Grain-oriented electrical steel sheet, and method for forming an intermediate layer and insulating coating of a grain-oriented electrical steel sheet.

Abstract

Disclosed is a grain-oriented electrical steel sheet which comprises a base steel sheet, an intermediate layer that is disposed on the surface of the base steel sheet, and an insulating coating film that is disposed on the surface of the intermediate layer, wherein the intermediate layer has an average thickness of 20 nm to 200 nm, and contains one or more elements that are selected from the group consisting of V, Mo, W and Zr, while containing phosphorus, fluorine, and one or more elements that are selected from the group consisting of nitrogen and oxygen. Also disclosed is a method for forming an intermediate layer and an insulating coating film of this grain-oriented electrical steel sheet.

Description

Technical Field

[0001] The present invention relates to a grain-oriented electrical steel sheet, and a method for forming an intermediate layer and an insulating film of the grain-oriented electrical steel sheet. This application claims priority based on Japanese Patent Application No. 2023-019767 filed in Japan on February 13, 2023, the content of which is incorporated herein by reference.

Background Art

[0002] Grain-oriented electrical steel sheets are mainly used in transformers. Transformers are continuously excited over a long period from installation to disposal and continue to generate energy losses. Therefore, the energy loss when magnetized with alternating current, that is, the iron loss, becomes a major index determining the performance of the transformer.

[0003] In order to reduce the iron loss of grain-oriented electrical steel sheets, many techniques have been developed so far from the viewpoints of (a) enhancing the aggregation in the {110}<001> orientation (Goss orientation), (b) increasing the content of solid solution elements such as Si to increase the electrical resistance of the steel sheet, or (c) reducing the thickness of the electrical steel sheet.

[0004] Also, applying tension to the steel sheet is effective in reducing iron loss. Forming a film of a material with a smaller coefficient of thermal expansion than the steel sheet on the steel sheet surface at a high temperature is an effective means for reducing iron loss. The forsterite-based film (inorganic film) with excellent film adhesion, which is formed by the reaction of the oxide on the steel sheet surface and the annealing separation agent in the finish annealing process of the grain-oriented electrical steel sheet, is a film that can apply tension to the steel sheet.

[0005] Also, for example, the method of forming an insulating film by baking a coating liquid mainly composed of colloidal silica and phosphate disclosed in Patent Document 1 on the steel sheet surface is an effective method for reducing iron loss because the effect of applying tension to the steel sheet is large. Therefore, it is a general method for manufacturing grain-oriented electrical steel sheets to leave the forsterite-based film generated in the finish annealing process and apply an insulating film mainly composed of phosphate thereon.

[0006] However, in recent years, there has been a growing demand for smaller and more powerful transformers. To achieve this miniaturization, grain-oriented electrical steel sheets are required to exhibit excellent high-field iron loss properties, meaning that iron loss is good even at high magnetic flux densities. At the same time, it has recently become clear that forsterite coatings hinder the movement of magnetic domain walls and adversely affect iron loss.

[0007] In grain-oriented electrical steel sheets, magnetic domains change as domain walls move under an alternating magnetic field. Smooth and rapid movement of these domain walls is effective in reducing iron loss. However, forsterite-based coatings are nonmagnetic themselves and have an uneven structure at the steel sheet / coating interface. This uneven structure is thought to hinder the movement of domain walls and thus adversely affect iron loss.

[0008] Therefore, as a means of improving high-field iron loss, research is being conducted on technologies to manufacture grain-oriented electrical steel sheets without forsterite coatings by removing forsterite coatings using mechanical means such as polishing or chemical means such as pickling, or by preventing the formation of forsterite coatings during high-temperature finish annealing, as well as technologies to make the steel sheet surface mirror-like (in other words, technologies to magnetically smooth the steel sheet surface).

[0009] As a technique for preventing the formation of inorganic coatings, for example, Patent Document 2 discloses a technique in which, after normal finish annealing, surface deposits are removed by pickling, and then the steel sheet surface is polished to a mirror finish by chemical polishing or electrolytic polishing. It has been found that by forming an insulating coating for tension on the surface of a grain-oriented electrical steel sheet that does not have a forsterite coating, obtained by such a known method, an even better iron loss improvement effect can be obtained. In addition, an insulating coating for tension can impart various properties other than iron loss improvement, such as corrosion resistance, heat resistance, and slipperiness.

[0010] However, forsterite-based coatings not only exhibit insulating properties but also act as an intermediate layer to ensure film adhesion when forming tension coatings (insulating coatings for tension application). In other words, because forsterite-based coatings are formed deeply embedded in the steel sheet, they exhibit excellent adhesion to the steel sheet, which is a metal. Therefore, when a tension-applying insulating coating, mainly composed of colloidal silica or phosphates, is formed on the surface of a forsterite-based coating, excellent film adhesion is achieved. On the other hand, bonding between metals and oxides is generally difficult. Therefore, in the absence of a forsterite-based coating, it was difficult to ensure sufficient film adhesion between the insulating coating and the steel sheet surface.

[0011] Therefore, when forming an insulating coating for tensioning on grain-oriented electrical steel sheets that do not have a forsterite coating, it is being considered to provide a layer that replaces the role of the forsterite coating as an intermediate layer.

[0012] For example, Patent Document 3 discloses a technique for forming an SiO2 layer on the surface of a grain-oriented electrical steel sheet without a forsterite coating by annealing it in a weakly reducing atmosphere and selectively thermally oxidizing the silicon that is inevitably contained in the silicon steel sheet, and then forming a tension-imparting insulating coating.

[0013] Patent Document 4 discloses a technique for forming an SiO2 layer on the surface of a grain-oriented electrical steel sheet without a forsterite coating by anodic electrolytic treatment in a silicate aqueous solution, and then forming a tension-imparting insulating coating.

[0014] Patent Document 5 discloses a technique for ensuring the adhesion of a tension-imparting insulating film by applying an intermediate coating beforehand when forming the tension-imparting coating.

[0015] Patent Document 6 discloses a grain-oriented electrical steel sheet comprising a base steel sheet and a tension-imparting insulating coating, wherein the tension-imparting insulating coating 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 exists between the base steel sheet and the tension-imparting insulating coating. [Prior art documents] [Patent Documents]

[0016] [Patent Document 1] Japanese Patent Publication No. 48-039338 [Patent Document 2] Japanese Patent Publication No. 49-96920 [Patent Document 3] Japanese Patent Publication No. 6-184762 [Patent Document 4] Japanese Patent Application Publication No. 11-209891 [Patent Document 5] Japanese Patent Application Publication No. 5-279747 [Patent Document 6] Japanese Patent Publication No. 2020-111814 [Overview of the project] [Problems that the invention aims to solve]

[0017] However, the technology disclosed in Patent Document 3 requires the preparation of annealing equipment capable of controlling the atmosphere in order to perform annealing in a weakly reducing atmosphere, which presents a problem in terms of processing costs.

[0018] In the technology disclosed in Patent Document 4, obtaining an SiO2 layer on the surface of a steel sheet that maintains sufficient adhesion to a tension-impregnating insulating coating by performing anodic electrolysis in an aqueous silicate solution requires the preparation of new electrolytic treatment equipment, which presents a problem in terms of treatment costs.

[0019] The technology disclosed in Patent Document 5 has the problem that it is not possible to maintain a tension-applying insulating coating with high tension with excellent adhesion.

[0020] In the technique disclosed in Patent Document 6, in order to form an iron-based oxide layer, in an atmosphere where the oxygen concentration is 1 to 21% by volume and the dew point is -20 to 30°C, the surface-treated grain-oriented electrical steel sheet is heat-treated at a steel sheet temperature of 700 to 900°C for 5 to 60 seconds. Therefore, when manufacturing a steel sheet having a forsterite-based film on the same line, it is necessary to change the atmosphere of the annealing furnace, and the workability is inferior.

[0021] As described above, on the premise of equipment constraints and a method that does not deteriorate workability, it has been difficult to provide a grain-oriented electrical steel sheet that does not have a forsterite-based film, has excellent film adhesion, high film tension, and excellent magnetic properties.

[0022] Also, in a grain-oriented electrical steel sheet that does not have a forsterite-based film, in order to ensure the film adhesion (adhesion between the base steel sheet and the insulating film), there is a method of forming an intermediate layer containing a crystalline metal phosphate between the base steel sheet and the insulating film. According to this method, the film adhesion can be ensured. However, in this method, since it is necessary to increase the thickness of the intermediate layer, there is room for improvement in increasing the stacking factor when the grain-oriented electrical steel sheets are laminated to form a laminated core.

[0023] Therefore, an object of the present invention is to provide a grain-oriented electrical steel sheet that does not have a forsterite-based film, has excellent film adhesion, film tension, and magnetic properties, and can increase the stacking factor when formed into a laminated core. Another object of the present invention is to provide a grain-oriented electrical steel sheet that has the above characteristics and is excellent in elution properties and corrosion resistance, which are generally required characteristics of grain-oriented electrical steel sheets. Furthermore, an object of the present invention is to provide a method for forming the intermediate layer and the insulating film of the above grain-oriented electrical steel sheet.

Means for Solving the Problems

[0024] The inventors of the present invention investigated the above problems. As a result, the inventors found that in grain-oriented electrical steel sheets without a forsterite coating, the above problems can be solved by having an intermediate layer between the base steel sheet and the insulating coating that contains one or more elements selected from the group consisting of V, Mo, W, and Zr.

[0025] This invention was made based on the above findings. The gist of this invention is as follows: [1] Base material steel plate and An intermediate layer disposed on the surface of the base steel sheet, The intermediate layer has an insulating coating disposed on its surface, The aforementioned intermediate layer is The average thickness is 20-200 nm. A grain-oriented electrical steel sheet characterized by containing one or more elements selected from the group consisting of V, Mo, W, and Zr, and also containing one or more elements selected from the group consisting of phosphorus, fluorine, nitrogen, and oxygen. [2] In the grain-oriented electrical steel sheet described in [1] above, The aforementioned intermediate layer is It may contain one or more substances selected from the group consisting of vanadic acid, vanadium oxide, molybdic acid, phosphomolybdic acid, molybdenum oxide, tungstic acid, phosphotungstic acid, tungsten oxide, zirconic acid, and zirconium oxide. [3] In the grain-oriented electrical steel sheet described in [1] or [2] above, The aforementioned intermediate layer is It may contain one or more elements selected from the group consisting of Na, K, and Li. [4] A method for forming an intermediate layer and an insulating coating in the grain-oriented electrical steel sheet described in [1] above, The process involves applying an annealing release agent containing 10-100% by mass of Al2O3 to a steel plate, drying it, and then performing a finish annealing step. An annealing separating agent removal step is performed on the steel plate after the finish annealing step to remove any excess annealing separating agent, The steel sheet after the annealing separation agent removal step is immersed for 5 to 90 seconds in a chemical conversion treatment solution having a liquid temperature of 30 to 60°C and containing one or more metal elements selected from the group consisting of V, Mo, W, and Zr, with a concentration of the metal elements of 0.01 to 2.00 atomic percent. A drying step is performed in which the steel plate is removed from the chemical treatment solution after the immersion step, the excess chemical treatment solution is removed, and then the plate is dried. A method for forming an intermediate layer and an insulating film in a grain-oriented electrical steel sheet, comprising: a step of applying a coating solution containing phosphate and colloidal silica to the steel sheet after the drying step, wherein the amount of colloidal silica is 30 to 150 parts by mass per 100 parts by mass of phosphate, drying the solution, and then holding the sheet at a temperature of 750 to 900°C for 10 to 50 seconds. [Effects of the Invention]

[0026] According to the above-described embodiment of the present invention, it is possible to provide a grain-oriented electrical steel sheet that does not have a forsterite-based coating, has excellent coating adhesion, coating tension, elution properties, corrosion resistance and magnetic properties, and can increase the packing ratio when used as a laminated core. Furthermore, according to the above-described embodiment of the present invention, a method for forming an intermediate layer and an insulating coating on the grain-oriented electrical steel sheet can be provided. [Brief explanation of the drawing]

[0027] [Figure 1] This is an example of a cross-sectional view of a grain-oriented electrical steel sheet according to this embodiment. [Modes for carrying out the invention]

[0028] This document describes a grain-oriented electrical steel sheet (grain-oriented electrical steel sheet according to this embodiment) according to one embodiment of the present invention, and a method for manufacturing a grain-oriented electrical steel sheet according to this embodiment, including a method for forming the intermediate layer and insulating coating provided in the grain-oriented electrical steel sheet according to this embodiment. First, the grain-oriented electrical steel sheet according to this embodiment will be described.

[0029] As shown in Figure 1, the grain-oriented electrical steel sheet 10 according to this embodiment comprises a base steel sheet 1, an intermediate layer 2 disposed on the surface of the base steel sheet 1, and an insulating coating 3 disposed on the surface of the intermediate layer 2. Furthermore, the grain-oriented electrical steel sheet 10 has substantially no forsterite-based coating on the surface of the base steel sheet 1. In this embodiment, "substantially no forsterite-based coating" means that the amount of forsterite-based coating attached to one side of the base steel sheet 1 is 2 g / m². 2 This can be rephrased as "less than." Please note that reference numbers for drawings may be omitted in the following explanation.

[0030] <Base material steel plate> (chemical composition) The grain-oriented electrical steel sheet 10 according to this embodiment is characterized by an intermediate layer 2 formed on the surface of the base steel sheet 1. The base steel sheet 1 of the grain-oriented electrical steel sheet 10 is not limited in its chemical composition and may be within the known range. To obtain the properties generally required for grain-oriented electrical steel sheets, it is preferable that the chemical composition includes the following.

[0031] The base steel sheet 1 has a chemical composition in mass%, C: 0.010% or less, Si: 2.50~4.00%, Mn: 0.01~0.50%, N: 0.010% or less, sol.Al: 0.020% or less S: 0.010% or less, Sn: 0~0.50%, Cu: 0~0.50%, Se: 0~0.020%, Sb: 0~0.50%, and, The remainder may consist of Fe and impurities.

[0032] In this embodiment, percentages related to chemical composition are mass percentages unless otherwise specified. Furthermore, the numerical limits indicated by "~" below include both a lower and upper limit. Values ​​indicated as "less than" or "greater than" do not include those values ​​within the numerical range. The following describes each element.

[0033] C: 0.010% or less Carbon (C) is an effective element for controlling the microstructure of steel sheets during the manufacturing process up to the completion of the decarburization annealing process. However, if the C content exceeds 0.010%, the magnetic properties of the grain-oriented electrical steel sheet, which is the finished product, deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the C content is preferably 0.010% or less. More preferably, the C content is 0.005% or less. While a lower C content is preferable, reducing the C content to less than 0.0001% saturates the effect of tissue control, only increasing manufacturing costs. Therefore, a C content of 0.0001% or more is acceptable.

[0034] Si: 2.50~4.00% Silicon (Si) is an element that increases the electrical resistance of grain-oriented electrical steel sheets and improves iron loss characteristics. If the Si content is less than 2.50%, a sufficient eddy current loss reduction effect cannot be obtained. Therefore, it is preferable that the Si content be 2.50% or more. More preferably, the Si content is 2.70% or more, and even more preferably 3.00% or more. On the other hand, if the Si content exceeds 4.00%, the grain-oriented electrical steel sheet becomes brittle, and its treadability deteriorates significantly. In addition, the workability of the grain-oriented electrical steel sheet decreases, and the likelihood of the sheet fracturing during rolling increases. For this reason, it is preferable to keep the Si content at 4.00% or less. More preferably, the Si content is 3.80% or less, and even more preferably 3.70% or less.

[0035] Mn: 0.01~0.50% Manganese (Mn) is an element that combines with sulfur (S) during the manufacturing process to form MnS. This precipitate functions as an inhibitor (an agent that suppresses normal grain growth) and causes secondary recrystallization in steel. Furthermore, Mn is an element that also improves the hot workability of steel. If the Mn content is less than 0.01%, the above effects cannot be fully obtained. Therefore, it is preferable that the Mn content be 0.01% or more. More preferably, the Mn content is 0.02% or more. On the other hand, if the Mn content exceeds 0.50%, secondary recrystallization does not occur, and the magnetic properties of the steel deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the Mn content is preferably 0.50% or less. More preferably, the Mn content is 0.20% or less, and even more preferably 0.10% or less.

[0036] N: 0.010% or less Nitrogen (N) is an element that combines with Al during the manufacturing process to form AlN, which functions as an inhibitor. However, if the N content exceeds 0.010%, an excess of inhibitor remains in the grain-oriented electrical steel sheet, leading to a decrease in magnetic properties. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the N content is preferably 0.010% or less. More preferably, the N content is 0.008% or less. On the other hand, there is no specific lower limit for the N content, but reducing it to less than 0.001% would only increase manufacturing costs. Therefore, the N content may be 0.001% or higher.

[0037] sol.Al: 0.020% or less sol.Al (acid-soluble aluminum) is an element that, in the manufacturing process of grain-oriented electrical steel sheets, combines with N to form AlN, which functions as an inhibitor. However, if the sol.Al content of the base steel sheet exceeds 0.020%, an excess of inhibitor remains in the base steel sheet, reducing its magnetic properties. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the sol.Al content is preferably 0.020% or less. More preferably, the sol.Al content is 0.010% or less, and even more preferably less than 0.001%. While there is no specific lower limit for the sol.Al content, reducing it to less than 0.0001% would only increase manufacturing costs. Therefore, the sol.Al content may be 0.0001% or higher.

[0038] S: 0.010% or less S (sulfur) is an element that combines with Mn during the manufacturing process to form MnS, which functions as an inhibitor. However, if the S content exceeds 0.010%, the magnetic properties will deteriorate due to the remaining inhibitor. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment, the S content is preferably 0.010% or less. A lower S content is even more preferable, for example, less than 0.001%. However, reducing the S content to less than 0.0001% would only increase manufacturing costs. Therefore, the S content may be 0.0001% or more.

[0039] Remainder: Fe and impurities The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to this embodiment contains the above-mentioned elements (basic elements), with the remainder being Fe and impurities. However, for the purpose of improving magnetic properties, etc., one or more of Sn, Cu, Se, and Sb may be further included in the ranges shown below. Furthermore, even if one or more of the following elements are included in total at 1.0% or less (whether intentionally added or included as impurities), such as W, Nb, Ti, Ni, Co, V, Cr, and Mo, this will not hinder the effects of the grain-oriented electrical steel sheet according to this embodiment. Here, "impurities" refers to elements that are mixed in during the industrial manufacturing of the base steel sheet from raw materials such as ore, scrap, or the manufacturing environment, and which are permitted to be present in amounts that do not adversely affect the function of the grain-oriented electrical steel sheet according to this embodiment.

[0040] Sn: 0~0.50% Tin (Sn) is an element that contributes to improving magnetic properties through the control of the primary recrystallization structure. To obtain the effect of improving magnetic properties, it is preferable to have a Sn content of 0.01% or more. More preferably, the Sn content is 0.02% or more, and even more preferably 0.03% or more. On the other hand, if the Sn content exceeds 0.50%, secondary recrystallization becomes unstable, and the magnetic properties deteriorate. Therefore, it is preferable to keep the Sn content at 0.50% or less. More preferably, the Sn content is 0.30% or less, and even more preferably 0.10% or less.

[0041] Cu: 0~0.50% Copper (Cu) is an element that contributes to increasing the Goss orientation occupancy in the secondary recrystallized structure. To obtain the above effect, it is preferable to have a Cu content of 0.01% or more. More preferably, the Cu content is 0.02% or more, and even more preferably 0.03% or more. On the other hand, if the Cu content exceeds 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 this embodiment, it is preferable to have a Cu content of 0.50% or less. The Cu content is more preferably 0.30% or less, and even more preferably 0.10% or less.

[0042] Se: 0~0.020% Se (selenium) is an element that has the effect of improving magnetic properties. When Se is included, it is preferable to have a Se content of 0.001% or more in order to exhibit a good effect of improving magnetic properties. The Se content is more preferably 0.003% or more, and even more preferably 0.006% or more. On the other hand, if the Se content exceeds 0.020%, the adhesion of the coating deteriorates. Therefore, it is preferable to keep the Se content at 0.020% or less. More preferably, the Se content is 0.015% or less, and even more preferably 0.010% or less.

[0043] Sb: 0~0.50% Antimony (Sb) is an element that improves magnetic properties. When Sb is included, it is preferable to have an Sb content of 0.005% or more in order to exhibit a good magnetic property improvement effect. More preferably, the Sb content is 0.01% or more, and even more preferably 0.02% or more. On the other hand, if the Sb content exceeds 0.50%, the adhesion of the coating deteriorates significantly. Therefore, it is preferable to keep the Sb content at 0.50% or less. More preferably, the Sb content is 0.30% or less, and even more preferably 0.10% or less.

[0044] As described above, the chemical composition of the base steel sheet 1 of the grain-oriented electrical steel sheet 10 according to this embodiment is exemplified by containing the above-mentioned basic elements with the remainder being Fe and impurities, or containing the basic elements and further containing one or more other arbitrary elements with the remainder being Fe and impurities.

[0045] The chemical composition of the base steel sheet 1 of the grain-oriented electrical steel sheet 10 according to this embodiment can be measured using a known ICP emission spectrometry method. The Si content is determined by the method specified in JIS G 1212-1997 (silicon determination method). Specifically, when chips are dissolved in acid, silicon oxide precipitates as a precipitate, and this precipitate (silicon oxide) is filtered out with filter paper, its mass is measured, and the Si content is determined.

[0046] The carbon (C) and sulfur (S) content will be determined by the well-known high-frequency combustion method (combustion-infrared absorption method). Specifically, the solution will be combusted in an oxygen stream using high-frequency heating, and the generated carbon dioxide and sulfur dioxide will be detected to determine the C and S content. The nitrogen content is determined using the well-known inert gas fusion-thermal conductivity method.

[0047] However, if an intermediate layer 2 and an insulating coating 3 are formed on the surface of the base steel sheet 1 during measurement, these must be removed before measurement. The removal method involves immersing the grain-oriented electrical steel sheet 10 in a high-concentration alkaline solution (for example, a 30% sodium hydroxide solution heated to 85°C) for 20 minutes or more. Whether or not the coating has been removed can be determined visually. For small samples, surface grinding may also be used for removal.

[0048] The base steel sheet 1 is used to ensure the properties of the grain-oriented electrical steel sheet 10 as the base steel sheet 1, {110} <001> It is preferable that the B8 / Bs ratio, which is an indicator of orientation concentration, is 0.93 or higher. B8 is the magnetic flux density when a magnetic field of 800 A / m is applied, and Bs is the saturation magnetic flux density in the component system of the base steel sheet 1. It is more preferable that the B8 / Bs ratio is 0.95 or higher.

[0049] <Middle class> The grain-oriented electrical steel sheet 10 according to this embodiment has an intermediate layer 2 on the surface of the base steel sheet 1. As described above, the grain-oriented electrical steel sheet 10 according to this embodiment does not have a forsterite-based coating. Nor does it have an SiO2 layer as shown in Patent Documents 3 and 4. Therefore, the intermediate layer 2 is formed in direct contact with the base steel sheet 1.

[0050] Intermediate layer 2 is a layer (coating) with an average thickness of 20 to 200 μm, containing one or more elements selected from the group consisting of V, Mo, W, and Zr, and also containing one or more elements selected from the group consisting of phosphorus, fluorine, nitrogen, and oxygen. As mentioned above, grain-oriented electrical steel sheets generally have a forsterite-based coating formed in the finish annealing process and an insulating coating formed on top of it to impart tension. However, in recent years, it has become clear that this forsterite-based coating hinders the movement of magnetic domain walls and adversely affects iron loss, so grain-oriented electrical steel sheets without the forsterite-based coating are being investigated in order to further improve magnetic properties. However, in the absence of the forsterite-based coating, it is difficult to ensure sufficient coating adhesion between the insulating coating and the base steel sheet.

[0051] In the grain-oriented electrical steel sheet 10 according to this embodiment, an intermediate layer 2 containing one or more elements selected from the group consisting of V, Mo, W, and Zr is provided between the base steel sheet 1 and the insulating coating 3, thereby improving the adhesion between the base steel sheet 1 and the insulating coating 3 via the intermediate layer 2.

[0052] If the intermediate layer 2 contains one or more elements selected from the group consisting of V, Mo, W, and Zr, the adhesion between the intermediate layer 2 and the insulating film 3 can be improved. Furthermore, if the intermediate layer 2 is formed by immersion in a chemical conversion treatment solution, as described later, the intermediate layer 2 can be formed on the surface of the base steel sheet 1 using a chemical reaction, and the adhesion between the intermediate layer 2 and the base steel sheet 1 can also be ensured.

[0053] Furthermore, by including one or more elements selected from the group consisting of V, Mo, W, and Zr in the intermediate layer 2, good adhesion between the base steel sheet 1 and the insulating film 3 can be ensured even when the average thickness is reduced to 200 nm or less. By reducing the average thickness to 200 nm or less, the packing ratio can be increased when the grain-oriented electrical steel sheet 10 is applied to a laminated core. If the intermediate layer 2 does not include one or more elements selected from the group consisting of V, Mo, W, and Zr, it becomes necessary to increase the average thickness to improve the film adhesion. As a result, the packing ratio cannot be increased when the grain-oriented electrical steel sheet is applied to a laminated core. To further increase the packing ratio of the laminated core, it is preferable that the average thickness of the intermediate layer 2 be 180 nm or less, 160 nm or less, or 150 nm or less.

[0054] If the average thickness of the intermediate layer 2 is less than 20 nm, the intermediate layer is too thin to improve the adhesion between the base steel sheet 1 and the insulating coating 3. Therefore, the average thickness of the intermediate layer 2 should be 20 nm or more. From the viewpoint of further improving the adhesion between the base steel sheet 1 and the insulating coating 3, it is preferable that the average thickness of the intermediate layer 2 be 100 nm or more.

[0055] This section explains how to identify the metallic elements contained in the intermediate layer 2. A sample is taken from the grain-oriented electrical steel sheet 10 so that the cross-section of the sheet thickness can be observed. The cross-section of the sheet thickness is observed using a transmission electron microscope. By observing the electron image obtained using the transmission electron microscope, it is possible to infer how many layers make up the cross-sectional structure of the sheet thickness.

[0056] Next, in order to identify each phase in the cross-sectional structure, line analysis of five lines along the thickness direction of the plate is performed using TEM-EDS (Energy Dispersive X-ray Spectroscopy), and the chemical composition of each layer is quantitatively analyzed. Based on the observation results from the electron images and the quantitative analysis results from TEM-EDS, each layer is identified.

[0057] If the Fe content is 80 atomic percent or more on average in a region, and the line segment (thickness) on the scanning line of the line analysis corresponding to this region is 300 nm or more, then this region is determined to be the base steel sheet 1, and the regions excluding this base steel sheet 1 are determined to be the intermediate layer 2 and the insulating coating 3. Excluding the base steel sheet 1, any region where the Fe content is less than 80 atomic percent on average, one or more of V, Mo, W, and Zr are present at 2 atomic percent or more on average, and the Si content is less than 50 atomic percent on average is determined to be the intermediate layer 2. Excluding the base steel sheet 1, areas where the Fe content is less than 80 atomic percent on average, the P content is less than 50 atomic percent on average, and the Si content is 20 atomic percent or more on average are determined to be insulating coating 3.

[0058] Furthermore, by calculating the average thickness of the region determined to be intermediate layer 2, the average thickness of intermediate layer 2 can be obtained.

[0059] In the intermediate layer 2, V, Mo, W, and Zr are preferably contained in the form of vanadic acid, vanadium oxide, molybdic acid, phosphomolybdic acid, molybdenum oxide, tungstic acid, phosphotungstic acid, tungsten oxide, zirconic acid, and zirconium oxide, respectively. That is, the intermediate layer 2 preferably contains one or more selected from the group consisting of vanadic acid, vanadium oxide, molybdic acid, phosphomolybdic acid, molybdenum oxide, tungstic acid, phosphotungstic acid, tungsten oxide, zirconic acid, and zirconium oxide.

[0060] Furthermore, the intermediate layer 2 contains one or more selected from the group consisting of phosphates, hydrofluoric acid salts, and nitrates. By including one or more of these, the processing speed of the intermediate layer can be increased. This improves the density of the intermediate layer. In the analytical method described later, phosphates are detected as phosphorus, hydrofluoric acid as fluorine, and nitrates as nitrogen and oxygen. Since the nitrogen detected in the intermediate layer of this embodiment originates from nitrates, both nitrogen and oxygen are detected simultaneously according to the analytical method described later. For example, if the nitrogen in the intermediate layer originates from nitrides bonded with metal elements rather than from nitric acid, both nitrogen and oxygen will not be detected simultaneously.

[0061] Furthermore, it is preferable that the intermediate layer 2 contains one or more elements selected from the group consisting of Na, K, and Li. Including one or more of these elements can prevent a decrease in corrosion resistance.

[0062] Whether or not the intermediate layer 2 contains vanadic acid, vanadium oxide, molybdic acid, phosphomolybdic acid, molybdenum oxide, tungstic acid, phosphotungstic acid, tungsten oxide, zirconic acid, or zirconium oxide can be determined by the following method. Samples are taken from grain-oriented electrical steel sheets 10, and the intermediate layer of the sheet thickness cross-section is analyzed by XPS (X-ray photoelectron spectroscopy) to determine the chemical state of each element. By analyzing the energy shift (chemical shift) of each element by XPS for vanadium, molybdenum, tungsten, and zirconium, it is determined whether each element is in an oxidized state or not. If vanadium is detected in an oxidized state, it is determined that the intermediate layer contains vanadic acid or vanadium oxide. If molybdenum is detected in an oxidized state, it is determined that the intermediate layer contains molybdic acid, phosphomolybdic acid, or molybdenum oxide. If tungsten is detected in an oxidized state, it is determined that the intermediate layer contains tungstic acid, phosphotungstic acid, or tungsten oxide. If zirconium is detected in an oxidized state, it is determined that the intermediate layer contains zirconic acid or zirconium oxide. Furthermore, measurements will be taken on the intermediate layer identified from the observation results of the electron image and the quantitative analysis results of TEM-EDS mentioned above.

[0063] The phosphorus in phosphates, the fluorine in hydrofluoricates, the nitrogen and oxygen in nitrates, and the elements Na, K, and Li can be identified using the transmission electron microscope and TEM-EDS methods described above.

[0064] (Insulating coating 3) In the grain-oriented electrical steel sheet 10 according to this embodiment, an insulating coating 3 is provided on the surface of the intermediate layer 2. The insulating coating 3 is not particularly limited as long as it is used as an insulating coating for grain-oriented electrical steel sheets. From the viewpoint of adhesion to the intermediate layer 2 (adhesion of the coating to the base steel sheet 1 via the intermediate layer 2), it is preferable to contain 30 parts by mass or more of silica per 100 parts by mass of phosphate. This silica is derived from the colloidal silica of the coating liquid. Since too much silica content can cause powdering, it is preferable that the silica content be 150 parts by mass or less per 100 parts by mass of phosphate.

[0065] The insulating coating 3 preferably contains 70% by mass or more of phosphate and silica in total. The remainder other than phosphate and silica may include ceramic fine particles such as alumina or silicon nitride.

[0066] The average thickness of the insulating film 3 is not particularly limited, but it is preferably 2.0 to 10.0 μm. By setting the average thickness of the insulating film 3 to 2.0 μm or more, sufficient film tension can be obtained. In addition, excessive elution of phosphoric acid can be suppressed, and excellent elution properties can be obtained. Furthermore, stickiness and deterioration of corrosion resistance can be suppressed, and film peeling can be prevented. In addition, by setting the average thickness of the insulating film 3 to 10.0 μm or less, a decrease in the packing factor when the grain-oriented electrical steel sheet 10 is applied to a laminated iron core can be suppressed, preventing deterioration of magnetic properties, deterioration of film adhesion due to cracking, and deterioration of corrosion resistance.

[0067] The average thickness of the insulating film 3 can be measured using the same method as for the intermediate layer 2.

[0068] <Manufacturing method> The grain-oriented electrical steel sheet 10 according to this embodiment can be suitably manufactured by a manufacturing method that satisfies the manufacturing conditions described below. However, naturally, the grain-oriented electrical steel sheet 10 according to this embodiment is not particularly limited to the manufacturing method. That is, a grain-oriented electrical steel sheet 10 having the above-described configuration is considered to be the grain-oriented electrical steel sheet 10 according to this embodiment, regardless of its manufacturing conditions.

[0069] The grain-oriented electrical steel sheet 10 according to this embodiment is (I) A hot rolling process to obtain a hot-rolled sheet by hot-rolling a steel billet having a predetermined chemical composition, (II) A hot-rolled sheet annealing step in which the hot-rolled sheet is annealed, (III) A cold rolling step in which the hot-rolled sheet after the hot-rolled sheet annealing step is subjected to cold rolling to obtain a steel sheet (cold-rolled sheet), (IV) A decarburization annealing step in which decarburization annealing is performed on the steel sheet after the cold rolling step, (V) A finish annealing step is performed on the steel sheet after the decarburization annealing step, in which an annealing separating agent containing 10 to 100% by mass of Al2O3 is applied, dried, and then finish annealing is performed. (VI) An annealing separating agent removal step in which excess annealing separating agent is removed from the steel sheet after the finish annealing step, (VII) An immersion step in which the steel sheet after the annealing separation agent removal step is immersed for 5 to 90 seconds in a chemical conversion treatment solution having a liquid temperature of 30 to 60°C and containing one or more metal elements selected from the group consisting of V, Mo, W, and Zr, with a concentration of the metal elements of 0.01 to 2.00 atomic%, (VIII) A drying step in which the steel plate after the immersion step is removed from the chemical treatment solution, excess chemical treatment solution is removed, and then the plate is dried. (IX) An insulating film formation step is performed on the steel sheet after the drying step, in which a coating solution containing phosphate and colloidal silica is applied in a ratio of 30 to 150 parts by mass of colloidal silica to 100 parts by mass of phosphate, and after drying, the sheet is held at a temperature of 750 to 900°C for 10 to 50 seconds. It can be manufactured by a manufacturing method that includes [the specified element].

[0070] Furthermore, the manufacturing method of the grain-oriented electrical steel sheet 10 according to this embodiment further includes: (X) Between the decarburization annealing step and the finish annealing step, a nitriding step is performed on the steel sheet, (XI) After the tension coating layer formation step, a magnetic domain subdivision step is performed to control the magnetic domains of the steel plate, It may include either or both of the following: Furthermore, the method for manufacturing grain-oriented electrical steel sheets according to this embodiment further includes the following steps between the annealing separating agent removal step and the immersion step: (XII) Surface adjustment steps to control the reactivity of the surface of the steel sheet, It may include this. Of these, the characteristic features in the manufacturing of the grain-oriented electrical steel sheet 10 according to this embodiment are the processes (V) finish annealing process to (IX) insulating film formation process, which are mainly related to the formation of the intermediate layer 2 and the insulating film 3, and known conditions can be adopted for other processes or conditions not described. The following explains these processes.

[0071] <Hot rolling process> In the hot rolling process, a steel billet, such as a slab having a predetermined chemical composition, is heated and then hot-rolled to obtain a hot-rolled sheet. The heating temperature of the steel billet is preferably in the range of 1100 to 1450°C. More preferably, the heating temperature is 1300 to 1400°C.

[0072] The chemical composition of the steel billet can be changed according to the chemical composition of the grain-oriented electrical steel sheet 10 that you ultimately want to obtain. For example, a chemical composition can be exemplified by containing, in mass%, C: 0.01~0.20%, Si: 2.50~4.00%, sol.Al: 0.01~0.040%, Mn: 0.01~0.50%, N: 0.020% or less, S: 0.005~0.040%, Cu: 0~0.50%, Sn: 0~0.50%, Se: 0~0.020%, Sb: 0~0.50%, with the remainder being Fe and impurities.

[0073] The hot rolling conditions are not particularly limited and should be set appropriately based on the desired characteristics. The thickness of the hot-rolled sheet is preferably, for example, 2.0 to 3.0 mm.

[0074] <Hot-rolled sheet annealing process> The hot-rolled sheet annealing process is a process of annealing the hot-rolled sheet manufactured through the hot-rolling process. This annealing treatment is preferable because it induces recrystallization in the steel sheet structure, making it possible to achieve good magnetic properties.

[0075] When performing hot-rolled sheet annealing, the hot-rolled sheet manufactured through the hot-rolling process should be annealed according to known methods. The means of heating the hot-rolled sheet during annealing are not particularly limited, and known heating methods can be used. Similarly, the annealing conditions are not particularly limited. For example, the hot-rolled sheet can be annealed at a temperature range of 900 to 1200°C for 10 seconds to 5 minutes.

[0076] <Cold rolling process> In the cold rolling process, the hot-rolled sheet, after the hot-rolled sheet annealing process, is subjected to cold rolling to obtain a steel sheet (cold-rolled sheet). Cold rolling may be performed in a single cold rolling cycle (a series of cold rolling cycles that do not include annealing in between), or multiple cold rolling cycles may be performed with intermediate annealing in between, by interrupting the cold rolling before the final pass of the cold rolling process and performing at least one or more intermediate annealing cycles.

[0077] When performing intermediate annealing, it is preferable to hold the material at a temperature of 1000-1200°C for 5-180 seconds. The annealing atmosphere is not particularly limited. Considering the manufacturing cost, it is preferable to perform intermediate annealing no more than three times. Furthermore, the surface of the hot-rolled sheet may be pickled before the cold-rolling process.

[0078] In the cold rolling process according to this embodiment, the hot-rolled sheet after the hot-rolled sheet annealing process is cold-rolled to form a steel sheet according to a known method. For example, the cumulative reduction ratio can be in the range of 80 to 95%. If the cumulative reduction ratio is 80% or more, {110} <001> This is preferable because it allows for the acquisition of Goss nuclei with a high degree of concentration in the rolling direction. On the other hand, if the cumulative reduction ratio exceeds 95%, it is undesirable because there is a high possibility that secondary recrystallization will become unstable in the subsequent finish annealing process.

[0079] <Decarburization annealing process> In the decarburization annealing process, the obtained steel sheet is subjected to decarburization annealing. In decarburization annealing, the conditions are not limited as long as the steel sheet is subjected to primary recrystallization and carbon, which adversely affects the magnetic properties, is removed from the steel sheet. Examples of decarburization annealing conditions include setting the degree of oxidation (PH2O / PH2) in the annealing atmosphere (furnace atmosphere) to 0.3 to 0.6, and holding the annealing temperature at 800 to 900°C for 10 to 600 seconds.

[0080] <Nitriding process> Nitriding may be performed between the decarburization annealing process and the finish annealing process described later. In the nitriding process, for example, the steel sheet after the decarburization annealing process is subjected to nitriding by maintaining it at approximately 700-850°C in a nitriding atmosphere (an atmosphere containing gases with nitriding ability such as hydrogen, nitrogen, and ammonia). When using AlN as an inhibitor, it is preferable to make the N content of the steel sheet after the nitriding process 40 ppm or more through the nitriding process. On the other hand, if the nitrogen content of the steel sheet after the nitriding process exceeds 1000 ppm, excess AlN will remain in the steel sheet even after secondary recrystallization is completed during finish annealing. Such AlN can cause iron loss degradation. For this reason, it is preferable to keep the nitrogen content of the steel sheet after the nitriding process below 1000 ppm.

[0081] <Finishing annealing process> In the finish annealing process, an annealing release agent containing 10-100% by mass of Al2O3 is applied to the steel sheet after the decarburization annealing process, or after further nitriding treatment (after the nitriding treatment process), and after drying, finish annealing is performed.

[0082] In conventional methods for manufacturing grain-oriented electrical steel sheets, a forsterite-based coating was formed on the surface of the steel sheet (cold-rolled sheet) by applying an annealing separation agent mainly composed of MgO and performing finish annealing. In contrast, in the manufacturing method of the grain-oriented electrical steel sheet 10 according to this embodiment, an annealing separation agent containing Al2O3 is used so as not to form a forsterite-based coating.

[0083] On the other hand, while the proportion of Al2O3 may be 100% by mass, in order to prevent Al2O3 from burning onto the surface of the steel sheet, it is preferable that the annealing separating agent in the manufacturing method of the grain-oriented electrical steel sheet 10 according to this embodiment contains MgO. While the amount of MgO may be 0%, in order to obtain the above effect, it is preferable that the proportion of MgO be 5% by mass or more. When MgO is included, the proportion of MgO should be 90% by mass or less in order to ensure that 10% by mass or more of Al2O3 is secured. Preferably, the proportion of MgO is 50% by mass or less.

[0084] Furthermore, in the manufacturing method of the grain-oriented electrical steel sheet 10 according to this embodiment, the annealing separating agent may further contain chlorides. By including chlorides in the annealing separating agent, the effect of making it more difficult for forsterite-based coatings to form can be obtained. The chloride content is not particularly limited and may be 0%, but 0.5 to 10% by mass is preferred to obtain the above effect. Examples of effective chlorides include bismuth chloride, calcium chloride, cobalt chloride, iron chloride, nickel chloride, etc.

[0085] The finish annealing conditions are not limited, but for example, conditions such as holding at a temperature range of 1150 to 1250°C for 10 to 60 hours can be used.

[0086] <Annealing Separating Agent Removal Process> After the finish annealing process, excess annealing separator is removed from the steel sheet. For example, excess annealing separator can be removed by washing with water.

[0087] <Surface conditioning process> A surface adjustment step may be performed between the annealing separation agent removal step and the immersion step to control the surface reactivity of the steel sheet. The conditions for the surface conditioning process are not limited, but an example of such a process is to immerse the steel sheet, after the annealing separation agent removal process, in a commercially available surface conditioning agent for 30 seconds to 1 minute.

[0088] <Soaking process> <Drying process> After the annealing separation agent removal process (or after further surface adjustment processes as necessary), the steel sheet is immersed for 5 to 90 seconds in a chemical conversion treatment solution having a liquid temperature of 30 to 60°C and containing one or more metal elements selected from the group consisting of V, Mo, W, and Zr, with a concentration of the metal elements of 0.01 to 2.00 atomic percent (immersion process). After that, the sheet is removed from the chemical conversion treatment solution, excess chemical conversion treatment solution is removed, and then it is dried (drying process). This forms an intermediate layer 2 on the surface of the steel sheet (base steel sheet).

[0089] If the liquid temperature is below 30°C or the immersion time is less than 5 seconds, it is not possible to form an intermediate layer 2 with a sufficient average thickness. On the other hand, if the liquid temperature is above 60°C or the immersion time is above 90 seconds, the average thickness of the intermediate layer 2 becomes too thick. An immersion time of 30 to 60 seconds is more preferable.

[0090] Furthermore, if the concentration of metal elements in the chemical treatment solution is less than 0.01 atomic%, the formation of the intermediate layer 2 is slow, leading to increased industrial costs. To ensure a uniform thickness of the intermediate layer 2, it is preferable that the concentration of metal elements be 0.10 atomic% or higher. The concentration of metal elements referred to here is the concentration in atomic percent of one or more elements selected from the group consisting of V, Mo, W, and Zr in the chemical treatment solution.

[0091] On the other hand, if the concentration of metal elements exceeds 2.00 atomic percent, it may cause grain coarsening and a decrease in coating adhesion. The V, Mo, W, and Zr contained in the chemical conversion solution should be vanadic acid, vanadium oxide, molybdic acid, phosphomolybdic acid, molybdenum oxide, tungstic acid, phosphotungstic acid, tungsten oxide, zirconic acid, and zirconium oxide, respectively.

[0092] The pH of the chemical treatment solution is preferably adjusted according to the metal elements contained in the solution. When the metal element contained in the chemical treatment solution is V, the pH is preferably adjusted to 1 to 7; when it is Mo, it is preferably adjusted to 4 to 9; when it is W, it is preferably adjusted to 1 to 4; and when it is Zr, it is preferably adjusted to 1 to 6. pH can be adjusted by using a buffer.

[0093] The chemical treatment solution contains one or more of the following compounds: phosphate, hydrofluoric acid, and nitrate. It may also contain one or more of the following compounds: ammonium salts and sodium. The chemical conversion solution may contain one or more additives, such as ethanolamine, 1-amino-2-propanol, ethylenediamine, and ammonium dihydrogen phosphate. Because these additives have low boiling points, they disappear after the insulating film is formed and are therefore not detected in the intermediate layer and insulating film of the grain-oriented electrical steel sheet.

[0094] If the drying temperature is too high, voids may form and the adhesion of the coating may deteriorate; therefore, it is preferable to keep the drying temperature below 300°C. More preferably, the drying temperature should be below 200°C. Furthermore, it is preferable to keep the drying temperature above 100°C.

[0095] <Insulating film formation process> In the insulating film formation process, a coating solution containing a metal phosphate salt and colloidal silica is applied to the steel sheet after the drying process (a steel sheet with an intermediate layer formed on the base steel sheet), and after drying, the sheet is held at a temperature of 750 to 900°C for 10 to 50 seconds to form the insulating film 3.

[0096] If the plate temperature during holding is below 750°C, the tension will be low and the magnetic properties of the grain-oriented electrical steel sheet 10 will deteriorate. Therefore, it is preferable to keep the plate temperature at 750°C or higher. On the other hand, if the plate temperature exceeds 900°C, the rigidity of the base steel sheet 1 will decrease and it will become more susceptible to deformation. In this case, the base steel sheet 1 may become strained due to transport, etc., and the magnetic properties of the grain-oriented electrical steel sheet 10 may deteriorate. Therefore, it is preferable to keep the plate temperature at 900°C or lower.

[0097] Furthermore, if the holding time is less than 10 seconds, the leaching properties of the grain-oriented electrical steel sheet 10 deteriorate. Therefore, the holding time should be 10 seconds or longer. On the other hand, if the holding time exceeds 50 seconds, productivity decreases. Therefore, the holding time should be 50 seconds or less.

[0098] The coating solution shall contain a phosphate and colloidal silica, with a concentration of 30 to 150 parts by mass of colloidal silica per 100 parts by mass of phosphate. As the phosphate, one or more types selected from aluminum phosphate, zinc phosphate, magnesium phosphate, nickel phosphate, copper phosphate, lithium phosphate, cobalt phosphate, etc., can be used.

[0099] The coating solution may also contain additional elements such as V, W, Mo, and Zr. If these elements are included, they can be added to the coating solution, for example, as an oxygen acid.

[0100] Colloidal silica can be of either S-type or C-type. S-type colloidal silica refers to silica solutions that are alkaline, while C-type colloidal silica refers to silica particles treated with aluminum, resulting in a silica solution that is alkaline to neutral. S-type colloidal silica is widely used and relatively inexpensive, but caution is needed as it may aggregate and precipitate when mixed with acidic metal phosphate solutions. C-type colloidal silica is stable even when mixed with metal phosphate solutions and does not precipitate, but it is relatively more expensive due to the increased processing steps. It is preferable to choose the type of colloidal silica based on the stability of the coating solution being prepared.

[0101] <Magnetic domain refining process> In the manufacturing method of the grain-oriented electrical steel sheet 10 according to this embodiment, a magnetic domain subdivision step may be included in which magnetic domain subdivision is performed on the steel sheet after the insulating film formation step. By performing magnetic domain subdivision processing, the iron loss of the grain-oriented electrical steel sheet 10 can be further reduced.

[0102] Methods for refining magnetic domains include a method of narrowing the width of 180° magnetic domains (refining 180° magnetic domains) by forming linear or point-shaped grooves extending in a direction intersecting the rolling direction at predetermined intervals along the rolling direction, and a method of narrowing the width of 180° magnetic domains (refining 180° magnetic domains) by forming linear or point-shaped stress-strain areas or grooves extending in a direction intersecting the rolling direction at predetermined intervals along the rolling direction.

[0103] When forming stress-strained areas, laser beam irradiation and electron beam irradiation can be applied. Furthermore, when forming grooves, mechanical groove formation methods using gears, chemical groove formation methods using electrolytic etching, and thermal groove formation methods using laser irradiation can be applied. If the insulating coating is damaged due to the formation of stress-strained areas or grooves, and its properties such as insulation deteriorate, the insulating coating may be reapplied to repair the damage. [Examples]

[0104] The effects of one aspect of the present invention will be described in more detail below with reference to examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples of conditions. The present invention can adopt various conditions as long as they do not depart from the spirit of the invention and achieve the objectives of the present invention.

[0105] A slab was cast containing, by mass%, C: 0.08%, Si: 3.31%, sol.Al: 0.028%, N: 0.008%, Mn: 0.07%, and S: less than 0.0005%, with the remainder being Fe and impurities. This slab was heated to 1350°C, then hot-rolled to produce a hot-rolled sheet with a thickness of 2.2 mm. This hot-rolled sheet was annealed at 1100°C for 10 seconds, and then cold-rolled until the sheet thickness was 0.22 mm to obtain a steel sheet (cold-rolled sheet). This steel plate was subjected to decarburization annealing at 830°C for 90 seconds in an atmosphere with a (PH2O / PH2) ratio of 0.4.

[0106] Subsequently, an annealing separation agent containing 48% by mass of Al2O3, 48% by mass of MgO, and 4% by mass of bismuth chloride was applied to the steel plate, dried, and then subjected to finish annealing at 1200°C for 20 hours. After the finish annealing process, excess annealing separator was removed from the steel sheet by washing with water, and no forsterite-based coating was found to have formed on the surface of the steel sheet.

[0107] The steel plate was immersed in the treatment solution shown in Table 1 under the conditions (immersion time) shown in Table 2, and then heated to 100-150°C and dried to form an intermediate layer. The temperature of the treatment solution was set to 30-60°C.

[0108] Furthermore, EA, IPA, EN, and AHP in Table 2 represent the following, respectively. In addition, the pH of the chemical treatment solution was adjusted to 1-7 if the metal element contained in the chemical treatment solution was V, to 4-9 if it was Mo, to 1-4 if it was W, and to 1-6 if it was Zr. EA: Ethanolamine IPA: 1-amino-2-propanol EN: Ethylenediamine AHP: Ammonium dihydrogen phosphate

[0109] The steel sheet with the intermediate layer formed was cut into multiple pieces as needed, and a coating solution containing phosphoric acid and colloidal silica as shown in Table 2 was applied to each steel sheet. An insulating film was formed on the surface by baking it in a drying oven for the time shown in Table 2 to the plate temperature shown in Table 2. Some of the coating solutions contained alumina or silicon nitride as the remainder. The phosphates used in the coating solution included aluminum phosphate containing 100% by mass of Al, and aluminum phosphate and magnesium phosphate containing 75% by mass of Al and 25% by mass of Mg.

[0110] Grain-oriented electrical steel sheets were manufactured using the method described above.

[0111] The average thickness of the intermediate layer and insulating coating, as well as the chemical composition, of the obtained grain-oriented electrical steel sheets were measured and analyzed using the method described above. Furthermore, an investigation of the chemical composition of the base steel sheet revealed that it contained Si: 3.31%, C: 0.001%, sol.Al: less than 0.001%, N: 0.001%, Mn: 0.07%, S: less than 0.0005%, with the remainder being Fe and impurities.

[0112] Cross-sectional observations of Examples 1-8 revealed the base steel sheet, intermediate layer, and insulating coating. In the intermediate layer, the metal elements contained in each treatment solution were observed in their oxidized state. Furthermore, phosphorus was detected in the intermediate layer in the case where the treatment solution contained phosphate, fluorine was detected in the case where it contained hydrofluoric acid, both nitrogen and oxygen were detected in the case where it contained nitrate, sodium was detected in the intermediate layer in the case where it contained sodium, potassium was detected in the case where it contained potassium, and lithium was detected in the case where it contained lithium. Furthermore, the average thickness of the insulating coating was 2.0 to 10.0 μm.

[0113] Furthermore, the coating adhesion, coating tension, corrosion resistance, elution resistance, packing factor, and magnetic properties of these grain-oriented electrical steel sheets were determined using the method described later. The results are shown in Table 3.

[0114] [Coating adhesion] Coating adhesion was evaluated by taking a 30mm wide and 300mm long sample from a grain-oriented electrical steel sheet, performing stress-relieving annealing at 800°C for 2 hours in a nitrogen atmosphere, then winding it around a 10mm diameter cylinder and unwinding it, followed by a bending adhesion test, and finally measuring the degree of peeling of the insulating coating. The evaluation criteria were as follows: a rating of 3 or higher was considered excellent in terms of coating adhesion and was deemed acceptable. Conversely, a rating of less than 3 was considered poor in terms of coating adhesion and was deemed unacceptable. 5: There is no peeling at all. 4: There is almost no peeling. 3: Peeling of several millimeters is observed. Peeling is observed at a ratio of 2:1 / 3 to 1 / 2. 1: It is peeling off almost completely.

[0115] [Coating tension] The coating tension was calculated by taking a sample from a grain-oriented electrical steel sheet and working backward from the curvature observed when the insulating coating on one side of the sample was peeled off. If the obtained coating tension was 4.0 MPa or higher, it was judged to be excellent in terms of coating tension and was deemed acceptable. On the other hand, if the obtained coating tension was less than 4.0 MPa, it was judged to be inferior in terms of coating tension and was deemed unacceptable.

[0116] [Corrosion resistance] In accordance with the salt spray test of JIS Z 2371:2015, a 5% NaCl aqueous solution was allowed to naturally fall onto the sample in a 35°C atmosphere for 7 hours. Subsequently, the rusted area was evaluated on a 10-point scale. The evaluation criteria were as follows: a score of 5 or higher (5-10) was judged as passing, indicating excellent corrosion resistance. Conversely, a score below 5 (1-4) was judged as failing, indicating poor corrosion resistance. 10: No rust occurred. 9: Rust formation is minimal (area ratio of 0.1% or less). 8: Area percentage where rust occurred = greater than 0.10% and less than or equal to 0.25%. 7: Area percentage where rust occurred = greater than 0.25% and less than or equal to 0.50%. 6: Area percentage where rust occurred = greater than 0.50% and less than or equal to 1.0%. 5: Area percentage where rust occurred = greater than 1.0% and 2.5% or less. 4: Area percentage where rust occurred = more than 2.5% and 5.0% or less. 3: Area percentage where rust occurred = more than 5.0% and 10% or less. 2: Area percentage where rust occurred = more than 10% and 25% or less. 1: Area percentage where rust occurred = more than 25% and 50% or less.

[0117] [Dissolution] Samples were taken from the obtained grain-oriented electrical steel sheets, boiled in boiling pure water for 10 minutes, and the amount of phosphoric acid dissolved into the pure water was measured. The amount of dissolved phosphoric acid was divided by the area of ​​the insulating coating on the boiled grain-oriented electrical steel sheet to determine the elution rate (mg / m²).2 ) was evaluated. The amount of phosphate dissolved in pure water was measured by cooling the pure water (solution) containing the dissolved phosphate, and then measuring the phosphate concentration of the sample obtained by diluting the cooled solution with pure water using ICP-AES. The elution rate per unit area is 40 mg / m². 2 If the value was less than 40 mg / m², it was judged to be acceptable due to its excellent dissolution properties. On the other hand, the dissolution amount per unit area was 40 mg / m². 2 If the above conditions were met, the product was deemed unsuitable due to poor elution properties.

[0118] [Occupancy rate] The packing factor was measured according to the method compliant with JIS C 2550-5:2020. Thirty test specimens, each 30 mm wide and 320 mm long, were taken from grain-oriented electrical steel sheets. After measuring the total mass of the samples, the packing factor was calculated by measuring the distance between the upper and lower backing plates sandwiching the laminate while under a pressure of 1.00 MPa. If the packing ratio was 95.0% or higher, it was judged as acceptable because the packing ratio could be increased by using a laminated core. On the other hand, if the packing ratio was less than 95.0%, it was judged as unacceptable because the packing ratio could not be increased by using a laminated core.

[0119] [Magnetic properties] The magnetic properties measured were iron loss W17 / 50 and magnetic flux density B8. Iron loss W17 / 50 was measured by taking the average value of the iron loss obtained by exciting five samples taken from grain-oriented electrical steel sheets to 1.7T at 50Hz. Magnetic flux density B8 was measured by taking five samples taken from grain-oriented electrical steel sheets and applying a magnetic field of 800A / m at 50Hz. These magnetic properties were measured in accordance with the Single Sheet Tester (SST) method specified in JIS C 2556:2015. If the iron loss W17 / 50 was 0.70 W / kg or less and the magnetic flux density B8 was 1.90 T or more, the material was judged to have excellent magnetic properties and was deemed acceptable. If either condition was not met, the material was judged to have inferior magnetic properties and was deemed unacceptable.

[0120] [Table 1]

[0121] [Table 2]

[0122] [Table 3]

[0123] As shown in Tables 1 to 3, the grain-oriented electrical steel sheet according to the present invention example exhibits excellent coating adhesion, coating tension, elution resistance, corrosion resistance, and magnetic properties, and can also increase the packing ratio when used in a laminated core. On the other hand, the grain-oriented electrical steel sheet according to the comparative example exhibits inferiority in one or more of these properties. [Industrial applicability]

[0124] According to the above-described embodiment of the present invention, it is possible to provide a grain-oriented electrical steel sheet that does not have a forsterite-based coating, has excellent coating adhesion, coating tension, elution properties, corrosion resistance and magnetic properties, and can increase the packing ratio when used as a laminated core. Furthermore, according to the above-described embodiment of the present invention, a method for forming an intermediate layer and an insulating coating on the grain-oriented electrical steel sheet can be provided. [Explanation of symbols]

[0125] 1 Base steel plate 2. Middle class 3. Insulating coating 10 Grain-oriented electrical steel sheet

Claims

1. Base material steel plate and An intermediate layer disposed on the surface of the base steel sheet, The intermediate layer has an insulating coating disposed on its surface, The aforementioned intermediate layer is The average thickness is 20 to 200 nm. It contains one or more elements selected from the group consisting of V, Mo, W, and Zr, and also contains one or more elements selected from the group consisting of phosphorus, fluorine, nitrogen, and oxygen. A grain-oriented electrical steel sheet characterized by containing one or more selected from the group consisting of vanadic acid, vanadium oxide, molybdic acid, phosphomolybdic acid, molybdenum oxide, tungstic acid, phosphotungstic acid, tungsten oxide, zirconic acid, and zirconium oxide.

2. The aforementioned intermediate layer is The grain-oriented electrical steel sheet according to claim 1, characterized by containing one or more elements selected from the group consisting of Na, K, and Li.

3. A method for forming an intermediate layer and an insulating coating in a grain-oriented electrical steel sheet according to claim 1, On the steel plate, Al ２ O ３ A finish annealing step involves applying an annealing release agent containing 10 to 100% by mass of [the substance], drying it, and then performing finish annealing. An annealing separating agent removal step is performed on the steel plate after the finish annealing step to remove any excess annealing separating agent, The steel sheet after the annealing separation agent removal step is immersed for 5 to 90 seconds in a chemical conversion treatment solution having a liquid temperature of 30 to 60°C, containing one or more metal elements selected from the group consisting of V, Mo, W, and Zr, with a concentration of the metal elements of 0.01 to 2.00 atomic%, and A drying step is performed in which the steel plate is removed from the chemical treatment solution after the immersion step, the excess chemical treatment solution is removed, and then the plate is dried. A method for forming an intermediate layer and an insulating film in a grain-oriented electrical steel sheet, comprising: a step of forming an insulating film, wherein a coating solution comprising phosphate and colloidal silica, wherein the ratio of colloidal silica to phosphate is 30 to 150 parts by mass per 100 parts by mass of phosphate, is applied to the steel sheet after the drying step, and after drying, the sheet temperature is maintained at 750 to 900°C for 10 to 50 seconds.

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