GRAIN-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR FORMING INSULATING COATING

Description

44 GRAIN-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR FORMING INSULATING COATING TECHNICAL FIELD

[001] The present invention relates to a grain-oriented electrical steel sheet and to a method for forming an insulating coating embedded in the grain-oriented electrical steel sheet.

[002] Priority is claimed in Japanese Patent Application No. 2023-065386, filed on April 13, 2023, the contents of which are incorporated herein by reference. FUNDAMENTALS OF THE TECHNIQUE

[003] A grain-oriented electrical steel sheet is mainly used in a transformer. The transformer is continuously magnetized for a long period of time, from installation to disposal, and continues to generate energy loss. Therefore, the energy loss when the transformer is magnetized by alternating current, i.e., the iron loss, is a primary index for determining the transformer's performance.

[004] To reduce iron loss from grain-oriented electrical steel sheet, many techniques have been developed so far from the point of view of (a) increasing development in the orientation {110} <001> (Goss orientation), (b) increasing the content of a solid solution element, such as Si, to increase the electrical resistance of the steel sheet, or (c) reducing the thickness of the electrical steel sheet.

[005] In addition, applying tension to the steel sheet is effective in reducing iron loss. It is an effective means of reducing iron loss to form a coating made of a material with a coefficient of thermal expansion lower than that of the steel sheet on a sheet surface at a high temperature. A forsterite film (inorganic coating) with excellent coating adhesion, generated by a reaction between an oxide in Petition 870250091781, dated 08 / 10 / 2025, page 12 / 60 / 44 surface of a sheet and an annealing separator in a finishing annealing step of an electrical steel sheet, is a coating capable of applying tension to the steel sheet.

[006] For example, a method for forming an insulating coating by baking a coating liquid containing mainly colloidal silica and a phosphate onto the surface of a sheet, described in Patent Document 1, is an effective method for reducing iron loss because the method is highly effective in applying stress to the steel sheet. Therefore, a general method for manufacturing a grain-oriented electrical steel sheet is to leave the forsterite film generated in the finishing annealing step and form an insulating coating containing mainly a phosphate onto the forsterite film.

[007] However, in recent years, there has been a growing demand for miniaturization and high performance of a transformer, and to miniaturize the transformer, it is necessary that a grain-oriented electrical steel sheet have excellent iron loss in a high magnetic field, so that the iron loss is favorable even when the magnetic flux density is high. At the same time, in recent years, it has been clarified that a forsterite film hinders the movement of a magnetic domain wall and adversely affects the iron loss. In a grain-oriented electrical steel sheet, a magnetic domain changes by the movement of a magnetic domain wall under an alternating magnetic field.The smooth and rapid movement of the magnetic domain wall is effective in reducing iron loss, but the forsterite film itself is a non-magnetic body and has an irregular structure at the interface between the steel plate and the coating, and this irregular structure is considered to hinder the movement of the magnetic domain wall and therefore negatively affect iron loss.

[008] Therefore, as a means of improving iron loss in high Petition 870250091781, dated 08 / 10 / 2025, page 13 / 60 / 44 magnetic field, a technique for manufacturing a grain-oriented electrical steel sheet without forsterite film, or a technique for bringing the surface of a sheet to a mirror-like surface state (in other words, a technique for magnetically smoothing the surface of a sheet) was studied by: removing a forsterite film using a mechanical means, such as polishing, or a chemical means, such as pickling; or preventing the generation of a forsterite film in high-temperature finish annealing.

[009] As a technique for avoiding the generation of a forsterite film, for example, Patent Document 2 describes a technique in which a product formed on the surface is removed by pickling after normal finish annealing, and then a sheet surface is brought to a mirror surface state by chemical polishing or electrolytic polishing. It has been found that a better iron loss improvement effect can be obtained by forming a voltage-applied insulating coating on the surface of a grain-oriented electrical steel sheet without a forsterite film, obtained by using a known method. Furthermore, the voltage-applied insulating coating can impart various characteristics such as corrosion resistance, heat resistance and slip resistance, in addition to improving iron loss.

[0010] However, the forsterite film has the effect of exhibiting an insulating property and an intermediate layer effect to ensure adhesion when a tension coating (tension-applied insulating coating) is formed. That is, as the forsterite film is formed in a state of deep penetration into the steel sheet, the forsterite film has excellent adhesion to the steel sheet, which is metallic. Therefore, when a tension-applied coating (tension coating) containing colloidal silica, phosphate or similar as a main component is formed on the surface of the forsterite film, the adhesion of Petition 870250091781, dated 08 / 10 / 2025, page 14 / 60 / 44. The coating is excellent. On the other hand, since it is generally difficult to bond a metal and an oxide, it is difficult to guarantee sufficient adhesion between a tension coating and a sheet surface when a forsterite film is not present.

[0011] Thus, in the case of forming a tension coating on a grain-oriented electrical steel sheet without a forsterite film, the provision of a layer that substitutes for a forsterite film as an intermediate layer was studied.

[0012] Patent Document 3 describes a technique for ensuring the adhesion of a voltage-applied insulating coating by forming a coating that serves as an intermediate layer in advance when a voltage-applied coating is formed.

[0013] However, the technique described in Patent Document 3 has a problem in that a high-voltage applied insulating coating cannot be maintained with good adhesion.

[0014] Furthermore, for example, Patent Document 4 describes a grain-oriented electrical steel sheet, including a base steel sheet and an insulating coating formed on a surface of the base steel sheet, wherein the insulating coating includes an intermediate layer formed on one side of the base steel sheet and containing a crystalline metallic phosphate and a tension coating layer formed on one side of the insulating coating surface. Patent Document 4 shows that a grain-oriented electrical steel sheet does not have a forsterite film, has excellent coating adhesion, excellent coating tension, and excellent magnetic characteristics.

[0015] On the other hand, to improve the magnetic characteristics of a grain-oriented electrical steel sheet, a technique called magnetic domain refinement is known, in which the width of the magnetic domain present in a steel sheet is reduced. As a method of Petition 870250091781, dated 08 / 10 / 2025, page 15 / 60 / 44 magnetic domain control, as described in Patent Document 5, a method in which a surface of a grain-oriented electrical steel sheet, after annealing finishing, is irradiated with a laser beam to refine a magnetic domain and reduce eddy current loss and, as a result, iron loss is reduced, is known. However, this method utilizes a magnetic domain refinement phenomenon caused primarily by thermal deformation introduced into the steel sheet by laser irradiation.A wound core, primarily used in small to medium-sized transformers, is generally manufactured according to a core fabrication method that utilizes mechanical bending. In this manufacturing method, to eliminate an increase in iron loss due to processing stress introduced into a steel sheet due to bending, a core shape is manufactured by machining and then, generally, stress-relief annealing is performed (e.g., about 2 to 4 hours at 800°C). Although the machining deformation introduced into the core by such stress-relief annealing is reduced or eliminated, the thermal deformation introduced for refining the magnetic domain in the steel sheet subjected to magnetic domain control by laser irradiation is eliminated.Thus, it is generally considered that a grain-oriented electrical steel sheet subjected to magnetic domain refinement through the introduction of thermal deformation typified by laser irradiation cannot be applied to a wound core.

[0016] As a magnetic domain control technique in which the magnetic domain control effect is not lost even when the stress-relief annealing described above is performed, a “groove introduction type magnetic domain control technique” in which linear grooves are periodically formed in a direction that intersects a rolling direction is widely known. Assuming the application Petition 870250091781, dated 08 / 10 / 2025, page 16 / 60 / 44 in a wound core, it is necessary to assume the application of a slot-introduction type magnetic domain control technique.

[0017] Here, in the technique described in Patent Document 4, it is possible to obtain a grain-oriented electrical steel sheet that does not have an inorganic coating, has excellent coating adhesion, excellent coating tension, and excellent magnetic characteristics. However, in Patent Document 4, stress-relief annealing and groove formation are not sufficiently considered.

[0018] As a result of the examination carried out by the present inventors, it was verified that in the method described in Patent Document 4, when a groove is formed, the adhesion of the insulating coating to the grooved part is not sufficient and, as a result, a sufficient effect of improving the magnetic characteristics and corrosion resistance after stress relief annealing is not necessarily obtained. List of Citations Patent Documents

[0019] Patent Document 1: Unexamined Japanese Patent Application, First Publication No. S48-039338

[0020] Patent Document 2: Unexamined Japanese Patent Application, First Publication No. S49-96920

[0021] Patent Document 3: Unexamined Japanese Patent Application, First Publication No. H05-279747

[0022] Patent Document 4: International Publication PCT No. WO 2022 / 215709

[0023] Patent Document 5: Unexamined Japanese Patent Application, First Publication No. S56-51522 SUMMARY OF THE INVENTION Technical Problem

[0024] As described above, conventionally, on a plate Petition 870250091781, dated 08 / 10 / 2025, page 17 / 60 / 44 of grain-oriented electrical steel in which a groove is formed in a base steel sheet, it is not easy to simultaneously improve coating adhesion and magnetic characteristics without providing a forsterite film.

[0025] Therefore, an object of the present invention is to provide a grain-oriented electrical steel sheet in which a groove is formed in a base steel sheet, the grain-oriented electrical steel sheet not having a forsterite film and having excellent coating adhesion and magnetic characteristics. Another object of the present invention is to provide a method for forming an insulating coating embedded in the grain-oriented electrical steel sheet. However, even if the coating adhesion is improved, it is not practically preferable that the coating tension, corrosion resistance and dissolution property be reduced and, therefore, it is assumed that these characteristics do not deteriorate. Solution to the Problem

[0026] The present inventors have found that, in a grain-oriented electrical steel sheet in which a groove is formed in a base steel sheet, an intermediate layer is formed under a specific treatment condition and then the groove formation condition is also controlled so that a sufficient intermediate layer remains in the grooved part as well.

[0027] The present invention was made in view of the above verifications. The essence of the present invention is as follows.

[0028] [1] A grain-oriented electrical steel sheet according to an aspect of the present invention is a grain-oriented electrical steel sheet comprising a base steel sheet and an insulating coating formed on a surface of the base steel sheet, wherein the base steel sheet includes a flat surface portion and a grooved portion extending in a direction of 45 to 135° relative to a rolling direction, the portion Petition 870250091781, dated 08 / 10 / 2025, page 18 / 60 / 44, the grooved section has a depth of 10 to 30 μm and a width of 10 to 200 μm, the insulating coating includes an intermediate layer formed on one side of the base steel sheet, containing a crystalline metallic phosphate and having a thickness of 0.1 to 15.0 μm, and a tension coating layer formed on one side of the insulating coating surface, and the base steel sheet is covered with the insulating coating including the intermediate layer and the tension coating layer in 60% or more of the grooved part in terms of area ratio.

[0029] [2] In the grain-oriented electrical steel sheet according to [1], the crystalline metallic phosphate contained in the intermediate layer may be one or two or more of zinc phosphate, manganese phosphate, iron phosphate and calcium and zinc phosphate, and the tension coating layer may contain a metallic phosphate and silica, and the silica content in the tension coating layer may be from 20 to 60% by mass.

[0030] [3] A method for forming an insulating coating according to another aspect of the present invention is a method for forming the insulating coating embedded in grain-oriented electrical steel sheet according to [1], the method including: a finishing annealing step to apply an annealing separator containing 10 to 100% by mass of Al2O3 to a steel sheet, drying the annealing separator and then performing the finishing annealing; an annealing separator removal step to remove excess annealing separator from the steel sheet after the finishing annealing step; a light pickling step to pickle the steel sheet after the annealing separator removal step with one or two or more inorganic acids selected from sulfuric acid, phosphoric acid and hydrochloric acid at a concentration of 0.1 to 10% by mass and at normal or higher temperature for 1 to 20 seconds;an intermediate layer formation step to immerse the steel sheet after the light pickling step; Petition 870250091781, dated 08 / 10 / 2025, p.19 / 60 / 44 a treatment liquid with a liquid temperature of 30 to 95°C, a phosphate concentration of 1.0 to 15.0% by mass and a pH of 1.5 to 6.0 for 5 to 90 seconds, wash and remove the treatment liquid with water and then dry the steel sheet; a groove forming step to form a grooved part that extends in a direction of 45 to 135° relative to a rolling direction on the steel sheet after the intermediate layer forming step through machining; and a tension coating layer formation step to apply, to the steel sheet after the groove forming step, a coating liquid containing a metallic phosphate and colloidal silica such that the colloidal silica is contained in an amount of 30 to 150 parts by mass relative to 100 parts by mass of the metallic phosphate, dry the coating liquid and then hold the steel sheet at a sheet temperature of 700 to 950°C for 10 to 90 seconds.

[0031] [4] In the method for forming the insulating coating according to [3], the annealing separator may additionally contain one or both of 5 to 90% by mass of MgO and 0.5 to 10.0% by mass of chloride. Advantageous Effects of the Invention

[0032] In accordance with the above aspects of the present invention, it is possible to provide a grain-oriented electrical steel sheet with excellent coating adhesion and magnetic characteristics, and a method for forming an insulating coating embedded in the grain-oriented electrical steel sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] [Figure 1] A diagram illustrating a schematic diagram of a grain-oriented electrical steel sheet according to the present embodiment.

[0034] [Figure 2] A schematic view of a cross-section taken along line AA in Figure 1, illustrating a grooved section. DESCRIPTION OF THE MODALITIES

[0035] A grain-oriented electrical steel sheet will be described Petition 870250091781, dated 08 / 10 / 2025, page 20 / 60 / 44 in accordance with an embodiment of the present invention (grain-oriented electrical steel sheet according to the present embodiment) and a method for its manufacture.

[0036] As illustrated in figures 1 and 2, a grain-oriented electrical steel sheet 1 according to the present embodiment includes a base steel sheet 11 and an insulating coating 21 formed on a surface of the base steel sheet 11, and has substantially no forsterite film (also called glass coating) on ​​the surface of the base steel sheet 11 (the forsterite film is not intentionally formed, and even if it is unintentionally formed and remains, the amount thereof is 0.5 g / m2 or less).

[0037] The insulating coating 21 includes an intermediate layer 211 formed on the base steel sheet side and a tension coating layer 212 formed on the surface side.

[0038] In the grain-oriented electrical steel sheet 1 according to the present embodiment, the base steel sheet 11 has a flat surface portion 2 and a grooved portion 3 extending in a direction of 45 to 135° relative to a rolling direction RD. Furthermore, 50% or more of the area of ​​the grooved portion 3 is covered with the insulating coating 21.

[0039] Both of the above cases will be described next.<Revestimento Isolante>

[0040] The insulating coating 21 has an intermediate layer 211 formed on the base steel sheet side, containing a crystalline metallic phosphate and having a thickness of 0.1 to 15.0 μm, and a tension coating layer 212 formed on the surface side. [Intermediate Layer]

[0041] The intermediate layer is a layer (coating) formed on the base steel sheet side of the insulating sheathing, contains a crystalline metallic phosphate and has a thickness of 0.1 to 15.0 μm. Petition 870250091781, dated 08 / 10 / 2025, page 21 / 60 / 44

[0042] As described above, in general, a grain-oriented electrical steel sheet has a forsterite film (inorganic coating) formed in a finishing annealing step and an insulating coating (tension-insulating coating) formed over it. However, in recent years, it has been clarified that the forsterite film hinders the movement of a magnetic domain wall and adversely affects iron loss, and therefore, to further improve the magnetic characteristics, a grain-oriented electrical steel sheet without the forsterite film was studied. However, in the case where there is no forsterite film, it is difficult to ensure sufficient adhesion between the tension-insulating coating layer and the surface of the base steel sheet.

[0043] In the grain-oriented electrical steel sheet 1 according to the present embodiment, the intermediate layer 211 containing a crystalline metallic phosphate is formed between the base steel sheet 11 and the tension coating layer 212 to improve the adhesion between the base steel sheet 11 and the tension coating layer 212 by means of the intermediate layer 211.

[0044] This occurs because, when the intermediate layer 211 contains a crystalline metallic phosphate, a tension coating (which becomes the tension coating layer 212 after formation) formed on it also contains a metallic phosphate and, therefore, the affinity is high and the adhesion between the intermediate layer 211 and the tension coating layer 212 is excellent. Furthermore, as will be described later, in the case where the intermediate layer 211 is formed by immersion in a treatment liquid containing a metallic phosphate, the intermediate layer 211 can be formed on a surface of the base steel sheet 11 using a chemical reaction, and the adhesion between the intermediate layer 211 and the base steel sheet 11 can also be ensured.

[0045] When the intermediate layer 211 does not contain a phosphate Petition 870250091781, dated 08 / 10 / 2025, page 22 / 60 / 44 metallic crystalline, the above effect cannot be obtained.

[0046] The percentage of crystalline metal phosphate in the intermediate layer is preferably 80% by mass or more, and may be 100% by mass. The metal phosphate is preferably one or two or more of zinc phosphate, manganese phosphate, iron phosphate and calcium and zinc phosphate, from the point of view of adhesion.

[0047] The intermediate layer 211 may contain, like the rest in addition to metallic phosphate, an oxide or an element diffused from the base steel sheet, such as Fe or Si.

[0048] Intermediate layer 211 is formed at a different time than the tension coating formed over it, but both intermediate layer 211 and tension coating layer 212 exhibit an effect like the insulating coating 21.

[0049] When the average thickness of the intermediate layer 211 is less than 0.1 μm, the effect of improving adhesion between the base steel sheet and the insulating coating through the intermediate layer will not be sufficient. On the other hand, when the average thickness of the intermediate layer is more than 15.0 μm, the deterioration in magnetic characteristics is significant. The thickness here is the thickness of the base steel sheet 11 on the flat surface part 2. On the other hand, for the grooved part 3, the average thickness of the intermediate layer is preferably from 0.1 to 9.0 μm.

[0050] In the grooved part 3, the thickness of the intermediate layer may be reduced due to the formation of the groove, but also in the grooved part, the thickness of the intermediate layer is preferably 0.1 μm or more (remaining at a thickness of 0.1 μm or more) in both the flat surface part and the grooved part. [Tension Layer Coating]

[0051] In the grain-oriented electrical steel sheet 1 according to the present embodiment, the tension coating layer 212 is provided in Petition 870250091781, dated 08 / 10 / 2025, page 23 / 60 / 44 side to be the surface of the insulating coating 21, forming the tension coating on the surface of the intermediate layer 211.

[0052] The tension coating layer 212 is not particularly limited, provided it is used as an insulating coating of a grain-oriented electrical steel sheet, but preferably contains a metallic phosphate and silica (derived from colloidal silica of a coating liquid) such that the silica content is 20% by mass or more from the point of view of adhesion to the intermediate layer 211 (adhesion to the base steel sheet 11 by means of the intermediate layer 211). On the other hand, when the silica content of the tension coating layer 212 is more than 60% by mass, pulverization occurs and therefore it is preferable that the silica content be 60% by mass or less.

[0053] The tension coating layer 212 preferably contains a metal phosphate and silica in a total amount of 70% by mass or more. As a remainder, in addition to the metal phosphate and silica, alumina or fine ceramic particles, such as silicon nitride, may be contained.

[0054] The thickness of the tension coating layer 212 is not limited, but the average thickness of the insulating coating 21 (the intermediate layer 211 + the tension coating layer 212) is preferably from 2.0 to 15.0 μm in both the flat surface part and the grooved part. When the average thickness of the insulating coating 21 is less than 2.0 μm, sufficient coating tension cannot be obtained. Furthermore, the dissolution of phosphoric acid increases. In this case, this can cause deterioration of adhesion and corrosion resistance, and may cause peeling of the coating. On the other hand, when the thickness of the insulating coating 21 is more than 15.0 μm, a space factor decreases, so that magnetic characteristics deteriorate, or adhesion decreases, or corrosion resistance decreases due to cracking or similar. Petition 870250091781, dated 08 / 10 / 2025, page 24 / 60 / 44

[0055] The thickness of the insulating coating 21 is obtained using the following method.

[0056] In the flat surface part, a cross-section of a sample is observed with a scanning electron microscope, and the thicknesses of five or more points are measured and averaged, so that the average thickness of each can be measured. In the insulating coating 21, the thicknesses of the intermediate layer 211 and the tension coating layer 212 can be determined from a detection quantity of silica-derived silicon (the tension coating layer contains silica as described above).

[0057] The sum of the average thickness of the intermediate layer 211 and the average thickness of the tension-layer coating 212 is the average thickness of the insulating coating 21.

[0058] In the grooved section, the thickness at the position of the lower portion is measured.

[0059] In the intermediate layer 211 and in the tension coating layer 212, the mass percentage of metallic phosphate and the type of metallic phosphate can be obtained using the following method.

[0060] Similar to the method for measuring the thicknesses of the intermediate layer 211 and the stress coating layer 212, it is possible to specify the mass percentage of metal phosphate and the type of metal phosphate using a scanning electron microscope and an energy-dispersive element analyzer.

[0061] Whether the metallic phosphate in the intermediate layer 211 is a crystalline metallic phosphate can be determined by X-ray crystallography.

[0062] The silica content in the stress coating layer 212 can be measured using a scanning electron microscope and an energy dispersive elemental analyzer. <Chapa de Aço Base> Petition 870250091781, dated 08 / 10 / 2025, page 25 / 60 / 44 [Chemical Composition]

[0063] The grain-oriented electrical steel sheet 1 according to the present embodiment has a significant feature in terms of the structure of the insulating coating 21 formed on the surface of the base steel sheet 11, and the base steel sheet 11 included in the grain-oriented electrical steel sheet 1 is not limited in terms of its chemical composition. However, to obtain characteristics generally required for a grain-oriented electrical steel sheet, it is preferable to include the following components as chemical components constituting the chemical composition. In the present embodiment, the % relating to the chemical composition is % by mass, unless otherwise specified. C: 0.010% or less

[0064] Carbon (C) is an effective element for controlling the microstructure of steel sheet in stages up to the completion of the decarburization annealing stage in the manufacturing process. However, when the C content exceeds 0.010%, the magnetic characteristics of the produced grain-oriented electrical steel sheet deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, the C content is preferably 0.010% or less. The C content is more preferably 0.005% or less. The C content is preferably as low as possible, but even when the C content is reduced to less than 0.0001%, a microstructure control effect is saturated and the manufacturing cost is only increased. Therefore, the C content can be 0.0001% or more. Yes: 2.50 to 4.00%

[0065] Si (silicon) is an element that increases the electrical resistance of a grain-oriented electrical steel sheet and improves iron loss characteristics. When the Si content is less than 2.50%, it is not possible to obtain a sufficient reduction in eddy current losses. Therefore, the Petition 870250091781, of 08 / 10 / 2025, page 26 / 60 / 44 Si content is preferably 2.50% or more. The Si content is more preferably 2.70% or more and even more preferably 3.00% or more.

[0066] On the other hand, when the Si content exceeds 4.00%, the grain-oriented electrical steel sheet becomes brittle and the passability deteriorates significantly. In addition, the workability of the grain-oriented electrical steel sheet deteriorates and the steel sheet may break during rolling. Therefore, the Si content is preferably set to 4.00% or less. The Si content is more preferably 3.80% or less and even more preferably 3.70% or less. Mn: 0.01 to 0.50%

[0067] Mn (manganese) is an element that binds to S in a manufacturing process to form MnS. This precipitate acts as an inhibitor (normal grain growth inhibitor) and causes secondary recrystallization in steel. Mn is also an element that enhances the hot workability of steel. When the Mn content is less than 0.01%, the above effect cannot be sufficiently obtained. Therefore, the Mn content is preferably 0.01% or more. The Mn content is more preferably 0.02% or more.

[0068] On the other hand, when the Mn content exceeds 0.50%, secondary recrystallization does not occur and the magnetic characteristics of the steel deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the embodiment, the Mn content is preferably 0.50% or less. The Mn content is more preferably 0.20% or less and even more preferably 0.10% or less. N: 0.010% or less

[0069] N (nitrogen) is an element that binds to Al in the manufacturing process to form AlN, which acts as an inhibitor. However, when the N content exceeds 0.010%, the inhibitor remains excessively in the base steel sheet of the grain-oriented electrical steel sheet, and the Petition 870250091781, dated 08 / 10 / 2025, page 27 / 60 / 44 magnetic characteristics deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the embodiment, the N content is preferably 0.010% or less. The N content is more preferably 0.008% or less.

[0070] On the other hand, the lower limit value of the N content is not particularly restricted, but even when the N content is reduced to less than 0.001%, the manufacturing cost is only increased. Therefore, the N content can be 0.001% or more. Al sol.: 0.020% or less

[0071] Al sol. (acid-soluble aluminum) is an element that is bonded to N in the manufacturing process of grain-oriented electrical steel sheet to form AlN, which acts as an inhibitor. However, when the Al sol. content in the base steel sheet exceeds 0.020%, the inhibitor remains excessively in the base steel sheet, so that the magnetic characteristics deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the embodiment, the Al sol. content is preferably 0.020% or less. The Al sol. content is more preferably 0.010% or less and even more preferably less than 0.001%. The lower limit value of the Al sol. content is not particularly restricted, and even when the content is reduced to less than 0.0001%, the manufacturing cost is only increased. Therefore, the Al sol. content can be 0.0001% or more. S: 0.010% or less

[0072] Sulfur (S) is an element that binds to Mn in the manufacturing process to form MnS, which acts as an inhibitor. However, when the S content exceeds 0.010%, the remaining inhibitor causes the magnetic characteristics to deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, the S content is preferably 0.010% or less. The S content in the steel sheet Petition 870250091781, dated 08 / 10 / 2025, page 28 / 60 / 44. The sulfur content of grain-oriented electrical steel is preferably as low as possible. For example, the sulfur content is less than 0.001%. However, even if the sulfur content in the base steel sheet of grain-oriented electrical steel sheet is reduced to less than 0.0001%, the manufacturing cost is only increased. Therefore, the sulfur content in the base steel sheet of grain-oriented electrical steel sheet can be 0.0001% or more. Remaining: Iron and impurities

[0073] The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment may contain the elements described above, with the remainder being Fe and impurities. However, the base steel sheet may also contain Sn, Cu, Se, and Sb in the following ranges in order to improve magnetic and similar characteristics. Furthermore, for example, even when the base steel sheet contains any one or more selected from W, Nb, Ti, Ni, Co, V, Cr, and Mo in a total amount of 1.0% or less as elements other than these elements, the effect of the grain-oriented electrical steel sheet according to the present embodiment is not impaired.

[0074] Here, an impurity is an element that is a contaminant derived from ore or scrap as a raw material, a manufacturing environment or similar when the base steel sheet is manufactured industrially, and means an element that may be included in a content that does not adversely affect the effect of the grain-oriented electrical steel sheet according to the embodiment. Sn: 0 to 0.50%

[0075] Sn (tin) is an element that contributes to the improvement in magnetic characteristics through the control of the primary recrystallization structure. In order to obtain the effect of improving magnetic characteristics, the Sn content is preferably 0.01% or more. The Sn content is more preferably 0.02% or more and even more preferably 0.03% or more. Petition 870250091781, dated 08 / 10 / 2025, p. 29 / 60 / 44

[0076] On the other hand, when the Sn content exceeds 0.50%, secondary recrystallization is unstable and the magnetic characteristics deteriorate. Therefore, the Sn content is preferably 0.50% or less. The Sn content is more preferably 0.30% or less and even more preferably 0.10% or less. Cu: 0 to 0.50%

[0077] Cu (copper) is an element that contributes to an increase in the occupation of the Goss orientation in a secondary recrystallization structure. To obtain the above effect, the Cu content is preferably 0.01% or more. The Cu content is more preferably 0.02% or more and even more preferably 0.03% or more.

[0078] On the other hand, when the Cu content exceeds 0.50%, the steel sheet becomes weakened during hot rolling. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the embodiment, the Cu content is preferably 0.50% or less. The Cu content is more preferably 0.30% or less and even more preferably 0.10% or less. If: 0 to 0.020%

[0079] Se (selenium) is an element that has an effect of improving magnetic characteristics. When Se is contained, the Se content is preferably 0.001% or more, so that Se favorably exhibits the effect of improving magnetic characteristics. The Se content is more preferably 0.003% or more and even more preferably 0.006% or more.

[0080] On the other hand, when the Se content exceeds 0.020%, the adhesion of a coating deteriorates. Therefore, the Se content is preferably 0.020% or less. The Se content is more preferably 0.015% or less and even more preferably 0.010% or less. Sb: 0 to 0.50% Petition 870250091781, dated 08 / 10 / 2025, p. 30 / 60 / 44

[0081] Sb (antimony) is an element that has an effect of improving magnetic characteristics. When Sb is present, the Sb content is preferably 0.005% or more, so that Sb favorably exhibits the effect of improving magnetic characteristics. The Sb content is more preferably 0.01% or more and even more preferably 0.02% or more.

[0082] On the other hand, when the Sb content exceeds 0.50%, the adhesion of a coating deteriorates significantly. Therefore, the Sb content is preferably 0.50% or less. The Sb content is more preferably 0.30% or less and even more preferably 0.10% or less.

[0083] As described above, for example, the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment contains the elements described above, with the remainder being Fe and impurities.

[0084] The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment can be measured using a known ICP emission spectrometry. Note that, at the time of measurement, in the case where an insulating coating is formed on a surface, the measurement is performed after the insulating coating has been peeled off. As a peeling method, it is possible to peel off the insulating coating by immersing the base steel sheet with the insulating coating in a high-concentration alkaline solution (e.g., a 30% sodium hydroxide solution heated to 85°C) for 20 minutes or more. It is possible to visually determine whether or not the insulating coating has been peeled off. In the case of a small sample, the insulating coating can be peeled off by grinding the surface. [Grooved Part]

[0085] The base steel plate 11 has a flat surface part 2 and a grooved part 3 on a rolled surface of the same. The control of the magnetic domain can be achieved by the periodic formation of grooves. Petition 870250091781, dated 08 / 10 / 2025, page 31 / 60 / 44 linear (grooved parts) in a direction that crosses the rolling direction.

[0086] In the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, the depth D of the grooved part is from 10 to 30 μm, and the width W of the grooved part 3 is from 10 to 200 μm.

[0087] When the depth of the grooved part is less than 10 μm, the magnetic domain control effect becomes poor. On the other hand, when the depth is more than 30 μm, the decrease in the B8 value of the magnetic flux density becomes too large. When the width of the grooved part is less than 10 μm, the magnetic domain control effect becomes poor. On the other hand, when the width W is more than 200 μm, the decrease in the B8 value of the magnetic flux density becomes too large.

[0088] Furthermore, it is preferable that a plurality of grooved parts be periodically present in the rolling direction, and that the interval between adjacent grooved parts in the rolling direction be from 1.0 to 20.0 mm. The interval between grooved parts is a distance from the center of the width of the grooved part to the center of the width of the adjacent grooved part.

[0089] The shape of the grooved part is not limited and, for example, its cross-section has a substantially rectangular shape or a substantially triangular shape. In addition, the cross-section may have an arc shape or something similar, forming part of a circle.

[0090] In the present embodiment, the direction crossing the rolling direction is a direction of 45 to 135° relative to the rolling direction (90±45° relative to the rolling direction). As the magnetic domain control effect becomes greater as the angle approaches 90° relative to the rolling direction, the angle can be set to 70 to 110° relative to the rolling direction. Petition 870250091781, dated 08 / 10 / 2025, page 32 / 60 / 44

[0091] In the grain-oriented electrical steel sheet according to the present embodiment, 60% or more of the surface area of ​​the grooved part 3 is covered with an insulating coating (the intermediate layer 211 and the tension coating layer 212) (the coverage is 60% or more).

[0092] When the coverage is less than 60%, the adhesion of the tension coating after stress-relief annealing deteriorates, so that the tension coating is partially peeled off or has low corrosion resistance.

[0093] In the grain-oriented electrical steel sheet according to the present embodiment, as will be described later, since the insulating coating is formed under specific treatment conditions, the adhesion of the insulating coating is high and the coverage is high even in the grooved part.

[0094] Conventionally, after the formation of a grooved section, a stripped insulating coating on the grooved section is formed again, but in this case, it is not easy to form an intermediate layer on the grooved section. This is because if the intermediate layer has to be formed again after the formation of the tension coating layer, there is a problem, as the tension coating, different from that on the grooved section, is dissolved when the intermediate layer is immersed in a treatment liquid to form the intermediate layer. Therefore, in such a method, it is not easy to form the intermediate layer and the tension coating layer on the grooved section.In the grain-oriented electrical steel sheet according to the present embodiment, the intermediate layer is formed under specific conditions at the time of manufacture of the grain-oriented electrical steel sheet, and the grooved part is formed by machining to prevent peeling of the intermediate layer, even in the grooved part (inside the groove), so that the coverage of the insulating coating with the intermediate layer and the tension coating layer is 60% or more, even in the grooved part. Petition 870250091781, dated 08 / 10 / 2025, page 33 / 60 / 44

[0095] The depth and width of the grooved part are obtained using the following method.

[0096] A steel sheet is cut into squares of a few millimeters to include the vicinity of a portion where a groove is visually determined to be formed, and ion milling (CP processing) is performed to remove micro-defects in shape, such as sagging and cracks in a cross-section, and then a cross-section parallel to a rolling direction and a sheet thickness direction of the steel sheet is observed with a scanning electron microscope at a magnification of 1000 times, and one or a plurality of recessed parts formed at predetermined intervals are determined to be grooves.In the observed cross-section, a portion that has the longest (deepest) length of a perpendicular line drawn vertically from an extension line of the surface of the base steel plate in the recessed part is determined as the bottom of the groove, and a direct distance connecting one end portion and the other end portion of the recessed part on the surface extension line is determined as the width. Here, the end portion of the recessed part indicates a position where the recessed part begins to be recessed with a gradient of 30° or more relative to the surface extension line of the flat surface part.

[0097] Three or more grooved parts are randomly observed as described above, and the averages of the respective measurement values ​​are defined as the depth and width of the grooved part.

[0098] The insulating coating coverage on the grooved part is obtained using the following method.

[0099] Similar to the method of observing the grooved part, after the ionic milling process is carried out, a cross-section parallel to the rolling direction and the sheet thickness direction of the steel sheet is observed with a scanning electron microscope. Petition 870250091781, dated 08 / 10 / 2025, page 34 / 60 / 44, with a 1000x magnification, and the proportion of the portion not covered with the insulating coating on the surface (lateral surface and bottom surface) in the grooved part is calculated. However, since the effect of the insulating coating cannot be obtained in a portion where the insulating coating is less than 1.0 μm, it is determined that the insulating coating is not formed.

[00100] Also in the coverage calculation, three or more grooved parts are observed, and an average value of the respective measurement values ​​is adopted. <Método de Fabricação>

[00101] According to a manufacturing method that satisfies the manufacturing conditions described below, the grain-oriented electrical steel sheet according to the present embodiment can be suitably manufactured. Note that, naturally, the grain-oriented electrical steel sheet according to the present embodiment is not particularly limited in its manufacturing method. That is, a grain-oriented electrical steel sheet having the configuration described above is considered to be the grain-oriented electrical steel sheet according to the present embodiment, regardless of its manufacturing conditions.

[00102] Grain-oriented electrical steel sheet according to the present embodiment includes: (I) a hot rolling step for hot rolling a piece of steel having a predetermined chemical composition to obtain a hot-rolled sheet; (II) a hot-rolled sheet annealing step to anneal the hot-rolled sheet; (III) a cold rolling stage to cold roll the hot-rolled sheet after the annealing stage of the hot-rolled sheet to obtain a cold-rolled sheet; (IV) a decarburization annealing step to carry out Petition 870250091781, dated 08 / 10 / 2025, page 35 / 60 / 44 regarding decarburization annealing on cold-rolled sheet metal; (V) a finishing annealing step to apply an annealing separator containing 10 to 100% by mass of AhOt to the cold-rolled sheet (steel sheet) after the decarburization annealing step, dry the annealing separator and then perform the finishing annealing; (VI) an annealing separator removal step to remove excess annealing separator from the steel sheet after the finishing annealing step; (VII) a light pickling step to pickle the steel sheet after the annealing separator removal step with one or two or more inorganic acids selected from sulfuric acid, phosphoric acid and hydrochloric acid with a concentration of 0.1 to 10% by mass and a normal or higher temperature for 1 to 20 seconds; (VIII) an intermediate layer formation step to immerse the steel sheet after the light pickling step in a treatment liquid with a liquid temperature of 30 to 95°C, and having a phosphate concentration of 1.0 to 15.0% by mass and a pH of 1.5 to 6.0 for 5 to 90 seconds, wash and remove the treatment liquid with water and then dry the steel sheet; (IX) a groove forming step to form a grooved portion extending in a direction of 45 to 135° relative to a rolling direction in the steel sheet after the intermediate layer forming step by machining; and (X) a tension coating layer forming step to apply, to the steel sheet after the groove forming step, a coating liquid containing a metallic phosphate and colloidal silica such that the colloidal silica is contained in an amount of 30 to 150 parts by mass relative to 100 parts by mass of the metallic phosphate, dry Petition 870250091781, dated 08 / 10 / 2025, page 36 / 60 / 44 the coating liquid and then hold the steel sheet at a sheet temperature of 700 to 950°C for 10 to 90 seconds.

[00103] In addition, the method for manufacturing grain-oriented electrical steel sheet according to the present embodiment may include further: (XI) a nitriding treatment step to subject the cold-rolled sheet to a nitriding treatment between the decarburization annealing step and the finishing annealing step.

[00104] Among them, the manufacture of the grain-oriented electrical steel sheet according to the present embodiment is distinguished by the steps (method for forming insulating coating) from (V) the finishing annealing step to (X) the step of forming the coating layer by tension mainly related to the formation of the insulating coating, and other steps or conditions not described may adopt known conditions.

[00105] Hereafter, the respective steps will be described. <Etapa de Laminação a Quente>

[00106] In the hot rolling stage, a piece of steel having a predetermined chemical composition, such as a plate, is heated and then hot rolled to obtain a hot-rolled sheet. The heating temperature of the steel piece is preferably set in a range of 1100 to 1450°C. The heating temperature is more preferably 1300 to 1400°C.

[00107] The chemical composition of the steel part can be altered according to the chemical composition of a grain-oriented electrical steel sheet to be finally obtained, but examples of this include a chemical composition containing, in % by mass, C: 0.01 to 0.20%, Si: 2.50 to 4.00%, Al sol.: 0.01 to 0.040%, Mn: 0.01 to 0.50%, N: 0.020% or less, S: 0.005 to 0.040%, Cu: 0 to 0.50%, Sn: 0 to 0.50%, Se: 0 to 0.020%, and Sb: 0 to 0.50%, with the remainder being Fe and impurities.

[00108] Hot rolling conditions are not particularly Petition 870250091781, dated 08 / 10 / 2025, page 37 / 60 / 44 limited, and are adjusted accordingly to the required characteristics. The sheet thickness of the hot-rolled sheet is preferably, for example, in a range of 2.0 mm or more and 3.0 mm or less. <Etapa de Recozimento de Chapa Laminada a Quente>

[00109] The hot-rolled sheet annealing step is an annealing step of hot-rolled sheet manufactured through the hot rolling step. By performing such annealing treatment, recrystallization occurs in the metallographic structure and favorable magnetic characteristics can preferably be achieved.

[00110] When annealing hot-rolled sheet metal is performed, the hot-rolled sheet metal manufactured through the hot rolling stage can be annealed according to a known method. The means for heating the hot-rolled sheet metal at the time of annealing are not particularly limited, and a known heating method can be adopted. The annealing conditions are not particularly limited. For example, hot-rolled sheet metal can be annealed in a temperature range of 900 to 1200°C for 10 seconds to 5 minutes. <Etapa de Laminação a Frio>

[00111] In the cold rolling stage, the hot-rolled sheet after the annealing stage is subjected to cold rolling to obtain a cold-rolled sheet. Cold rolling can be performed once or, before the final pass of the cold rolling stage, cold rolling can be interrupted and at least one or two intermediate annealing passes can be performed to perform a plurality of cold rolling passes to interpose the intermediate annealing.

[00112] When intermediate annealing is performed, it is preferable to hold the hot-rolled sheet at a temperature of 1,000 to 1,200°C for 5 to 180 seconds. The annealing atmosphere is not particularly Petition 870250091781, dated 08 / 10 / 2025, page 38 / 60 / 44 limited. The number of times the intermediate annealing is preferably 3 or less considering the manufacturing cost.

[00113] In addition, prior to the cold rolling stage, the surface of the hot-rolled sheet may be subjected to pickling.

[00114] In the cold rolling stage according to the present embodiment, the hot-rolled sheet can be subjected to cold rolling according to a known method to obtain a cold-rolled sheet. For example, the final rolling reduction can be in a range of 80 to 95%. When the final rolling reduction is 80% or more, a Goss core in which the orientation {110} <001> A high degree of development in one rolling direction can be achieved, which is preferable. On the other hand, when the final rolling reduction exceeds 95%, there is a high possibility that secondary recrystallization will be unstable in the subsequent finishing annealing step, which is not preferable.

[00115] Final rolling reduction is a cumulative cold rolling reduction and, when intermediate annealing is performed, final rolling reduction is a cumulative cold rolling reduction after final intermediate annealing. <Etapa de Recozimento por Descarburação>

[00116] In the decarburization annealing stage, the cold-rolled sheet obtained is subjected to decarburization annealing. In decarburization annealing, the conditions for decarburization annealing are not limited, provided that the cold-rolled sheet can be recrystallized primarily and the C that adversely affects the magnetic characteristics can be removed from the steel sheet, but, for example, the cold-rolled sheet is held at an annealing temperature of 800 to 900°C for 10 to 600 seconds with a degree of oxidation (PH2O / PH2) of 0.3 to 0.6 in an annealing atmosphere (furnace atmosphere). <Etapa de Tratamento por Nitretação> Petition 870250091781, dated 08 / 10 / 2025, pages 39 / 60 / 44

[00117] A nitriding treatment can be performed between the decarburization annealing step and the finishing annealing step, which will be described later.

[00118] In the nitriding treatment stage, for example, the steel sheet subjected to decarburization annealing is maintained at approximately 700 to 850°C in a nitriding treatment atmosphere (an atmosphere containing a gas with nitriding capacity, such as hydrogen, nitrogen, or ammonia) to perform the nitriding treatment. When AlN is used as an inhibitor, the nitrogen concentration of the steel sheet is preferably set to 40 ppm or more through the nitriding treatment. On the other hand, when the nitrogen concentration of the steel sheet exceeds 1000 ppm, AlN is excessively present in the steel sheet, even after the completion of secondary recrystallization in the finishing annealing. Such AlN causes iron loss deterioration. Therefore, the nitrogen concentration of the steel sheet after nitriding treatment is preferably set to 1000 ppm or less. <Etapa de Recozimento de Acabamento>

[00119] In the finishing annealing stage, an annealing separator containing 10 to 100% by mass of AFol· is applied to the cold-rolled sheet that has undergone decarburization annealing or subsequently nitrided and dried, and then the finishing annealing is performed.

[00120] In a conventional manufacturing method for a grain-oriented electrical steel sheet, a forsterite film is formed on the surface of a steel sheet (cold-rolled sheet) by applying an annealing separator containing mainly MgO and performing the finishing annealing. In contrast, in the method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment, an annealing separator containing Al2O3 is used so as not to form a Petition 870250091781, dated 08 / 10 / 2025, page 40 / 60 / 44 forsterite film.

[00121] On the other hand, the percentage of Al2O3 can be 100% by mass, but, in the method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment, the annealing separator preferably contains MgO from the point of view of preventing AFOt from burning on a sheet surface. The MgO can be 0%, but the percentage of MgO is preferably set to 5% by mass or more when the above effect is obtained. When MgO is contained, the percentage of MgO is 90% by mass or less to ensure 10% by mass or more of AFOt. The percentage of MgO is preferably 50% by mass or less. AFOt and MgO can have more than 50% by mass in total in terms of solid content relative to the annealing separator.

[00122] Furthermore, in the method for manufacturing grain-oriented electrical steel sheet according to the present embodiment, the annealing separator may also contain a chloride. When the annealing separator contains a chloride, a difficult-to-form forsterite film formation effect can be obtained. The chloride content is not particularly limited and can be 0%, but is preferably from 0.5 to 10% by mass when the above effect is to be obtained. As chlorides, for example, bismuth chloride, calcium chloride, cobalt chloride, iron chloride and nickel chloride are effective.

[00123] Finish annealing conditions are not limited, but, for example, a condition of holding the steel sheet at a temperature of 1150 to 1250°C for 10 to 60 hours may be adopted. [Annealing Separator Removal Step]

[00124] In the annealing separator removal stage, excess annealing separator is removed from the steel sheet after the finishing annealing stage. For example, excess annealing separator can be removed by washing with water. Petition 870250091781, dated 08 / 10 / 2025, page 41 / 60 / 44 [Light Pickling Stage]

[00125] In the light pickling stage, the steel sheet after the removal of the annealing separator is pickled for 1 to 20 seconds with one or two or more inorganic acids selected from sulfuric acid, phosphoric acid and hydrochloric acid having a concentration of 0.1 to 10% by mass and a normal temperature (20°C) or higher. As a result, it is possible to obtain an effect in which a residue of the annealing separator attached to the surface of the sheet and a residue of forsterite are removed.

[00126] If the pickling conditions are not preferable, for example, if the concentration of the inorganic acid is low or the temperature of the inorganic acid is low, and the annealing separator residue or the forsterite residue is not removed, a problem arises, as the phosphate concentration to form the intermediate layer changes over time, and the intermediate layer is not sufficiently formed. [Intermediate Layer Formation Stage]

[00127] In the intermediate layer formation stage, the steel sheet after the light pickling stage is immersed in a treatment liquid with a liquid temperature of 30 to 95°C, a phosphate concentration of 1.0 to 15.0% by mass and a pH of 1.5 to 6.0 for 5 to 90 seconds. The treatment liquid is then rinsed with water and removed, and the steel sheet is dried. As a result, an intermediate layer containing a crystalline metallic phosphate and with a thickness of 0.1 to 15.0 μm is formed.

[00128] When the liquid temperature is less than 30°C or the immersion time is less than five seconds, it will not be possible to obtain an intermediate layer of sufficient thickness. On the other hand, when the liquid temperature is above 95°C or the immersion time is greater than 90 seconds, the thickness of the intermediate layer is excessive.

[00129] When the phosphate concentration (the concentration of metallic phosphate) of the treatment liquid is less than 1.0% by mass, the formation Petition 870250091781, dated 08 / 10 / 2025, page 42 / 60 / 44, states that the intermediate layer is delayed. On the other hand, when the phosphate concentration is more than 15.0% by mass, the intermediate layer becomes too thick. Therefore, the phosphate concentration of the treatment liquid is defined as 1.0 to 15.0% by mass. The metallic phosphate contained in the treatment liquid is preferably one or two or more of zinc phosphate, manganese phosphate, and calcium zinc phosphate.

[00130] When the pH of the treatment liquid is less than 1.5, the intermediate layer becomes too thick. When the pH is greater than 6.0, the formation of the intermediate layer is delayed.

[00131] The treatment liquid may also contain a pH adjusting agent or a sludge inhibitor, such as a chelate, as needed. [Groove Formation Stage]

[00132] In the groove forming stage, a grooved portion extending in a direction of 45 to 135° relative to a rolling direction is formed in the steel sheet after the intermediate layer forming stage through machining.

[00133] For the formation of a groove (grooved part) for controlling the magnetic domain of a grain-oriented electrical steel sheet, the application of a laser or similar is also known. However, when laser irradiation is performed, an intermediate layer within the groove disappears. Therefore, in the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment, laser irradiation is not performed, and the groove formation is performed by machining using a blade or similar.

[00134] In this case, the groove depth is 10 to 30 μm and the groove width is 10 to 200 μm. When the groove depth is less than 10 μm, it is not possible to obtain a sufficient iron loss reduction effect, which is not preferable. When the groove depth is more than 30 μm, the residual coating ratio decreases, or the decrease in Petition 870250091781, dated 08 / 10 / 2025, page 43 / 60 / 44, the B8 value of the magnetic flux density becomes too large, which is not preferable. Therefore, the groove depth is 10 to 30 μm. When the width of the grooved part is less than 10 μm, the effect of controlling the magnetic domain becomes poor. On the other hand, when the width W is more than 200 μm, the decrease in the B8 value of the magnetic flux density becomes too large. [Stretching Coating Layer Formation Stage]

[00135] In the tension coating stage, a coating liquid containing a metallic phosphate and colloidal silica, such that the colloidal silica is contained in an amount of 30 to 150 parts by mass relative to 100 parts by mass of the metallic phosphate, is applied to the steel sheet after the groove formation stage and dried, and then the steel sheet is held (baked) for 10 to 90 seconds at a sheet temperature of 700 to 950°C. Thus, a tension coating is formed. The layer formed by the tension coating (tension coating layer) and the intermediate layer serve as an insulating coating.

[00136] When the plate temperature is below 700°C, the voltage is low and the magnetic characteristics are poor. Therefore, the plate temperature is preferably set to 700°C or higher. On the other hand, when the plate temperature is above 950°C, the stiffness of the steel plate decreases and the steel plate is easily deformed. In this case, the steel plate may become distorted due to transfer or something similar, resulting in poor magnetic characteristics. Therefore, the plate temperature is preferably set to 950°C or lower.

[00137] When the retention time is less than 10 seconds, the dissolution property is poor. Therefore, the retention time is set to 10 seconds or more. On the other hand, when the retention time is more than 90 seconds, productivity is poor. Therefore, the retention time is Petition 870250091781, dated 08 / 10 / 2025, page 44 / 60 / 44 preferably 90 seconds or less.

[00138] The coating liquid contains a metallic phosphate and colloidal silica, such that the colloidal silica is contained in an amount of 30 to 150 parts by mass relative to 100 parts by mass of the metallic phosphate. The total metallic phosphate and colloidal silica may be more than 50% by mass in terms of solid content relative to the coating liquid. As metallic phosphate, for example, one or a mixture of two or more selected from aluminum phosphate, zinc phosphate, magnesium phosphate, nickel phosphate, copper phosphate, lithium phosphate and cobalt phosphate may be used.

[00139] The coating liquid may contain vanadium, tungsten, molybdenum, zirconium and similar elements as additional elements.

[00140] Like colloidal silica, either type S or type C colloidal silica can be used. Type S colloidal silica means colloidal silica in which the silica solution is alkaline, and type C colloidal silica means colloidal silica in which the silica particle surface is subjected to an aluminum treatment, and the silica solution is alkaline to neutral. Type S colloidal silica is widely used and has a relatively low price, but care must be taken because type S colloidal silica can aggregate and precipitate when mixed with an acidic metal phosphate solution. Type C colloidal silica is stable even when mixed with a metal phosphate solution, and there is no possibility of precipitation, but type C colloidal silica is relatively expensive because of the number of treatment steps required. It is preferable to select and use them according to the stability of a coating liquid to be prepared. Examples

[00141] A plate containing, in mass %, C: 0.08%, Si: 3.31%, Al sol.: 0.028%, N: 0.008%, Mn: 0.07% and S: less than 0.0005%, with the remainder being Fe and impurities, was melted. Petition 870250091781, dated 08 / 10 / 2025, p. 45 / 60 / 44

[00142] This plate was heated to 1350°C and then hot-rolled to form a hot-rolled plate with a plate thickness of 2.2 mm.

[00143] This hot-rolled sheet was annealed (hot-rolled sheet annealing) at 1100°C for 10 seconds and then cold-rolled until the sheet thickness became 0.22 mm to obtain a cold-rolled sheet.

[00144] This cold-rolled plate was subjected to decarburization annealing at 830°C for 90 seconds in an atmosphere with (PH2O / PH2) of 0.4.

[00145] Subsequently, except for No. 108, an annealing separator containing 50% by mass of AhO3, 46.5% by mass of MgO and 3.5% by mass of BiCh as a bismuth chloride was applied to the cold-rolled and dried sheet, and then finish annealing was carried out at 1200°C for 20 hours. For No. 108, an annealing separator containing only Al2O3 (100% by mass) was applied to the cold-rolled and dried sheet, and then finish annealing was carried out at 1200°C for 20 hours.

[00146] The steel sheet after the finishing annealing step was washed with water to remove excess annealing separator, and subsequently subjected to light pickling under the conditions of Table 2. No forsterite film formed on the surface of the sheet after light pickling.

[00147] An intermediate layer was formed on the steel plate under the conditions shown in Table 1. The average thickness of the intermediate layer was as shown in Table 1. As a result of X-ray crystallography, all metal phosphates were crystalline metal phosphates, and the proportion of crystalline metal phosphates in the intermediate layer was 80% by mass or more. Petition 870250091781, dated 08 / 10 / 2025, page 46 / 60 / 44 [Table 1] Intermediate Layer Average Thickness (pm) 3.5 10.5 12.8 cd i—1 7.4 cd 0.4 6.8 Γ9Ϊ 9.4 0.6 10.8 0.3 Metallic Phosphate Detected at 5% by mass or more Manganese Phosphate Manganese Phosphate + Iron Phosphate Manganese Phosphate + Iron Phosphate Zinc Phosphate Calcium and Zinc Phosphate Zinc Phosphate Iron Phosphate Manganese Phosphate Manganese Phosphate Zinc Phosphate Zinc Phosphate Zinc Phosphate Zinc Phosphate Treatment Conditions Time (sec.) cd i—1 oo OO o cd cd 180 ml Temperature (°C) o 00 00 ooooo 00 20 96 Treatment Liquid pH OO I—1 Cd cd cd 3.8 3.4 1.4 oI 4.8 2.5 cd Cd i—1 cd cd Phosphate Concentration (% by mass) c4 3.2 2.8 3.7 i—1 OO I—1 i—1 ol 00*1 5.4 3.6 Cd Type of Phosphate Metallic Manganese Phosphate Iron and Manganese Phosphate Iron and Manganese Phosphate Zinc Phosphate Calcium Phosphate Zinc Phosphate Iron Phosphate Manganese Phosphate Manganese Phosphate Zinc Phosphate Zinc Phosphate Zinc Phosphate Zinc Phosphate Intermediate Layer No. i—1 rd «n 00 O' i—1 i—1 cd i—1 i—1. Petition 870250091781, dated 08 / 10 / 2025, page 47 / 60 / 44

[00148] A grooved section was formed using a blade on the steel sheet that has the intermediate layer. Except for Nos. 111 and 112, a grooved section with a width of 60 μm and a depth of 15 μm in a direction of 75° relative to the rolling direction was formed in a pitch of 5.0 mm in the rolling direction. For Nos. 111 and 112, a grooved section with a width of 70 μm and a depth of 20 μm was formed in a pitch of 6.0 mm in the rolling direction in a direction that crosses the rolling direction at 82°.

[00149] The steel sheet after groove formation was cut into a plurality of pieces as needed, a coating liquid containing a metallic phosphate and colloidal silica shown in Table 2 was applied to each steel sheet, and the steel sheet was baked in a drying oven for the time shown in Table 2 until the sheet temperature in Table 2 was reached, thus forming a tension coating on the surface. When vanadium was contained in the coating liquid, vanadium was added as an oxygenated acid (V2O4) in the molar ratio shown in Table 2. During formation, the thickness of the tension coating layer was altered by changing the amount of coating liquid applied. Some of the coating liquids contained alumina or silicon nitride as the residue.

[00150] Consequently, samples (grain-oriented electrical steel sheets) nos. 101 to 122 were manufactured.

[00151] For these steel sheets, the thicknesses of the flat surface and grooved portions of the intermediate layer and the average thickness of the insulating coating were obtained using the method described above. In addition, the coverage of the insulating coating on the grooved portion was measured. Table 2 shows the results. Petition 870250091781, dated 08 / 10 / 2025, page 48 / 60 / 44 [Table 2] Insulating Coating is g 11 M 3 I 6.3 6Á 3.8 4.7 1—1 6Á 5.3 4.2 4.7 2.5 2.5 °°e 1—1 Average Thickness of the Flat Surface Part I r4 1—1 1—1 oT O r4 1—1 1—1 oT 1—1 Coverage of the Grooved Part (% by area) i—l 00 0 0 0 O 1—1 0 1—1 0 0 0 §1 Intermediate Layer Average Thickness of the Grooved Part -da I i—lo' OC (N 1—1 o' 0 0 0 Thickness of the Flat Surface Part I 1—1 OC 1—1 (N 1—1 1—1 OC 1—1 (N 1—1 (N 1—1 (N 1—1 r4 à o Silica Content (% by mass) 00 í7> í7> í7> í7> Stress Coating Formation Conditions Treatment Conditions Time (sec·) o 0 (N 1—1 0 0 0 0 O 0 OO 0 Temperature (°C) o 00 0 O 00 00 00 00 00 0 OO 00 Treatment Liquid Colloidal Silica (parts by mass) o 0 0 00 0 0 0 0 00 00 00 00 00 0 Phosphate (100 parts by mass) Aluminum Phosphate Aluminum / Zinc Phosphate Aluminum / Manganese Phosphate Aluminum / Vanadium Phosphate Aluminum / Zinc PhosphateAluminum / Lithium Phosphate Aluminum / Barium Phosphate Aluminum / Potassium Phosphate Aluminum / Potassium Phosphate Aluminum / Potassium Phosphate Aluminum / Zinc Phosphate Intermediate Layer No. i—l (N 1—1 (N 1I Light Pickling Conditions Pickling Time (sec) i—l 1—1 C4 C4 1—1 1—1 1—1 1—1 1—1 1—1 1—1 Inorganic Acid Temperature (C) 00 00 0 0 O 00 0 00 00 00 O Concentration (% by mass) i—l OC OC 00 θ' θ' 1—1 1—1 OC 1—1 r4 0 1—1 1—1 O Λ H H2SO4 H2SO4 H3PO4 H3PO4 õ s õ s H2SO4 H2SO4 H2SO4 H2SO4 H2SO4 H2SO4 H3PO4 Sample No. 1—1 1—1 0 1—1 1—1 1—1 1—1 1—1 1—1 00 1—1 1—1 1—1 1—1 (N 1—1 1—1 Petition 870250091781, dated 08 / 10 / 2025, pages 49 / 60 / 44 i—1 0.6 i—1 i—1 0.4 2.4 0.2 3.6 3.6 00 18.5 ¢11 r4 12.9 2.4 12.6 12.6 45 10 30 20 10 30 45 45 i—1 0.3 0.8 0.0 i—1 0.0 i—1 i—1 0.4 6.8 Γ9Ϊ 9.4 0.6 10.8 0.3 10.5 10.5 44 44 44 44 00 00 ο 0 0 0 0 0 0 0 0 850 850 850 850 850 850 850 850 850 Ο 0 0 00 00 00 00 0 0 Aluminum / Zinc Phosphate Aluminum / Zinc Phosphate Aluminum / Zinc Phosphate Aluminum / Potassium Phosphate Aluminum / Potassium Phosphate Aluminum / Potassium Phosphate Aluminum / Potassium Phosphate Aluminum Phosphate r-ι 001 CM 10 11 12 13 (N (N i—1 i—1 i—1 i—1 i—1 i—1 C4 30 ο Ο OOO 0 OO 0 i—1 2.8 3.5 i—1 i—1 i—1 13 oc H3PO4 H3PO4 H3PO4 H2SO4 H2SO4 H2SO4 H2SO4 H2SO4 H2SO4 114 115 116 117 OO i—1 119 120 121 122 Petition 870250091781, dated 08 / 10 / 2025, pages 50 / 60 / 44

[00152] As a result of obtaining the chemical composition of the base steel sheet according to the method above, C: 0.001%, Si: 3.31%, Al sol.: less than 0.001%, N: 0.001%, Mn: 0.07% and S: less than 0.0005% were contained, and the remainder was Fe and impurities.

[00153] For these steel plates, the adhesion, coating tension, corrosion resistance, dissolution properties, and magnetic characteristics of an insulating coating were obtained using methods that will be described later. The results of these are shown in Table 3. [Adhesion]

[00154] Coating adhesion was evaluated by the degree of peeling (area ratio) of the coating on the entire sample, including the grooved part and the flat surface part, after a bending adhesion test performed in which a sample with a width of 30 mm and a length of 300 mm was removed from the steel plate, the sample was subjected to stress-relief annealing at 850°C for 2 hours in a nitrogen stream and then rolled onto a 10 mm cylinder and unwound.

[00155] The evaluation criteria were as follows and, in the case of A or B, it was determined that the coating adhesion was excellent.

[00156] A: Peeling area ratio of 0 to 0.5% B: Peeling area ratio of more than 0.5% and 5.0% or less C: Peeling area ratio of more than 5.0% and 20% or less D: Peeling area ratio of more than 20% and 50% or less E: Peeling area ratio greater than 50% [Coating Stress]

[00157] The coating stress was calculated by collecting a sample from a steel plate and counting backward from a state of Petition 870250091781, dated 08 / 10 / 2025, page 51 / 60 / 44 bending when an insulating coating on a sample surface was peeled off.

[00158] When the coating stress obtained was 4.0 MPa or more, it was determined that the coating stress was excellent. [Corrosion Resistance]

[00159] According to a salt spray test from JIS Z2371:2015, a 5% aqueous NaCl solution was naturally poured onto a sample for seven hours in an atmosphere of 35°C.

[00160] Subsequently, an area of ​​rust was assessed at 10 points.

[00161] The evaluation criteria were as follows, and a score of 5 or more (5 to 10) was determined to have excellent corrosion resistance.

[00162] 10: No rust generation.

[00163] 9: Rust was generated in an extremely small quantity (area ratio was 0.10% or less) 8: Rust was generated in an area ratio of more than 0.10% and 0.25% or less. 7: Rust was generated in an area ratio of more than 0.25% and 0.50% or less. 6: Rust was generated in an area ratio of more than 0.50% and 1.0% or less. 5: Rust was generated in an area ratio of more than 1.0% and 2.5% or less. 4: Rust was generated in an area ratio of more than 2.5% and 5.0% or less. 3: Rust was generated in an area ratio of more than 5.0% and 10% or less. 2: Rust was generated in an area ratio of more than 10% and 25% or less. Petition 870250091781, dated 08 / 10 / 2025, page 52 / 60 / 44: Rust was generated in an area ratio of more than 25% and 50% or less. [Dissolving Property]

[00164] A sample was collected from the obtained steel sheet, the sample was boiled in pure water for 10 minutes and the amount of phosphoric acid eluted in the pure water was measured. By dividing the amount of phosphoric acid eluted by the area of ​​the insulating coating of the boiled grain-oriented electrical steel sheet, the dissolution property (mg / m2) was evaluated.

[00165] The amount of phosphoric acid eluted in pure water was calculated by cooling the pure water (solution) in which the phosphoric acid was eluted, diluting the cooled solution with pure water, and measuring the phosphoric acid concentration of the sample using ICP-AES.

[00166] When the amount of dissolution per unit area was less than 40 mg / m2, it was determined that the dissolution property was excellent. [Magnetic Features]

[00167] B8 (magnetic flux density at a magnetizing force of 800 A / m) and W17 / 50 (iron loss per mass at a magnetic flux density amplitude of 1.7 T and 50 Hz) were measured as magnetic characteristics after stress-relief annealing at 850°C for 2 hours in a nitrogen flow.

[00168] These characteristic values ​​were measured using the single plate tester (SST) in accordance with JIS C2556:2015. Table 3] Sample No. Adhesion Coating Tension Corrosion Resistance Dissolution Property Iron Loss (W17 / 50) Observations MPa mg / m2 W / kg 101 B 8.4 8 18 0.74 Example of Invention 102 B 8.6 8 36 0.71 Example of Invention 103 A 9.5 9 24 0.70 Example of Invention 104 A 6.1 8 15 0.75 Example of Invention Petition 870250091781, dated 08 / 10 / 2025, pages 53 / 60 / 44 105 B 6.9 7 14 0.74 Example of Invention 106 B 7.7 7 20 0.73 Example of Invention 107 A 9.4 8 17 0.68 Example of Invention 108 A 11.1 9 9 0.66 Example of Invention 109 B 6.5 7 12 0.71 Example of Invention 110 B 5.4 8 24 0.72 Example of Invention 111 B 7.1 7 28 0.69 Example of Invention 112 B 7.4 7 31 0.68 Example of Invention 113 C 4.3 3 38 0.81 Comparative Example 114 C 3.2 3 40 0.84 Comparative Example 115 D 3.6 3 46 0.78 Example Comparative 116 C 6.8 6 62 0.79 Example Comparative 117 D 3.5 6 19 0.86 Example Comparative 118 D 2.8 3 30 0.81 Example Comparative 119 C 4.4 4 33 0.78 Example Comparative 120 D 1.5 2 21 0.84 Example Comparative 121 C 3.8 3 22 0.83 Example Comparative 122 C 3.3 2 23 0.82 Example Comparative

[00169] As shown in Tables 1 to 3, in the examples of the invention, after light pickling, an intermediate layer was formed using a specific treatment method, and then a groove was formed, so that a predetermined grooved part was formed on the base steel sheet by the formation of an insulating coating (intermediate layer and tension coating) on ​​the surface of the base steel sheet under specific treatment conditions, and the coverage of the grooved part with the predetermined insulating coating was 50% of the area or more. As a result, the coating adhesion and magnetic characteristics were excellent. In addition, the coating tension, corrosion resistance, and dissolution properties were also sufficient.

[00170] On the other hand, in the comparative examples, the grooved part was not sufficiently covered with the insulating coating, and the coating adhesion and / or magnetic characteristics were poor. INDUSTRIAL APPLICABILITY

[00171] According to the present invention, it is possible to provide a Petition 870250091781, dated 08 / 10 / 2025, pp. 54 / 60 / 44, describes a grain-oriented electrical steel sheet with excellent coating adhesion and magnetic characteristics, and a method for forming an insulating coating embedded in the grain-oriented electrical steel sheet. Therefore, its industrial applicability is high. LIST OF REFERENCE SIGNS

[00172] 1 Grain-oriented electrical steel sheet flat surface part grooved part Base steel plate Insulating coating 211 Intermediate layer 212 Tension coating layer RD Rolling Direction TD Width Direction ND Sheet thickness direction D Groove depth W Slot width Petition 870250091781, dated 08 / 10 / 2025, pages 55 / 60

Claims

1 / 3 CLAIMS 1. Grain-oriented electrical steel sheet, characterized in that it comprises: a base steel sheet; and an insulating coating formed on a surface of the base steel sheet, wherein the base steel sheet includes: a flat surface portion, and a grooved portion extending in a direction of 45 to 135° relative to a rolling direction, the grooved portion having a depth of 10 to 30 μm and a width of 10 to 200 μm, the insulating coating includes: an intermediate layer formed on one side of the base steel sheet, containing a crystalline metallic phosphate and having a thickness of 0.1 to 15.0 μm, and a tension coating layer formed on one side of the surface of the insulating coating, and the base steel sheet is covered with the insulating coating including the intermediate layer and the tension coating layer in 60% or more of the grooved portion in terms of area ratio.

2. Grain-oriented electrical steel sheet according to claim 1, characterized in that the crystalline metallic phosphate contained in the intermediate layer is one or two or more of zinc phosphate, manganese phosphate, iron phosphate, and calcium zinc phosphate, and the tension bonding layer contains a metallic phosphate and silica, and a silica content in the tension bonding layer is 20 to 60% by mass. Petition 870250091781, dated 08 / 10 / 2025, pp. 56 / 60 2 / 3 3. Method for forming the insulating coating included in the grain-oriented electrical steel sheet as defined in claim 1, the method characterized in that it comprises: a finishing annealing step to apply an annealing separator containing 10 to 100% by mass of AhOE to a steel sheet, drying the annealing separator and then performing the finishing annealing; an annealing separator removal step to remove excess annealing separator from the steel sheet after the finishing annealing step; a light pickling step to pickle the steel sheet after the annealing separator removal step with one or two or more inorganic acids selected from sulfuric acid, phosphoric acid and hydrochloric acid at a concentration of 0.1 to 10% by mass and at normal or higher temperature for 1 to 20 seconds;an intermediate layer formation step to immerse the steel sheet after the light pickling step in a treatment liquid with a liquid temperature of 30 to 95°C, a phosphate concentration of 1.0 to 15.0% by mass and a pH of 1.5 to 6.0 for 5 to 90 seconds, wash and remove the treatment liquid with water and then dry the steel sheet; a groove formation step to form a grooved part that extends in a direction of 45 to 135° relative to a rolling direction on the steel sheet after the intermediate layer formation step through machining;and a tension coating layer formation step to apply, to the steel sheet after the groove forming step, a coating liquid containing a metallic phosphate and colloidal silica such that the colloidal silica is contained in an amount of 30 to 150 parts by mass Petition 870250091781, dated 08 / 10 / 2025, page 57 / 60 3 / 3 in relation to 100 parts by mass of the metallic phosphate, dry the coating liquid and then hold the steel sheet at a sheet temperature of 700 to 950°C for 10 to 90 seconds.; 4. Method for forming the insulating coating according to claim 3, characterized in that the annealing separator additionally contains one or both of 5 to 90% by mass of MgO and 0.5 to 10.0% by mass of chloride. Petition 870250091781, dated 08 / 10 / 2025, pp. 58 / 60

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