oxygen concentration and dew point, and subsequently forming an insulating coating. In Patent Document 5, etch pits are formed on the surface of the base steel sheet, a silica-containing oxide layer and an iron-based oxide layer are formed on the base steel sheet, and an insulating coating is formed on the iron-based oxide layer. Patent Document 5 attempts to improve coating adhesion by creating etch pits on the surface of the base steel sheet. 【0016】 The technology disclosed in Patent Document 6 involves performing finish annealing using an annealing separating agent containing bismuth chloride, and then forming an insulating coating containing a metal compound and an insulating coating without a metal compound. In Patent Document 6, an intermediate layer is formed on the base steel sheet, and an insulating coating is formed on the intermediate layer. Patent Document 6 attempts to improve coating adhesion by optimally controlling each of the manufacturing processes. [Prior art documents] [Patent Documents] 【0017】 [Patent Document 1] Japanese Patent Publication No. 49-096920 [Patent Document 2] Japanese Patent Publication No. 06-049534 [Patent Document 3] Japanese Patent Publication No. 07-054155 [Patent Document 4] International Publication No. 2020 / 012666 [Patent Document 5] International Publication No. 2020 / 149345 [Patent Document 6] International Publication No. 2020 / 149325 [Overview of the project] [Problems that the invention aims to solve] 【0018】 As mentioned above, to reduce iron loss in grain-oriented electrical steel sheets, it is effective to smooth the surface of the base steel sheet without the presence of a forsterite coating. However, this technique has the problem that it is difficult to obtain the coating adhesion necessary for reducing iron loss. 【0019】 The technologies disclosed in Patent Documents 4-6 attempt to improve coating adhesion without relying on forsterite coatings. While these technologies do improve coating adhesion to some extent, it would be preferable if coating adhesion could be improved using technologies different from those disclosed in Patent Documents 4-6, as this would increase industrial options. 【0020】 This invention was made in view of the above-mentioned problems. The object of this invention is to provide a grain-oriented electrical steel sheet with excellent coating adhesion without relying on a forsterite coating, and a method for manufacturing the same. [Means for solving the problem] 【0021】 The gist of this invention is as follows: 【0022】 (1) A grain-oriented electrical steel sheet according to one aspect of the present invention is It comprises a base steel plate and an insulating coating disposed in contact with the base steel plate, The aforementioned base steel sheet has a chemical composition of, in mass%, Si: 3.0~4.0%, Mn: 0.010~0.50%, It contains, with the remainder being Fe and impurities. When viewed from a cross-section parallel to the thickness direction and perpendicular to the width direction, the area from the interface between the base steel sheet and the insulating coating toward the base steel sheet in the thickness direction is defined as the base steel sheet inner layer region, and the area from the interface toward the insulating coating in the thickness direction is defined as the insulating coating inner layer region, and the average Fe quantitative value of the base steel sheet inner layer region is expressed as I in mass%. base The average Fe quantitative value in the inner layer region of the insulating film is expressed as I in mass%. coating In that case, The above I base and the aforementioned I coating And, 0.010≦I coating / I base It satisfies ≤0.50. (2) In the grain-oriented electrical steel sheet described in (1) above, The aforementioned base steel sheet has the following chemical composition in mass%, C: 0.010% or less, N: 0.010% or less, Acid-soluble Al: 0.020% or less, P:0.040% or less, Total of S and Se: 0.010% or less. Sn: 0.50% or less, Cu: 0.50% or less, Cr: 0.50% or less, Sb: 0.50% or less, Mo: 0.10% or less, Bi: 0.10% or less, may be included. (3) In the grain-oriented electrical steel sheet described in (1) or (2) above, when observing the cut surface at 10 observation points spaced apart from each other on the sheet surface, when the I base and the I coating satisfy 0.010 ≦ I coating / I base ≦ 0.50, the number of observation points may be 5 or more. (4) The method for manufacturing the grain-oriented electrical steel sheet according to any one of (1) to (3) above includes a hot rolling process, a hot rolled steel sheet annealing process, a cold rolling process, a decarburization annealing process, a finish annealing process, a thermal oxidation annealing process, and an insulating film forming process. In the finish annealing process, after applying and drying an annealing separating agent having 20 to 99.5% by mass of alumina, 0.5 to 20% by mass of bismuth chloride, and the balance being magnesia and impurities in terms of solid content conversion to the steel sheet after the decarburization annealing process, finish annealing is carried out. In the thermal oxidation annealing process, as a heating-up process, the steel sheet after the finish annealing process is controlled to be heated from room temperature to a temperature range of 600 to 1000 °C in an atmosphere having an oxygen concentration of 1.0 to 25% by volume. as a soaking process, the steel sheet after the heating-up process is soaked for 5 to 200 seconds in a temperature range of 800 to 1100 °C in an atmosphere having an oxygen concentration of less than 1.0% by volume and an oxygen potential PH2O / PH2 of 0.0001 to 10. In the insulating film forming process, an insulating film forming liquid is applied to the steel sheet after the thermal oxidation annealing process, and the steel sheet is soaked for 5 to 200 seconds in a temperature range of 700 to 1000 °C in an atmosphere having an oxygen potential PH2O / PH2 of 0.10 to 10. (5) In the method for manufacturing the grain-oriented electrical steel sheet described in (4) above, in the thermal oxidation annealing process, As a first surface treatment, the steel sheet after the finish annealing process is immersed for 3 to 60 seconds in a first treatment solution containing at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with a total acid concentration of 1 to 20% by mass and a liquid temperature of 50 to 90°C. As a heat treatment, the steel plate after the first surface treatment may be subjected to the aforementioned heating and soaking. (6) In the method for manufacturing grain-oriented electrical steel sheets described in (4) or (5) above, In the aforementioned thermal oxidation annealing process, As a second surface treatment, the steel plate after heating and soaking may be immersed for 3 to 60 seconds in a second treatment solution containing at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with a total acid concentration of 1 to 10% by mass and a liquid temperature of 50 to 90°C. [Effects of the Invention] 【0023】 According to the above embodiment of the present invention, it is possible to provide a grain-oriented electrical steel sheet and a method for manufacturing the same that have excellent coating adhesion without relying on a forsterite coating. In this grain-oriented electrical steel sheet, the surface of the base steel sheet is smooth because there is no forsterite coating, and the base steel sheet and the insulating coating are preferably controlled, resulting in excellent coating adhesion. Therefore, it is possible to favorably improve the iron loss characteristics. [Brief explanation of the drawing] 【0024】 [Figure 1] This is a schematic cross-sectional view showing a grain-oriented electrical steel sheet according to one embodiment of the present invention. [Figure 2] This flowchart illustrates the manufacturing method of grain-oriented electrical steel sheets according to this embodiment. [Modes for carrying out the invention] 【0025】 Preferred embodiments of the present invention are described in detail below. However, the present invention is not limited to the configuration disclosed in these embodiments, and various modifications are possible without departing from the spirit of the invention. Furthermore, the numerical limit ranges described below include both lower and upper limits. Numerical values ​​indicated as "greater than" or "less than" are not included in the numerical range. 【0026】 As mentioned above, smoothing the surface of the base steel sheet of a grain-oriented electrical steel sheet without a forsterite coating facilitates the movement of magnetic domain walls when the grain-oriented electrical steel sheet is magnetized, improving iron loss characteristics. However, this technology has the challenge of making it difficult to obtain the coating adhesion necessary for reducing iron loss. 【0027】 As a result of diligent research, the inventors have discovered a grain-oriented electrical steel sheet that exhibits excellent coating adhesion without relying on a forsterite coating. The grain-oriented electrical steel sheet according to this embodiment will be described in detail below. 【0028】 Figure 1 is a schematic cross-sectional view showing a grain-oriented electrical steel sheet according to this embodiment. As shown in Figure 1, the grain-oriented electrical steel sheet 1 according to this embodiment has a base steel sheet 11 and an insulating coating 12 arranged in contact with the base steel sheet 11 when viewed from a cross-section where the cutting direction is parallel to the thickness direction and perpendicular to the width direction. The layer structure in which the insulating coating 12 is arranged in contact with the base steel sheet 11 means that there is no forsterite coating and that the base steel sheet 11 has a smooth surface (a smooth surface equivalent to that of a cold-rolled steel sheet). Furthermore, in the grain-oriented electrical steel sheet 1 according to this embodiment, when viewed from the above cross-section, the range from 100 to 200 nm in the thickness direction toward the base steel sheet 11 from the interface between the base steel sheet 11 and the insulating coating 12 is defined as the base steel sheet inner layer region, and the range from 50 to 150 nm in the thickness direction toward the insulating coating 12 from the above interface is defined as the insulating coating inner layer region, and the average Fe quantitative value of the base steel sheet inner layer region is expressed as I base The average Fe quantitative value in the inner layer region of the insulating film is expressed as I in mass%. coating In that case, the above I base and the above I coating And, 0.010≦I coating / I base It satisfies ≤0.50. 【0029】 As described above, in order to improve iron loss characteristics, it is effective to smooth the surface of the base steel sheet to facilitate magnetic domain wall movement, and to ensure close contact between the base steel sheet and the insulating coating to apply tension to the base steel sheet and ensure electrical insulation between the steel sheets. In the grain-oriented electrical steel sheet according to this embodiment, the surface smoothness of the base steel sheet is ensured by having the insulating coating placed in contact with the base steel sheet (no forsterite coating is present), and the adhesion between the base steel sheet and the insulating coating is ensured by controlling the average Fe quantitative value in the inner layer region of the base steel sheet and the average Fe quantitative value in the inner layer region of the insulating coating. Therefore, the grain-oriented electrical steel sheet according to this embodiment has excellent iron loss characteristics. 【0030】 The presence or absence of the base steel plate and insulating coating described above can be confirmed by observing the cross-section where the cutting direction is parallel to the plate thickness direction and perpendicular to the plate width direction. For example, the cross-section can be observed using a transmission electron microscope (TEM). 【0031】 Specifically, first, a test specimen is cut using FIB (Focused Ion Beam) processing so that the cutting direction is parallel to the thickness direction and perpendicular to the width direction of the plate. The cross-sectional structure of this cut surface is then observed with a TEM at a magnification that allows each layer to be included in the observation field. If each layer does not fit in the observation field, the cross-sectional structure is observed using multiple consecutive fields. For example, observation should be performed using a field of view of 1 μm × 1 μm or larger, preferably around 10 μm × 8 μm. The acceleration voltage should also be set to 200 kV. When observing with only one field of view, it is difficult to obtain average information about the steel plate, so it is advisable to observe and judge 10 randomly selected locations that are spaced apart from each other. 【0032】 To identify each layer in the cross-sectional structure, line analysis is performed along the plate thickness direction using EDS (Energy Dispersive X-ray Spectroscopy) attached to the TEM, and the chemical composition of each layer is quantitatively analyzed. The elements to be quantitatively analyzed are Fe, P, Si, O, and Mg. 【0033】 Based on the TEM-EDS quantitative analysis results described above, the layered region located at the deepest position in the thickness direction, and where the Fe content is 80 atomic percent or more after excluding measurement noise, is determined to be the base steel sheet, and the region excluding this base steel sheet is determined to be other coatings. 【0034】 When determining the region that is the base steel sheet as described above, precipitates, inclusions, and voids contained within each layer are not included in the determination. Instead, the region that satisfies the above quantitative analysis results as the matrix phase is determined to be the base steel sheet. For example, if precipitates, inclusions, and voids are confirmed to be present on the scanning lines of the line analysis from bright-field images, dark-field images, or line analysis results, this region is not included in the determination, and the determination is made based on the quantitative analysis results as the matrix phase. Note that precipitates, inclusions, and voids can be distinguished from the matrix phase by contrast, and in quantitative analysis results, they can be distinguished from the matrix phase by the abundance of constituent elements. When identifying the base steel sheet, it is preferable to identify it at a location where precipitates, inclusions, and voids are not included on the scanning lines of the line analysis. 【0035】 Regarding the region excluding the base steel sheet identified above, based on the quantitative analysis results of TEM-EDS, after removing measurement noise, the region where the Fe content is less than 80 atomic%, the P content is 5 atomic% or more, and the O content is 30 atomic% or more is determined to be an insulating coating (phosphate-based coating). In addition to the three elements listed above that are used to identify phosphate-based coatings, phosphate-based coatings may also contain aluminum, magnesium, nickel, etc., derived from phosphates. Furthermore, silicon derived from colloidal silica may also be included. 【0036】 When determining the region that is a phosphate-based coating as described above, precipitates, inclusions, and vacancies contained within each coating are not included in the determination. Instead, the region that satisfies the above quantitative analysis results as the matrix phase is determined to be a phosphate-based coating. For example, if precipitates, inclusions, and vacancies are confirmed to be present on the scanning line of the line analysis from bright-field images, dark-field images, or line analysis results, this region is not included in the determination, and the determination is made based on the quantitative analysis results of the matrix phase. Note that precipitates, inclusions, and vacancies can be distinguished from the matrix phase by contrast, and in quantitative analysis results, they can be distinguished from the matrix phase by the abundance of constituent elements. When identifying a phosphate-based coating, it is preferable to identify it at a position where precipitates, inclusions, and vacancies are not included on the scanning line of the line analysis. 【0037】 The grain-oriented electrical steel sheet according to this embodiment does not have an intermediate ceramic layer such as a forsterite coating or an external oxide film. Therefore, when the layer structure is identified by the method described above, the base steel sheet and the insulating coating placed in contact with the base steel sheet are identified. For example, the base steel sheet has a thickness of 0.17 to 0.29 mm, and the insulating coating has a thickness of 0.5 to 10 μm. 【0038】 However, if the electrical steel sheet has a forsterite coating as an intermediate ceramic layer, the forsterite coating will be confirmed between the base steel sheet identified by the above method and the insulating coating (phosphate-based coating). This forsterite coating satisfies, for example, the following on average for the entire coating: Fe content of less than 80 atomic%, P content of less than 5 atomic%, Si content of 5 atomic% or more, O content of 30 atomic% or more, and Mg content of 10 atomic% or more. Note that the quantitative analysis results of the forsterite coating are quantitative analysis results for the matrix phase and do not include analysis results for precipitates, inclusions, and vacancies contained in the forsterite coating. When identifying the forsterite coating, it is preferable to identify it at a position where precipitates, inclusions, and vacancies are not included on the scanning line of the line analysis. Generally, the forsterite coating has a thickness of 0.1 to 10 μm. 【0039】 Similarly, when the electrical steel sheet has an external oxide film as an intermediate ceramic layer, the external oxide film is confirmed between the base steel sheet identified by the above method and the insulating coating (phosphate-based coating). This external oxide film satisfies, for example, the following on average for the entire oxide film: Fe content of less than 80 atomic%, P content of less than 5 atomic%, Si content of 20 atomic% or more, O content of 30 atomic% or more, and Mg content of less than 10 atomic%. Note that the quantitative analysis results of the external oxide film are quantitative analysis results for the matrix phase, and do not include analysis results for precipitates, inclusions, and vacancies contained in the external oxide film. When identifying the external oxide film, it is preferable to identify it at a position where precipitates, inclusions, and vacancies are not included on the scanning line of the line analysis. Generally, the thickness of the external oxide film is 2 to 500 nm. 【0040】 In the grain-oriented electrical steel sheet according to this embodiment, the base steel sheet and insulating coating specified above satisfy the following characteristics. 【0041】 Specifically, using the interface between the base steel sheet and the insulating coating at the above cross-section as a reference, the average Fe quantitative value (mass%) I of the inner layer region of the base steel sheet, which is in the range of 100-200 nm in the thickness direction toward the base steel sheet side, is measured. base The average Fe quantitative value (mass%) of the inner layer region of the insulating film, which is in the range of 50-150 nm in the thickness direction toward the insulating film side, is I. coating And, 0.010≦I coating / I base If the value ≤0.50 is satisfied, the adhesion between the base steel plate and the insulating coating improves. The technical reason for this is presumed to be as follows. 【0042】 Generally, insulating coatings do not contain Fe. For example, in conventional grain-oriented electrical steel sheets, I coating / I base The result is less than 0.010. On the other hand, in the grain-oriented electrical steel sheet according to this embodiment, the atmosphere during the heating process and soaking process of thermal oxidation annealing is optimally controlled, and the atmosphere during the formation of the insulating film is optimally controlled, coating / I base Set it to 0.010-0.50. 【0043】 In the grain-oriented electrical steel sheet according to this embodiment, I coating / I base By controlling the above, it is believed that the Fe contained near the interface of the insulating film and the Fe contained near the interface of the base steel sheet chemically interact, thereby improving the adhesion of the film. Therefore, in the grain-oriented electrical steel sheet according to this embodiment, unlike the conventional technology, it is important to increase the Fe contained near the interface of the insulating film, and then to comprehensively control the average Fe quantitative value in the inner layer region of the insulating film and the average Fe quantitative value in the inner layer region of the base steel sheet. 【0044】 Furthermore, in the grain-oriented electrical steel sheet according to this embodiment, the Fe contained in the inner layer region of the insulating coating is considered to form an Fe-Al alloy layer. However, coating / I base If the above conditions are satisfied, the adhesion of the coating will improve, so in the grain-oriented electrical steel sheet according to this embodiment, the form of Fe contained in the inner layer region of the insulating coating is not particularly limited. 【0045】 As mentioned above, I coating / I base If the value is 0.010 or higher, the adhesion of the coating will improve. coating / I base It is preferably 0.05 or higher, and more preferably 0.10 or higher. On the other hand, I coating / I base However, if the value exceeds 0.50, the excessive concentration of Fe within the coating can lead to the formation of inclusions such as Fe oxides, which can become the starting point for coating delamination. As a result, the coating adhesion decreases. Therefore, coating / I base It shall be 0.50 or less. coating / I base It is preferably 0.45 or less, preferably 0.40 or less, and more preferably 0.35 or less. 【0046】 The average Fe quantitative values ​​in the inner layer region of the base steel sheet and the inner layer region of the insulating coating can be confirmed as follows. For example, similar to the above, line analysis is performed along the thickness direction using the EDS attached to the TEM to perform quantitative analysis of the inner layer region of the base steel sheet and the inner layer region of the insulating coating. The elements to be quantitatively analyzed are the five elements Fe, P, Si, O, and Mg. 【0047】 Specifically, using the interface between the base steel sheet and the insulating coating identified by the method described above as a reference, and based on the quantitative analysis results of the line analysis described above, the average Fe quantitative value (mass%) I of the inner layer region of the base steel sheet, which is in the range of 100-200 nm in the thickness direction toward the base steel sheet, is determined. base The average Fe quantitative value (mass%) of the inner layer region of the insulating film, which is in the range of 50-150 nm in the thickness direction toward the insulating film side, is I. coating The following can be determined. The measurement length can be, for example, 1000 nm, and the step size for line analysis can be 5 nm or 10 nm. When the starting point of the line analysis (0 nm) is the base steel sheet, it is preferable that the interface between the insulating coating and the base steel sheet is included in the range of 100 to 500 nm. 【0048】 Furthermore, in the grain-oriented electrical steel sheet according to this embodiment, when the above-mentioned cross-section is observed at 10 observation points spaced apart from each other on the sheet surface, I coating / I base It is preferable that there are five or more observation points where the value of is between 0.010 and 0.50. When this condition is satisfied, I coating / I base The characteristic of this feature is that it is controlled over a wide range on the surface of the grain-oriented electrical steel sheet, and as a result, the adhesion of the coating is favorably improved. 【0049】 I coating / I base It is preferable that there are 8 or more observation points where the value is between 0.010 and 0.50. coating / I base There is no particular limit to the number of observation points where the value is between 0.010 and 0.50; however, a larger value is preferable, so there may be as many as 10 points. coating / I baseThe number of observation points where the value is between 0.010 and 0.50 may be nine or fewer. 【0050】 Furthermore, in the grain-oriented electrical steel sheet according to this embodiment, when the grain-oriented electrical steel sheet is wrapped around a cylinder with a diameter of 20 mm and bent 180°, the remaining coating area ratio is preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more. The upper limit of the remaining coating area ratio is not particularly limited, but for example, it may be 100%. 【0051】 The above-mentioned coating retention rate can be evaluated by wrapping the test specimen around a 20 mm diameter cylinder and bending it 180°. The area ratio of the remaining coating surface to the area of ​​the steel plate in contact with the cylinder can be calculated, and the area of ​​the steel plate in contact with the roll can be determined by calculation. The area of ​​the remaining surface can be determined by taking a photograph of the steel plate after the test and performing image analysis on the photographic image. 【0052】 Furthermore, in the grain-oriented electrical steel sheet according to this embodiment, the base steel sheet has a chemical composition that includes basic elements, optional elements as needed, and the remainder consists of Fe and impurities. 【0053】 For example, the base steel sheet has a chemical composition in mass percent, Si: 3.0~4.0%, Mn: 0.010~0.50%, C: 0~0.010%, N: 0~0.010%, Acid soluble Al: 0~0.020%, P: 0~0.040%, Total of S and Se: 0-0.010% Sn: 0~0.50%, Cu: 0~0.50%, Cr: 0~0.50%, Sb: 0~0.50%, Mo: 0~0.10%, Bi: 0~0.10%, It should contain [the specified substance], with the remainder consisting of Fe and impurities. 【0054】 Furthermore, the base steel sheet has a chemical composition in mass%, Sn: 0.0050~0.50%, Cu: 0.010~0.50%, Cr: 0.010~0.50%, Sb: 0.010~0.50%, Mo: 0.0050~0.10%, Bi: 0.00050~0.10%, It may contain at least one selected from the group consisting of the following. 【0055】 Si:3.0~4.0% by mass Silicon (Si) is a fundamental element for the base steel sheet. If the Si content is less than 3.0%, eddy current losses cannot be sufficiently reduced, and good magnetic properties cannot be obtained. Therefore, the Si content should be 3.0% or more. Preferably, the Si content is 3.10% or more, and more preferably 3.20% or more. On the other hand, if the Si content exceeds 4.0%, the steel sheet becomes brittle, and the passability during manufacturing deteriorates significantly, so the Si content should be 4.0% or less. Preferably, the Si content is 3.70% or less, more preferably 3.60% or less, and more preferably 3.50% or less. 【0056】 Mn:0.010~0.50% by mass Manganese (Mn) is a fundamental element for the base steel sheet. If the Mn content is less than 0.010%, it is difficult to form MnS and MnSe, which function as inhibitors, and secondary recrystallization does not proceed sufficiently, resulting in poor magnetic properties. Therefore, the Mn content should be 0.010% or more. Preferably, the Mn content is 0.030% or more, and more preferably 0.050% or more. On the other hand, if the Mn content exceeds 0.50%, the steel undergoes a phase transformation during secondary recrystallization annealing, and secondary recrystallization does not proceed sufficiently, resulting in poor magnetic properties. Therefore, the Mn content should be 0.50% or less. Preferably, the Mn content is 0.20% or less, more preferably 0.15% or less, and more preferably 0.10% or less. 【0057】 C:0~0.010% by mass Carbon (C) is a selective element for the base steel sheet. Although C is contained in the steel billet (slab), if an excessive amount of C remains in the base steel sheet after finish annealing, good iron loss characteristics may not be obtained. Therefore, the C content of the base steel sheet should be 0.010% or less. Preferably, the C content is 0.0050% or less, and more preferably 0.0030% or less. On the other hand, there is no particular lower limit to the C content of the base steel sheet, and it may be 0%. However, since it is not industrially easy to make the C content 0%, the C content may be greater than 0%, and may be 0.00010% or more. 【0058】 N:0~0.010% by mass Nitrogen (N) is a selective element for the base steel sheet. Although N is contained in the steel billet (slab), if an excess of N remains in the base steel sheet after finish annealing, it can adversely affect the magnetic properties. Therefore, the N content of the base steel sheet should be 0.010% or less. Preferably, the N content is 0.0090% or less, and more preferably 0.0080% or less. On the other hand, there is no particular lower limit to the N content of the base steel sheet, and it may be 0%. However, since N forms AlN and acts as an inhibitor during secondary recrystallization, the N content may be greater than 0%, and may be 0.00010% or more. 【0059】 Acid-soluble Al: 0~0.020% by mass Acid-soluble aluminum (sol.Al) is a selective element for the base steel sheet. Although acid-soluble Al is contained in the steel billet (slab), if an excess of acid-soluble Al remains in the base steel sheet after finish annealing, it may adversely affect the magnetic properties. Therefore, the acid-soluble Al content of the base steel sheet should be 0.020% or less. Preferably, the acid-soluble Al content is 0.0150% or less, and more preferably 0.010% or less. On the other hand, there is no particular lower limit to the acid-soluble Al content of the base steel sheet, and it may be 0%. However, since acid-soluble Al forms AlN and acts as an inhibitor during secondary recrystallization, the acid-soluble Al content may be greater than 0%, and may be 0.00010% or more. 【0060】 P:0~0.040% by mass Phosphorus (P) is a selective element for the base steel sheet. If the P content exceeds 0.040%, the workability of the steel sheet may decrease significantly. Therefore, the P content should be 0.040% or less. Preferably, the P content is 0.030% or less, and more preferably 0.020% or less. On the other hand, there is no particular lower limit to the P content, and it may be 0%. However, since P has the effect of improving the texture and the magnetic properties of the steel sheet, the P content may be greater than 0%, and may be 0.0020% or more. 【0061】 Total of S and Se: 0-0.010% by mass S (sulfur) and Se (selenium) are selective elements for the base steel sheet. S and Se are contained in the steel billet (slab), but if excess S and Se remain in the base steel sheet after finish annealing, it can adversely affect the magnetic properties. Therefore, the total content of S and Se in the base steel sheet should be 0.010% or less. On the other hand, there is no particular lower limit to the total content of S and Se in the base steel sheet, and it should be 0%. However, since S and Se form MnS and MnSe and act as inhibitors during secondary recrystallization, the total content of S and Se may be greater than 0%, and may be 0.0050% or more. 【0062】 Sn: 0~0.50% by mass Tin (Sn) is a selective element for the base steel sheet. If the Sn content exceeds 0.50%, secondary recrystallization becomes unstable, which can adversely affect the magnetic properties. Therefore, the Sn content should be 0.50% or less. Preferably, the Sn content is 0.30% or less, and more preferably 0.150% or less. On the other hand, there is no particular lower limit to the Sn content, and it may be 0%. However, since Sn has the effect of improving magnetic properties by increasing the concentration of Goss orientations, the Sn content may be greater than 0%, and may be 0.0050% or more. 【0063】 Cu:0~0.50% by mass Copper (Cu) is a selective element for the base steel sheet. If the Cu content exceeds 0.50%, the steel sheet may become brittle during hot rolling. Therefore, the Cu content should be 0.50% or less. Preferably, the Cu content is 0.30% or less, and more preferably 0.10% or less. On the other hand, there is no particular lower limit to the Cu content, and it may be 0%. However, since Cu has the effect of increasing the concentration of Goss orientation and improving magnetic properties, the Cu content may be greater than 0%, and may be 0.010% or more. 【0064】 Cr:0~0.50% by mass Cr (chromium) is a selective element for the base steel sheet. If the Cr content exceeds 0.50%, Cr oxide may form, which can adversely affect the magnetic properties. Therefore, the Cr content should be 0.50% or less. Preferably, the Cr content is 0.30% or less, and more preferably 0.10% or less. On the other hand, there is no particular lower limit to the Cr content, and it may be 0%. However, since Cr has the effect of improving magnetic properties by increasing the concentration of Goss orientation, the Cr content may be greater than 0%, and may be 0.010% or more. 【0065】 Sb:0~0.50% by mass Antimony (Sb) is a selective element for the base steel sheet. If the Sb content exceeds 0.50%, it may adversely affect the magnetic properties. Therefore, the Sb content should be 0.50% or less. Preferably, the Sb content is 0.30% or less, and more preferably 0.10% or less. On the other hand, there is no particular lower limit to the Sb content, and it may be 0%. However, since Sb functions as an inhibitor and has the effect of stabilizing secondary recrystallization, the Sb content may be greater than 0%, and may be 0.010% or more. 【0066】 Mo:0~0.10% by mass Mo (molybdenum) is a selective element for the base steel sheet. If the Mo content exceeds 0.10%, problems may arise with the rolling properties of the steel sheet. Therefore, the Mo content should be 0.10% or less. Preferably, the Mo content is 0.08% or less, and more preferably 0.05% or less. On the other hand, there is no particular lower limit to the Mo content, and it may be 0%. However, since Mo has the effect of improving magnetic properties by increasing the concentration of Goss orientation, the Mo content may be greater than 0%, and may be 0.0050% or more. 【0067】 Bi:0~0.10% by mass Bi (bismuth) is a selective element for the base steel sheet. If the Bi content exceeds 0.10%, the passability during cold rolling may deteriorate. Also, if the purification during finish annealing is insufficient and an excess of Bi remains, it may adversely affect the magnetic properties. Therefore, the Bi content should be 0.10% or less. Preferably, the Bi content is 0.050% or less, more preferably 0.020% or less, and more preferably 0.0010% or less. On the other hand, there is no particular lower limit for the Bi content, and it may be 0%. However, since Bi has the effect of improving magnetic properties, the Bi content may be greater than 0%, and may be 0.00050% or more. 【0068】 The base steel sheet of the grain-oriented electrical steel sheet according to this embodiment may contain impurities. "Impurities" refer to substances that are introduced during the industrial production of steel from raw materials such as ore and scrap, or from the manufacturing environment. 【0069】 The chemical composition of the base steel sheet described above can be measured using general analytical methods. For example, it can be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Acid-soluble Al can be measured using ICP-AES with the filtrate obtained after heating and decomposing the sample with acid. Furthermore, C and S can be measured using combustion-infrared absorption spectroscopy, N using inert gas fusion-thermal conductivity spectroscopy, and O using inert gas fusion-nondispersive infrared absorption spectroscopy. 【0070】 The above chemical composition refers to the components of the base steel sheet. If the grain-oriented electrical steel sheet used as the measurement sample has an insulating coating or the like on its surface, remove the coating or the like using the method described below before measuring the chemical composition. 【0071】 For example, one method for removing the insulating coating is to immerse the grain-oriented electrical steel sheet with the coating in a high-temperature alkaline solution. Specifically, the insulating coating can be removed from the grain-oriented electrical steel sheet by immersing it in a sodium hydroxide aqueous solution of NaOH: 30-50% by mass + H2O: 50-70% by mass at 80-90°C for 5-10 minutes, followed by rinsing with water and drying. The immersion time in the sodium hydroxide aqueous solution should be adjusted according to the thickness of the insulating coating. 【0072】 Furthermore, although the grain-oriented electrical steel sheet according to this embodiment does not have a forsterite coating, if it is desired to remove the forsterite coating, the electrical steel sheet from which the insulating coating has been removed by the above method can be immersed in high-temperature hydrochloric acid. Specifically, the preferred concentration of hydrochloric acid for removing the forsterite coating to be dissolved should be determined in advance, and the forsterite coating can be removed by immersing the sheet in hydrochloric acid of this concentration (for example, 30-40% by mass hydrochloric acid) at 80-90°C for 1-5 minutes, followed by rinsing with water and drying. Normally, an alkaline solution is used to remove the insulating coating, and hydrochloric acid is used to remove the forsterite coating, using different treatment solutions for each type of coating. 【0073】 Next, a method for manufacturing grain-oriented electrical steel sheets according to this embodiment will be described. Note that the method for manufacturing grain-oriented electrical steel sheets according to this embodiment is not limited to the method described below. The manufacturing method described below is one example for manufacturing grain-oriented electrical steel sheets according to this embodiment. 【0074】 Figure 2 is a flowchart illustrating a method for manufacturing grain-oriented electrical steel sheets according to this embodiment. The method for manufacturing grain-oriented electrical steel sheets according to this embodiment mainly includes a hot rolling step of hot rolling a slab (steel billet) having a predetermined chemical composition to obtain a hot-rolled steel sheet; a hot-rolled steel sheet annealing step of annealing the hot-rolled steel sheet to obtain a hot-rolled annealed sheet; a cold rolling step of subjecting the hot-rolled annealed sheet to one cold rolling or multiple cold rollings with annealing to obtain a cold-rolled steel sheet; a decarburization annealing step of subjecting the cold-rolled steel sheet to decarburization annealing to obtain a decarburized annealed sheet; a finish annealing step of applying an annealing separating agent to the decarburized annealed sheet and then performing finish annealing to obtain a finish annealed sheet; a thermal oxidation annealing step of subjecting the finish annealed sheet to thermal oxidation annealing to obtain a thermal oxidation annealed sheet; and an insulating film forming step of applying an insulating film forming liquid to the thermal oxidation annealed sheet and then performing heat treatment to form an insulating film on the surface of the thermal oxidation annealed sheet. 【0075】 Specifically, the method for manufacturing grain-oriented electrical steel sheets according to this embodiment is as follows: This process includes a hot rolling process, a hot-rolled steel sheet annealing process, a cold rolling process, a decarburization annealing process, a finish annealing process, a thermal oxidation annealing process, and an insulating coating formation process. In the above finish annealing process, After the decarburization annealing process described above, an annealing separation agent is applied to the steel sheet, which contains 20-99.5% by mass of alumina, 0.5-20% by mass of bismuth chloride, and the remainder being magnesia and impurities, on a solid content basis. After drying, finish annealing is performed. In the above thermal oxidation annealing process, As part of the heating process, the steel sheet after the above-mentioned finish annealing process is controlled and heated in an atmosphere with an oxygen concentration of 1.0 to 25 volume percent from room temperature to a temperature range of 600 to 1000°C. As a soaking process, the steel plate after the above heating process is soaked for 5 to 200 seconds at a temperature range of 800 to 1100°C in an atmosphere where the oxygen concentration is less than 1.0 volume% and the oxygen potential PH2O / PH2 is 0.0001 to 10. In the above insulating film formation process, After the above-mentioned thermal oxidation annealing process, an insulating film-forming solution is applied to the steel sheet, and it is heated to a uniform temperature of 700 to 1000°C for 5 to 200 seconds in an atmosphere with an oxygen potential of 0.10 to 10 (PH2O / PH2). 【0076】 Each of the above steps will be explained in detail. Note that if the conditions for each step are not specified in the following explanation, publicly known conditions should be applied as appropriate. 【0077】 Hot rolling process In the hot rolling process, a steel billet (for example, a steel ingot such as a slab) having a predetermined chemical composition is hot-rolled. For example, the slab (steel billet) used in the hot rolling process has a chemical composition of, in mass%, Si: 3.0~4.0%, Mn: 0.010~0.50%, C: 0.020~0.20%, N: 0.0020~0.020%, Acid soluble Al: 0.010~0.050%, P: 0~0.040%, Total of S and Se: 0.0010~0.040% Sn: 0~0.50%, Cu: 0~0.50%, Cr: 0~0.50%, Sb: 0~0.50%, Mo: 0~0.10%, Bi: 0~0.10%, It should contain [the specified substance], with the remainder consisting of Fe and impurities. 【0078】 Furthermore, the slab (steel billet) described above has a chemical composition in mass%, Sn: 0.0050~0.50%, Cu: 0.010~0.50%, Cr: 0.010~0.50%, Sb: 0.010~0.50%, Mo: 0.0050~0.10%, Bi: 0.00050~0.10%, It may contain at least one selected from the group consisting of the following. 【0079】 Si:3.0~4.0% by mass Silicon (Si) is a fundamental element for steel slabs. If the Si content is less than 3.0%, eddy current losses cannot be sufficiently reduced, and good magnetic properties cannot be obtained. Therefore, the Si content should be 3.0% or more. Preferably, the Si content is 3.10% or more, and more preferably 3.20% or more. On the other hand, if the Si content exceeds 4.0%, the steel sheet becomes brittle, and the passability during manufacturing deteriorates significantly, so the Si content should be 4.0% or less. Preferably, the Si content is 3.70% or less, more preferably 3.60% or less, and more preferably 3.50% or less. 【0080】 Mn:0.010~0.50% by mass Manganese (Mn) is a fundamental element for steel slabs. If the Mn content is less than 0.010%, inhibitors such as MnS and MnSe are less likely to form, secondary recrystallization does not proceed sufficiently, and good magnetic properties cannot be obtained. Therefore, the Mn content should be 0.010% or more. Preferably, the Mn content is 0.030% or more, and more preferably 0.050% or more. On the other hand, if the Mn content exceeds 0.50%, the steel undergoes a phase transformation during secondary recrystallization annealing, secondary recrystallization does not proceed sufficiently, and good magnetic properties cannot be obtained. Therefore, the Mn content should be 0.50% or less. Preferably, the Mn content is 0.20% or less, more preferably 0.15% or less, and more preferably 0.10% or less. 【0081】 C:0.020~0.20%mass% Carbon (C) is a fundamental element for steel billets (slabs). C is included to increase the concentration of Goss orientation in secondary recrystallization. The C content required for improving magnetic properties is 0.020% or more, preferably 0.040% or more, in the slab. However, if excessive C remains in the final product, it can become a factor in iron loss degradation. Therefore, decarburization treatment is necessary in the decarburization annealing process, but if the C content in the slab exceeds 0.20%, decarburization treatment becomes difficult. The C content in the slab is 0.20% or less, preferably 0.15% or less, and more preferably 0.10% or less. 【0082】 N:0.0020~0.020% by mass Nitrogen (N) is a fundamental element for steel billets (slabs). N forms the inhibitor AlN and is necessary to increase the concentration of Goss orientation during secondary recrystallization. The N content required for inhibitor formation in a slab is 0.0020% or more, preferably 0.0040% or more, and more preferably 0.0060% or more. On the other hand, if the N content in a slab exceeds 0.020%, blisters (voids) may form in the steel sheet during cold rolling, the strength of the steel sheet may increase, and the passability during manufacturing may deteriorate. The N content in a slab is 0.020% or less, preferably 0.015% or less, and more preferably 0.010% or less. Like C, excess N remaining in the final product can cause magnetic degradation. Therefore, N needs to be purified during finish annealing. 【0083】 Acid-soluble Al: 0.010~0.050% by mass Acid-soluble aluminum (Al) (sol.Al) is a fundamental element for steel billets (slabs). Acid-soluble Al forms the inhibitor AlN, which is necessary to enhance magnetic properties. The content of acid-soluble Al in a slab is 0.010% or more, preferably 0.015% or more, and more preferably 0.020% or more. On the other hand, if the slab contains an excess of acid-soluble Al, embrittlement may become significant. The content of acid-soluble Al in a slab is 0.050% or less, preferably 0.040% or less, and more preferably 0.030% or less. Similar to N, acid-soluble Al needs to be purified from the base steel sheet during finish annealing. 【0084】 P:0~0.040% by mass Phosphorus (P) is a selective element for steel billets (slabs). If the P content exceeds 0.040%, the workability of the steel sheet may decrease significantly. Therefore, the P content should be 0.040% or less. Preferably, the P content is 0.030% or less, and more preferably 0.020% or less. On the other hand, there is no particular lower limit to the P content, and it may be 0%. However, since P has the effect of improving the texture and the magnetic properties of the steel sheet, the P content may be greater than 0%, and may be 0.0020% or more. 【0085】 Total of S and Se: 0.0010~0.040% by mass S (sulfur) and Se (selenium) are fundamental elements for steel billets (slabs). S and Se are the elements that form the inhibitor MnS. The total content of S and Se in a slab is 0.0010% or more, preferably 0.010% or more, and more preferably 0.020% or more. On the other hand, if the total content of S and Se in a slab exceeds 0.040%, it can cause hot brittleness, making hot rolling difficult. The total content of S and Se in a slab is 0.040% or less, preferably 0.0350% or less, and more preferably 0.030% or less. If S and Se remain in excess in the final product, they can cause magnetic degradation. Therefore, S and Se also need to be purified from the base steel sheet during finish annealing. 【0086】 Sn: 0~0.50% by mass Tin (Sn) is a preferred element for steel billets (slabs). If the Sn content exceeds 0.50%, secondary recrystallization becomes unstable, which can adversely affect the magnetic properties. Therefore, the Sn content should be 0.50% or less. Preferably, the Sn content is 0.30% or less, and more preferably 0.150% or less. On the other hand, there is no particular lower limit to the Sn content, and it may be 0%. However, since Sn has the effect of improving magnetic properties by increasing the concentration of Goss orientations, the Sn content may be greater than 0%, and may be 0.0050% or more. 【0087】 Cu:0~0.50% by mass Copper (Cu) is a preferred element for steel billets (slabs). If the Cu content exceeds 0.50%, the steel sheet may become brittle during hot rolling. Therefore, the Cu content should be 0.50% or less. Preferably, the Cu content is 0.30% or less, and more preferably 0.10% or less. On the other hand, there is no particular lower limit to the Cu content, and it may be 0%. However, since Cu has the effect of increasing the concentration of Goss orientation and improving magnetic properties, the Cu content may be greater than 0%, and may be 0.010% or more. 【0088】 Cr:0~0.50% by mass Cr (chromium) is a preferred element for steel billets (slabs). If the Cr content exceeds 0.50%, Cr oxides may form, which can adversely affect the magnetic properties. Therefore, the Cr content should be 0.50% or less. Preferably, the Cr content is 0.30% or less, and more preferably 0.10% or less. On the other hand, there is no particular lower limit to the Cr content, and it may be 0%. However, since Cr has the effect of increasing the concentration of Goss orientation and improving magnetic properties, the Cr content may be greater than 0%, and may be 0.010% or more. 【0089】 Sb:0~0.50% by mass Antimony (Sb) is a preferred element for steel slabs. If the Sb content exceeds 0.50%, it may adversely affect the magnetic properties. Therefore, the Sb content should be 0.50% or less. Preferably, the Sb content is 0.30% or less, and more preferably 0.10% or less. On the other hand, there is no particular lower limit to the Sb content, and it may be 0%. However, since Sb functions as an inhibitor and has the effect of stabilizing secondary recrystallization, the Sb content may be greater than 0%, and may be 0.010% or more. 【0090】 Mo:0~0.10% by mass Mo (molybdenum) is a preferred element for steel billets (slabs). If the Mo content exceeds 0.10%, problems may arise with the rolling properties of the steel sheet. Therefore, the Mo content should be 0.10% or less. Preferably, the Mo content is 0.08% or less, and more preferably 0.05% or less. On the other hand, there is no particular lower limit to the Mo content, and it can be 0%. However, since Mo has the effect of improving magnetic properties by increasing the concentration of Goss orientation, the Mo content may be greater than 0%, and may be 0.0050% or more. 【0091】 Bi:0~0.10% by mass Bi (bismuth) is a selective element for steel billets (slabs). If the Bi content exceeds 0.10%, the passability during cold rolling may deteriorate. Also, if the purification during finish annealing is insufficient and an excess of Bi remains, it may adversely affect the magnetic properties. Therefore, the Bi content should be 0.10% or less. Preferably, the Bi content is 0.050% or less, more preferably 0.020% or less, and more preferably 0.0010% or less. On the other hand, there is no particular lower limit for the Bi content, and it may be 0%. However, since Bi has the effect of improving magnetic properties, the Bi content may be greater than 0%, and may be 0.00050% or more. 【0092】 The steel billets (slabs) used in the hot-rolling process may contain impurities. "Impurities" refer to substances that are introduced during the industrial production of steel, either from the raw materials (ore or scrap) or from the manufacturing environment. Furthermore, the chemical composition of the steel billets (slabs) used in the hot-rolling process can be measured using the same method as described above for the chemical composition of the base steel sheet. 【0093】 In the hot rolling process, the steel billet is first heat-treated. The heating temperature can be, for example, between 1200°C and 1600°C. Preferably, the lower limit of the heating temperature is 1280°C, and the upper limit is 1500°C. Next, the heated steel billet is hot-rolled. The thickness of the hot-rolled steel sheet after hot rolling is preferably in the range of, for example, 2.0 mm to 3.0 mm. 【0094】 Hot-rolled steel sheet annealing process In the hot-rolled steel sheet annealing process, the hot-rolled steel sheet obtained in the hot-rolling process is annealed. This hot-rolled steel sheet annealing induces recrystallization within the steel sheet, ultimately enabling the realization of good magnetic properties. The conditions for hot-rolled steel sheet annealing are not particularly limited, but for example, the hot-rolled steel sheet may be annealed at a temperature range of 900 to 1200°C for 10 seconds to 5 minutes. In addition, after hot-rolled steel sheet annealing but before cold rolling, the surface of the hot-rolled annealed sheet may be pickled. 【0095】 cold rolling process In the cold rolling process, the hot-rolled and annealed steel sheet undergoes either a single cold rolling or multiple cold rollings with an intermediate annealing in between. Since the hot-rolled and annealed steel sheet has a good shape due to the hot-rolled annealing process, the possibility of the steel sheet breaking during the first cold rolling is reduced. Furthermore, if intermediate annealing is performed between cold rollings, the heating method for the intermediate annealing is not particularly limited. Cold rolling may also be performed in three or more stages with an intermediate annealing in between, but since this increases manufacturing costs, it is preferable to perform cold rolling in one or two stages. 【0096】 The final cold rolling reduction ratio in cold rolling (cumulative cold rolling reduction ratio without intermediate annealing, or cumulative cold rolling reduction ratio after intermediate annealing) should be, for example, in the range of 80% to 95%. By setting the final cold rolling reduction ratio within the above range, the final {110} <001> This process increases the degree of concentration in a particular orientation and suppresses the destabilization of secondary recrystallization. The thickness of the cold-rolled steel sheet is usually the same as the thickness of the base steel sheet (final thickness) of the grain-oriented electrical steel sheet that is ultimately produced. The thickness of the cold-rolled steel sheet after cold rolling is preferably in the range of 0.17 mm to 0.29 mm. 【0097】 Decarburization annealing process In the decarburization annealing process, the cold-rolled steel sheet obtained in the cold-rolling process is decarburized and annealed. This decarburization annealing removes carbon contained in the cold-rolled steel sheet, resulting in primary recrystallization. Decarburization annealing is preferably performed in a humid atmosphere to remove carbon contained in the cold-rolled steel sheet. For example, annealing can be performed in a humid atmosphere at a temperature range of 700 to 1000°C for 10 seconds to 10 minutes. 【0098】 Alternatively, nitriding may be performed after decarburization annealing and before applying the annealing release agent. In nitriding, a nitrided steel sheet is produced by performing nitriding on the decarburized annealed steel sheet after decarburization annealing. For example, annealing may be performed for 10 to 60 seconds at a temperature range of 700 to 850°C in an atmosphere containing a gas with nitriding ability such as hydrogen, nitrogen, and ammonia. 【0099】 Finish annealing process In the finish annealing process, an annealing release agent is applied to the decarburized annealed sheet obtained in the decarburized annealing process, and then finish annealing is performed. Finish annealing can be performed by annealing the steel sheet for a long period of time while it is wound into a coil. To prevent the coiled steel sheet from seizing during finish annealing, an annealing release agent is applied to the decarburized annealed sheet and dried before the finish annealing process. 【0100】 The annealing separation agent contains magnesia (MgO), alumina (Al2O3), and bismuth chloride. In this annealing separation agent, the solid content is 20-99.5% by mass of alumina, 0.5-20% by mass of bismuth chloride, and the remainder is magnesia and impurities. The bismuth chloride can be bismuth oxychloride (BiOCl) or bismuth trichloride (BiCl3), etc. 【0101】 The annealing conditions for finish annealing are not particularly limited, and known conditions may be used as appropriate. For example, in finish annealing, a decarburized annealed plate coated with an annealing separating agent and dried may be held at a temperature range of 1000°C to 1300°C for 10 to 60 hours. The atmosphere during finish annealing may be, for example, a nitrogen atmosphere or a mixed atmosphere of nitrogen and hydrogen. After finish annealing, the surface of the finish annealed plate may be washed with water to remove dust. 【0102】 This finishing annealing process causes secondary recrystallization in the steel sheet, resulting in a crystal orientation of {110}. <001> The crystals are oriented in a specific direction. In this secondary recrystallized structure, the easy magnetization axes are aligned in the rolling direction, and the crystal grains are coarse. Excellent magnetic properties are obtained due to this secondary recrystallized structure. In this embodiment, since the annealing separating agent contains bismuth chloride, the formation of forsterite film is suppressed, resulting in a smooth surface on the finished annealed sheet. 【0103】 Alternatively, the atmosphere during finish annealing may be changed to a hydrogen atmosphere to perform a purification treatment. This purification treatment removes elements such as Al, N, S, and Se contained in the steel sheet as part of the steel composition, thereby purifying the steel sheet. 【0104】 Thermal oxidation annealing process In the thermal oxidation annealing process, the finished annealed sheet obtained in the finish annealing process is subjected to thermal oxidation annealing (heat treatment). Alternatively, a first surface treatment may be performed before the heat treatment, or a second surface treatment may be performed after the heat treatment. 【0105】 First surface treatment The finish annealed sheet obtained in the finish annealing process may be subjected to a first surface treatment as needed. While no specific pickling conditions are required for the first surface treatment, for example, the finish annealed sheet may be immersed in an acid of a specific concentration (first treatment solution). The first treatment solution may contain at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with a total acid concentration of 1-20% by mass and a liquid temperature of 50-90°C. The finish annealed sheet may then be surface treated with this first treatment solution for 3-60 seconds. 【0106】 In the first surface treatment, it is preferable to perform the surface treatment under conditions that activate the surface of the finished annealed plate, while at the same time not creating etch pits on the surface of the finished annealed plate. To achieve this, the above conditions should be controlled in a complex and inseparable manner. For example, if the pickling strength is increased for one of the above conditions, then the pickling strength of the other conditions should be decreased to achieve both an activated surface and a smooth surface. A person skilled in the art can perform surface control including pickling behavior, and by considering the effect of each of the above conditions on the pickling strength, it is possible to control the surface state by combining the above conditions. 【0107】 Furthermore, if the total acid concentration of the first treatment solution is less than 1% by mass, it is difficult to achieve an active surface state on the surface of the finished annealed plate. On the other hand, if the total acid concentration of the first treatment solution is greater than 20% by mass, etch pits are likely to form on the surface of the finished annealed plate. Similarly, if the temperature of the first treatment solution is less than 50°C, an active surface state cannot be obtained, and if the temperature of the first treatment solution is greater than 90°C, etch pits are likely to form. Similarly, if the treatment time for the first surface treatment is less than 3 seconds, an active surface state cannot be obtained, and if the treatment time for the first surface treatment is greater than 60 seconds, etch pits are likely to form. 【0108】 Heat treatment In the heat treatment, the finished annealed plate after the finish annealing process, or the finished annealed plate after the first surface treatment, is subjected to thermal oxidation annealing. In this heat treatment, the finished annealed plate is heated from room temperature and the heat treatment is carried out within the temperature range of 800 to 1100°C. The heating process from room temperature to a controlled temperature within the temperature range of 600 to 1000°C and the soaking process at a soaking temperature within the temperature range of 800 to 1100°C are controlled separately. 【0109】 During the heating process, the steel sheet is controlled and heated from room temperature to a temperature range of 600-1000°C in an atmosphere with an oxygen concentration of 1.0-25% by volume. By controlling the heating conditions to the above conditions, the average Fe quantitative value I of the inner layer region of the base steel sheet is ultimately obtained. base and the average Fe quantitative value I in the inner layer region of the insulating coating coating This allows for desirable control of the following. 【0110】 If the oxygen concentration is less than 1.0 volume%, coating / I base It is not possible to control it within the above range. Therefore, the oxygen concentration should be 1.0 volume% or higher. Preferably, the oxygen concentration should be 3 volume% or higher, and more preferably 5 volume% or higher. On the other hand, even if the oxygen concentration exceeds 25 volume%, coating / I base It is not possible to control this within the above range. Therefore, the oxygen concentration should be 25% by volume or less. Preferably, the oxygen concentration should be 18% by volume or less, and more preferably 16% by volume or less. For example, the atmosphere during the heating process can be air. 【0111】 Similarly, if the temperature control temperature is less than 600°C, coating / I base It is not possible to control it within the above range. Therefore, the temperature rise control temperature is set to 600°C or higher. Preferably, the temperature rise control temperature is 650°C or higher, and more preferably 700°C or higher. On the other hand, even if the temperature rise control temperature exceeds 1000°C, coating / I base It is not possible to control the temperature within the above range. Therefore, the temperature control temperature is set to 1000°C or lower. The target temperature is preferably 950°C or lower, and more preferably 900°C or lower. 【0112】 The heating rate during the heating process is not particularly limited, but it is preferable that the heating rate is 10°C / second or more, and also preferable that it is 100°C / second or less. 【0113】 In the soaking process, the steel sheet is heated for 5 to 200 seconds at a temperature range of 800 to 1100°C in an atmosphere where the oxygen concentration is less than 1.0 volume% and the oxygen potential PH2O / PH2 is 0.0001 to 10. By controlling the soaking conditions to the above conditions, the average Fe quantitative value in the inner layer region of the base steel sheet is ultimately determined. base and the average Fe quantitative value I in the inner layer region of the insulating coating coating This allows for desirable control of the following. 【0114】 If the oxygen concentration is 1.0 volume% or higher, coating / I base It is not possible to control this within the above range. Therefore, the oxygen concentration should be less than 1.0 volume%. Preferably, the oxygen concentration should be 0.5 volume% or less, and more preferably 0.1 volume% or less. On the other hand, there is no particular lower limit to the oxygen concentration, and the smaller the better. However, since it is industrially difficult to make the oxygen concentration 0 volume%, the oxygen concentration should be 1.0 × 10 -20 It may be greater than or equal to a volume percent. The oxygen concentration is 1.0 × 10⁻⁶. -19 Preferably, it is 1.0 × 10% or more by volume. -18 It is more preferable that it be 1% by volume or more. 【0115】 Similarly, if the oxygen potential PH2O / PH2 is 10 or greater, coating / I base It is not possible to control this within the above range. Therefore, the oxygen potential PH2O / PH2 is set to 10 or less. The oxygen potential PH2O / PH2 is preferably 0.25 or less, and more preferably 0.10 or less. On the other hand, the lower limit of the oxygen potential PH2O / PH2 is not particularly limited and may be, for example, 0. However, since it is difficult to actually obtain such an atmosphere, 0.0001 may be used as a practical lower limit. The oxygen potential PH2O / PH2 is preferably 0.0010 or more, and more preferably 0.0050 or more. The oxygen potential PH2O / PH2 can be defined by the ratio of the hydrogen partial pressure PH2 to the water vapor partial pressure PH2O in the annealing atmosphere. Furthermore, the oxygen potential PH2O / PH2 can be derived from the hydrogen concentration and dew point in the annealing atmosphere. 【0116】 Similarly, if the soaking temperature is less than 800°C, coating / I base It is not possible to control it within the above range. Therefore, the soaking temperature should be 800°C or higher. Preferably, the soaking temperature should be 830°C or higher, and more preferably 860°C or higher. On the other hand, even if the soaking temperature exceeds 1100°C, coating / I baseIt is not possible to control this within the above range. Therefore, the soaking temperature should be 1100°C or lower. Preferably, the soaking temperature should be 1050°C or lower, and more preferably 1000°C or lower. 【0117】 Similarly, if the soaking time is less than 5 seconds, coating / I base It is not possible to control it within the above range. Therefore, the soaking time should be 5 seconds or more. Preferably, the soaking time should be 10 seconds or more, and more preferably 15 seconds or more. On the other hand, even if the soaking time exceeds 200 seconds, coating / I base It is not possible to control this within the above range. Therefore, the soaking time should be 200 seconds or less. Preferably, the soaking time should be 150 seconds or less, and more preferably 100 seconds or less. 【0118】 Furthermore, if the heating control temperature in the heating process and the soaking temperature in the soaking process are different, the heating conditions or cooling conditions from the heating control temperature to the soaking temperature are not particularly limited. For example, after reaching the heating control temperature, the temperature can be raised or lowered to the soaking temperature in the same atmosphere as the soaking process. 【0119】 Second surface treatment A second surface treatment may be performed on the heat-treated, oxidized, and annealed plate, if necessary. While no specific pickling conditions are required for the second surface treatment, for example, the heat-treated, annealed plate may be immersed in an acid of a specific concentration (second treatment solution). The second treatment solution may contain at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with a total acid concentration of 1-10% by mass and a liquid temperature of 50-90°C. The heat-treated, annealed plate may then be surface-treated using this second treatment solution for 3-60 seconds. 【0120】 In the second surface treatment, residual oxides on the surface of the hot-oxidized annealed plate are pickled, but it is preferable to perform the surface treatment under conditions that do not create etch pits on the surface of the hot-oxidized annealed plate. To achieve this, the above conditions should be controlled in a combined and inseparable manner. For example, if the pickling intensity of one of the above conditions is increased, the pickling intensity of the other conditions should be decreased to achieve both oxide pickling and a smooth surface. A person skilled in the art can perform surface control including pickling behavior, and by considering the effect of each of the above conditions on the pickling intensity, it is possible to control the surface state by combining the above conditions. 【0121】 Furthermore, if the total acid concentration of the second treatment solution is less than 1% by mass, it is difficult to pickle residual oxides from the surface of the heat-oxidized annealed plate. On the other hand, if the total acid concentration of the second treatment solution is greater than 10% by mass, etch pits are likely to form on the surface of the heat-oxidized annealed plate. Similarly, if the temperature of the second treatment solution is less than 50°C, it is difficult to pickle residual oxides, and if the temperature of the second treatment solution is greater than 90°C, etch pits are likely to form. Likewise, if the treatment time for the second surface treatment is less than 3 seconds, it is difficult to pickle residual oxides, and if the treatment time for the second surface treatment is greater than 60 seconds, etch pits are likely to form. 【0122】 Insulating film formation process In the insulating film formation process, an insulating film forming solution is applied to the heat-oxidized annealed plate after the heat oxidation annealing process and then heat-treated. This heat treatment forms an insulating film on the surface of the heat-oxidized annealed plate. For example, the insulating film forming solution may contain colloidal silica and phosphate. It is preferable that the insulating film forming solution does not contain chromium. 【0123】 This insulating coating reduces iron loss in the steel sheet by applying tension to the grain-oriented electrical steel sheet, and also reduces iron loss in the core by ensuring electrical insulation between the steel sheets when grain-oriented electrical steel sheets are used in laminated form. 【0124】 The insulating coating is formed by applying an insulating coating-forming solution, mainly composed of phosphate or colloidal silica, to the surface of a thermally oxidized annealed plate, and then soaking it in an atmosphere with an oxygen potential of 0.10 to 10 at a temperature range of 700 to 1000°C for 5 to 200 seconds. 【0125】 As the phosphate, phosphates of Ca, Al, Sr, etc. are preferred, and among these, aluminum phosphate is more preferred. The colloidal silica is not particularly limited to colloidal silica with specific properties. The particle size is also not particularly limited to a specific size, but 200 nm (number average particle size) or less is preferred. For example, 5 to 30 nm is acceptable. If the particle size exceeds 200 nm, sedimentation may occur in the coating solution. 【0126】 If the oxygen potential PH2O / PH2 is greater than 10, coating / I base However, it cannot be controlled within the above range. Therefore, the oxygen potential PH2O / PH2 should be 10 or less. The oxygen potential PH2O / PH2 is preferably 7.5 or less, and more preferably 5.0 or less. On the other hand, even if the oxygen potential PH2O / PH2 is less than 0.10, coating / I base However, it cannot be controlled within the above range. Therefore, the oxygen potential PH2O / PH2 should be 0.10 or higher. Preferably, the oxygen potential PH2O / PH2 should be 0.3 or higher, and more preferably 0.5 or higher. 【0127】 Similarly, if the soaking temperature is less than 700°C, coating / I base However, it cannot be controlled within the above range. Therefore, the soaking temperature should be 700°C or higher. Preferably, the soaking temperature should be 750°C or higher, and more preferably 800°C or higher. On the other hand, even if the soaking temperature exceeds 1000°C, coating / I base However, it cannot be controlled within the above range. Therefore, the soaking temperature should be 1000°C or lower. Preferably, the soaking temperature should be 950°C or lower, and more preferably 900°C or lower. 【0128】 Similarly, if the soaking time is less than 5 seconds, coating / I base However, it cannot be controlled within the above range. Therefore, the soaking time should be 5 seconds or more. Preferably, the soaking time should be 10 seconds or more, and more preferably 15 seconds or more. On the other hand, even if the soaking time exceeds 200 seconds, coating / I base However, it cannot be controlled within the above range. Therefore, the soaking time should be 200 seconds or less. Preferably, the soaking time should be 150 seconds or less, and more preferably 100 seconds or less. 【0129】 In this embodiment, by including Bi chloride in the annealing separating agent, favorably controlling the heating conditions and soaking conditions in the thermal oxidation annealing process, and favorably controlling the heat treatment conditions in the insulating film formation process, the average Fe quantitative value in the inner layer region of the base steel sheet and the average Fe quantitative value in the inner layer region of the insulating film are favorably controlled. As a result, even though the insulating film is placed in contact with the base steel sheet without the presence of a forsterite film (the base steel sheet maintains a smooth surface after cold rolling), the base steel sheet and the insulating film adhere to each other favorably. 【0130】 After forming the insulating film, flattening annealing may be performed as needed to correct the shape. Performing flattening annealing on the steel plate makes it possible to further reduce iron loss. 【0131】 Magnetic domain control process In this embodiment, magnetic domain control processing may be performed before or after the insulating film formation process, if necessary. By performing magnetic domain control processing, iron loss in the grain-oriented electrical steel sheet can be further reduced. 【0132】 When magnetic domain control processing is performed before the insulating film formation process, linear or dot-shaped grooves extending in a direction intersecting the rolling direction should be formed at predetermined intervals along the rolling direction. Alternatively, when magnetic domain control processing is performed after the insulating film formation process, linear or dot-shaped stress-strain areas extending in a direction intersecting the rolling direction should be formed at predetermined intervals along the rolling direction. Magnetic domain control processing narrows the width of the 180° magnetic domains (the 180° magnetic domains are subdivided). 【0133】 When forming grooves, mechanical groove formation methods using gears, chemical groove formation methods using electrolytic etching, and thermal groove formation methods using laser irradiation can be applied. Furthermore, when forming stress-strained areas, laser beam irradiation and electron beam irradiation can be applied. [Examples] 【0134】 Next, the effects of one aspect of the present invention will be described in more detail with reference to examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples of conditions. The present invention can adopt various conditions as long as they do not depart from the spirit of the invention and achieve the objectives of the present invention. 【0135】 Slabs (steel billets) with the chemical composition shown in Table 1 were heated to 1350°C and subjected to hot rolling to obtain hot-rolled steel sheets with a thickness of 2.3 mm. These hot-rolled steel sheets were then annealed at 1100°C for 120 seconds and pickled. Subsequently, they were subjected to one cold rolling or multiple cold rollings with intermediate annealing in between to obtain cold-rolled steel sheets of the final thickness. These cold-rolled steel sheets were then subjected to decarburization annealing at 830°C for 140 seconds in a humid hydrogen atmosphere. After decarburization annealing, tests No. 23 to No. 29 shown in the table underwent nitriding treatment. 【0136】 The obtained decarburized annealed sheet was coated with the annealing release agents shown in Tables 3 to 6 and dried. In the tables, alumina and bismuth chloride represent the content in terms of solid content, and the remainder represents magnesia and impurities. Thereafter, final annealing was carried out by holding at 1200 °C for 20 hours. The final annealing atmosphere was a mixed atmosphere of nitrogen and hydrogen, and then a hydrogen atmosphere. After the final annealing, the steel sheet was washed with water to remove the excess annealing release agent. 【0137】 The obtained final annealed sheet was subjected to heat oxidation annealing, i.e., heat treatment (heating-up process and soaking process) under the conditions shown in Tables 3 to 10. As required, as shown in Tables 3 to 10, the first surface treatment and the second surface treatment were also carried out. In the tables, the "heating-up control temperature" represents the high-temperature side temperature of the temperature range controlled during the heating-up process. Also, in the heat oxidation annealing process, when the heating-up control temperature and the soaking temperature were different, after reaching the heating-up control temperature, the temperature was raised or lowered to the soaking temperature in the same atmosphere as the soaking process. 【0138】 An insulating film forming liquid containing colloidal silica and phosphate was applied to the surface of the obtained heat oxidation annealed sheet, and an insulating film was formed under the conditions shown in Tables 7 to 10 to manufacture a grain-oriented electrical steel sheet. The basis weight of the insulating film was 4 to 6 g / m 2 ². A magnetic domain control treatment of irradiating the obtained grain-oriented electrical steel sheet with a laser beam was carried out. 【0139】 Regarding the obtained grain-oriented electrical steel sheets No. 1 to No. 54, based on the above method, the chemical composition of the base steel sheet, the average Fe quantification value in the inner layer region of the base steel sheet, and the average Fe quantification value in the inner layer region of the insulating film were confirmed. For the materials with the intermediate ceramic layer "present", evaluation was not required. Also, regarding the obtained grain-oriented electrical steel sheets No. 1 to No. 54, the film adhesion and magnetic properties were evaluated. 【0140】 Coating adhesion was evaluated by measuring the percentage of the remaining coating area when a test specimen was wrapped around a 20 mm diameter cylinder and bent 180°. The area ratio of the remaining coating surface to the area of ​​the steel plate in contact with the cylinder was calculated. The area of ​​the steel plate in contact with the roll was determined by calculation. The area of ​​the remaining coating surface was determined by taking a photograph of the steel plate after the test and performing image analysis on the photographic image. A coating remaining area ratio of 95% or more was evaluated as Excellent (EX), 90% or more but less than 95% as Very Good (VG), 85% or more but less than 90% as Good (G), and less than 85% as Poor. A coating remaining area ratio of 85% or more was judged as passing. 【0141】 The iron loss characteristics were evaluated using the Single Sheet Tester (SST) method for test specimens. Under conditions of AC frequency: 50 Hz and excitation magnetic flux density: 1.7 T, the iron loss W17 / 50 (W / kg), defined as the power loss per unit weight (1 kg) of the steel sheet, was measured. A value of less than 0.75 W / kg for iron loss W17 / 50 was considered acceptable. The magnetic flux density was measured by applying a magnetic field of 800 A / m to the test specimen and measuring the magnetic flux density B8 (T) in the rolling direction. 【0142】 Tables 1 to 14 show the manufacturing conditions, manufacturing results, and evaluation results. In the tables, a "-" next to the chemical composition indicates that no alloying elements were intentionally added, while a "-" next to something other than chemical composition indicates that the process was not performed or is not applicable. 【0143】 Furthermore, in the table, "absent" for the intermediate ceramic layer means that there is no intermediate ceramic layer such as a forsterite coating, and the insulating coating is placed in contact with the base steel plate, and the base steel plate has a smooth surface. Conversely, "present" for the intermediate ceramic layer indicates the presence of an intermediate ceramic layer such as a forsterite coating that adversely affects the magnetic properties. The intermediate ceramic layer causes magnetic degradation. Also, in the table, "I coating / I base " is the average Fe quantitative value I in the inner layer region of the base steel sheet. base And the average Fe quantitative value I in the inner layer region of the insulating coating coatingThis represents the ratio to [the specified value]. Furthermore, the "frequency of presence in 10 fields of view" in the table indicates that when the cross-section was observed at 10 observation points spaced apart on the plate surface, "I coating / I base This represents the number of locations where the value is between 0.010 and 0.50. 【0144】 Among Tests No. 1 to No. 54, the present invention example exhibited excellent coating adhesion and iron loss characteristics without relying on a forsterite coating. On the other hand, the comparative examples among Tests No. 1 to No. 54 did not exhibit excellent surface smoothness, coating adhesion, or iron loss characteristics. 【0145】 [Table 1] 【0146】 [Table 2] 【0147】 [Table 3] 【0148】 [Table 4] 【0149】 [Table 5] 【0150】 [Table 6] 【0151】 [Table 7] 【0152】 [Table 8] 【0153】 [Table 9] 【0154】 [Table 10] 【0155】 [Table 11] 【0156】 [Table 12] 【0157】 [Table 13] 【0158】 [Table 14] [Industrial applicability] 【0159】 According to the above embodiment of the present invention, it is possible to provide a grain-oriented electrical steel sheet and a method for manufacturing the same that have excellent coating adhesion without relying on a forsterite coating. In this grain-oriented electrical steel sheet, the surface of the base steel sheet is smooth because there is no forsterite coating, and the base steel sheet and the insulating coating are preferably controlled, resulting in excellent coating adhesion. Therefore, it is possible to favorably improve the iron loss characteristics. Consequently, it has high industrial applicability. [Explanation of symbols] 【0160】 1 Grain-oriented electrical steel sheet 11 Base steel plate 12. Insulating coating

Claims

[Claim 1] In a grain-oriented electrical steel sheet having a base steel sheet and a phosphate-based insulating coating disposed in contact with the base steel sheet, The aforementioned base steel sheet has a chemical composition of, in mass%, Si: 3.0 to 4.0%, Mn: 0.010 to 0.50%, It contains, with the remainder being Fe and impurities. When viewed as a cross-section parallel to the thickness direction and perpendicular to the width direction, the area from the interface between the base steel sheet and the phosphate-based insulating coating toward the base steel sheet in the thickness direction is defined as the base steel sheet inner layer region, and the area from the interface toward the phosphate-based insulating coating in the thickness direction is defined as the insulating coating inner layer region, and the average Fe quantitative value of the base steel sheet inner layer region is expressed as I in mass%. ｂａｓｅ The average Fe quantitative value of the inner layer region of the insulating film is expressed as I in mass%. ｃｏａｔｉｎｇ In that case, The above I ｂａｓｅ and the aforementioned I ｃｏａｔｉｎｇ And, 0.010 ≤ I ｃｏａｔｉｎｇ / I ｂａｓｅ Satisfying ≤ 0.50 A grain-oriented electrical steel sheet characterized by the following features. [Claim 2] The aforementioned base steel sheet has the following chemical composition in mass%, C: 0.010% or less, N: 0.010% or less, Acid-soluble Al: 0.020% or less, P: 0.040% or less, Total of S and Se: 0.010% or less. Sn: 0.50% or less, Cu: 0.50% or less, Cr: 0.50% or less, Sb: 0.50% or less, Mo: 0.10% or less Bi: 0.10% or less, including The grain-oriented electrical steel sheet according to claim 1. [Claim 3] When observing the cut surface at 10 observation points spaced apart from each other on the board surface, when the I ｂａｓｅ and the I ｃｏａｔｉｎｇ and 0.010 ≤ I ｃｏａｔｉｎｇ / I ｂａｓｅ ≤ 0.50, there are 5 or more observation points that satisfy this condition A grain-oriented electrical steel sheet according to claim 1 or 2. [Claim 4] A method for manufacturing grain-oriented electrical steel sheets according to claim 1 or claim 2, This process includes a hot rolling process, a hot-rolled steel sheet annealing process, a cold rolling process, a decarburization annealing process, a finish annealing process, a thermal oxidation annealing process, and a phosphate-based insulating coating formation process. In the aforementioned finish annealing process, After the decarburization annealing process, an annealing separation agent is applied to the steel sheet, which contains 20 to 99.5% by mass of alumina, 0.5 to 20% by mass of bismuth chloride, with the remainder being magnesia and impurities, on a solid content basis. After drying, finish annealing is performed. In the aforementioned thermal oxidation annealing process, As part of the heating process, the steel sheet after the finish annealing process is controlled and heated in an atmosphere with an oxygen concentration of 1.0 to 25 volume percent from room temperature to a temperature range of 600 to 1000°C. As a soaking process, the steel plate after the heating process is heated to an oxygen concentration of less than 1.0 volume% and an oxygen potential pH ２ O / PH ２ In an atmosphere where the ratio is 0.0001 to 10, the mixture is heated to a temperature range of 800 to 1100°C for 5 to 200 seconds. In the phosphate-based insulating coating formation step, After the thermal oxidation annealing process, an insulating film forming solution is applied to the steel sheet, and the oxygen potential pH is ２ O / PH ２ In an atmosphere where the pressure is 0.10 to 10, the mixture is heated to a temperature range of 700 to 1000°C for 5 to 200 seconds. A method for manufacturing grain-oriented electrical steel sheets, characterized by the following features. [Claim 5] In the aforementioned thermal oxidation annealing process, As a first surface treatment, the steel sheet after the finish annealing process is immersed for 3 to 60 seconds in a first treatment solution containing at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with a total acid concentration of 1 to 20% by mass and a liquid temperature of 50 to 90°C. As a heat treatment, the steel plate after the first surface treatment is subjected to the heating and soaking process. The method for manufacturing grain-oriented electrical steel sheets according to feature 4. [Claim 6] In the aforementioned thermal oxidation annealing process, As a second surface treatment, the steel plate, after heating and soaking, is immersed for 3 to 60 seconds in a second treatment solution containing at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with a total acid concentration of 1 to 10% by mass and a liquid temperature of 50 to 90°C. The method for manufacturing grain-oriented electrical steel sheets according to feature 4.

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