Insulating coating composition for electrical steel sheet, electrical steel sheet and method for producing same

Abstract

An object of the present invention is to provide an insulating coating composition for electrical steel sheet, which has high functionality such as high insulation, high-temperature resistance, corrosion resistance, adhesion, and recoatability at a customer's company, an electrical steel sheet, and a manufacturing method thereof. [Solution] The insulating coating composition for electrical steel sheet of the present invention contains, per 100 parts by weight of solids, 30 to 60 parts by weight of an organic / inorganic composite in which inorganic nanoparticles are substituted for a resin, 15 to 45 parts by weight of a metal phosphate, 10 to 40 parts by weight of kaolin, 1 to 10 parts by weight of an inorganic dispersant, and 0.1 to 5 parts by weight of a carbon structure.

Description

[Technical field]

[0001] The present invention relates to an insulating coating composition for electrical steel sheets, an electrical steel sheet, and a manufacturing method thereof, and more particularly to an insulating coating composition for electrical steel sheets, an electrical steel sheet, and a manufacturing method thereof, in which components and component ratios in the insulating coating composition for electrical steel sheets are adjusted to improve insulation properties, high-temperature resistance, corrosion resistance, adhesion, and recoatability at customer companies. [Background technology]

[0002] Electrical steel sheets are used as materials for transformers, motors, and electrical equipment, and unlike general carbon steels, which emphasize workability such as mechanical properties, they are functional products that emphasize electrical properties. Required electrical properties include low iron loss, and high magnetic flux density, magnetic permeability, and space factor. Electrical steel sheets are classified into oriented electrical steel sheets and non-oriented electrical steel sheets. Grain-oriented electrical steel sheets are made using the abnormal grain growth phenomenon known as secondary recrystallization to create a Goss texture ({110} <001> A non-oriented electrical steel sheet has a uniform magnetic property in all directions on the rolled sheet, and has a texture formed throughout the entire sheet. Non-oriented electrical steel sheets are steel sheets with uniform magnetic properties in all directions on the rolled sheet, and are widely used in motors, generator cores, electric motors, small transformers, etc. In particular, non-oriented electrical steel sheets are tending to be made more luxurious in order to reduce iron loss to reduce electrical loss (refrigerators, factory motors), to increase magnetic flux density to make them smaller and more efficient (vacuum cleaner motors, etc.), and to be made extremely thin to accommodate increased frequencies for higher output (office equipment, electric vehicle drive motors), etc.

[0003] For these increasingly high-grade non-oriented electrical steel sheets, thick insulating coatings (thick films) are essential for high insulation in terms of efficient energy utilization. For example, non-oriented electrical steel sheets used in medium and large electric motors, generators, and transformers require insulating coatings that provide a high level of insulation to minimize interlaminar current loss when laminates made of steel are used in a punched state. Such high levels of insulation may also be required after heat treatments such as stress-relief annealing (SRA). In addition, high-grade non-oriented electrical steel sheets have a high silicon content, which increases the hardness of the material, causing a problem of poor workability in that it places a lot of stress on the slitter and press during slitting and punching processes, so a thick coating is required. Meanwhile, insulating coating solutions used to form insulating coatings on non-oriented electrical steel sheets can be broadly divided into three types: inorganic, organic, and organic-inorganic hybrid coating solutions. Research is also being conducted on a method in which an inorganic coating solution is first applied, and then an organic coating solution is applied. Inorganic coating solutions, which contain inorganic substances such as phosphate as the main component, can form coatings with excellent high-temperature resistance, weldability, lamination properties, etc., and are used for EI cores. However, because the insulating coating has a high hardness, it damages the die more quickly during punching than organic-containing coating materials, making it an insulating coating solution that is not advantageous for punching workability. Organic coating solutions, which contain organic substances as their main components, are excellent in terms of punchability. In addition, since they have good adhesion even when the film is thick, they are often used for large iron cores that require high interlayer insulation. The weldability of organic coatings cannot be good because resin decomposition gas is generated during welding. For this reason, organic-inorganic composite coating solutions that use both organic and inorganic materials at the same time have been developed, focusing on heat resistance and insulation, and making up for the shortcomings of inorganic materials such as phosphates and chromates in terms of punching workability. Films formed using such insulating coating solutions simultaneously satisfy the high-temperature resistance properties of inorganic materials and the lubricity properties of organic materials, and also have a beautiful surface appearance. As an insulating coating composition using an organic-inorganic coating solution, an insulating coating composition containing aluminum phosphate, inorganic fine silicate, and acrylic resin is known. However, this insulating coating composition uses metal phosphate, and the free phosphoric acid present in the phosphate may cause problems of the coating being sticky and free phosphate precipitation. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an insulating coating composition for electrical steel sheets, an electrical steel sheet, and a manufacturing method thereof. Specifically, it is to provide an insulating coating composition for electrical steel sheets, an electrical steel sheet, and a manufacturing method thereof that have high functionality, such as high insulation, high temperature resistance, corrosion resistance, adhesion, and recoatability at customer companies. [Means for solving the problem]

[0005] The insulating coating composition for electrical steel sheet of the present invention is characterized in that it contains, per 100 parts by weight of solids, 30 to 60 parts by weight of an organic / inorganic composite in which inorganic nanoparticles are substituted for a resin, 15 to 45 parts by weight of a metal phosphate, 10 to 40 parts by weight of kaolin, 1 to 10 parts by weight of an inorganic dispersant, and 0.1 to 5 parts by weight of a carbon structure.

[0006] The organic / inorganic composite in which inorganic nanoparticles are substituted for the resin contains 25 to 45 parts by weight of the resin and 5 to 15 parts by weight of the inorganic nanoparticles.

[0007] The resin includes at least one selected from the group consisting of epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenol resins, styrene resins, vinyl resins, ethylene resins, and urethane resins.

[0008] The inorganic nanoparticles have an average particle size of 10 to 50 nm.

[0009] The inorganic nanoparticles include one or more of SiO2, Al2O3, TiO2, MgO, ZnO, CaO, and ZrO2.

[0010] The metal phosphates include one or more of the metals Al, Mg, Ca, Co, Mn, Zn, Zr, and Fe.

[0011] The metal phosphate includes Al phosphate, and includes one or more metal phosphates of Mg, Ca, Co, Mn, Zn, Zr, and Fe.

[0012] The inorganic dispersing agent includes one or more of titanium dioxide (TiO2), barium sulfate (Ba2SO4), calcium carbonate (CaCO3), silicon dioxide (SiO2), and talc (3MgO·4SiO2·H2O).

[0013] The inorganic dispersant has an average particle size of 0.05 to 10 μm.

[0014] The carbon structures include one or more of natural graphite, synthetic graphite, carbon black, carbon nanotubes, carbon fibers, and graphene.

[0015] An electrical steel sheet according to one embodiment of the present invention includes an electrical steel sheet substrate and an insulating coating located on a surface of the electrical steel sheet substrate, the insulating coating including 30 to 60 parts by weight of an organic / inorganic composite in which inorganic nanoparticles are substituted for a resin, 15 to 45 parts by weight of a metal phosphate, 10 to 40 parts by weight of kaolin, 1 to 10 parts by weight of an inorganic dispersant, and 0.1 to 5 parts by weight of a carbon structure.

[0016] The insulating coating has a thickness of 1 to 10 μm.

[0017] A method for manufacturing an electrical steel sheet according to one embodiment of the present invention includes the steps of preparing an electrical steel sheet substrate, applying an insulating coating composition to a surface of the electrical steel sheet substrate, and heat treating the electrical steel sheet substrate to which the insulating coating composition has been applied. Effect of the Invention

[0018] The present invention does not contain chromium and has excellent solution stability. Furthermore, the present invention provides excellent high temperature resistance, corrosion resistance, adhesion, and recoatability at the customer's company. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram of a cross section of an electrical steel sheet according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Terms such as first, second and third are used to describe various parts, components, regions, layers and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Thus, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention. The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular form includes the plural form unless the phrase clearly indicates otherwise. As used herein, the meaning of "comprising" embodies certain features, regions, integers, steps, operations, elements and / or components and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements and / or components. When a part is referred to as being "on" or "on" another part, this means that it is directly on or above the other part, or there may be other parts in between. In contrast, when a part is referred to as being "directly on" another part, there are no other parts in between. Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and the currently disclosed content, and are not interpreted in an ideal or very formal sense unless otherwise defined.

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a semiconductor device according to an embodiment of the present invention;

[0022] An insulating coating composition for electrical steel sheet according to one embodiment of the present invention contains, per 100 parts by weight of solids, 30 to 60 parts by weight of an organic / inorganic composite in which inorganic nanoparticles are substituted for a resin, 15 to 45 parts by weight of a metal phosphate, 10 to 40 parts by weight of kaolin, 1 to 10 parts by weight of an inorganic dispersant, and 0.1 to 5 parts by weight of a carbon structure.

[0023] The insulating coating composition for electrical steel sheets according to an embodiment of the present invention can improve insulation properties, high temperature resistance, corrosion resistance, adhesion, and recoatability at customer companies by adjusting the components and component ratios in the composition.

[0024] The components of the insulating coating composition for electrical steel sheets according to one embodiment of the present invention will be specifically described below.

[0025] An insulating coating composition for electrical steel sheets according to an embodiment of the present invention contains 30 to 60 parts by weight of an organic / inorganic composite in which inorganic nanoparticles are substituted for a resin, based on 100 parts by weight of solid content.

[0026] The organic / inorganic composite is composed of a resin and inorganic nanoparticles, and may exist in the composition in a state where the inorganic nanoparticles are substituted for some or all of the functional groups of the resin, and the resin and the inorganic nanoparticles are bonded together. When the inorganic nanoparticles are added alone without being bonded to the resin, the inorganic nanoparticles may aggregate with each other and may not be dispersed.

[0027] The resin in the organic / inorganic composite provides insulation to the insulating coating and ensures adhesion between the insulating coating and the steel sheet substrate, while the inorganic nanoparticles prevent the precipitation and agglomeration of metal phosphate and contribute to the development of more excellent surface characteristics after stress relief annealing.

[0028] The organic / inorganic complex contains 30 to 60 parts by weight of the insulating coating composition relative to 100 parts by weight of the solid content. If the organic / inorganic complex is contained in an excessively small amount, it is difficult to adequately ensure the above-mentioned insulation properties and adhesion. Conversely, if the organic / inorganic complex is contained in an excessively large amount, the amount of metal phosphate added is relatively reduced, and it may be difficult to ensure high temperature resistance. More specifically, the organic / inorganic complex contains 35 to 55 parts by weight of the insulating coating composition relative to 100 parts by weight of the solid content. In one embodiment of the present invention, the part by weight refers to the relative ratio between the weights of the components. The solid content refers to the weight of the remaining components in the insulating coating composition excluding volatile components such as solvents.

[0029] Resin refers to a polymer compound, and is a concept that is contrasted with monomer. The resin may be contained in an amount of 25 to 45 parts by weight per 100 parts by weight of solids in the insulating coating composition for electrical steel sheets. If the resin content is low, it is difficult to adequately ensure insulation properties, adhesion, etc. Conversely, if the resin content is too high, it is difficult to adequately ensure high temperature resistance and corrosion resistance. More specifically, the resin may be contained in an amount of 25 to 35 parts by weight.

[0030] Specifically, the resin may include one or more selected from epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenol resins, styrene resins, vinyl resins, ethylene resins, and urethane resins. More specifically, the resin may include one or more of epoxy resins, ester resins, melamine resins, and acrylic resins. Here, epoxy resin means that, for example, an epoxy group or a group derived from an epoxy group is present in the main chain.

[0031] The inorganic nanoparticles prevent the precipitation and agglomeration of the insulating coating composition, and contribute to the development of more excellent properties after stress relief annealing. The inorganic nanoparticles may be included in an amount of 5 to 15 parts by weight based on 100 parts by weight of the solid content of the insulating coating composition for electrical steel sheets. When the inorganic nanoparticles are included in a small amount, it is difficult to adequately ensure dispersibility, high temperature resistance, and the like. On the other hand, when the inorganic nanoparticles are included in an excessively large amount, it is difficult to adequately ensure adhesion. More specifically, the inorganic nanoparticles may be included in an amount of 25 to 35 parts by weight. The inorganic nanoparticles may have an average particle size of 10 to 50 nm. The inorganic nanoparticles may include one or more of SiO2, Al2O3, TiO2, MgO, ZnO, CaO, and ZrO2. More specifically, the inorganic nanoparticles may include one or more of SiO2, Al2O3, and TiO2.

[0032] The metal phosphate is contained in an amount of 15 to 45 parts by weight based on 100 parts by weight of the solid content of the insulating coating composition for electrical steel sheets.

[0033] The metal phosphate used in one embodiment of the present invention is M x (H2PO4) y It has the function of ensuring high temperature resistance.

[0034] The metal phosphate may include one or more metals selected from Al, Mg, Ca, Co, Mn, Zn, Zr, and Fe. For example, the phosphate containing Al may be monoaluminum phosphate (Al(H3PO4)3). More specifically, the metal phosphate may include Al phosphate and one or more metal phosphates selected from Mg, Ca, Co, Mn, Zn, Zr, and Fe.

[0035] Metal phosphates are metal hydroxides (M x (OH) y ) or metal oxide (M x It can be produced using the reaction of 1,2-dihydropyridine (1,2,3,4-tetrahydrofuran) with phosphoric acid (H3PO4). For example, a metal hydroxide (M x (OH) y ) or metal oxide (M x O) and reacting at 80 to 90° C. for 6 to 10 hours, the respective metal phosphates can be obtained.

[0036] The insulating coating composition for electrical steel sheets contains 10 to 40 parts by weight of kaolin per 100 parts by weight of solids. Kaolin (Al2Si2O5(OH)4) is also called clay and serves as an extender pigment. Kaolin serves to improve the corrosion resistance of the insulating coating. If the amount of kaolin is too small, the corrosion resistance may be poor. If the amount of kaolin is too large, the adhesion of the insulating coating may be poor. More specifically, the amount of kaolin may be 20 to 35 parts by weight.

[0037] The insulating coating composition for electrical steel sheets contains 1 to 10 parts by weight of inorganic dispersant per 100 parts by weight of solids. The inorganic dispersant serves to properly disperse the above-mentioned kaolin within the composition. If the kaolin is not properly dispersed, it may be difficult to ensure the corrosion resistance provided by the kaolin. If the amount of inorganic dispersant is too small, the corrosion resistance may be poor. If the amount of inorganic dispersant is too large, the adhesion of the insulating coating may be poor.

[0038] The kaolin may have an average particle size of 0.2 to 0.8 μm and kaolin in the form of platelet crystals may be used.

[0039] The inorganic dispersant may include one or more of titanium dioxide (TiO2), barium sulfate (Ba2SO4), calcium carbonate (CaCO3), silicon dioxide (SiO2), and talc (3MgO·4SiO2·H2O). More specifically, it may include titanium dioxide (TiO2).

[0040] The inorganic dispersant may have an average particle size of 0.05 to 10 μm. The inorganic dispersant may have different shapes depending on the type. For example, in the case of barium sulfate, a rod shape may be used, in the case of titanium dioxide, a spherical shape may be used, in the case of calcium carbonate and silicon dioxide, an amorphous shape may be used, and in the case of talc, a plate-like crystal shape or a lump shape may be used. For example, in the case of titanium dioxide, a spherical shape with an average particle size of 50 to 100 nm may be used.

[0041] The insulating coating composition for electrical steel sheets contains 0.1 to 5 parts by weight of the carbon structure per 100 parts by weight of the solid content of the insulating coating composition for electrical steel sheets. The carbon structure plays a role in improving the corrosion resistance of the insulating coating and at the same time, in removing defects such as cracks present in the steel sheet substrate. If the carbon structure is contained in an excessively small amount, it may be difficult to properly perform the above-mentioned role. If the carbon structure is contained in an excessively large amount, the adhesion and insulation of the insulating coating may be deteriorated. More specifically, the insulating coating composition for electrical steel sheets may contain 0.1 to 1 part by weight of the carbon structure per 100 parts by weight of the solid content of the insulating coating composition for electrical steel sheets.

[0042] The carbon structure may include one or more of natural graphite, artificial graphite, carbon black, carbon nanotubes, carbon fibers, and graphene. More specifically, the carbon structure may include carbon black.

[0043] In addition to the above-mentioned components, the insulating coating composition may contain a solvent to facilitate application and to disperse the components uniformly. The amount of the solvent is not particularly limited, but may be 50 to 500 parts by weight per 100 parts by weight of the total solid content.

[0044] 1 shows a schematic cross-sectional view of an electrical steel sheet 100 according to an embodiment of the present invention. As shown in FIG. 1, the electrical steel sheet 100 according to an embodiment of the present invention includes an electrical steel sheet substrate 10 and an insulating coating 20 located on the electrical steel sheet substrate 10.

[0045] A general non-oriented or oriented electrical steel sheet may be used without any restrictions as the electrical steel sheet substrate 10. In one embodiment of the present invention, the main component is forming an insulating coating 20 having a special composition on the electrical steel sheet substrate 10, so a detailed description of the electrical steel sheet substrate 10 will be omitted.

[0046] The thickness of the insulating coating 20 may be 1 to 10 μm. If the thickness of the insulating coating 20 is too thin, it is difficult to ensure appropriate insulation. If the thickness of the insulating coating 20 is too thick, the space factor may be low. In one embodiment of the present invention, appropriate insulation can be ensured even when the insulating coating 20 is formed to a thin thickness. More specifically, the thickness of the insulating coating 20 may be 2 to 5 μm.

[0047] The insulating coating 20 may maintain the solid components and content ratios in the insulating coating composition described above. Specifically, the insulating coating 20 includes, relative to 100 parts by weight of the total insulating coating, 30 to 60 parts by weight of an organic / inorganic composite in which inorganic nanoparticles are substituted for a resin, 15 to 45 parts by weight of a metal phosphate, 10 to 40 parts by weight of kaolin, 1 to 10 parts by weight of an inorganic dispersant, and 0.1 to 5 parts by weight of a carbon structure.

[0048] Furthermore, the configuration of the insulating coating 20 has been described in detail in relation to the insulating coating composition, so a duplicated description will be omitted.

[0049] A method for manufacturing an electrical steel sheet according to one embodiment of the present invention includes the steps of preparing an electrical steel sheet substrate, applying an insulating coating composition to a surface of the electrical steel sheet substrate, and heat treating the electrical steel sheet substrate to which the insulating coating composition has been applied.

[0050] First, an electromagnetic steel sheet substrate is prepared. The electromagnetic steel sheet substrate 10 may be a general non-oriented or oriented electromagnetic steel sheet without any restrictions. In one embodiment of the present invention, the main component is to form an insulating coating 20 having a special composition on the electromagnetic steel sheet substrate 10, so a detailed description of a manufacturing method for the electromagnetic steel sheet substrate 10 will be omitted.

[0051] Next, an insulating coating composition is applied to the surface of the electrical steel sheet substrate. As the insulating coating composition has been described above, a detailed description thereof will be omitted.

[0052] Next, the electrical steel sheet substrate coated with the insulating coating composition is heat-treated. The heat treatment temperature may be 300 to 750°C. If the temperature is too low, it may take a long time to form the coating, and whitening may occur. If the temperature is too high, cracks may occur, resulting in a decrease in heat resistance and bluing resistance.

[0053] Hereinafter, preferred examples of the present invention, comparative examples for comparison, and evaluation examples thereof will be described. However, the following examples are merely preferred examples of the present invention, and the present invention is not limited to the following examples.

[0054] Working Example A blank specimen was prepared using a non-oriented electrical steel sheet (150*50mm) containing 3.15wt% silicon (Si) by weight and 0.27mm thick, and the insulating coating composition solution shown in Table 1 was applied to the blank specimen using a bar coater and a roll coater so that a 6μm coating was formed on each blank specimen. The blank specimen was then placed in a drying oven at a temperature range of about 400℃ for 30 seconds and slowly cooled in air. The insulating coating was evaluated using the following method and the results are shown in Table 2.

[0055] The surface condition was evaluated according to the degree of surface streaks and defects after coating and curing. When there were no surface streaks or defects, it was rated as excellent (◎), when there were almost no surface streaks or defects, it was rated as excellent (○), when there were only some surface streaks or defects, it was rated as fair (△), and when there were severe surface streaks and defects, it was rated as poor (×).

[0056] Insulation was measured using a Franklin Insulation Tester, a single plate test device that measures the surface insulation resistance of electrical steel sheets under a constant pressure and voltage. The current range is 0 to 1,000 Amp, and the insulation measurement method involves placing one test piece on a plate so that all electrode contacts are in contact, and then applying pressure of 300 psi (20.4 atm) using a pressure device. When the test pressure is reached, the slide resistor is adjusted and the ammeter scale is read under a voltage of 0.5 V. Five pieces were evaluated for each test solution. The insulation resistance value was 100 Ω·cm. 2 / lamination or more, very good (◎), 60 Ω cm 2 / lamination or more: Good (○), 40Ω·cm 2 For lamination and above, normal (△), 40Ω·cm 2 If the lamination was less than 1 / lamination, it was marked as defective (×).

[0057] Corrosion resistance was evaluated by immersing the specimen in a 5% NaCl solution at 35°C for 8 hours and evaluating whether rust had developed on the specimen. If the area of ​​rust developed was 2% or less, it was rated as excellent (◎), if it was 5% or less, it was rated as excellent (○), if it was 30% or less, it was rated as average (△), and if it was 50% or less, it was rated as poor (×).

[0058] High temperature resistance was evaluated using the IEC60404-12 continuous rating (180+30℃, 2500h), and the insulation resistance, adhesion (cylindrical mandrel bending) and space factor change were evaluated before and after the high temperature heat resistance evaluation. If the change in insulation resistance, adhesion and space factor after the continuous rating evaluation was less than 5%, it was categorized as excellent (◎), if it was less than 10%, it was excellent (○), if it was less than 30%, it was average (△), and if it was 30% or more, it was poor (×).

[0059] Adhesion was expressed as the minimum arc diameter at which the coating did not peel off when the test specimen was bent 180 degrees in contact with an arc of 5, 10, 20, 30 or 100 mmφ. Here, the minimum arc diameter was categorized as excellent (◎) for 5 mmφ or less, excellent (○) for 10 mmφ or less, fair (△) for 20 mmφ or less, and poor (×) for over 20 mmφ.

[0060] The recoatability was evaluated by applying a secondary coating solution of Comparative Example 1 on the coating layer of the specimen coated with the solution of the Example and drying it, and then evaluating the surface condition of the secondary coating layer and its adhesion to the primary coating layer.

[0061] The solution stability was investigated by checking whether or not a precipitate occurred while the solution was left to stand for one week. If no precipitate occurred, it was rated as good (O), and if a precipitate occurred, it was rated as bad (x).

[0062] The insulating properties were measured on the top of the coating using a Franklin tester according to the ASTM A717 international standard.

[0063] Carbon aggregates were analyzed by analyzing the cross section perpendicular to the rolling direction as TEM images and carbon EDS mapping images, and aggregates containing one or more 10 to 500 nm particles were determined to be carbon aggregates, and vacant spaces were determined to be pores.

[0064] [Table 1] JPEG2025501113000003.jpg118163

[0065] [Table 2]

[0066] As shown in Table 1, it can be seen that the examples in which the organic / inorganic composite, metal phosphate, kaolin, inorganic dispersant, and carbon structure were appropriately contained were excellent in surface condition, insulation, corrosion resistance, high temperature resistance, adhesion, and recoatability. In contrast, it can be seen that the comparative examples in which the kaolin, inorganic dispersant, and carbon structure were not appropriately contained were inferior in one or more of the surface condition, insulation, corrosion resistance, high temperature resistance, adhesion, and recoatability.

[0067] The present invention is not limited to the embodiments, and can be manufactured in various different forms, and a person having ordinary skill in the art to which the present invention pertains should understand that the present invention can be embodied in other specific forms without changing the technical concept or essential features of the present invention. Therefore, the embodiments described above should be understood to be illustrative in all respects and not limiting. [Explanation of symbols]

[0068] 100:Electromagnetic steel plate 10:Electromagnetic steel plate base material 20: Insulating coating

Claims

1. For 100 parts by weight of solids, 30 to 60 parts by weight of an organic / inorganic composite in which inorganic nanoparticles are substituted for a resin; 15 to 45 parts by weight of a metal phosphate, 10 to 40 parts by weight of kaolin, 1 to 10 parts by weight of an inorganic dispersant, and 1. An insulating coating composition for electrical steel sheets, comprising 0.1 to 5 parts by weight of a carbon structure.

2. 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein the organic / inorganic composite in which inorganic nanoparticles are substituted for the resin comprises 25 to 45 parts by weight of the resin and 5 to 15 parts by weight of the inorganic nanoparticles.

3. 2. The insulating coating composition for electrical steel sheet according to claim 1, wherein the resin comprises at least one selected from the group consisting of epoxy-based resins, ester-based resins, melamine-based resins, siloxane-based resins, acrylic-based resins, phenol-based resins, styrene-based resins, vinyl-based resins, ethylene-based resins, and urethane-based resins.

4. 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein the inorganic nanoparticles have an average particle size of 10 to 50 nm.

5. The inorganic nanoparticles are SiO ２ , Al ２ O ３ , TiO ２ , MgO, ZnO, CaO, and ZrO ２ 2. The insulating coating composition for electrical steel sheet according to claim 1, further comprising at least one of the following:

6. 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein the metal phosphate contains one or more metals selected from the group consisting of Al, Mg, Ca, Co, Mn, Zn, Zr, and Fe.

7. 2. The insulating coating composition for electrical steel sheet according to claim 1, wherein the metal phosphate comprises an Al phosphate and at least one metal phosphate selected from the group consisting of Mg, Ca, Co, Mn, Zn, Zr, and Fe.

8. The inorganic dispersant is titanium dioxide (TiO ２ ), barium sulfate (Ba ２ SO ４ ), calcium carbonate (CaCO ３ ), silicon dioxide (SiO ２ ) and talc (3MgO.4SiO ２ ・H ２ 2. The insulating coating composition for electrical steel sheet according to claim 1, further comprising at least one of the following:

9. 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein the inorganic dispersant has an average particle size of 0.05 to 10 [mu]m.

10. 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein the carbon structure comprises at least one of natural graphite, artificial graphite, carbon black, carbon nanotubes, carbon fibers, and graphene.

11. An electromagnetic steel sheet substrate; an insulating coating located on a surface of the electrical steel sheet substrate; The insulating coating comprises 30 to 60 parts by weight of an organic / inorganic composite in which inorganic nanoparticles are substituted for a resin, 15 to 45 parts by weight of a metal phosphate, 10 to 40 parts by weight of kaolin, 1 to 10 parts by weight of an inorganic dispersant, and 0.1 to 5 parts by weight of a carbon structure.

12. The electrical steel sheet according to claim 11, wherein the insulating coating has a thickness of 1 to 10 μm.

13. Preparing an electromagnetic steel sheet substrate; applying the insulating coating composition according to any one of claims 1 to 10 to a surface of the electrical steel sheet substrate; and heat treating the electrical steel sheet substrate to which the insulating coating composition has been applied.

Images