GRAIN-ORIENTED ELECTRICAL STEEL SHEET, AND METHOD FOR FORMING THE INSULATING COATING INCLUDED IN THE GRAIN-ORIENTED ELECTRICAL STEEL SHEET

Abstract

This text describes a grain-oriented electrical steel sheet and a method for forming the insulating coating included on the grain-oriented electrical steel sheet. It states that this grain-oriented electrical steel sheet includes: 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 formed on one side of the base steel sheet and containing a crystalline metal phosphate, and a tension coating layer formed on one side of the insulating coating surface. The surface of the base steel sheet has a groove-like structure, the average thickness of the intermediate layer is 0.2 to 10.0 µm, the average thickness of the insulating coating is 2.0 to 10.0 µm, the tension coating layer contains a metal phosphate and silica, and the amount of silica in the tension coating layer is 20 to 60% by mass.

Description

1 / 48 GRAIN-ORIENTED ELECTRICAL STEEL SHEET, AND METHOD FOR FORMING THE INSULATING COATING INCLUDED IN THE GRAIN-ORIENTED ELECTRICAL STEEL SHEET [Technical Field of the Invention]

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

[002] Priority is claimed in Japanese Patent Application No. 2021-064968, filed on April 6, 2021, the contents of which are incorporated herein by reference. [Related Technique]

[003] Grain-oriented electrical steel sheets are mainly used in transformers. A transformer is continuously excited for a long period of time, from installation to disposal, and continues to generate energy losses. Therefore, energy loss during magnetization with alternating current, i.e., iron loss, is the main index that determines the transformer's performance.

[004] In order to reduce iron loss from grain-oriented electrical steel sheet, many techniques have been developed from the point of view of (a) increasing development in an orientation {110} <001> (Goss orientation), (b) increase the electrical resistance of the steel plate by increasing the amounts of solute elements, such as Si, or (c) reduce the thickness of the electrical steel plate.

[005] Furthermore, applying tension to the steel plate is effective in reducing iron loss. Forming a coating of a material with a coefficient of thermal expansion lower than that of a steel plate on a surface of the steel plate at high temperature is an effective measure to reduce iron loss. A forsterite-based coating (inorganic coating) is generated by a reaction between an oxide on the surface of a steel plate and an annealing separation agent in a step of Petition 870260023815, dated 03 / 13 / 2026, page 10 / 113 2 / 48 annealing by secondary recrystallization of electrical steel sheet and has excellent coating adhesion is a coating that can apply tension to the steel sheet.

[006] Furthermore, for example, a method described in Patent Document 1 in which a coating liquid containing mainly colloidal silica and a phosphate is baked onto a steel sheet surface to form an insulating coating is highly effective in applying stress to the steel sheet and is therefore an effective method for reducing iron loss. Therefore, in a general method of manufacturing a grain-oriented electrical steel sheet, a forsterite-based coating generated in a secondary recrystallization annealing step is left and an insulating coating containing mainly a phosphate is applied over the forsterite-based coating.

[007] However, in recent years, there has been a growing demand for miniaturization and high performance of transformers, and for transformer miniaturization, a grain-oriented electrical steel sheet with good iron loss even at a high magnetic flux density is needed, i.e., with excellent high iron loss in the magnetic field. At the same time, in recent years, it has become clear that a forsterite-based coating hinders the movement of a magnetic domain wall and negatively affects iron loss. In grain-oriented electrical steel sheet, a magnetic domain changes due to the movement of a magnetic domain wall under an AC magnetic field. The smooth and rapid movement of the magnetic domain wall is effective in reducing iron loss.However, the forsterite-based coating itself is a non-magnetic material and has an irregular structure at the interface between a steel plate and the coating, and this irregular structure hinders the movement of the magnetic domain wall. Therefore, the forsterite-based coating is considered to have an adverse effect on iron loss. Petition 870260023815, dated 03 / 13 / 2026, page 11 / 113 3 / 48

[008] Therefore, as a measure to improve the high iron loss in the magnetic field, a method was studied to remove an inorganic coating by a mechanical method such as polishing or a chemical method such as pickling, a technique to manufacture an electrically oriented grain steel sheet without any inorganic coating avoiding the generation of an inorganic coating in annealing by secondary recrystallization at high temperature, and a technique to bring a steel sheet surface to a mirror surface state (in other words, a technique to magnetically smooth a steel sheet surface).

[009] As a technique for preventing the generation of an inorganic coating, for example, Patent Document 2 describes a technique in which pickling is performed after annealing by normal secondary recrystallization to remove surface formations, and a steel sheet surface is then brought to a mirror-like state by chemical polishing or electrolytic polishing. It has been found that by forming a voltage-applied insulating coating on a surface of an uncoated grain-oriented electrical steel sheet, which is obtained by a known method, better iron loss improvement effects can be achieved. Furthermore, according to the voltage-applied insulating coating, various properties such as corrosion resistance, heat resistance, and slip properties can be applied in addition to the improvement in iron loss.

[0010] However, the inorganic coating has the effect of providing insulating properties and an effect as an intermediate layer to ensure adhesion when forming a tension coating (tension application insulating coating). That is, as the inorganic coating is formed in a state of deep penetration into the steel sheet, the adhesion to the steel sheet, which is a metal, is excellent. Therefore, in a case where a tension application coating (tension coating) Petition 870260023815, dated 03 / 13 / 2026, page 12 / 113 4 / 48 containing mainly colloidal silica, a phosphate or similar is formed on the surface of the inorganic coating, the adhesion of the coating is excellent. On the other hand, in general, the bond between a metal and an oxide is difficult. Therefore, it has been difficult to ensure sufficient adhesion between the tension coating and the steel sheet surface in the absence of an inorganic coating.

[0011] Therefore, in the case of stress coating formation on grain-oriented electrical steel sheet without inorganic coating, it was studied to provide a layer that acts as an intermediate layer instead of the inorganic coating.

[0012] For example, Patent Document 3 describes a technique in which a grain-oriented electrical steel sheet without inorganic coating is annealed in a weakly reducing atmosphere, the silicon that is inevitably present in the silicon steel sheet is selectively thermally oxidized to form an S1O2 layer on a surface of the steel sheet, and then an insulating coating that applies voltage is formed. Patent Document 4 describes a technique in which a grain-oriented electrical steel sheet without inorganic coating is subjected to an anodic electrolytic treatment in an aqueous silicate solution to form an S1O2 layer on a surface of the steel sheet, and subsequently an insulating voltage-applying coating is formed.

[0013] Patent Document 5 describes a technique in which a coating that will become an intermediate layer is applied in advance when a voltage-applied coating is formed, thus ensuring the adhesion of a voltage-applied insulating coating.

[0014] Patent Document 6 describes a grain-oriented electrical steel sheet comprising a base steel sheet and a voltage-applied insulating coating, wherein the voltage-applied insulating coating Petition 870260023815, dated 03 / 13 / 2026, page 13 / 113 5 / 48 of a voltage is present on the surface of the grain-oriented electrical steel sheet, and an iron-based oxide layer with a thickness of 100 to 500 nm is present between the base steel sheet and the voltage-applied insulating coating.

[0015] Furthermore, it is also described that, in order to form a coating on the surface of a grain-oriented electrical steel sheet, without inorganic coating and with good adhesion, the surface of the steel sheet is controlled. For example, Patent Document 7 describes a grain-oriented electrical steel sheet including a voltage-applied insulating coating provided on a surface of the grain-oriented electrical steel sheet, wherein the surface of the grain-oriented electrical steel sheet on one side on which the voltage-applied insulating coating is provided has a fine rectangular structure. [Prior technique document] [Patent Document]

[0016] [Patent Document 1] Unexamined Japanese Patent Application, First Publication No. S48-039338

[0017] [Patent Document 2] Unexamined Japanese Patent Application, First Publication No. S49-96920

[0018] [Patent Document 3] Unexamined Japanese Patent Application, First Publication No. H6-184762

[0019] [Patent Document 4] Unexamined Japanese Patent Application, First Publication No. H11-209891

[0020] [Patent Document 5] Unexamined Japanese Patent Application, First Publication No. H5-279747

[0021] [Patent Document 6] Unexamined Japanese Patent Application, First Publication No. 2020-111814

[0022] [Patent Document 7] Unexamined Japanese Patent Application, First Publication No. 2018-062682 Petition 870260023815, dated 03 / 13 / 2026, page 14 / 113 6 / 48 [Description of the Invention] [Problems to be Solved by the Invention]

[0023] However, in the technique described in Patent Document 3, to perform annealing in a weakly reducing atmosphere, it is necessary to prepare an annealing plant capable of controlling the atmosphere, which creates a cost problem for the treatment. In the technique described in Patent Document 4, to obtain the S1O2 layer that has sufficient adhesion to the insulating coating applied to the surface of the steel sheet by performing anodic electrolytic treatment in an aqueous silicate solution, a new electrolytic treatment plant needs to be prepared, which creates a cost problem for the treatment.

[0024] In the technique described in Patent Document 5, there is a problem in that the insulating coating applied under high voltage cannot be maintained with good adhesion.

[0025] In the technique described in Patent Document 6, it is described that to form the iron-based oxide layer, the grain-oriented electrical steel sheet after a surface treatment is heated in an atmosphere with an oxygen concentration of 1 to 21% by volume and a dew point of -20°C to 30°C at a steel sheet temperature of 700°C to 900°C for 5 to 60 seconds. Therefore, in the case of manufacturing a steel sheet with an inorganic coating on the same line, it is necessary to change the atmosphere of an annealing furnace, resulting in inferior workability.

[0026] In addition, Patent Document 7 presents an irregular stripping problem.

[0027] Therefore, an objective of the present invention is to provide a grain-oriented electrical steel sheet having excellent coating adhesion, excellent coating tension, and excellent magnetic characteristics, and in which an inorganic coating is not provided. Another objective of the present invention is to provide a method for forming a Petition 870260023815, dated 03 / 13 / 2026, page 15 / 113 7 / 48 insulating coating included in the grain-oriented electrical steel sheet. [Means to Solve the Problem]

[0028] The present inventors studied the problems mentioned above. As a result, it was found that in an uncoated forsterite-based grain-oriented electrical steel sheet, by providing an attack cavity structure on the surface of a base steel sheet and an intermediate layer formed by a crystalline metal phosphate between the base steel sheet and a tension coating, the coating adhesion, coating tension, and magnetic characteristics can be improved.

[0029] The present invention was made based on the above findings. The essence of the present invention is as follows.

[0030] [1] An electrically oriented grain steel sheet according to one aspect of the present invention 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 formed on one side of the base steel sheet and containing a crystalline metal phosphate, and a tension coating layer formed on one side of the insulating coating surface, the surface of the base steel sheet has an attack cavity structure, an average thickness of the intermediate layer is 0.2 to 10.0 µm, an average thickness of the insulating coating is 2.0 to 10.0 µm, the tension coating layer contains a metal phosphate and silica, and an amount of silica in the tension coating layer is 20 to 60% by mass.

[0031] [2] In the grain-oriented electrical steel sheet according to [1], the crystalline metal phosphate of the intermediate layer can be one or two or more of zinc phosphate, manganese phosphate, iron phosphate and calcium and zinc phosphate.

[0032] [3] A method for forming an insulating coating according to another aspect of the present invention is a method for forming the Petition 870260023815, dated 03 / 13 / 2026, page 16 / 113 8 / 48 insulating coating included in grain-oriented electrical steel sheet according to [1], the method including: a secondary rccrystallization annealing process of applying an annealing separator containing 10 to 100% by mass of Al2O3 to a steel sheet, drying the steel sheet and performing secondary rccrystallization annealing on the steel sheet; an annealing separator removal process to remove an excess amount of the annealing separator from the steel sheet after the secondary rccrystallization annealing process; an acid treatment process of immersing the steel sheet after the annealing separator removal process in a mixed acid in which a concentration of one or two or more selected from sulfuric acid, phosphoric acid and nitric acid is 0.5 to 20% by weight and a liquid temperature is 40°C to 90°C for 5 to 50 seconds;A process of immersing the steel sheet after the acid treatment process in a treatment liquid containing 5 to 50% by mass of a metallic phosphate at a liquid temperature of 40°C to 85°C for 5 to 150 seconds; a drying process involving removing the steel sheet after the immersion process from the treatment liquid, removing an excess amount of the treatment liquid and drying the steel sheet; and a process of forming a tension coating layer for applying a coating liquid containing a metal phosphate and colloidal silica such that an amount of colloidal silica is 30 to 150 parts by mass relative to 100 parts by mass of the metal phosphate on the steel sheet after the drying process, drying the steel sheet and maintaining the steel sheet in a state in which the plate temperature is 700°C to 950°C for 10 to 120 seconds.

[0033] [4] In the method for forming the insulating coating according to [3], the annealing separator may additionally contain one or two of MgO: 5 to 90% by mass and a chloride: 0.5 to 10.0% by mass. Petition 870260023815, dated 03 / 13 / 2026, page 17 / 113 9 / 48 [Effects of the Invention]

[0034] According to the above aspect of the present invention, it is possible to provide a grain-oriented electrical steel sheet having excellent coating adhesion, excellent coating tension, and excellent magnetic characteristics, and in which a forsterite-based coating is not provided. Furthermore, according to the above aspect of the present invention, it is possible to provide a method for forming an insulating coating embedded in a grain-oriented electrical steel sheet with excellent coating adhesion and excellent magnetic characteristics. [Brief Description of the Drawings]

[0035] Figure 1 is an example of a cross-sectional view of a grain-oriented electrical steel sheet according to the present embodiment.

[0036] Figure 2 is a cross-sectional image showing an example of an attack cavity structure of grain-oriented electrical steel sheet according to the present embodiment. [Invention Modalities]

[0037] A grain-oriented electrical steel sheet according to an embodiment of the present invention (a grain-oriented electrical steel sheet according to the present embodiment) and a method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment including a method for forming an insulating coating embedded in the grain-oriented electrical steel sheet according to the present embodiment will be described.

[0038] First, the grain-oriented electrical steel sheet according to the present embodiment will be described.

[0039] As shown in Figure 1, a grain-oriented electrical steel sheet 100 according to the present embodiment includes a base steel sheet 1 and an insulating coating 2 formed on a surface of the sheet. Petition 870260023815, dated 03 / 13 / 2026, page 18 / 113 10 / 48 of base steel 1 and does not include a forsterite-based coating on the surface of the base steel 1 sheet.

[0040] In addition, an attack cavity structure 12 is formed on the surface of the base steel sheet 1, and the insulating coating 2 includes a tension coating layer 22 formed on one surface side of the insulating coating 2 (i.e., on one surface side of the grain-oriented electrical steel sheet 100) and an intermediate layer 21 formed on one side of the base steel sheet 1 and containing a crystalline metal phosphate. cBase steel sheet> (Chemical composition)

[0041] The grain-oriented electrical steel sheet 100 according to the present embodiment is significantly distinguished by an insulating coating structure 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 and may be within a known range. In the case of obtaining characteristics generally required for a grain-oriented electrical steel sheet, the following is preferably present as the chemical composition. In the present embodiment, the % related to the chemical composition is % by mass, unless otherwise specified. C: 0.010% or less

[0042] C (carbon) is an effective element for controlling the microstructure of steel sheet in stages up to the completion of a decarburizing annealing step in the manufacturing process. However, when a C content is greater than 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 present embodiment, the C content is preferably defined as 0.010% or less. The C content is more preferably 0.005%. Petition 870260023815, dated 03 / 13 / 2026, page 19 / 113 11 / 48 or less. The C content is preferably as low as possible. However, even if the C content is reduced to less than 0.0001%, the effect of microstructure control is saturated and the manufacturing cost only increases. Therefore, the C content can be set at 0.0001% or more. Yes: 2.50% to 4.00%

[0043] Si (silicon) is an element that increases the electrical resistance of grain-oriented electrical steel sheet and improves iron loss characteristics. When a Si content is less than 2.50%, a sufficient eddy current loss reduction effect cannot be obtained. Therefore, the Si content is preferably defined as 2.50% or more. The Si content is more preferably 2.70% or more, and even more preferably 3.00% or more.

[0044] On the other hand, when the Si content is greater than 4.00%, the grain-oriented electrical steel sheet becomes brittle and the workability deteriorates significantly. In addition, the workability of the grain-oriented electrical steel sheet deteriorates and the steel sheet may fracture during rolling. Therefore, the Si content is preferably defined as 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%

[0045] Mn (manganese) is an element that binds to S in the manufacturing steps to form MnS. These precipitates act as an inhibitor (inhibit normal grain growth) and cause secondary recrystallization in steel. Mn is an element that further increases the hot workability of steel. In a case where the Mn content is less than 0.01%, the above effects cannot be sufficiently obtained. Therefore, the Mn content is preferably set at 0.01% or more. The Mn content is more preferably 0.02% or more.

[0046] On the other hand, when the Mn content is greater than 0.50%, the Petition 870260023815, dated 03 / 13 / 2026, p. 20 / 113 12 / 48 Secondary crystallization is not caused and the magnetic characteristics of the steel deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, the Mn content is preferably defined as 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

[0047] N (nitrogen) is an element that binds to Al in the manufacturing steps to form A1N, which acts as an inhibitor. However, when the N content is greater than 0.010%, an excessive amount of the inhibitor remains in the grain-oriented electrical steel sheet, and the magnetic characteristics deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, the N content is preferably defined as 0.010% or less. More preferably, the N content is 0.008% or less.

[0048] On the other hand, although a lower limit for the N content is not specifically defined, even if the N content is reduced to less than 0.001%, the cost of production only increases. Therefore, the N content can be defined as 0.001% or more. Al sol.: 0.020% or less

[0049] Acid-soluble aluminum (Al sol.) is an element that binds to N in the manufacturing steps of grain-oriented electrical steel sheet to form AlN, which acts as an inhibitor. However, when the Al sol. content of the base steel sheet is greater than 0.020%, an excessive amount of the inhibitor remains in the base steel sheet, and the magnetic characteristics deteriorate. Therefore, in the base steel sheet of grain-oriented electrical steel sheet according to the present embodiment, the Al sol. content is preferably defined as 0.020% or less. The Al sol. content is more preferably 0.010% or less, and even more preferably lower. Petition 870260023815, dated 03 / 13 / 2026, p. 21 / 113 13 / 48 that is 0.001%. Although a lower limit for the Al sol. content is not specifically defined, even if the Al sol. content is reduced to less than 0.0001%, the manufacturing cost only increases. Therefore, the Al sol. content can be defined as 0.0001% or more. S: 0.010% or less

[0050] Sulfur (S) is an element that binds to Mn during manufacturing to form MnS, which acts as an inhibitor. However, if the S content is greater than 0.010%, the magnetic characteristics deteriorate due to the remaining inhibitor. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, the S content is preferably defined as 0.010% or less. The S content in the grain-oriented electrical steel sheet is most preferably as low as possible. For example, the S content is less than 0.001%. However, even if the S content in the grain-oriented electrical steel sheet is reduced to less than 0.0001%, the manufacturing cost only increases. Therefore, the S content in the grain-oriented electrical steel sheet can be defined as 0.0001% or more. Remaining: Iron and impurities

[0051] 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 (base elements), with the remainder being Fe and impurities. However, in order to improve magnetic and similar characteristics, one or more of Sn, Cu, Se, and Sb may be additionally present in the ranges shown below. Furthermore, even if other elements besides these, for example, any one or two or more of W, Nb, Ti, Ni, Co, V, Cr, and Mo are present (intentionally or as impurities) in a total amount of 1.0% or less, the effects of the grain-oriented electrical steel sheet according to the present embodiment are not impaired. Petition 870260023815, dated 03 / 13 / 2026, page 22 / 113 14 / 48

[0052] Here, impurities mean elements that are incorporated from the ore as raw material, scrap, or manufacturing environment when the base steel sheet is industrially manufactured, and may be present in quantities that do not adversely affect the actions of the grain-oriented electrical steel sheet according to the present embodiment. Sn: 0% to 0.50%

[0053] Tin (Sn) is an element that contributes to the improvement of magnetic characteristics through the control of the microstructure of the primary crystallization. To obtain the effect of improving magnetic characteristics, a Sn content is preferably defined as 0.01% or more. The Sn content is more preferably 0.02% or more, and even more preferably 0.03% or more.

[0054] On the other hand, in a case where the Sn content is greater than 0.50%, secondary recrystallization becomes unstable and the magnetic characteristics deteriorate. Therefore, the Sn content is preferably defined as 0.50% or less. The Sn content is preferably 0.30% or less, and more preferably 0.10% or less. Cu: 0% to 0.50%

[0055] Cu (copper) is an element that contributes to an increase in the participation of Goss orientation in a secondary recrystallization structure. To obtain the above effect, a Cu content is preferably defined as 0.01% or more. The Cu content is more preferably 0.02% or more, and even more preferably 0.03% or more.

[0056] On the other hand, in the case where the Cu content is greater than 0.50%, the steel sheet becomes brittle during hot rolling. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment, the Cu content is preferably defined as 0.50% or less. The Cu content is more preferably 0.30% or less, and even more preferably 0.10% or less. Petition 870260023815, dated 03 / 13 / 2026, p. 23 / 113 15 / 48 If: 0% to 0.020%

[0057] Se (selenium) is an element that has the effect of improving magnetic characteristics. In a case where Se is present, a Se content is preferably defined as 0.001% or more in order to satisfactorily exhibit the effect of improving magnetic characteristics. The Se content is more preferably 0.003% or more, and even more preferably 0.006% or more.

[0058] On the other hand, when the Se content is greater than 0.020%, the coating adhesion deteriorates. Therefore, the Se content is preferably defined as 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%

[0059] Sb (antimony) is an element that has the effect of improving magnetic characteristics. In a case where Sb is present, an Sb content is preferably defined as 0.005% or more in order to satisfactorily exhibit the effect of improving magnetic characteristics. The Sb content is more preferably 0.01% or more, and even more preferably 0.02% or more.

[0060] On the other hand, when the Sb content is greater than 0.50%, the coating adhesion deteriorates significantly. Therefore, the Sb content is preferably defined as 0.50% or less. The Sb content is more preferably 0.30% or less, and even more preferably 0.10% or less.

[0061] As described above, by way of example, the base steel sheet of the grain-oriented electrical steel sheet in the present embodiment contains, as its chemical composition, the base elements described above and the remainder being Fe and impurities, or contains the base elements and additionally contains one or more other optional elements and the remainder being Petition 870260023815, dated 03 / 13 / 2026, page 24 / 113 16 / 48 Fe and impurities.

[0062] 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 atomic emission spectrometry. Si is obtained by a method specified in JIS G 1212 (1997) (Methods for determining silicon content). Specifically, when the chips are dissolved in an acid, silicon oxide precipitates as a precipitate. This precipitate (silicon oxide) is filtered with filter paper and its mass is measured to obtain the Si content.

[0063] The C content and S content are obtained by a well-known high-frequency combustion method (infrared absorption combustion method). Specifically, the solution described above is burned by high-frequency heating in an oxygen gas stream, and the carbon dioxide and sulfur dioxide thus generated are detected to obtain the C content and S content.

[0064] The N content is obtained using a well-known method of thermal conductivity by inert gas fusion.

[0065] However, when the measurement is performed, in a case where the insulating coating is formed on the surface, the measurement is performed after the removal of the insulating coating. As a removal method, the insulating coating can be removed by immersion in a high-concentration alkaline solution (e.g., a 30% sodium hydroxide solution heated to 85°C) for 20 minutes or more. Whether or not flaking has occurred can be determined visually. In the case of a small sample, flaking can be performed by surface sanding. (Attack cavity structure)

[0066] As shown in Figure 2, the grain-oriented electrical steel sheet 100 according to the present embodiment has the structure of an attack cavity 12 (attack cavities (portions indicated by arrows in Petition 870260023815, dated 03 / 13 / 2026, page 25 / 113 17 / 48 Figure 2) are formed) on the surface of the base steel plate 1.

[0067] The attack cavity structure is a rectangular structure formed by attack cavities formed by the corrosion of a (110) plane, which is a crystalline structure of the grain-oriented electrical steel sheet, and is a structure in which the surface of the steel sheet appears to be coated with minute rectangles in a case where the surface of the grain-oriented electrical steel sheet is observed with a scanning electron microscope (SEM) at a predetermined magnification (5,000 times in Figure 2). In the present embodiment, a rectangular structure in which the size (average size) of a structure is about 0.01 to 0.10 pm in the rolling direction of the grain-oriented electrical steel sheet, which is the base steel sheet, and about 0.005 to 0.050 pm in an orthogonal direction, which is a direction orthogonal to the rolling direction, is defined as the attack cavity structure.

[0068] It is assumed that when an intermediate layer, which will be described later, is formed on the base steel plate having such an attack cavity structure, the attack cavity portion serves as an origin for the formation of a dense intermediate layer, and an effect of improving adhesion is obtained.

[0069] In the attack cavity structure of the grain-oriented electrical steel sheet according to the present embodiment, as shown in Figure 2, a base angle of a recessed piece is about 90°, since a crystal orientation (in which the sharp GOSS orientation is increased) of a base metal is reflected.

[0070] An area ratio, which is the ratio of an area occupied by the rectangular thin structure as described above on the surface of the base steel sheet, is preferably 5% or more in order to obtain a sufficient effect. By making the thin structure as described above have an area ratio of 10% or more, the adhesion between the grain-oriented electrical steel sheet Petition 870260023815, dated 03 / 13 / 2026, page 26 / 113 18 / 48, which is the base steel plate, and the tension application coating is further improved. The area ratio is most preferably 15% and even more preferably 20%. A higher area ratio is not particularly specified, but an area ratio value need not be very large because the intermediate layer itself also has the effect of adhesion to the steel plate.

[0071] In grain-oriented electrical steel sheet, which is the base steel sheet, most crystal orientations are <110> (001). Therefore, in a case where a cross-section is observed in a thickness direction of the steel sheet in the direction orthogonal to the rolling direction, the lead cavity appears as a linear depression having an included angle of 45°. Therefore, the area ratio of the lead cavity structure can be measured by measuring the lengths occupied by the depressions caused by the lead cavities in the measured lengths. <Revestimento Isolante>

[0072] In the grain-oriented electrical steel sheet 100 according to the present embodiment, the insulating coating 2 is formed on the surface of the base steel sheet 1. More specifically, the grain-oriented electrical steel sheet 100 according to the present embodiment does not have a forsterite-based coating. Furthermore, an S1O2 layer as shown in Patent Documents 3 and 4 is also not provided. Therefore, the insulating coating 2 is formed in direct contact with the base steel sheet 1.

[0073] In addition, the insulating coating 2 includes the intermediate layer 21 and the tension coating layer 22, in order from the side of the base steel sheet 1. (Intermediate Layer)

[0074] Intermediate layer 21 is a layer (coating) containing a crystalline metal phosphate and with a thickness of 0.2 to 10.0 pm. Petition 870260023815, dated 03 / 13 / 2026, page 27 / 113 19 / 48

[0075] As described above, in general, a grain-oriented electrical steel sheet has a forsterite-based coating generated in a secondary recrystallization annealing step and an insulating coating (voltage insulating coating) formed over it. However, in recent years, it has become clear that this forsterite-based coating hinders the movement of the magnetic domain walls and has an adverse effect on iron loss, and a grain-oriented electrical steel sheet without a forsterite-based coating has been examined in order to further improve the magnetic characteristics. However, in a case where the forsterite-based coating is not present, it is difficult to ensure sufficient adhesion between the voltage coating and the surface of the base steel sheet.

[0076] In the grain-oriented electrical steel sheet according to the present embodiment, the intermediate layer 21 containing crystalline metal phosphate is formed between the base steel sheet 1 and the tension coating, whereby the adhesion between the base steel sheet 1 and the tension coating layer 22 is improved by means of the intermediate layer 21.

[0077] This occurs because when the intermediate layer 21 contains the crystalline metal phosphate, the strain coating (which becomes the strain coating layer 22 after formation) formed on the intermediate layer 21 also contains the metal phosphate and therefore has a high affinity, and the adhesion between the intermediate layer and the strain coating layer is excellent. Furthermore, as will be described later, in a case where the intermediate layer is formed by immersion in a treatment liquid containing a metal phosphate, the intermediate layer can be formed on the surface of the base steel plate 1 using a chemical reaction, the adhesion between the intermediate layer 21 and the base steel plate 1 can also be guaranteed.

[0078] In a case where the intermediate layer 21 does not contain Petition 870260023815, dated 03 / 13 / 2026, page 28 / 113 20 / 48 a crystalline metal phosphate, the above effect cannot be obtained. A proportion of crystalline metal phosphate in the intermediate layer is preferably 80% by mass or more, and more preferably 90% by mass or more, and may be 100% by mass. The metal phosphate is one or two or more among zinc phosphate, manganese phosphate, iron phosphate and zinc-calcium phosphate in terms of adhesion.

[0079] In terms of adhesion to the base steel sheet, in metal phosphate, the total amount (mol) of a metal (M) and Fe is preferably 2.0 times or more, and more preferably 3.0 times or more the amount (mol) of P.

[0080] When the metal phosphate is a hydrate, the corrosion resistance decreases. Therefore, it is preferable that the metal phosphate not be a hydrate. In the hydrate, the total amount (mol) of the metal (M) and Fe described above is generally 1.5 times or less the amount (mol) of P. Even in the grain-oriented electrical steel sheet according to the present embodiment, there are cases where a hydrate inevitably generated in an intermediate layer formation process ultimately remains, but in small quantity (typically less than 5.0% by mass of the entire insulating coating 2).

[0081] From the point of view of adhesion, colloidal silica is not present in the treatment liquid when the intermediate layer is formed. There are cases where a remnant other than metal phosphate in the intermediate layer contains an oxide or an element such as Fe or Si diffused from the base steel sheet, but silica is not intentionally present as described above. Therefore, the Si content is, for example, 1.0% by mass or less.

[0082] Although intermediate layer 21 is formed at a different time than the voltage coating formed in intermediate layer 21, both intermediate layer 21 and voltage coating layer 22 are effective as insulating coating 2. Petition 870260023815, dated 03 / 13 / 2026, page 29 / 113 21 / 48

[0083] The amount (mol) of metal (M), the amount (mol) of Fe and the amount (mol) of P in the metal phosphate are obtained by analyzing a cross-section of the insulating coating in the thickness direction using electron scattering spectroscopy (EDS). The measurement is performed at approximately three locations, and an average value thereof is considered as the amount (mol) of the corresponding element.

[0084] Furthermore, the amount of hydrate can be obtained approximately by measuring the amount of water by a thermoequilibrium method.

[0085] An average thickness of the intermediate layer 21 is 0.2 to 10.0 pm.

[0086] When the average thickness of the intermediate layer 21 is less than 0.2 µm, the effect of improving adhesion between the base steel sheet and the insulating coating through the intermediate layer is insufficient. On the other hand, when the average thickness of the intermediate layer is greater than 10.0 µm, the deterioration of the magnetic characteristics becomes significant. (Tension coating layer)

[0087] In the grain-oriented electrical steel sheet according to the present embodiment, the voltage coating layer 22 is provided on the surface side of the insulating coating 2 forming the voltage coating on a surface of the intermediate layer 21.

[0088] The tension coating layer 22 is not particularly limited, provided that the tension coating layer 22 is used as an insulating coating of the grain-oriented electrical steel sheet, but from the point of view of adhesion to the intermediate layer 21 (adhesion to the base steel sheet 1 through the intermediate layer 21), it contains a metal phosphate and silica (derived from colloidal silica in the coating liquid) such that a silica content is 20% by mass or more. On the other hand, when the content of Petition 870260023815, dated 03 / 13 / 2026, p. 30 / 113 22 / 48 silica in the tension coating layer is greater than 60% by mass, as silica causes pulverization. Therefore, the silica content of the tension coating layer is defined as 60% by mass or less.

[0089] The 22 tension coating layer preferably contains 70% or more by mass of metal phosphate and silica in total. There are cases where a remainder in addition to metal phosphate and silica contains fine ceramic particles, such as alumina and silicon nitride.

[0090] The thickness of the tension coating layer 22 is not limited, but an average thickness of the insulating coating 2 (the intermediate layer 21 + the tension coating layer 22) is defined as 2.0 to 10.0 pm in a case where the average thickness of the intermediate layer 21 is within the above range. When the average thickness of the insulating coating 2 is less than 2.0 pm, it is not possible to obtain sufficient coating tension. Furthermore, the elution of phosphoric acid increases. In this case, stickiness or decreased corrosion resistance may occur, which can cause coating flaking. Additionally, when the thickness of the insulating coating 2 is greater than 10.0 pm, its lamination factor decreases and the magnetic characteristics deteriorate, or cracks or similar cause a decrease in adhesion or a decrease in corrosion resistance.

[0091] The thickness of the insulating coating 2 is obtained by the following method.

[0092] An average thickness can be measured by observing a cross-section of a sample with a scanning electron microscope and measuring thicknesses at five or more points. In the insulating coating 2, the intermediate layer 21 and the tension coating layer 22 can be distinguished from each other by the amount of silicon (Si) derived from silica (the tension coating layer contains silica as described above).

[0093] In addition, the average thickness of the insulating coating 2 can Petition 870260023815, dated 03 / 13 / 2026, page 31 / 113 23 / 48 can be obtained by adding the average thickness of the intermediate layer 21 and the average thickness of the tension coating layer 22.

[0094] In the intermediate layer 21 and in the stress coating layer 22, a mass ratio of metal phosphate and a type of metal phosphate can be obtained by the following methods.

[0095] Similar to the method for measuring the thicknesses of the intermediate layer 21 and the stress coating layer 22, the mass ratio of the metal phosphate and the type of metal phosphate can be specified using a scanning electron microscope and an EDS probe.

[0096] Furthermore, whether or not the intermediate layer metal phosphate 21 is a crystalline metal phosphate can be determined by an X-ray crystal structure analysis method.

[0097] In addition, the silica content of the 22 tension coating layer can be measured using a scanning electron microscope and an EDS probe. <Método de fabricação>

[0098] 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. However, naturally, the grain-oriented electrical steel sheet according to the present embodiment is not particularly limited to the manufacturing method. That is, the grain-oriented electrical steel sheet with the configuration described above is considered to be the grain-oriented electrical steel sheet according to the present embodiment, regardless of its manufacturing conditions.

[0099] Grain-oriented electrical steel sheet according to the present embodiment can be manufactured by a manufacturing method that includes: Petition 870260023815, dated 03 / 13 / 2026, page 32 / 113 24 / 48 (I) a hot rolling step of carrying out hot rolling on a piece of steel with a predetermined chemical composition to obtain a hot-rolled sheet (hot-rolled steel sheet); (II) a hot-rolled sheet annealing step for annealing the hot-rolled sheet; (III) a cold rolling stage to perform cold rolling on hot-rolled sheet after annealing the hot-rolled sheet to obtain a steel sheet (cold-rolled sheet); (IV) a decarburization annealing step to perform decarburization annealing on the steel sheet; (V) a secondary recrystallization annealing step involving the application of an annealing separation agent containing 10 to 100% by mass of Al2O3 to the steel sheet after the decarburization annealing step, drying of the steel sheet and subsequently performing secondary recrystallization annealing on the steel sheet; (VI) an annealing separation agent removal step to remove an excess amount of the annealing separation agent from the steel sheet after the secondary recrystallization annealing step; (VII) an acid treatment step of immersing the steel plate after the removal of the annealing separating agent step in a mixed acid in which a concentration of one or two or more selected from sulfuric acid, phosphoric acid and nitric acid is 0.5 to 20% by weight and a liquid temperature is 40°C to 90°C for 5 to 50 seconds; (VIII) a step of immersing the steel sheet after the acid treatment step in a treatment liquid containing 5 to 50% by mass of a metal phosphate at a liquid temperature of 40°C to 85°C for 5 to 150 seconds; (IX) a drying step which involves removing the sheet from Petition 870260023815, dated 03 / 13 / 2026, page 33 / 113 25 / 48 steel after the treatment liquid immersion step, removal of an excess amount of the treatment liquid, and subsequent drying of the steel sheet; and (X) a tension coating layer formation step for applying a coating liquid containing a metal phosphate and colloidal silica, such that the amount of colloidal silica is 30 to 150 parts by mass in relation to 100 parts by mass of metal phosphate on the steel sheet after the drying step, drying of the steel sheet and subsequently maintaining the steel sheet in a state where the sheet temperature is 700°C to 950°C for 10 to 120 seconds.

[00100] In addition, the method of manufacturing the grain-oriented electrical steel sheet according to the present embodiment may further include either or both of (XI) a nitriding treatment step to perform a nitriding treatment on the steel sheet between the decarburizing annealing step and the secondary recrystallization annealing step, and (XII) a magnetic domain refinement step to perform magnetic domain control on the steel sheet after the stress coating layer formation step.

[00101] In addition, the method of manufacturing the grain-oriented electrical steel sheet according to the present embodiment may additionally include, between the annealing separation agent removal step and the immersion step, (XIII) a surface adjustment step to control the reactivity of a steel sheet surface.

[00102] Among the steps, the manufacturing of the grain-oriented electrical steel sheet according to the present embodiment is distinguished by the steps from (V) the secondary recrystallization annealing step to (X) the stress coating layer formation step, which are related Petition 870260023815, dated 03 / 13 / 2026, page 34 / 113 26 / 48 mainly to the formation of the insulating coating, and known conditions may be adopted for the other stages or conditions not described.

[00103] These steps will be described next. <Etapa de laminação a quente>

[00104] In the hot rolling stage, a piece of steel, such as a plate with a predetermined chemical composition, is heated and then hot-rolled to obtain a hot-rolled sheet. The heating temperature of the steel piece is preferably set to be in a range of 1,100°C to 1,450°C. The heating temperature is more preferably 1,300°C to 1,400°C.

[00105] The chemical composition of the steel part can be altered depending on the chemical composition of the grain-oriented electrical steel sheet to be finally obtained. For example, 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%, Sb: 0% to 0.50%, and the remainder being Fe and impurities may be present as an example of the chemical composition.

[00106] The hot rolling conditions are not particularly limited and can be suitably defined based on the required characteristics. The sheet thickness of the hot-rolled sheet is preferably in a range of, for example, 2.0 mm or more and 3.0 mm or less. <Etapa de recozimento de chapa laminada a quente>

[00107] The annealing stage of hot-rolled sheet is an annealing stage of hot-rolled sheet manufactured through the hot rolling stage. By performing such an annealing treatment, recrystallization occurs in a structure of the steel sheet, and good magnetic characteristics can be obtained, which is preferable.

[00108] In the case of annealing hot-rolled sheet metal, Petition 870260023815, dated 03 / 13 / 2026, page 35 / 113 27 / 48 Hot-rolled sheet manufactured through the hot rolling stage can be annealed according to a known method. A measure for heating the hot-rolled sheet during annealing is not particularly limited, and a known heating method can be adopted. Furthermore, the annealing conditions are not particularly limited. For example, the hot-rolled sheet can be annealed in a temperature range of 900°C to 1200°C for 10 seconds to 5 minutes. <Etapa de laminação a frio>

[00109] In the cold rolling stage, cold rolling is performed on hot-rolled sheet after the annealing stage of the hot-rolled sheet to obtain a steel sheet (cold-rolled sheet). Like cold rolling, cold rolling can be performed once (a series of passes without annealing between them), or cold rolling can be performed a plurality of times with process annealing between them, stopping the cold rolling before the final pass of the cold rolling stage and performing process annealing at least one or two or more times.

[00110] In the case of carrying out the annealing process, the holding time is preferably achieved at a temperature of 1,000°C to 1,200°C for 5 to 180 seconds. An annealing atmosphere is not particularly limited. The number of times the annealing process is carried out is preferably 3 or less, considering the manufacturing cost.

[00111] In addition, a surface of the hot-rolled sheet can be pickled before the cold rolling stage.

[00112] In the cold rolling stage according to the present embodiment, the hot-rolled sheet after the annealing stage of the hot-rolled sheet can be cold-rolled to obtain a steel sheet according to a known method. For example, a final rolling reduction can be in the range of 80% to 95%. When the final rolling reduction Petition 870260023815, dated 03 / 13 / 2026, page 36 / 113 28 / 48 is 80% or more, Goss grains with a sharp Goss orientation can be obtained in which a {110} orientation <001> It is aligned in a rolling direction, which is preferable. On the other hand, in a case where the final rolling reduction is greater than 95%, it is highly likely that the secondary recrystallization will become unstable in the subsequent secondary recrystallization annealing step, which is not preferable.

[00113] Final rolling reduction is a cumulative cold rolling reduction and is a cumulative cold rolling reduction after final process annealing in a case where process annealing is performed. <Etapa de recozimento por descarbonetação>

[00114] In the decarburization annealing stage, decarburization annealing is performed on the steel sheet obtained after the cold rolling stage. In decarburization annealing, the conditions for annealing are not limited, provided that the steel sheet can be primarily recrystallized and C, which adversely affects magnetic characteristics, can be removed from the steel sheet. However, as an example, holding at an annealing temperature of 800°C to 900°C is carried out with a degree of oxidation (PH2O / PH2) of 0.3 to 0.6 in an annealing atmosphere (atmosphere in the furnace) for 10 to 600 seconds. <Etapa de Tratamento de Nitretação>

[00115] A nitriding treatment can be performed between the decarburization annealing step and the secondary recrystallization annealing step described below.

[00116] In the nitriding treatment stage, for example, the nitriding treatment is carried out by maintaining the steel sheet after the decarburizing annealing stage at approximately 700°C to 850°C in a nitriding treatment atmosphere (an atmosphere containing a gas with nitriding capacity, such as hydrogen, nitrogen, and ammonia). In a Petition 870260023815, dated 03 / 13 / 2026, page 37 / 113 29 / 48 In cases where A1N is used as an inhibitor, it is preferable that the N content of the steel sheet after the nitriding treatment step be set to 40 ppm or more by the nitriding treatment. On the other hand, in a case where the N content of the steel sheet after the nitriding treatment step is greater than 1,000 ppm, an excessive amount of A1N is present in the steel sheet even after the completion of secondary recrystallization in secondary recrystallization annealing. Such A1N causes iron loss deterioration. Therefore, the N content of the steel sheet after the nitriding treatment step is preferably set to 1,000 ppm or less. <Etapa de recozimento por rccristalização secundária>

[00117] In the secondary rccrystallization annealing step, an annealing separation agent containing 10 to 100% by mass of Al2O3 is applied to the steel sheet after the decarburization annealing step or additionally after nitriding treatment (after the nitriding treatment step) and dried, and subsequently secondary rccrystallization annealing is performed.

[00118] In a method of manufacturing a grain-oriented electrical steel sheet in the related art, a forsterite-based coating is formed on the surface of a steel sheet (cold-rolled sheet) by applying an annealing separation agent containing mainly MgO and performing secondary recrystallization annealing. On the other hand, in the method of manufacturing the grain-oriented electrical steel sheet according to the present embodiment, the annealing separation agent containing Al2O3 is used so as not to form a forsterite-based coating.

[00119] On the other hand, an Al2O3 proportion can be 100% by mass. However, from the point of view of preventing Al2O3 from adhering to the surface of the steel sheet, in the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment, the agent of Petition 870260023815, dated 03 / 13 / 2026, page 38 / 113 30 / 48 annealing separation preferably contains MgO. The proportion of MgO can be 0%. However, in order to obtain the above effect, the proportion of MgO is preferably set at 5% by mass or more. In a case where MgO is present, the proportion of MgO is set at 90% by mass or less in order to ensure 10% by mass or more of Al2O3. The proportion of MgO is preferably 50% by mass or less.

[00120] Furthermore, in the manufacturing method of grain-oriented electrical steel sheet according to the present embodiment, the annealing separating agent may additionally contain a chloride. When the annealing separating agent contains a chloride, an effect of preventing the formation of a forsterite-based coating can be obtained. A chloride content is not particularly limited and can be 0%. However, in the case of obtaining the above effect, the chloride content is preferably from 0.5 to 10% by mass. As chlorides, for example, bismuth chloride, calcium chloride, cobalt chloride, iron chloride and nickel chloride are effective.

[00121] Although the conditions for annealing by secondary recrystallization are not limited, for example, conditions can be adopted in which maintenance at a temperature of 1,150°C to 1,250°C is carried out for 10 to 60 hours. <Etapa de remoção do agente de separação de recozimento>

[00122] An excess amount of the annealing separator is removed from the steel sheet after the annealing step by secondary recrystallization. For example, an excess amount of the annealing separator can be removed by washing with water. <Etapa de tratamento ácido>

[00123] The steel sheet after the removal of the annealing separator agent is immersed in a mixed acid in which the concentration of one or two or more acids selected from sulfuric acid, phosphoric acid and nitric acid is 0.5 to 20% by weight and the liquid temperature is 40°C to Petition 870260023815, dated 03 / 13 / 2026, page 39 / 113 31 / 48 90°C for 5 to 50 seconds to form attack cavities on the surface. The above conditions cause a difference in the corrosion rate depending on the crystal orientations, and under these conditions, predetermined attack cavities are formed.

[00124] When the acid used for immersion is an acid other than sulfuric acid, phosphoric acid, and nitric acid, the formation of attack cavities is insufficient and adhesion becomes inferior.

[00125] When the acid concentration is less than 0.5% by weight, it takes a long time to form attack cavities, and the formation of attack cavities is insufficiently achieved by usual treatment. When the acid concentration is greater than 20% by weight, the solubility of the acid is very high and it becomes difficult to form attack cavities, so adhesion becomes inferior.

[00126] When the liquid temperature is below 40°C, it takes a long time to form attack cavities, which is cost-effective. When the liquid temperature is above 90°C, the acid solubility is very high, making it difficult to form attack cavities and resulting in lower adhesion. When the immersion time is less than 5 seconds, the formation of attack cavities is insufficient and adhesion is lower. When the immersion time is greater than 50 seconds, the iron dissolves excessively, making it difficult to form attack cavities and resulting in lower adhesion. <Etapa de ajuste de superfície>

[00127] The surface treatment step to control the reactivity of the steel sheet surface can be performed between the annealing separation agent removal step and the immersion step.

[00128] Although the conditions of the surface adjustment step are not limited, the conditions under which the steel sheet after the removal of the annealing separation agent is immersed in an agent of Petition 870260023815, dated 03 / 13 / 2026, page 40 / 113 32 / 48 surface adjustments commercially available for 30 seconds to 1 minute can be used as an example. <Etapa de Imersão> <Etapa de secagem>

[00129] The steel sheet after the acid treatment step (or additionally after performing the surface treatment step as needed) is immersed in a treatment liquid containing 5 to 50% by mass of a predetermined metal phosphate at a liquid temperature of 40°C to 85°C for 5 to 150 seconds (immersion step). After that, the steel sheet is removed from the treatment liquid, an excess amount of the treatment liquid is removed, and then the steel sheet is dried (drying step). Consequently, an intermediate layer containing a crystalline metal phosphate is formed on the surface of the steel sheet (base steel sheet).

[00130] When the liquid temperature is less than 40°C or the immersion time is less than 5 seconds, it is not possible to obtain an intermediate layer with sufficient thickness. On the other hand, when the liquid temperature is greater than 85°C or the immersion time is greater than 150 seconds, the thickness of the intermediate layer becomes excessive.

[00131] Furthermore, when the amount of metal phosphate in the treatment liquid is less than 5% by mass, the formation of the intermediate layer is slow and incurs a high industrial cost. Additionally, in a case where the thickness of the intermediate layer coating is uniform, the amount of metal phosphate is preferably 10% by mass or more. On the other hand, when the amount of metal phosphate is greater than 50% by mass, the crystal grains may become coarse and cause a decrease in adhesion. The metal phosphate present in the treatment liquid may be one or two or more types of zinc phosphate, manganese phosphate, or zinc-calcium phosphate. Petition 870260023815, dated 03 / 13 / 2026, page 41 / 113 33 / 48

[00132] Furthermore, when the drying temperature is high, there is concern that voids will be generated and adhesion will be inferior. Therefore, the drying temperature is preferably set to 300°C or lower. The drying temperature is more preferably 200°C or lower. The drying temperature is preferably 100°C or higher. <Etapa de formação da camada de revestimento de tensão>

[00133] In the tensioned coating layer formation stage, a solution (coating liquid) containing a metal phosphate and colloidal silica is applied to the steel sheet after the drying stage (the steel sheet in which the intermediate layer is formed on the base steel sheet) and dried, and subsequently the steel sheet is held in a state where the sheet temperature is 700°C to 950°C for 10 to 120 seconds to form a tension coating. A layer formed by the tension coating (tension coating layer 22) and the intermediate layer 21 become the insulating coating 2.

[00134] When the plate temperature is below 700°C, the magnetic characteristics become inferior due to the low voltage. 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, there are instances where the steel plate undergoes deformation due to heat transfer or something similar, and the magnetic characteristics become inferior. Therefore, the plate temperature is preferably set to 950°C or lower.

[00135] Furthermore, when the retention time is less than 10 seconds, the elution property becomes less effective. Therefore, the retention time is defined as 10 seconds or more. On the other hand, when the waiting time is greater than 120 seconds, productivity becomes less effective. Therefore, the retention time is preferably 120 seconds or less. Petition 870260023815, dated 03 / 13 / 2026, page 42 / 113 34 / 48 less.

[00136] The coating liquid contains metal phosphate and colloidal silica, such that the colloidal silica is present in an amount of 30 to 150 parts by mass relative to 100 parts by mass of metal phosphate. As 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, barium phosphate, cobalt phosphate, strontium phosphate and the like may be used.

[00137] The coating liquid may contain vanadium, tungsten, molybdenum, zirconium and the like as additional elements. In the case where these elements are present, they may be added to the coating liquid, for example, in the form of an oxyacid.

[00138] As colloidal silica, either type S or type C colloidal silica can be used. Type S colloidal silica refers to colloidal silica in which the silica solution is alkaline, and type C refers to colloidal silica in which the silica solution is alkaline to neutral and in which an aluminum treatment is performed on a silica particle surface. Type S colloidal silica is widely used and relatively inexpensive, but there is concern that type S colloidal silica will aggregate and precipitate when mixed with an acidic metal phosphate solution. Therefore, caution is necessary. Type C colloidal silica is stable even when mixed with a metal phosphate solution and there is no concern about precipitation. However, the number of treatment steps is large and type C colloidal silica is relatively expensive. It is preferable to use colloidal silica appropriately depending on the stability of the coating liquid to be prepared. <Etapa de Refino do Domínio Magnético>

[00139] The manufacturing method for grain-oriented electrical steel sheet according to the present embodiment may additionally include the step of refining the magnetic domain to perform domain refinement. Petition 870260023815, dated 03 / 13 / 2026, page 43 / 113 35 / 48 magnetic on steel plate.

[00140] By performing a magnetic domain refining treatment, the iron loss from grain-oriented electrical steel sheet can be further reduced.

[00141] As a magnetic domain refinement treatment method, there is a method for narrowing a magnetic domain width by 180° (refining a 180° magnetic domain) by forming linear or point-shaped groove portions that extend in a direction that crosses a rolling direction at predetermined intervals along the rolling direction, and as a magnetic domain control treatment method, in a case where the magnetic domain control treatment is performed after the formation of the insulating coating, there is a method for narrowing a magnetic domain width by 180° (refining a 180° magnetic domain) by forming stress-strain portions or linear or point-shaped groove portions that extend in a direction that crosses a rolling direction at predetermined intervals along the rolling direction.

[00142] In the case of forming stress-strain portions, laser beam irradiation, electron beam irradiation, or similar methods may be applied. In the case of forming groove portions, a mechanical groove-forming method using a gear or similar, a chemical groove-forming method to form a groove by electrolytic etching, or a thermal groove-forming method using laser irradiation or similar methods may be applied.

[00143] In a case where the insulating coating is damaged due to the formation of stress zones or grooves and characteristics such as insulation properties deteriorate, the insulating coating can be reformed to repair the damage. Petition 870260023815, dated 03 / 13 / 2026, page 44 / 113 36 / 48 [Examples]

[00144] A plate containing, in % by mass, C: 0.08%, Si: 3.29%, Al sol.: 0.028%, N: 0.008%, Mn: 0.15%, S: 0.007%, and a remainder being Fe and impurities was melted.

[00145] This plate was heated to 1,350°C and then hot-rolled to obtain a hot-rolled sheet with a sheet thickness of 2.2 mm.

[00146] This hot-rolled sheet was annealed at 1,100°C for 10 seconds (hot-rolled sheet annealing) and then cold-rolled until the sheet thickness reached 0.22 mm to obtain a steel sheet.

[00147] This steel plate was subjected to decarburization annealing in an atmosphere of (PH2O / PH2) of 0.4 at 830°C for 90 seconds.

[00148] Subsequently, excluding No. 115, an annealing separation agent containing 48% by mass of Al2Oβ, 48% by mass of MgO and 4% by mass of bismuth chloride was applied to the steel plate and dried, and then secondary recrystallization annealing was performed on the steel plate at 1200°C for 20 hours. For No. 115, an annealing separation agent containing only Al2O3 (100% by mass) was applied to the steel plate and dried, and then secondary recrystallization annealing was performed on the steel plate at 1200°C for 20 hours.

[00149] When an excessive amount of the annealing separation agent was removed from the steel sheet after the secondary recrystallization annealing step by washing with water, no forsterite-based coating was formed on the surface of the steel sheet.

[00150] As shown in Table 2, this steel plate was subjected to an acid treatment in which the steel plate was immersed in an acid under any of the conditions in Table 1 to form attack cavities.

[00151] After that, the steel plate was immersed in the liquid of Petition 870260023815, dated 03 / 13 / 2026, page 45 / 113 37 / 48 treatment shown in Table 2 and then heated to 100°C to 150°C and dried to form an intermediate layer. An average thickness of the intermediate layer is shown in Table 2.

[00152] As a result of an X-ray crystal structure analysis method, the metal phosphates in the intermediate layers from numbers 101 to 126 were all crystalline metal phosphates. In these crystalline metal phosphates, the ratio between the total amount (mol) of a metal (M) and Fe and the amount of P (mol) was approximately 2:1 or 3:1. Petition 870260023815, dated 03 / 13 / 2026, page 46 / 113 38 / 48 [Table 1] No. of Condition Acid Treatment Liquid Treatment Conditions Temperature (°C) Time (s) 1 5% by weight sulfuric acid 85 15 2 10% by weight phosphoric acid 85 10 3 10% by weight sulfuric acid + 2% by weight nitric acid 80 5 4 2% by weight sulfuric acid + 3% by weight phosphoric acid 85 45 5 20% by weight phosphoric acid 80 12 6 0.3% by weight sulfuric acid 85 10 7 10% by weight sulfuric acid + 25% by weight phosphoric acid 80 15 8 5% by weight sulfuric acid 85 3 9 5% by weight sulfuric acid 85 100 10 5% by weight hydrochloric acid 80 15 Petition 870260023815, dated 03 / 13 / 2026, page 47 / 113 σχ CO Intermediate Layer I Average Thickness (pm) 1 ãi 0.7 | 2.1 0.9 | 4.5 3.2 o' 3.6 9'1 2.4 1 9I 4.1 3.8 1 1 1.9 | 1 z'i 1 1 9I 0.9 | Metal Phosphate Proportion (% by mass) 94 94 00 OS | Z6 00 OS 94 CN OS 00 OS 06 00 OS 94 00 OS 00 OS 1 94 94 1 94 94 | 176 Metal phosphate detected at 5% by mass or more Zinc phosphate | Zinc phosphate | Manganese phosphate + iron phosphate Zinc phosphate | Manganese phosphate + iron phosphate Manganese phosphate Zinc phosphate | Manganese phosphate + iron phosphate Calcium and zinc phosphate Manganese phosphate Zinc phosphate | Manganese phosphate Manganese phosphate Zinc phosphate | Zinc phosphate | Zinc phosphate | Zinc phosphate | Zinc phosphate | Zinc phosphate | Immersion step Treatment conditions Time (s) 30 30 O 30 V) 30 or—d 09 20 25 S© 140 100 60 60 30 30 30 Temperature (°C) 1 Ofr 1 Ofr 80 1 017 80 60 40 | 75 75 60 1 Ofr 65 65 1 sp 1 1 sp 1 1 Ofr 1 Ofr 1 Ofr Amount of metal phosphate in the treatment liquid (% by mass)| 0Z | OZ V) cn | OZ V) cn cn SO V) cn CN O r—d | OZ cn cn 1 0Z 1 1 0Z 1 | OZ | OZ | OZ Metal phosphate present in the treatment liquid Zinc phosphate | Zinc phosphate | Manganese phosphate Zinc phosphate | Manganese phosphate Manganese phosphate Zinc phosphate | Manganese phosphate Calcium and zinc phosphate Manganese phosphate Zinc phosphate | Manganese phosphate Manganese phosphate Zinc phosphate | Zinc phosphate | Zinc phosphate | Zinc phosphate | Zinc phosphate | Ratio of attack cavity structure area to surface area (%) V) cn 1 sz 1 00 30 | or—d 25 V) V) 00 70 V) 1 0* 20 or—d V) cn 1 £9 cn o cn n° of Acid treatment condition cn Tt V) cn V) C4 cn Tf V) s© 00 □NO CN O 103 o 105 106 δ 108 109 110 111 112 113 s© 117 8Π Petition 870260023815, dated 03 / 13 / 2026, page 48 / 113 Intermediate Layer I Average Thickness (pm) 3.3 3.4 0.1 12.8 00 0' 3.4 0.5 o' Metal Phosphate Proportion (% by mass) 00 0.5 00 0.5 97 96 | 96 94 | 96 | 176 Metal Phosphate detected at 5% by mass or more Manganese Phosphate Manganese Phosphate Manganese Phosphate Manganese Phosphate Zinc Phosphate | Manganese Phosphate Zinc Phosphate | Zinc Phosphate | Immersion Step Treatment Conditions Time (s) V) V) <nl 160 sd 120 30 temperatura (°c) 80 40 06 1 ofr | i 0* quantidade de fosfato metal no líquido tratamento (% em massa) v) cn 0z o r—d cn 20 fosfato presente manganês zinco razão da área estrutura cavidade ataque para a superfície (%) o sz n° condição ácido os c4 □n 119 121 122 123 124 126Petition 870260023815, dated 03 / 13 / 2026, p. 49 / 113 41 / 48

[00153] The steel sheet on which the intermediate layer was formed was cut into a plurality of pieces as needed, a coating liquid containing the metal phosphate and colloidal silica shown in Table 3 was applied to each of the plurality of pieces of the steel sheet and baked in a drying oven for the time shown in Table 3 so that the temperature of the sheet reached the temperature shown in Table 3, whereby a stress coating was formed on the surface. In a case where vanadium, tungsten, molybdenum, and zirconium were present in the coating liquid, vanadium, tungsten, molybdenum, and zirconium were added in the molar ratios shown in Table 3 in the form of oxyacids (V2O4, WO3, MoOs, and Z1I2). The thickness of the stress coating layer was altered by changing the amount of coating liquid applied during formation. A portion of the coating liquid contained alumina or silicon nitride as residue.

[00154] Thus, steel sheets (grain-oriented electrical steel sheets) No. 101 to 126 were manufactured.

[00155] For these steel sheets, the amounts of silica and metal phosphate in the tension coating layer and the average thickness of the insulating coating were obtained by the methods described above.

[00156] The results are shown in Table 3.

[00157] Furthermore, as a result of examining the chemical composition of a base steel plate, the following were present: Si: 3.28%, C: 0.001%, Al sol.: less than 0.001%, N: 0.001%, Mn: 0.07%, S: less than 0.0005%, and a remainder being Fe and impurities. Petition 870260023815, dated 03 / 13 / 2026, page 50 / 113 o 0) 0) 0) 0) 0) 0) 0) 0) 0) 0) 0) 0) 0) ice 0) 0) 0) 0) 0) ice lc$ rP O rP O rP O rP O r P O R ü O r ü O r ü ap α p α p α p 0) p 0) P 0) P0) P0) P0 P0) 0) P 0) -O RH k .9 δ È k .9 δ e k .9 δ e k .9 RH 0) ek .9 δ e k .9 δ e k .9 RH week .9 RW week www. 42 / 48 [Table 3]___________________________________________________________________________________ Conditions for ~x,T, ., , .x £J . Cladding bed of Coating liquid form coating . ~ Thickness Petition 870260023815, dated 03 / 13 / 2026, p. 51 / 113 Observation Example of invention Example of invention Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Comparative Average thickness of insulating coating (uni) 5.4 5.6 4.6 5.2 4.2 cn 4.4 3.2 9.4 1.6 11.6 4.6 4.2 Tension coating layer Total amount of metal phosphate and silica (% by mass) 100 100 100 100 100 100 100 cn os cn os 100 100 100 100 Silica content (% by mass) 40 40 40 40 40 52 52 52 52 40 52 18 63 Conditions for forming tension coating Time (s) 30 30 30 30 30 25 25 25 25 25 30 30 30 Plate temperature (°C) 860 860 860 860 860 820 820 820 820 820 850 800 860 Coating liquid Colloidal silica parts by mass 65 65 65 65 65 115 115 115 115 65 115 20 160 Type type C type C type C type C type C type S type S type S type S type C type C type C Additional element molar ratio 0.17 0.18 0.67 0.67 0.67 0.67 0.67 1 1 1 1 0.14 0.14 Metal phosphate parts by mass Type Aluminum / tungsten phosphate Aluminum / zirconium phosphate Aluminum / magnesium phosphate Aluminum / magnesium phosphate Aluminum / magnesium phosphate Aluminum / magnesium phosphate Aluminum / magnesium phosphate Aluminum / magnesium phosphate Aluminum phosphate Zinc phosphate Aluminum phosphate Zinc phosphate Aluminum / copper phosphate Aluminum / copper phosphate □N 114 115 116 117 118 119 120 121 122 123 124 125 126 Petition 870260023815, dated 03 / 13 / 2026, page 52 / 113 44 / 48

[00158] In addition, for these steel plates, the adhesion of the insulating coating, the coating tension, the corrosion resistance, the elution property and the magnetic characteristics were obtained by the methods described below. The results of each are shown in Table 4. [Adherence]

[00159] For coating adhesion, a sample 30 mm wide and 300 mm long was collected from the steel plate and subjected to stress-relief annealing at 800°C for 2 hours in a nitrogen gas stream. Then, the sample was rolled around a 10 πηφ cylinder and unwound for a bending adhesion test. Subsequently, the coating adhesion was evaluated by the degree of flaking (area ratio) of the coating.

[00160] The evaluation criteria were defined as follows. In case A or B, it was determined that the coating adhesion was excellent.

[00161] 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 of more than 50% [Coating tension]

[00162] The coating stress was calculated by collecting a sample of the steel sheet and performing a regression calculation from a bent state when the insulating coating on a surface of the sample was removed. Petition 870260023815, dated 03 / 13 / 2026, page 53 / 113 45 / 48

[00163] In a case where the obtained coating stress was 4.0 MPa or more, the coating stress was determined to be excellent. [Corrosion resistance]

[00164] According to a salt spray test of the JIS Z 2371:2015 standard, a 5% aqueous NaCl solution was allowed to drip naturally onto the sample in an atmosphere of 35 °C for 7 hours.

[00165] From there, a rusty area was evaluated on a 10-point scale.

[00166] The evaluation criteria were defined as follows, and a score of 5 or higher (5 to 10) was determined as excellent in corrosion resistance.

[00167] 10: No rust was generated 9: Very small amount of rust generated (area ratio of 0.1% or less) 8: Ratio of rust area generated = more than 0.1% and 0.25% or less 7: Ratio of rust area generated = more than 0.25% and 0.50% or less 6: Ratio of rust area generated = more than 0.50% and 1% or less 5: Ratio of rust area generated = more than 1% and 2.5% or less 4: Ratio of rust area generated = more than 2.5% and 5% or less 3: Ratio of rust area generated = more than 5% and 10% or less 2: Ratio of rust area generated = more than 10% and 25% or less 1: Ratio of rust area generated = more than 25% and 50% or Petition 870260023815, dated 03 / 13 / 2026, page 54 / 113 46 / 48 less [Elution Property]

[00168] A sample was collected from the obtained steel sheet, the sample was boiled in pure boiling water for 10 minutes and the amount of phosphoric acid eluted in the pure water was measured. The elution property (mg / m2) was evaluated by dividing the amount of phosphoric acid eluted by the area of ​​the insulating coating of the boiled grain-oriented electrical steel sheet.

[00169] To measure the amount of phosphoric acid eluted in pure water, the pure water (solution) in which the phosphoric acid was eluted was cooled, and a phosphoric acid concentration of a sample obtained by diluting the cooled solution with pure water was measured by ICP-AES and calculated.

[00170] When the amount of elution per unit area was less than 140 mg / m2, the elution property was determined to be excellent. [Magnetic Features]

[00171] Iron loss was evaluated as magnetic characteristics. Specifically, the obtained steel sheet was irradiated with a laser beam under a UA (irradiation energy density) condition of 2.0 mJ / mm2 to perform a magnetic domain refinement treatment, and iron loss (iron loss W17 / 50 at 50 Hz and 1.7 T) after the magnetic domain refinement treatment was measured.

[00172] When the iron loss was 0.70 W / kg or less, the magnetic characteristics were determined to be excellent. Petition 870260023815, dated 03 / 13 / 2026, page 55 / 113 47 / 48 [Table 4] Coating Adhesion No. Coating Tension Corrosion Resistance Elution Property Iron Loss (W17 / 50) Observation (MPa) (mg / m2) (W / kg) 101 B 5.7 7 10 0.66 Example of invention 102 B 7.4 10 6 0.64 Example of invention 103 A 12.1 10 21 0.61 Example of invention 104 B 11.6 8 33 0.59 Example of invention 105 A 9.7 6 19 0.61 Example of invention 106 A 9.8 7 24 0.61 Example of invention 107 B 7.4 10 38 0.64 Example of invention 108 A 10.3 8 32 0.59 Example of invention 109 B 6.4 7 37 0.63 Example of invention 110 A 9.4 7 14 0.62 Example of invention 111 B 5.4 6 28 0.66 Example of invention 112 A 12.3 8 84 0.57 Example of invention 113 A 11.4 7 76 0.59 Example of invention 114 B 5.2 9 46 0.66 Example of invention 115 B 5.9 6 54 0.66 Example of invention 116 C 4.4 6 60 0.78 Comparative Example 117 C 3.4 4 36 0.81 Comparative Example 118 C 3.6 4 124 0.74 Comparative Example 119 C 7.4 7 27 0.68 Comparative Example 120 B 6.8 4 35 0.71 Comparative Example 121 B 4.6 3 153 0.73 Comparative Example 122 B 11.6 7 141 0.82 Comparative Example 123 C 2.1 2 38 0.79 Comparative Example 124 C 8.8 8 120 0.77 Comparative Example 125 B 4.6 5 167 0.71 Comparative Example 126 B 5.4 6 36 0.73 Comparative Example, Petition 870260023815, dated 03 / 13 / 2026, page 56 / 113 48 / 48

[00173] As shown in Tables 1 to 4, numbers 101 to 115, which are examples of the present invention, were excellent in coating adhesion, excellent in coating tension, and excellent in magnetic characteristics. Furthermore, corrosion resistance and elution properties were sufficient. In contrast, numbers 116 to 126 were inferior in at least one aspect of coating adhesion, coating tension, and magnetic characteristics. In addition, there were cases where corrosion resistance and elution properties were also inferior. [Brief Description of Reference Symbols]

[00174] 1 Base steel plate attack cavity structure Insulating coating Intermediate layer Tension coating layer 100 Grain Oriented Electrical Steel Sheet Petition 870260023815, dated 03 / 13 / 2026, page 57 / 113< / nl>

Claims

1 / 3 CLAIMS 1. Grain-oriented electrical steel sheet, characterized by comprising: 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 metal phosphate which is not a hydrate, and a tension coating layer formed on one side of the insulating coating surface, the surface of the base steel sheet having an attack cavity structure, an average thickness of the intermediate layer is 0.2 to 10.0 µm, an average thickness of the insulating coating is 2.0 to 10.0 µm, the tension coating layer contains a metal phosphate and silica, an amount of silica in the tension coating layer is 20 to 60% by mass, a proportion of crystalline metal phosphate in the intermediate layer is 80% by mass or more,and the attack cavity structure is a rectangular structure in which the average size of a structure is 0.01 to 0.10 pm in the rolling direction of the grain-oriented electrical steel sheet, which is the base steel sheet, and 0.005 to 0.050 pm in an orthogonal direction, which is a direction orthogonal to the rolling direction.

2. Grain-oriented electrical steel sheet according to claim 1, characterized in that the crystalline metal phosphate of the intermediate layer is one or two or more of zinc phosphate, manganese phosphate, iron phosphate, and zinc-calcium phosphate.

3. Method for forming the insulating coating included in the grain-oriented electrical steel sheet as defined in claim 1, characterized by comprising: a secondary recrystallization annealing process of applying an annealing separator containing 10 to 100% by mass of Al2O3 to a steel sheet, drying the steel sheet and performing secondary recrystallization annealing on the steel sheet; a process for removing the annealing separator to remove an excess amount of the annealing separator from the steel sheet after the secondary recrystallization annealing process; an acid treatment process of immersing the steel sheet after the annealing separator removal process in a mixed acid in which a concentration of one or two or more selected from sulfuric acid, phosphoric acid and nitric acid is 0.5 to 20% by weight and a liquid temperature is 40°C to 90°C for 5 to 50 seconds;a process of immersing the steel plate after the acid treatment process in a treatment liquid containing 5 to 50% by mass of a metal phosphate, which is one or two or more of zinc phosphate, manganese phosphate and calcium zinc phosphate, at a liquid temperature of 40°C to 85°C for 5 to 150 seconds; a drying process that involves removing the steel plate after the immersion process from the treatment liquid, removing an excessive amount of the treatment liquid and drying the steel plate;and a process for forming a tension coating layer by applying a coating liquid containing a metal phosphate and colloidal silica, such that the amount of colloidal silica is 30 to 150 parts by mass relative to 100 parts by mass of metal phosphate on the steel sheet after the drying process, drying the steel sheet and maintaining the steel sheet at a temperature of 700°C to 950°C for 10 to 120 seconds.

4. Method for forming the insulating coating according to claim 3, characterized in that the annealing separator additionally contains one or two of MgO: 5 to 90% by mass and a chloride: 0.5 to 10.0% by mass. Petition 870260023815, dated 03 / 13 / 2026, pp. 60 / 113

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