Grain-oriented electrical steel sheet and method for forming insulating coating.

Description

/ 42 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 a method for forming the insulating coating.

[002] Priority is claimed in Japanese Patent Application No. 2023-064840, filed on April 12, 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 amount of a solid solution element, such as Si, to increase the electrical resistance of the steel sheet, or (c) reducing the thickness of the sheet of the electrical steel sheet.

[005] Furthermore, applying tension to the steel plate is effective in reducing iron loss. It is an effective means of reducing iron loss to form a coating made of a material having a coefficient of thermal expansion lower than that of the steel plate on a plate surface at a high temperature. A forsterite-based coating (inorganic coating) having excellent coating adhesion, generated by a reaction between an oxide on the surface of a plate and an annealing separator in a Petition 870250091782, dated 08 / 10 / 2025, page 58 / 99 / 42, the finishing annealing stage 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 has a large stress application effect on the steel sheet. Therefore, a general method for manufacturing a grain-oriented electrical steel sheet is to leave the forsterite-based coating generated in the finishing annealing step and form an insulating coating containing mainly a phosphate onto the forsterite-based coating.

[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 forsterite-based coating hinders the movement of a domain wall and adversely affects iron loss. In a grain-oriented electrical steel sheet, a magnetic domain changes by the movement of a domain wall under an alternating magnetic field.The smooth and rapid movement of the domain wall is effective in reducing iron loss, but the forsterite-based coating itself is a non-magnetic body and has an irregular structure at the steel plate / coating interface, and this irregular structure hinders domain wall movement. Therefore, the forsterite-based coating is considered to adversely affect iron loss.

[008] Therefore, as a means of improving iron loss in high magnetic fields, a technique for manufacturing an electrical steel sheet of Petition 870250091782, dated 08 / 10 / 2025, page 59 / 99 / 42 oriented grain having no forsterite-based coating 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) were studied for: a method for removing a forsterite-based coating by using a mechanical means, such as polishing, or a chemical means, such as pickling; or prevention of the generation of a forsterite-based coating in high-temperature finish annealing.

[009] As a technique for avoiding the generation of a forsterite-based coating, 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-like 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-based coating, obtained by 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-based coating has an effect of exhibiting insulating properties and an effect of an intermediate layer to ensure adhesion when a tension coating (tension-applied insulating coating) is formed. That is, as the forsterite-based coating is formed in a state of deep penetration into the steel sheet, the forsterite-based coating has excellent adhesion to the steel sheet, which is metallic. Therefore, when a tension-applied coating (tension coating) containing colloidal silica, a phosphate or similar as a main component is formed on the surface of the forsterite-based coating, the coating adhesion is excellent. By Petition 870250091782, dated 08 / 10 / 2025, page 60 / 99 / 42 on the other hand, as it is generally difficult to bond metal and oxide to each other, it is difficult to ensure sufficient adhesion between the tension coating and the surface of a steel sheet when the forsterite-based coating is not present.

[0011] Therefore, in a case where a tension coating is formed on a grain-oriented electrical steel sheet having no forsterite-based coating, it was studied to form a layer that alternatively plays a role as an intermediate layer of the forsterite-based coating.

[0012] For example, Patent Document 3 describes a technique in which a grain-oriented electrical steel sheet having no forsterite-based coating (organic coating) is annealed in a weakly reducing atmosphere, and the silicon inevitably contained in a silicon steel sheet is selectively thermally oxidized to form a SiO2 layer on the sheet surface, and then a voltage-applied type insulating coating is formed. Patent Document 4 describes a technique in which a grain-oriented electrical steel sheet having no forsterite-based coating (organic coating) is subjected to an anodic electrolytic treatment in an aqueous silicate solution to form a SiO2 layer on the sheet surface, and then a voltage-applied type insulating coating is formed.

[0013] However, in the technique described in Patent Document 3, it is necessary to prepare an annealing plant capable of controlling an atmosphere to perform annealing in a weakly reducing atmosphere, and there is a problem with the cost of the treatment. In the technique described in Patent Document 4, it is necessary to prepare a new electrolysis treatment plant to obtain a SiO2 layer that maintains sufficient adhesion to a voltage-applied insulating coating on a sheet surface, performing an anodic electrolytic treatment in an aqueous solution of Petition 870250091782, dated 08 / 10 / 2025, page 61 / 99 / 42 silicate, and there is a problem with the cost of treatment.

[0014] On the other hand, Patent Document 5 describes a grain-oriented electrical steel sheet comprising: a base steel sheet and an insulating coating formed on the surface of the base steel sheet, wherein the insulating coating includes an intermediate layer that is formed on the side of the base steel sheet and contains a crystalline metallic phosphate and a tension coating layer formed on the surface side of the insulating coating. In the grain-oriented electrical steel sheet, the intermediate layer may be formed by chemical conversion treatment. List of Citations Patent Document

[0015] Patent Document 1: Unexamined Japanese Patent Application, First Publication No. S48-039338

[0016] Patent Document 2: Unexamined Japanese Patent Application, First Publication No. S49-96920

[0017] Patent Document 3: Unexamined Japanese Patent Application, First Publication No. H06-184762

[0018] Patent Document 4: Unexamined Japanese Patent Application, First Publication No. H11-209891

[0019] Patent Document 5: International Publication PCT No. WO 2022 / 215709 SUMMARY OF THE INVENTION Technical Problem

[0020] In the technique of Patent Document 5, coating adhesion, coating tension, and magnetic characteristics can be improved by an intermediate layer made of a crystalline metallic phosphate included between the base steel sheet and the tension coating. Furthermore, since the intermediate layer can be formed by chemical conversion treatment, no special equipment is required. Therefore, the Petition 870250091782, dated 08 / 10 / 2025, page 62 / 99 / 42 technique is useful.

[0021] On the other hand, in the technique of Patent Document 5, there is a problem in that productivity becomes low when adhesion is further improved. This is because it takes time to precipitate a crystalline metallic phosphate through chemical conversion treatment.

[0022] In order to solve the above problem, it is possible to precipitate a crystalline metallic phosphate by electrolytic chemical conversion treatment. However, when attempting to form a crystalline metallic phosphate layer by means of electrolytic chemical conversion treatment on the surface of an uncoated forsterite-based grain-oriented electrical steel sheet, the metallic phosphate crystal may become coarse. When the metallic phosphate crystal increases in size, the actually manufactured transformer has a reduced space factor.

[0023] Therefore, an objective of the present invention is to provide a grain-oriented electrical steel sheet having a layer containing a metallic phosphate formed by chemical conversion treatment on the surface of an uncoated forsterite-based steel sheet, which is excellent in adhesion with a tensile coating and magnetic characteristics and does not reduce the space factor of a transformer (core). However, it is assumed that the basic characteristics required for a coating, such as corrosion resistance and resistance to phosphoric acid elution, are not deteriorated. Solution to the Problem

[0024] Assuming a method for forming a crystalline metallic phosphate layer by an electrolytic chemical conversion treatment on the surface of a grain-oriented electrical steel sheet having no forsterite-based coating, the present inventors studied a method for obtaining a grain-oriented electrical steel sheet that is excellent in adhesion with a tension coating and characteristics Petition 870250091782, dated 08 / 10 / 2025, page 63 / 99 / 42 magnetic and does not reduce the space factor of a transformer (core). As a result, it was verified that a chemical electrolytic conversion treatment is carried out with a treatment liquid whose concentration of metal ions, concentration of phosphate ions and concentration of nitrate ions are in specific ranges, and the chemical electrolytic conversion treatment is carried out at a specific current density and thus the thickening of the crystalline metal phosphate can be suppressed. Furthermore, it was verified that grain-oriented electrical steel sheet having a crystalline metal phosphate layer has excellent adhesion with a voltage and magnetism coating and increases the space factor of a transformer.

[0025] The present invention was made in view of the above verifications. The essence of the present invention is as follows.

[0026] [1] In one embodiment of the present invention, a grain-oriented electrical steel sheet includes: 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 that is formed on one side of the base steel sheet and contains a crystalline metallic phosphate; and a tension coating layer formed on one side of the surface of the insulating coating, and the crystalline metallic phosphate has plate form and an average grain size of 0.5 to 3.0 μm.

[0027] [2] In the grain-oriented electrical steel sheet according to [1], in the intermediate layer, the crystalline metallic phosphate may include at least one of zinc phosphate, manganese phosphate, ferromanganese phosphate and calcium zinc phosphate.

[0028] [3] In the grain-oriented electrical steel sheet according to [1], the intermediate layer can have a thickness of 0.1 to 9.0 μm.

[0029] [4] In one embodiment of the present invention, a method for forming an insulating coating, which is a method for forming the Petition 870250091782, of 08 / 10 / 2025, page 64 / 99 / 42 insulating coating included in grain-oriented electrical steel sheet according to [1], includes: a finishing annealing step of applying an annealing separator containing AhO / in an amount of 10 to 100% by mass to a steel sheet, drying the steel sheet and then annealing the steel sheet to finish; an annealing separator removal step of removing an excess of the 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 0.1 to 10.0% by mass of an inorganic acid selected from sulfuric acid, chloric acid, nitric acid and phosphoric acid at a liquid temperature of 20 to 90°C for 1 to 20 seconds;an intermediate layer formation step of washing the steel sheet after the light pickling step with water and then energizing the steel sheet for 3 to 30 seconds at a current density of 1.0 to 50 A / dm2 in a mixed treatment liquid with a metal ion concentration of 10 to 50 g / l, a phosphate ion concentration of 10 to 100 g / l, and a nitrate ion concentration of 20 to 80 g / l at a liquid temperature of 30 to 90°C; a drying step of pulling the steel sheet after the intermediate layer formation step from the mixed treatment liquid, removing the excess mixed treatment liquid and then drying the steel sheet;and a step in forming a tension coating layer of applying a coating liquid containing a metallic phosphate and colloidal silica, the metallic phosphate and colloidal silica contained in a total concentration of 10 to 40% by mass, to the steel sheet after the drying step, drying the steel sheet and then heating and holding the steel sheet at a sheet temperature of 700 to 950°C for 10 to 60 seconds. Advantageous Effects of the Invention

[0030] According to the present invention, it is possible to provide a grain-oriented electrical steel sheet that is excellent in adhesion with Petition 870250091782, dated 08 / 10 / 2025, page 65 / 99 / 42 a voltage coating and magnetic characteristics that does not reduce the space factor of a transformer (core). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] [Figure 1] An example of a cross-sectional view of a grain-oriented electrical steel sheet according to the embodiment. DESCRIPTION OF EMBARRASSMENTS

[0032] A grain-oriented electrical steel sheet according to an embodiment of the present invention (grain-oriented electrical steel sheet according to the embodiment) and a method for manufacturing a grain-oriented electrical steel sheet according to the embodiment will be described, the method including a method for forming an insulating coating embedded in the grain-oriented electrical steel sheet according to the embodiment.

[0033] First, a grain-oriented electrical steel sheet will be described according to the embodiment.

[0034] As illustrated in Figure 1, a grain-oriented electrical steel sheet 100 according to the embodiment has a base steel sheet 1 and an insulating coating 2 formed on the surface of the base steel sheet 1. In the grain-oriented electrical steel sheet 100 according to the embodiment, a forsterite-based coating is not intentionally formed on the surface of the base steel sheet 1, and no forsterite-based coating is generally present. However, when the amount of forsterite-based coating is 1.0 g / m2 or less, its presence is permitted (in this case, in a part between the base steel sheet 1 and the insulating coating 2).

[0035] The insulating coating 2 has a tension coating layer 22 formed on the surface side of the insulating coating 2 (i.e., the surface side of the grain-oriented electrical steel sheet 100) and an intermediate layer 21 formed on the side of the base steel sheet 1 and containing a crystalline metallic phosphate. Petition 870250091782, dated 08 / 10 / 2025, pp. 66 / 99 / 42

[0036] Furthermore, in the intermediate layer 21, the crystalline metallic phosphate has a plate-like shape and an average grain size of 0.5 to 3.0 μm.

[0037] Each will be described below. <Chapa de Aço Base> (Chemical Composition)

[0038] The grain-oriented electrical steel sheet 100 according to the embodiment has a significant feature in the structure of the insulating coating 2 formed on the surface of the base steel sheet 1. The chemical composition of the base steel sheet 1 included in the grain-oriented electrical steel sheet 100 is not limited. However, in order to obtain characteristics generally required for a grain-oriented electrical steel sheet, the base steel sheet 1 preferably contains the following components as a chemical composition. In the embodiment, the % relating to the chemical composition is % by mass, unless otherwise specified. C: 0.010% or less

[0039] Carbon (C) is an effective element in controlling the microstructure of steel sheet in stages prior 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 grain-oriented electrical steel sheet, which is a product sheet, deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the 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%, the 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%

[0040] Si (silicon) is an element that increases electrical resistance. Petition 870250091782, of 08 / 10 / 2025, p. 67 / 99 / 42 of 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 effect on eddy current losses. Therefore, the 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.

[0041] 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 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%

[0042] Mn (manganese) is an element that binds to S in the 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.

[0043] On the other hand, when the Mn content exceeds 0.50%, secondary recrystallization does not occur, and the magnetic characteristics of the steel are deteriorated. 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

[0044] NO (nitrogen) is an element that binds to Al in the manufacturing process to form AlN, which acts as an inhibitor. However, Petition 870250091782, dated 08 / 10 / 2025, page 68 / 99 / 42 when the N content is more than 0.010%, the inhibitor remains excessively in the grain-oriented electrical steel sheet, and the magnetic characteristics are deteriorated. 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.

[0045] On the other hand, the lower limit 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

[0046] Al sol. (acid-soluble aluminum) is an element that binds 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 and deteriorates the magnetic characteristics. 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 of the Al sol. content is not particularly limited, 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

[0047] Sulfur (OS) 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 deteriorates the magnetic characteristics. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the modality, the S content is Petition 870250091782, dated 08 / 10 / 2025, page 69 / 99 / 42 preferably 0.010% or less. The S content in grain-oriented electrical steel sheet is most preferably as low as possible. For example, the S content is less than 0.001%. However, even when the S content is reduced to less than 0.0001% in grain-oriented electrical steel sheet, the manufacturing cost only increases. Therefore, the S content can be 0.0001% or more in grain-oriented electrical steel sheet. Remaining: Iron and impurities

[0048] The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the 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 of 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 embodiment is not impaired.

[0049] Here, impurities are contaminated by ore or scrap as raw material, or by a manufacturing environment or similar when the base steel sheet is industrially manufactured. Impurities mean elements that may be included in such a quantity that the action of the grain-oriented electrical steel sheet according to the modality is not adversely affected. Sn: 0 to 0.50%

[0050] Tin (Sn) is an element that contributes to the improvement of 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 Petition 870250091782, dated 08 / 10 / 2025, page 70 / 99 / 42 preferably 0.03% or more.

[0051] On the other hand, when the Sn content exceeds 0.50%, secondary recrystallization is unstable and the magnetic characteristics are deteriorated. 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%

[0052] Copper (Cu) is an element that contributes to an increase in the occupation of the Goss orientation in a secondary recrystallization structure. In order 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.

[0053] 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%

[0054] Selenium is an element that has an effect of improving magnetic characteristics. When Se is included, 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.

[0055] On the other hand, when the Se content exceeds 0.020%, the coating adhesion is deteriorated. 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. Petition 870250091782, dated 08 / 10 / 2025, p. 71 / 99 / 42 Sb: 0 to 0.50%

[0056] Sb (antimony) is an element that has an effect of improving magnetic characteristics. When Sb is included, 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.

[0057] On the other hand, when the Sb content exceeds 0.50%, the coating adhesion is significantly deteriorated. 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.

[0058] As described above, for example, the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the embodiment contains the elements described above, with the remainder being Fe and impurities.

[0059] The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the embodiment can be measured using a known ICP emission spectrometry. Note that, at the time of measurement, in a case where an insulating coating is formed on the 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 steel sheet 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 they have been peeled off. In the case of a small sample, the insulating coating can be peeled off by grinding the surface. <Revestimento Isolante>

[0060] In the grain-oriented electrical steel sheet 100 according to the embodiment, the insulating coating 2 is formed on the surface of the sheet. Petition 870250091782, dated 08 / 10 / 2025, p. 72 / 99 / 42 steel base 1.

[0061] The insulating coating 2 includes the intermediate layer 21 and the tension coating layer 22 in this order starting from the side of the base steel sheet 1. (Intermediate Layer)

[0062] As described above, in general, a grain-oriented electrical steel sheet has a forsterite-based coating generated 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-based coating 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-based coating was studied. However, when the forsterite-based coating is not present, it is difficult to ensure sufficient adhesion between a tension coating and the surface of a base steel sheet.

[0063] In the grain-oriented electrical steel sheet 100 according to the embodiment, the intermediate layer 21 containing a crystalline metallic phosphate is formed between the base steel sheet 1 and the tension coating to improve the adhesion between the base steel sheet 1 and the tension coating layer 22 by means of the intermediate layer 21.

[0064] This occurs because, when the intermediate layer 21 contains a crystalline metallic phosphate, the tension coating formed over it (after formation, it becomes the tension coating layer 22) also contains a metallic phosphate and therefore has a high affinity for it, thus exhibiting excellent adhesion between the intermediate layer and the tension coating layer. Furthermore, as described later, when the intermediate layer is formed by immersion in a treatment liquid containing a metallic phosphate, the intermediate layer can be Petition 870250091782, dated 08 / 10 / 2025, page 73 / 99 / 42 formed on the surface of the base steel plate 1 using a chemical reaction, and the adhesion between the intermediate layer 21 and the base steel plate 1 can also be ensured.

[0065] When the intermediate layer 21 does not contain a crystalline metallic phosphate, the above effect cannot be obtained. The percentage of crystalline metallic phosphate in the intermediate layer is preferably 80% by mass or more, and may be 100% by mass. As for the metallic phosphate, at least one of zinc phosphate, manganese phosphate, iron phosphate, and calcium zinc phosphate is preferably used from the point of view of adhesion.

[0066] The intermediate layer may contain, like the rest of the metallic phosphate, an oxide or an element diffused from the base steel sheet, such as Fe or Si.

[0067] However, when the crystalline metal phosphate crystal becomes thick in the intermediate layer, the effectively manufactured transformer has a reduced space factor, resulting in a reduced magnetic flux density per unit volume and an increased iron loss from the transformer.

[0068] Therefore, in the grain-oriented electrical steel sheet according to the embodiment, the crystalline metallic phosphate contained in the intermediate layer has a plate shape and an average grain size of 0.5 to 3.0 μm. Here, plate shape refers to a shape in which one side in the three crystal directions is less than 1 / 5 times longer than the other two sides. On the other hand, columnar shape refers to a shape in which one of the sides in the three crystal directions is 5 or more times longer than the other two sides, and the other two sides are 0.5 times to less than 2.0 times longer than each other. Particle shape refers to a shape in which the three crystal directions are 0.5 times to less than 2.0 times longer than the others. Needle shape refers to a shape in which a Petition 870250091782, dated 08 / 10 / 2025, page 74 / 99 / 42 of the sides in the three directions of the crystal is 20 or more times larger than the other two sides, and the other two sides are 0.5 to less than 2.0 times larger than each other.

[0069] When crystalline metal phosphate does not have a plate shape, the space factor decreases or adhesion becomes poor.

[0070] Furthermore, when the average grain size is less than 0.5 μm, the crystals are sparse and the adhesion is poor. When the average grain size is more than 3.0 μm, the spacing factor is poor.

[0071] Although the intermediate layer 21 and the voltage coating formed over it are formed at different times, both the intermediate layer 21 and the voltage coating layer 22 exhibit the effect of the insulating coating 2.

[0072] The thickness of the intermediate layer is preferably from 0.1 to 9.0 μm from the point of view of obtaining adhesion and magnetism. When the average thickness of the intermediate layer 21 is less than 0.1 μm, the effect of improving adhesion between the base steel sheet and the insulating coating by means of the intermediate layer is often not sufficiently achieved. On the other hand, when the average thickness of the intermediate layer exceeds 9.0 μm, the magnetic characteristics may deteriorate.

[0073] Regarding the crystalline metallic phosphate in the intermediate layer, the mass ratio of the metallic phosphate and the type of metallic phosphate are determined by measuring the cross-section of the intermediate layer along the thickness direction with a scanning electron microscope and an energy-dispersive element analyzer. Whether the metallic phosphate in intermediate layer 21 is a crystalline metallic phosphate can be determined by X-ray crystallography.

[0074] Regarding the thickness of the intermediate layer, a cross-section of a sample is observed with a scanning electron microscope, and the thicknesses at five or more points are measured, using the Petition 870250091782, dated 08 / 10 / 2025, page 75 / 99 / 42, which an average thickness can be measured. The base steel sheet and the insulating coating can be determined based on the concentration of P (phosphorus) derived from metallic phosphate (the insulating coating can be determined when the P content is 1.0% by mass or more, and the base steel sheet can be determined when the P content is less than 1.0% by mass). In the insulating coating 2, the intermediate layer 21 and the tension coating layer 22 can be determined by detecting silicon (Si) derived from silica (the tension coating layer contains silica, as described later).

[0075] The average grain size of crystalline metallic phosphate can be determined by the following method.

[0076] A sample of steel sheet is cut into squares of a few millimeters and subjected to the ion milling process (CP process) to remove microscopic shape defects, such as sagging and cracks. The steel sheet is then observed with a scanning electron microscope in a cross-section along the rolling direction of the steel sheet and in a cross-section along the direction perpendicular to the rolling direction of the steel sheet. When the observed metallic phosphate includes, as its crystalline form, two or more crystals in which one side is 1 / 5 or less longer than the other sides, it is determined that a plate-shaped crystal is generated. Furthermore, the average grain size is determined by measuring the long side of five or more crystals among the observed metallic phosphate crystals and calculating their average. The electron microscope observation is performed at a magnification of 1000x at five observation points. [Tension Coating Layer]

[0077] The grain-oriented electrical steel sheet 100 according to the embodiment, in which a tension coating is formed on the surface of the intermediate layer 21, has the tension coating layer 22 on the side Petition 870250091782, dated 08 / 10 / 2025, page 76 / 99 / 42 of the insulating coating surface 2.

[0078] The tension coating layer 22 is not particularly limited, provided it is used as an insulating coating of an electrically oriented grain steel sheet, but preferably has a composition containing mainly a metallic phosphate from the point of view of adhesion to the intermediate layer 21 (adhesion to the base steel sheet 1 by means of the intermediate layer 21). The tension coating layer 22 is preferably made substantially of metallic phosphate and silica.

[0079] The stress coating layer 22 preferably contains a metal phosphate and silica (derived from colloidal silica in the coating liquid), such that the silica content is 20% by mass or more. On the other hand, when the silica content in the stress coating layer 22 is more than 60% by mass, pulverization occurs. Therefore, the silica content is preferably 60% by mass or less. The metal phosphate and silica are preferably contained in a total amount of 70% by mass or more. The total metal phosphate and silica can be 100% by mass. As a remainder, in addition to the metal phosphate and silica, fine ceramic particles such as alumina and silicon nitride may be included. The metal phosphate is preferably aluminum phosphate from the point of view of heat resistance.

[0080] The thickness of the tension coating layer 22 is not limited, but the average thickness of the insulating coating 2 (intermediate layer 21 + tension coating layer 22) is preferably from 1.0 to 20.0 μm when the average thickness of the intermediate layer 21 is in the above range. When the average thickness of the insulating coating 2 is less than 1.0 μm, sufficient coating tension cannot be obtained. Furthermore, the elution of phosphoric acid increases. In this case, this can cause deterioration of adhesion and corrosion resistance, and may cause peeling of the coating. When the thickness of the insulating coating Petition 870250091782, dated 08 / 10 / 2025, page 77 / 99 / 42 is more than 20.0 μm, the space factor decreases to deteriorate the magnetic characteristics, the adhesion decreases due to cracks or similar, or the corrosion resistance decreases.

[0081] In the 22 tension coating layer, the mass percentage of metallic phosphate and the type of metallic phosphate can be determined in the cross-section along the thickness direction in the same way as in the intermediate layer.

[0082] As described above, the tension coating layer and the intermediate layer can be determined by the difference in silica content.

[0083] The thickness of the tension coating layer 22 can be determined in the same way as for the intermediate layer 21. The sum of the thickness of the tension coating layer 22 and the thickness of the intermediate layer 21 is determined as the thickness of the insulating coating 2.<Método de Fabricação>

[0084] According to the manufacturing method that satisfies the manufacturing conditions described below, the grain-oriented electrical steel sheet according to the embodiment can be properly manufactured. Note that, naturally, the grain-oriented electrical steel sheet according to the embodiment is not particularly limited in its manufacturing method. That is, a grain-oriented electrical steel sheet having the configurations described above is considered the grain-oriented electrical steel sheet according to the embodiment, regardless of its manufacturing conditions.

[0085] Grain-oriented electrical steel sheet according to the modality can be manufactured by a manufacturing method that includes the following steps: (I) a hot rolling stage of hot rolling a piece of steel having a predetermined chemical composition to obtain a Petition 870250091782, dated 08 / 10 / 2025, page 78 / 99 / 42 hot band; (II) a hot band annealing step of annealing the hot band; (III) a cold rolling step of cold rolling the hot strip after the hot strip annealing step to obtain a steel sheet (cold strip); (IV) a decarburization annealing step to decarburize the steel sheet after the cold rolling step; (V) a finishing annealing step of applying an annealing separator containing AbO; in an amount of 10 to 100% by mass onto a steel sheet, drying the steel sheet and then annealing the steel sheet to finish; (VII) an annealing separator removal step to remove excess annealing separator from the steel sheet after the finishing annealing step; (VIII) a light pickling step of pickling the steel sheet after the annealing separator removal step with 0.1 to 10.0% by mass of an inorganic acid selected from sulfuric acid, chloric acid, nitric acid and phosphoric acid at a liquid temperature of 20 to 90°C for 1 to 20 seconds; (IX) an intermediate layer formation step of washing the steel sheet after the light pickling step with water and then energizing the steel sheet for 3 to 30 seconds at a current density of 1.0 to 50 A / dm2 in a mixed treatment liquid with a metal ion concentration of 10 to 50 g / l, a phosphate ion concentration of 10 to 100 g / l and a nitrate ion concentration of 20 to 80 g / l and a liquid temperature of 30 to 90°C; (X) a drying step of pulling the steel sheet after the intermediate layer formation step from the treatment liquid Petition 870250091782, of 08 / 10 / 2025, p. 79 / 99 / 42 mixed, remove excess mixed treatment liquid and then dry the steel plate; and (XI) a tension coating layer formation step of applying a coating liquid containing a metallic phosphate and colloidal silica, the metallic phosphate and colloidal silica contained in a total concentration of 10 to 40% by mass to the steel plate after the drying step, dry the steel plate and then heat and hold the steel plate at a plate temperature of 700 to 950°C for 10 to 60 seconds.

[0086] In addition, the method of manufacturing the grain-oriented electrical steel sheet according to the embodiment may additionally include one or both of (XII) a nitriding treatment step of subjecting the steel sheet to a nitriding treatment between the decarburizing annealing step and the finishing annealing step, and (XIII) a magnetic domain refinement step of performing magnetic domain control of the steel sheet after the tension coating layer formation step.

[0087] Among these steps, the (V) finishing annealing step to the (XI) tension coating layer formation step (also collectively referred to as the method for forming insulating coating), which are mainly related to the formation of the insulating coating, are characteristic in the manufacture of grain-oriented electrical steel sheet according to the embodiment, and known conditions may be adopted for other steps or conditions not described.

[0088] From here on, the respective steps will be described. [Hot Rolling Stage]

[0089] 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 strip. The temperature of Petition 870250091782, dated 08 / 10 / 2025, p. 80 / 99 / 42 The heating of the steel part is preferably defined in a range of 1100 to 1450°C. The heating temperature is more preferably 1300 to 1400°C.

[0090] The chemical composition of the steel part is altered according to the chemical composition of the grain-oriented electrical steel sheet to be obtained for finishing, but, for example, the chemical composition includes, in terms of % by mass, 0.01 to 0.20% C, 2.50 to 4.00% Si, 0.01 to 0.040% Al sol., 0.01 to 0.50% Mn, 0.020% or less N, 0.005 to 0.040% S, 0 to 0.50% Cu, 0 to 0.50% Sn, 0 to 0.020% Se, 0 to 0.50% Sb and a remainder including Fe and impurities.

[0091] The hot rolling conditions are not particularly limited and can be adjusted accordingly based on the required characteristics. The thickness of the hot web sheet is preferably, for example, in a range of 2.0 to 3.0 mm. [Hot Band Annealing Stage]

[0092] The hot band annealing step is a step of annealing the hot band manufactured by means of the hot rolling step. By performing such annealing treatment, recrystallization occurs in the metallographic structure and favorable magnetic characteristics can preferably be achieved.

[0093] When hot strip annealing is performed, the hot strip manufactured via the hot rolling step is annealed according to a known method. The means for heating the hot strip at the time of annealing are not particularly limited, and a known heating method may be adopted. The annealing conditions are not particularly limited. For example, the hot strip may be annealed in a temperature range of 900 to 1200°C for 10 seconds to 5 minutes. [Cold Rolling Step]

[0094] In the cold rolling stage, the hot strip, after the stage of Petition 870250091782, dated 08 / 10 / 2025, page 81 / 99 / 42, hot strip annealing is subjected to cold rolling to obtain a steel sheet (cold strip). Cold rolling can be performed once (performed continuously without intervening intermediate annealing(s)). Alternatively, before the final passage in the cold rolling stage, intermediate annealing can be performed at least once or two or more times interrupting the cold rolling, i.e., cold rolling can be performed several times with intervening intermediate annealing(s).

[0095] When intermediate annealing is performed, it is preferable to hold the hot strip at a temperature of 1000 to 1200°C for 5 to 180 seconds. The annealing atmosphere is not particularly limited. The number of times intermediate annealing is preferably 3 or less considering the manufacturing cost.

[0096] In addition, before the cold rolling stage, the surface of the hot strip may be subjected to pickling.

[0097] In the cold rolling stage according to the embodiment, the hot strip after the hot strip annealing stage is cold rolled according to a known method to form a steel sheet. For example, the final rolling reduction may 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.

[0098] 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. Petition 870250091782, dated 08 / 10 / 2025, page 82 / 99 / 42 [Decarbonization Annealing Stage]

[0099] In the decarburization annealing stage, the resulting steel sheet is subjected to decarburization annealing. In decarburization annealing, the conditions for decarburization annealing are not limited, as long as the steel sheet can be recrystallized primarily and C, which negatively affects magnetic characteristics, can be removed from the steel sheet. For example, the steel 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). [Nitriding Treatment Stage]

[00100] A nitriding treatment can be performed between the decarbonization annealing step and the finishing annealing step described later.

[00101] In the nitriding treatment step, for example, the steel sheet, after the decarburization annealing step, is held 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 N content of the steel sheet after the nitriding treatment step is preferably 40 ppm or more. On the other hand, when the N content of the steel sheet after the nitriding treatment step 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 N content of the steel sheet after the nitriding treatment step is preferably 1000 ppm or less. [Finish Annealing Stage]

[00102] In the finishing annealing stage, a separator of Petition 870250091782, dated 08 / 10 / 2025, page 83 / 99 / 42 annealing containing 10 to 100% by mass of Al2O3 is applied to the steel sheet that is after the decarburization annealing stage or has been subjected to nitriding treatment (after the nitriding treatment stage) and dried, and then the finishing annealing is performed.

[00103] In a conventional manufacturing method for a grain-oriented electrical steel sheet, a forsterite-based coating is formed on the surface of a steel sheet (cold band) by applying an annealing separator containing mainly MgO and performing a finishing annealing.

[00104] On the other hand, in the manufacturing method of grain-oriented electrical steel sheet according to the embodiment, an annealing separator containing AhOt is used to form virtually no forsterite-based coating.

[00105] On the other hand, the AhOt percentage can be 100% by mass. However, in the manufacturing method of grain-oriented electrical steel sheet according to the embodiment, the annealing separator preferably contains MgO from the point of view of preventing the sheet surface from being annealed with AhOt. The MgO can be 0%, but the MgO percentage is preferably 5% by mass or more to obtain the above effect. When MgO is contained, the MgO percentage is 90% by mass or less to ensure 10% by mass or more of AhOt. The MgO percentage is preferably 50% by mass or less. The total AhOt and MgO can be more than 50% by mass in terms of solids content relative to the annealing separator.

[00106] Furthermore, in the manufacturing method of grain-oriented electrical steel sheet according to the embodiment, the annealing separator may additionally contain a chloride. When the annealing separator contains a chloride, a more difficult formation effect of a forsterite-based coating can be obtained. The amount of chloride is not Petition 870250091782, dated 08 / 10 / 2025, page 84 / 99 / 42 particularly limited and may be 0%, but is preferably 0.5 to 10% by mass when the above effect is to be obtained. As chloride, for example, bismuth chloride, calcium chloride, cobalt chloride, iron chloride and nickel chloride are effective.

[00107] 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 Stage]

[00108] 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. [Light Pickling Stage]

[00109] In the light pickling stage, the steel sheet, after the annealing separator removal stage, is pickled with 0.1 to 10.0% by mass of an inorganic acid selected from sulfuric acid, chloric acid, nitric acid and phosphoric acid at a liquid temperature of 20 to 90°C for 1 to 20 seconds. In this way, the densification effect of the crystalline phosphate is obtained.

[00110] When light pickling conditions are not adequate, the adhesion of the tension coating layer becomes weak. [Intermediate Layer Formation Stage] [Drying Stage]

[00111] In the intermediate layer formation stage, the steel sheet, after the light pickling stage, is washed with water and then immersed in a treatment liquid. While the steel sheet is immersed, the treatment liquid is energized, thus forming an intermediate layer. In the drying stage, the steel sheet, after the intermediate layer formation stage, is removed from the treatment liquid, and the excess of Petition 870250091782, dated 08 / 10 / 2025, page 85 / 99 / 42: The treatment liquid is removed, and then the steel plate is dried. In this way, the intermediate layer is formed on the surface of the base steel plate.

[00112] Here, the treatment liquid is a mixed treatment liquid with a metal ion concentration of 10 to 50 g / l, a phosphate ion concentration of 10 to 100 g / l and a nitrate ion concentration of 20 to 80 g / l.

[00113] When the mixed treatment liquid has a metal ion concentration of less than 10 g / l, the generation of crystalline metal phosphate is suppressed, and the crystal has a particle shape and poor adhesion. On the other hand, when the metal ion concentration is more than 50 g / l, the generation of crystalline metal phosphate varies easily, and coarse crystals are developed, so that the space factor is reduced, and the intermediate layer is formed irregularly. Furthermore, when the mixed treatment liquid has a phosphate ion concentration of less than 10 g / l, the crystalline metal phosphate takes time to precipitate, and coarse crystals are developed, so that the space factor becomes poor.On the other hand, when the phosphate ion concentration is more than 100 g / l, the generation of crystalline metallic phosphate varies easily, and coarse crystals are developed and the surface of the steel sheet is etched, so that the space factor is reduced, or the corrosion resistance and coating tension are reduced. Furthermore, when the mixed treatment liquid has a nitrate ion concentration of less than 20 g / l, the generation of hydrogen gas cannot be suppressed and the current becomes difficult to flow uniformly: in the part through which the current flows, the intermediate layer is partially formed to be excessively thick, thus reducing adhesion; and, in the part through which no current flows, the intermediate layer is thin, thus reducing coating tension.On the other hand, when the nitrate ion concentration is more than 80 g / l, the phosphate ion concentration decreases, so that the crystalline metallic phosphate takes time to precipitate, and thick, needle-shaped crystals are developed, so that the space factor becomes... Petition 870250091782, dated 08 / 10 / 2025, page 86 / 99 / 42 bad.

[00114] During immersion, the temperature of the mixed treatment liquid varies from 30 to 90°C. When the temperature of the mixed treatment liquid is less than 30°C, the crystalline metallic phosphate takes a long time to precipitate, which is uneconomical. On the other hand, when the liquid temperature is more than 90°C, the mixed treatment liquid becomes unstable and the intermediate layer is formed irregularly.

[00115] During energization, the current density is 1.0 to 50 A / dm2. When the current density is less than 1.0 A / dm2, the crystalline metal phosphate takes a long time to precipitate, which is uneconomical.

[00116] On the other hand, when the current density is more than 50 A / dm2, the current becomes difficult to flow uniformly through the sample, causing an irregularly formed intermediate layer, called "transparent". When the energization time is short, it is easy for the intermediate layer to take a long time to form or to adhere poorly. On the other hand, when the energization time is long, the intermediate layer is generated excessively in some parts, and an irregular state called "adhesion irregularity" or "transparent" is easily generated. Therefore, the energization time is preferably 3 to 30 seconds.

[00117] When the drying temperature is high, there is a possibility of void formation, which leads to poor adhesion. Therefore, the drying temperature is preferably 300°C or lower, and more preferably 200°C or lower. The drying temperature is preferably 100°C or higher. [Tension Coating Layer Formation Stage]

[00118] In the tension coating layer formation step, a coating liquid containing metal phosphate and colloidal silica, the metal phosphate and colloidal silica contained in a total concentration of 10 Petition 870250091782, of 08 / 10 / 2025, p. 87 / 99 / 42 at 40% by mass, is applied to the steel sheet after the drying stage, the steel sheet is dried and then the steel sheet is heated and held at a sheet temperature of 700 to 950°C for 10 to 60 seconds, thus forming a tension coating layer on the surface of the intermediate layer.

[00119] When the sheet temperature is held below 700°C, the tension is low, and the magnetic characteristics are poor. Therefore, the sheet temperature is preferably 700°C or higher. On the other hand, when the sheet temperature is higher than 950°C, the stiffness of the steel sheet decreases, and the steel sheet is easily deformed. In this case, the steel sheet may become distorted due to transfer or something similar, resulting in poor magnetic characteristics. Therefore, the plate temperature is preferably 950°C or lower.

[00120] When the retention time is less than 10 seconds, the resistance to elution is poor. Therefore, the retention time is 10 seconds or more. On the other hand, when the retention time is greater than 60 seconds, the adhesion of the tension coating layer is poor. Therefore, the retention time is preferably 60 seconds or less.

[00121] The coating liquid (insulating coating solution) contains metallic phosphate and colloidal silica in a total amount of 10 to 40% by mass.

[00122] When the concentration is less than 10% by mass, the applied coating liquid flows easily, which can cause an uneven application amount. Furthermore, when the concentration is more than 40% by mass, the viscosity becomes too high, which can cause a pattern or irregularity in the coating.

[00123] As a metal 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. From the point of view of liquid stability Petition 870250091782, dated 08 / 10 / 2025, pp. 88 / 99 / 42, regarding coating, aluminum phosphate is preferable.

[00124] The coating liquid may contain vanadium, tungsten, molybdenum, zirconium and the like as additional elements. When these elements are present, they may be added to the coating liquid, for example, as an oxygenated acid.

[00125] Like colloidal silica, either type S or type C can be used. Type S colloidal silica is alkaline in silica solution. Type C has its silica particle surface treated with aluminum and is alkaline to neutral in silica solution. 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 the number of treatment steps is large. It is preferable to select and use them according to the stability of a coating liquid to be prepared. [Magnetic Domain Refinement Stage]

[00126] The manufacturing method of the grain-oriented electrical steel sheet according to the embodiment may additionally include a magnetic domain refinement step to perform magnetic domain refinement on the steel sheet after the tension coating layer formation step.

[00127] By performing magnetic domain refinement treatment, the iron loss of grain-oriented electrical steel sheet can be further reduced.

[00128] The magnetic domain refinement treatment method includes: a method for narrowing the width of a 180° magnetic domain (performing 180° magnetic domain refinement) by forming Petition 870250091782, dated 08 / 10 / 2025, page 89 / 99 / 42 of linear or dotted groove parts extending in a direction that crosses a rolling direction at predetermined intervals in the rolling direction; and a method for narrowing the width of a 180° magnetic domain (performing the refinement of a 180° magnetic domain) by forming linear or dotted stress-strain parts or groove parts extending in a direction that crosses a rolling direction at predetermined intervals in the rolling direction.

[00129] In a case where a stress-strain part is formed, laser beam irradiation, electron beam irradiation, and the like can be applied. In a case where a groove part is formed, a mechanical groove forming method using a gear or the like, a chemical groove forming method to form a groove by electrolytic corrosion, a thermal groove forming method by laser irradiation, and the like can be applied.

[00130] In a case where the insulating coating is damaged due to the formation of a stress-strain part or a groove part and characteristics such as insulation properties are deteriorated, the insulating coating can be reformed to repair the damage. Examples

[00131] A plate including, in terms of mass %, 0.08% C, 3.31% Si, 0.028% Al sol., 0.008% N, 0.07% Mn, less than 0.0005% S and a remainder including Fe and impurities was melted.

[00132] This plate was heated to 1350°C and then hot-rolled to form a hot strip having a plate thickness of 2.2 mm. The hot strip was annealed under holding conditions at 1100°C for 10 seconds.

[00133] Next, the hot strip was cold rolled to obtain a cold strip having a plate thickness of 0.22 mm. The cold strip was annealed by decarburization, holding it at 830°C for 90 seconds. Petition 870250091782, dated 08 / 10 / 2025, pp. 90 / 99 / 42

[00134] After decarbonation annealing, an annealing separator containing 45% by mass of MgO, 50% by mass of AbOE and 5% by mass of BiCl3 as a bismuth chloride was applied and dried, and then the finishing annealing was carried out at 1200°C for 20 hours.

[00135] After the finishing annealing, the steel sheet was washed with water to remove excess annealing separator. As a result, no forsterite-based coating was formed on the surface of the steel sheet.

[00136] The steel sheet was subjected to light pickling under the conditions of Tables 2 and 3.

[00137] After light pickling, an intermediate layer was formed from a treatment liquid in which a phosphate and an additive are mixed (mixed treatment liquid) using electrolytic treatment under the conditions shown in Table 1. The drying temperature was 200°C. The intermediate layer obtained was as shown in Tables 2 and 3. The percentage of crystalline metallic phosphate in the intermediate layer was 80% by mass or more.

[00138] Next, an insulating coating solution made of metallic phosphate and colloidal silica shown in Tables 2 and 3 was applied and dried at 850°C for 30 seconds to form a voltage-insulating coating on the surface of the steel sheet.

[00139] The thickness of the insulating coating (intermediate layer and voltage coating layer) was shown in Tables 2 and 3. The voltage coating layer was substantially made of metallic phosphate and silica. The shape, average grain size, and thickness were measured as described above. Petition 870250091782, dated 08 / 10 / 2025, pp. 91 / 99 / 42 [Table 1] Intermediate Layer No. Treatment Liquid Electrolytic Treatment Conditions Phosphate Treatment Liquid Ion Concentration (g / l) Metal Ion Phosphate Ion Nitrate Ion Others Treatment Liquid Temperature (°C) Current Density (A / dm2) Energization Time (s) 1 Manganese Phosphate 30 40 70 - 40 16 10 2 Manganese Phosphate 30 40 60 - 30 20 5 3 Zinc Phosphate 45 70 25 - 85 1.2 10 4 Zinc Phosphate 40 65 20 - 85 6 20 5 Calcium and Zinc Phosphate 15 30 30 - 80 20 12 6 Manganese Phosphate 10 25 20 - 40 45 4 7 Manganese phosphate 20 40 60 - 60 4 4 8 Zinc phosphate 15 18 25 - 50 16 10 9 Manganese phosphate 10 5 20 - 85 20 20 10 Manganese phosphate 30 160 60 - 40 20 10 11 Zinc phosphate 0.2 20 20 - 40 12 10 12 Zinc phosphate 120 40 60 - 85 20 20 13 Manganese phosphate 10 30 15 - 85 30 10 14 Manganese phosphate 30 40 100 - 50 50 5 15 Manganese phosphate 30 40 20 - 60 0,5 30 16 Manganese phosphate 30 40 20 - 50 150 5 17 Zinc phosphate 30 40 - - 40 16 10 18 Manganese phosphate 30 40 - Chloric acid: 10 40 20 10, Petition 870250091782, dated 08 / 10 / 2025, pages 92 / 99 / 42 [Table 2] of 08 / 10 / 2025, page 93 / 99 / 42 [Table 3] Observation Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Insulating Coating Thickness IHUli 5.8 12.4 13.4 10.1 4.3 14.2 4.5 7.5 6.7 L'L 6.9 Tension Coating Layer Silica Content (% by mass) 44 44 44 44 44 44 44 44 47 47 47 Tension Coating Layer Formation Step Coating Liquid Total Concentration of Metallic Phosphate and Colloidal Silica (% by mass) 35 £ £ £ £ £ £ £ £ £ £ Colloidal Silica Parts by mass QO QO QO QO QO QO QO QO QO QO QO Type Type S Type S Type S Type S Type S Type S Type S Type S Type S Type S Type S Molar ratio of metallic element 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0,17 Phosphate (100 parts by mass) Type Aluminum / lithium phosphate Aluminum / lithium phosphate Aluminum / lithium phosphate Aluminum / lithium phosphate Aluminum / lithium phosphate Aluminum / lithium phosphate Aluminum / copper phosphate Aluminum / copper phosphate Aluminum / copper phosphate Aluminum / copper phosphate Aluminum / copper phosphate Intermediate layer Thickness (hm) QO ο / ' 6.4 0.6 10.5 (N i—1 5.4 3.4 4.4 3.6 Crystalline metallic phosphate Average grain size (hm) 0.8 r4 4.1 (N i—1 °°<| a Γε , <oi z7ê lç forma formato de partícula colunar agulha etapa formação camada intermediária camada intermediária n° 11 12 13 14 15 16 17 18 (n decapagem leve tempo i—1 c4 09 tempera -tura do líquido u o s o £ qo concentração % em massa 2,0 3,5 4,5 4,0 13,0 6,0 tipo ácido h2so4 h3po4 hno3 õ § hcl on oo 22of 08 / 10 / 2025, page 94 / 99 / 42

[00140] The obtained steel sheet (grain-oriented electrical steel sheet) was irradiated with a laser beam under conditions where the UA (irradiation energy density) was 2.0 J and the irradiation interval was 5.0 mm pitch, thus performing magnetic domain refinement.

[00141] After magnetic domain refinement, the W17 / 50 iron loss of the steel sheet (iron loss at 50 Hz under 1.7 T) was measured by the Single Sheet Tester: SST according to JIS C2556 (2015) standard. When the W17 / 50 iron loss was 0.65 W / kg or less, it was determined that good magnetic characteristics were guaranteed.

[00142] In addition, the space factor was measured as follows. [Space Factor]

[00143] The space factor was measured by a method in accordance with JIS C 2550-5 (2020) standard. The test piece was 30 mm wide and 320 mm long, and 30 pieces were used. The samples were measured for total mass and then pressurized to 1 MPa, at which point the space between the top and bottom cover plates enclosing the laminate was measured to calculate the space factor.

[00144] When the space factor was 96.0% or more, it was determined that a high space factor was guaranteed.

[00145] In addition, coating adhesion, coating tension, corrosion resistance, elution resistance, and space factor of the steel sheet after magnetic domain refinement were evaluated by the following methods. Table 4 shows the results. [Coating Adhesion]

[00146] For coating adhesion, a sample with a width of 30 mm and a length of 300 mm was collected from the steel plate, and the sample was subjected to stress-relief annealing at 800°C for 2 hours in a nitrogen stream. The sample was then subjected to a test. Petition 870250091782, dated 08 / 10 / 2025, page 95 / 99 / 42 of bending and adhesion, in which the sample was rolled and unrolled around a 10 mm cylinder and then the coating was evaluated for the degree of peeling (area fraction).

[00147] The evaluation criteria were as follows: when a sample was evaluated as ◎ or 0, the sample was considered to have excellent coating adhesion.

[00148] Θ: Peeling area fraction: 0 to 0.5%

[00149] o: Peeling area fraction: more than 0.5% and 5.0% or less

[00150] △ : Fraction of peeling area: more than 5.0% and 20% or less

[00151] x: Fraction of peeling area: more than 20% and 50% or less

[00152] xx: Fraction of peeling area: more than 50% [Coating Stress]

[00153] The coating stress was calculated by reverse calculation from the curved state when a surface of the insulating coating was removed. When the coating stress obtained was 4.0 MPa or more, it was determined that the coating stress was sufficient. [Corrosion Resistance]

[00154] For corrosion resistance, a 5% aqueous NaCl solution was naturally added to the sample for 7 hours in an atmosphere of 35°C according to the JIS standard: Methods of salt spray testing (JIS Z2371:2015).

[00155] Subsequently, a rust area was evaluated on a 10-point scale. Here, the evaluation criteria are as follows. When the score was 5 or more, it was determined that the corrosion resistance was excellent.

[00156] 10: No rust generation occurred.

[00157] 9: Rust was generated in an extremely small quantity (the area fraction was 0.10% or less). Petition 870250091782, dated 08 / 10 / 2025, pages 96 / 99 / 42

[00158] 8: Rust was generated in an area fraction of more than 0.10% and 0.25% or less.

[00159] 7: Rust was generated in an area fraction of more than 0.25% and 0.50% or less.

[00160] 6: Rust was generated in an area fraction of more than 0.50% and 1.0% or less.

[00161] 5: Rust was generated in an area fraction of more than 1.0% and 2.5% or less.

[00162] 4: Rust was generated in an area fraction of more than 2.5% and 5.0% or less.

[00163] 3: Rust was generated in an area fraction of more than 5.0% and 10% or less.

[00164] 2: Rust was generated in an area fraction of more than 10% and 25% or less.

[00165] 1: Rust was generated in an area fraction of more than 25% and 50% or less. [Resistance to Elution]

[00166] Resistance to elution was evaluated by the possibility of suppressing the elution of phosphoric acid from the sample.

[00167] The method for measuring the amount of elution was as follows: the sample was boiled in pure boiled water for 10 minutes, the amount of phosphoric acid eluted in the pure water was measured, and the amount of phosphoric acid was divided by the area of ​​the insulating coating of the boiled grain-oriented electrical steel sheet. The amount of phosphoric acid eluted in pure water was measured and calculated as follows: the pure water in which the phosphoric acid was eluted (solution) was cooled, and the cooled solution was diluted with pure water to prepare a sample, and the sample was measured for the concentration of phosphoric acid with ICP-AES.

[00168] When the elution quantity was less than 40 mg / m2, it was Petition 870250091782, dated 08 / 10 / 2025, pp. 97 / 99 / 42, determined that the resistance to elution was excellent. [Table 4] Coating No. Coating Adhesion Coating Tension Corrosion Resistance Elution Resistance Space Factor Iron Loss (W17 / 50) Observation MPa mg / m2 (%) W / kg 1 Θ 7.6 8 22 97.4 0.62 Example of the Invention 2 Θ 8.5 7 28 97.1 0.61 Example of the Invention 3 Θ 8.9 7 31 97.4 0.60 Example of the Invention 4 Θ 9.6 8 20 97.8 0.60 Example of the Invention 5 Θ 9.4 9 13 96.6 0.58 Example of the Invention 6 Θ 6.8 7 35 96.4 0.61 Example of the Invention 7 Θ 6.4 8 28 97.0 0.63 Example of the Invention Example of the Invention 8 Θ 10.1 6 31 96.7 0.57 Example of the Invention 9 O 7.1 6 34 96.8 0.62 Example of the Invention 10 O 8.6 9 11 95.2 0.67 Comparative Example 11 O 3.2 3 47 94.6 0.73 Comparative Example 12 X 7.7 7 21 97.1 0.68 Comparative Example 13 O 6.8 7 37 94.0 0.69 Comparative Example 14 X 3.9 5 41 94.7 0.71 Comparative Example 15 O 9.8 8 12 94.8 0.66 Comparative Example 16 Δ 4.6 4 24 97.4 0.72 Example Comparative 17 X 9.8 6 48 93.3 0.69 Example Comparative 18 Δ 2.3 4 23 97.7 0.74 Example Comparative 19 O 6.5 7 41 95.8 0.72 Comparative Example 20 Δ 4.1 7 42 96.2 0.71 Comparative Example 21 Δ 4.4 8 52 95.9 0.73 Comparative Example 22 X 3.7 4 29 96.2 0.77 Comparative Example,

[00169] As can be seen in Tables 1 to 4, the Examples of The inventions are extremely excellent in key coating properties, such as adhesion, and are improved in iron loss and space factor.

[00170] On the other hand, in the Comparative Examples, the method for forming an insulating coating was outside the preferred conditions. Therefore, the intermediate layer did not contain a predetermined crystalline metallic phosphate, and at least one of coating adhesion, coating tension, corrosion resistance, elution resistance, and space factor was Petition 870250091782, dated 08 / 10 / 2025, pages 98 / 99 / 42 bad. LIST OF REFERENCE SIGNS

[00171] 100 Grain Oriented Electrical Steel Sheet Base steel plate Insulating coating Intermediate layer Tension coating layer INDUSTRIAL APPLICABILITY

[00172] According to the embodiment of the present invention, it is possible to provide a grain-oriented electrical steel sheet that is excellent in adhesion with a tensile coating and magnetic characteristics and that does not reduce the space factor of a transformer (core). Therefore, the resulting grain-oriented electrical steel sheet can be suitably applied to the iron core material of a transformer and thus has high industrial applicability. Petition 870250091782, dated 08 / 10 / 2025, page 99 / 99< / oi>

Claims

1 / 2 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 insulating coating includes: an intermediate layer that is formed on one side of the base steel sheet and contains a crystalline metallic phosphate; and a tension coating layer formed on one side of the surface of the insulating coating, and the crystalline metallic phosphate is plate-shaped and has an average grain size of 0.5 to 3.0 μm.

2. Grain-oriented electrical steel sheet according to claim 1, characterized in that, in the intermediate layer, the crystalline metallic phosphate includes at least one of zinc phosphate, manganese phosphate, ferromanganese phosphate, and calcium zinc phosphate.

3. Grain-oriented electrical steel sheet according to claim 1, characterized in that the intermediate layer has a thickness of 0.1 to 9.0 μm.

4. 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 of applying an annealing separator containing Al2O3 in an amount of 10 to 100% by mass onto a steel sheet, drying the steel sheet and then annealing the steel sheet to finish; an annealing separator removal step of removing an excess of the 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 0.1 to 10.0% by mass of an inorganic acid selected from sulfuric acid, chloric acid, nitric acid and phosphoric acid at a liquid temperature of 20 to 90°C for 1 to 20 seconds;an intermediate layer formation step of washing the steel sheet after the light pickling step with water and then energizing the steel sheet for 3 to 30 seconds at a current density of 1.0 to 50 A / dm2 in a mixed treatment liquid with a metal ion concentration of 10 to 50 g / l, a phosphate ion concentration of 10 to 100 g / l and a nitrate ion concentration of 20 to 80 g / l and a liquid temperature of 30 to 90°C; a drying step of pulling the steel sheet after the intermediate layer formation step out of the mixed treatment liquid, removing the excess mixed treatment liquid and then drying the steel sheet;and a step in forming a tension coating layer of applying a coating liquid containing a metallic phosphate and colloidal silica, the metallic phosphate and colloidal silica contained in a total concentration of 10 to 40% by mass to the steel sheet after the drying step, drying the steel sheet and then heating and holding the steel sheet at a sheet temperature of 700 to 950°C for 10 to 60 seconds. Petition 870250091782, dated 08 / 10 / 2025, page 54 / 99;

Images