Insulating coating composition for electromagnetic steel sheets, electromagnetic steel sheets, and method for manufacturing the same.

Abstract

The object of the present invention is to provide an electrical steel sheet insulating coating composition, an electrical steel sheet, and a method for manufacturing the same, which have high functionality such as high insulation, high temperature resistance, corrosion resistance, adhesion, and recoating capability at customer companies. [Solution] The insulating coating composition for electrical steel sheets of the present invention contains, per 100 parts by weight of solids, 30 to 60 parts by weight of a solid / inorganic composite in which inorganic nanoparticles are substituted in the 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 electrical steel sheet insulating coating composition, an electrical steel sheet, and a method for manufacturing the same. More specifically, it relates to an electrical steel sheet insulating coating composition, an electrical steel sheet, and a method for manufacturing the same, in which the components and component ratios within the electrical steel sheet insulating coating composition are adjusted to improve insulation properties, high temperature resistance, corrosion resistance, adhesion, and recoating properties at customer companies. [Background technology]

[0002] Electrical steel sheets are used as materials for transformers, motors, and electrical equipment. Unlike general carbon steel, which prioritizes mechanical properties and workability, electrical steel sheets are functional products that prioritize electrical properties. Required electrical properties include low iron loss and high magnetic flux density, permeability, and packing factor. Electrical steel sheets are classified into grain-oriented electrical steel sheets and non-oriented electrical steel sheets. Grain-oriented electrical steel sheets utilize an abnormal grain growth phenomenon called secondary recrystallization to create a Goss texture ({110} <001> An electrical steel sheet has a textured surface formed throughout the entire sheet, resulting in excellent magnetic properties in the rolling direction. A non-oriented electrical steel sheet is an electrical steel sheet in which the magnetic properties are uniform in all directions on the rolled 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, and small transformers. In particular, non-oriented electrical steel sheets are trending towards higher grades to reduce iron loss for reduced electrical loss (refrigerators, factory motors), increase magnetic flux density for miniaturization and high efficiency (vacuum cleaner motors, etc.), and make them extremely thin to accommodate increased frequencies for high output (office equipment, electric vehicle drive motors).

[0003] In these increasingly high-grade non-oriented electrical steel sheets, a thick insulating coating (thick film) is 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 an insulating coating that provides a high level of insulation when the laminate formed from steel is used in a punched state, in order to minimize interlayer current loss. Such a high level of insulation may also be required after heat treatment such as stress-relief annealing (SRA). Furthermore, high-grade non-oriented electrical steel sheets have a high silicon content, which increases the hardness of the material. This results in poor workability, as it places a lot of stress on the slitter and press during slitting and punching processes. Therefore, thick film coating is required. On the other hand, insulating coating solutions for forming insulating films on non-oriented electrical steel sheets can be broadly classified into three types: inorganic, organic, and organic-inorganic composite coating solutions. Methods in which an inorganic coating solution is first applied, followed by a coating with an organic coating solution, are also being studied. Inorganic coating solutions, primarily composed of inorganic substances such as phosphates, can form coatings with excellent high-temperature resistance, weldability, and lamination properties, and are used for EI cores. However, because the insulating coating has high hardness, the mold is damaged faster during punching than with organic-containing coatings, making it an insulating coating solution that is not advantageous for punching processes. Organic coating solutions, primarily composed of organic materials, exhibit excellent punchability. Furthermore, they maintain good adhesion even at high film thicknesses, making them widely used for large iron cores requiring high interlayer insulation. However, the weldability of organic coatings is compromised by the generation of resin decomposition gases during welding, resulting in undesirable properties. For these reasons, a composite coating solution using both organic and inorganic materials has been developed, prioritizing heat resistance and insulation while compensating for the punching processability shortcomings of inorganic materials such as phosphates and chromates. When a coating is formed using such an insulating coating solution, it simultaneously satisfies the high-temperature heat resistance characteristic of inorganic materials and the lubricating effect of organic materials, while also having a clean surface appearance. As insulating coating compositions using inorganic coating solutions, insulating coating compositions containing aluminum phosphate, inorganic fine silicate, and acrylic resin are known. However, with these insulating coating compositions, the use of metal phosphates can lead to problems such as the coating becoming sticky and free phosphate deposition due to the free phosphate present in the phosphate. [Overview of the project] [Problems that the invention aims to solve]

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

[0005] The insulating coating composition for electrical steel sheets of the present invention is characterized by containing, per 100 parts by weight of solids, 30 to 60 parts by weight of a composite material in which inorganic nanoparticles are substituted in the 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 resin-based / inorganic composite, in which inorganic nanoparticles are substituted for the resin, contains 25 to 45 parts by weight of resin and 5 to 15 parts by weight of inorganic nanoparticles.

[0007] The resin includes one or more resins selected from epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenolic resins, styrene resins, vinyl resins, ethylene resins, and urethane resins.

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

[0009] Inorganic nanoparticles include one or more of the following: SiO2, Al2O3, TiO2, MgO, ZnO, CaO, and ZrO2.

[0010] Metal phosphates contain one or more metals from among Al, Mg, Ca, Co, Mn, Zn, Zr, and Fe.

[0011] Metal phosphates include Al phosphates and one or more metal phosphates from among Mg, Ca, Co, Mn, Zn, Zr, and Fe.

[0012] The inorganic dispersant contains one or more of the following: 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 structure includes one or more of the following: natural graphite, artificial graphite, carbon black, carbon nanotubes, carbon fibers, and graphene.

[0015] An electrical steel sheet according to one embodiment of the present invention comprises an electrical steel sheet substrate and an insulating coating located on the surface of the electrical steel sheet substrate, wherein the insulating coating comprises 30 to 60 parts by weight of an inorganic / 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] The manufacturing method of an electromagnetic steel sheet according to an embodiment of the present invention includes a step of preparing an electromagnetic steel sheet substrate, a step of applying an insulating coating composition to the surface of the electromagnetic steel sheet substrate, and a step of heat-treating the electromagnetic steel sheet substrate coated with the insulating coating composition.

Effects of the Invention

[0018] According to the present invention, it is excellent in solution stability without containing chromium. Further, according to the present invention, it is excellent in high-temperature heat resistance, corrosion resistance, adhesion, and recoatability in a customer company.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 is a schematic view of a cross-section of an electromagnetic steel sheet according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[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 only used to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Therefore, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section within the scope not departing from the scope of the present invention. The technical terms used herein are only for referring to specific embodiments and are not intended to limit the present invention. The singular forms used herein include the plural forms as long as the context does not clearly indicate the contrary meaning. The meaning of "including" used in the specification does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components while specifying specific characteristics, regions, integers, steps, operations, elements, and / or components. When one part is described as being "on top of" or "above" another part, it means that it is either directly on top of or above the other part, or that the other part is located between them. In contrast, when one part is described as being "directly on top of" another part, it means that the other part is not located between them. Although not defined differently, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have the meaning consistent with the relevant technical literature and the present disclosure, and are not interpreted in their ideal or highly formal sense unless otherwise defined.

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings, so that those with ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention can be embodied in a variety of different forms and is not limited to the embodiments described herein.

[0022] An insulating coating composition for electrical steel sheets according to one embodiment of the present invention contains, per 100 parts by weight of solids, 30 to 60 parts by weight of a composite in which inorganic nanoparticles are substituted in the 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] An insulating coating composition for electrical steel sheets according to one embodiment of the present invention can improve insulation properties, high-temperature heat resistance, corrosion resistance, adhesion, and recoating properties at customer companies by adjusting the components and component ratios within the composition.

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

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

[0026] The inorganic / inorganic composite consists of a resin and inorganic nanoparticles, and some or all of the functional groups of the resin may be replaced by inorganic nanoparticles, and the resin and inorganic nanoparticles may be present in the composition bound together. If inorganic nanoparticles are added alone without being bound to the resin, they may aggregate with each other, preventing proper dispersion.

[0027] The resin within the inorganic / inorganic composite plays a role in imparting insulation properties to the insulating coating and ensuring adhesion between the insulating coating and the steel plate substrate, while the inorganic nanoparticles prevent precipitation and agglomeration of metal phosphates, contributing to the development of superior surface properties after stress relief annealing.

[0028] The inorganic / metallic composite in the insulating coating composition is contained in an amount of 30 to 60 parts by weight per 100 parts by weight of solids. If the amount of inorganic / metallic composite is excessively low, it is difficult to adequately ensure the aforementioned insulating properties, adhesion, etc. Conversely, if the amount of inorganic / metallic composite is excessively high, the addition of metal phosphates is relatively reduced, which may make it difficult to ensure high temperature resistance, etc. More specifically, the inorganic / metallic composite in the insulating coating composition is contained in an amount of 35 to 55 parts by weight per 100 parts by weight of solids. In one embodiment of the present invention, parts by weight refers to the relative ratio between the weights of the components. Solids refer to the weight of the remaining components in the insulating coating composition after removing volatile components such as solvents.

[0029] Resin refers to a polymer compound and is a concept contrasted with monomer. The insulating coating composition for electrical steel sheets may contain 25 to 45 parts by weight of resin per 100 parts by weight of solids. If the resin content is too low, it is difficult to adequately ensure insulation, 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 contain 25 to 35 parts by weight.

[0030] Specifically, the resin may contain one or more selected from epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenolic resins, styrene resins, vinyl resins, ethylene resins, and urethane resins. More specifically, it may contain one or more of epoxy resins, ester resins, melamine resins, and acrylic resins. Here, "epoxy" means, for example, that there are epoxy groups or groups derived from epoxy groups in the main chain.

[0031] Inorganic nanoparticles prevent precipitation and agglomeration of the insulating coating composition, contributing to the development of superior properties after stress relief annealing. The insulating coating composition for electrical steel sheets may contain 5 to 15 parts by weight of inorganic nanoparticles per 100 parts by weight of solids. If the amount of inorganic nanoparticles is too small, it is difficult to adequately ensure dispersibility, high-temperature heat resistance, etc. Conversely, if the amount of inorganic nanoparticles is excessively large, it is difficult to adequately ensure adhesion. More specifically, the inorganic nanoparticles may be included in amounts 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 contain one or more of SiO2, Al2O3, TiO2, MgO, ZnO, CaO, and ZrO2. More specifically, they may contain one or more of SiO2, Al2O3, and TiO2.

[0032] The insulating coating composition for electrical steel sheets contains 15 to 45 parts by weight of metal phosphate per 100 parts by weight of solids.

[0033] The metal phosphate used in one embodiment of the present invention is M x (H2PO4) y It is represented by the chemical formula shown and plays a role in ensuring high-temperature resistance.

[0034] The metal phosphate may contain one or more metals from among 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 contain Al phosphate and one or more metal phosphates from among 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 (O) with phosphoric acid (H3PO4). For example, using 100 parts by weight of an aqueous phosphoric acid solution containing 85% by weight of free phosphorus phosphate (H3PO4) as a basis, metal hydroxide (M x (OH) y ) or metal oxide (M x By adding each of the O) and reacting them 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), also known as clay, acts as an extender pigment. Kaolin improves the corrosion resistance of the insulating coating. If the amount of kaolin is too low, the corrosion resistance may be poor. If the amount of kaolin is too high, 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 an inorganic dispersant per 100 parts by weight of solids. The inorganic dispersant plays a role in properly dispersing the kaolin mentioned above within the composition. If the kaolin is not properly dispersed, it may be difficult to ensure corrosion resistance due to the kaolin. If the amount of inorganic dispersant is too low, corrosion resistance may be poor. If the amount of inorganic dispersant is too high, 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 plate-like crystalline kaolin may also be used.

[0039] The inorganic dispersant may contain one or more of the following: titanium dioxide (TiO2), barium sulfate (Ba2SO4), calcium carbonate (CaCO3), silicon dioxide (SiO2), and talc (3MgO·4SiO2·H2O). More specifically, it may contain 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 forms depending on its type. For example, barium sulfate may be in the form of a rod or column, titanium dioxide in the form of a sphere, calcium carbonate and silicon dioxide in the form of an amorphous form, and talc in the form of a plate-like crystal or a massive form. For example, in the case of titanium dioxide, a spherical form 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 carbon structure per 100 parts by weight of solid content. The carbon structure plays a role in improving the corrosion resistance of the insulating coating and simultaneously removing defects such as cracks present in the steel sheet substrate. If the amount of carbon structure is excessively low, it may be difficult to properly perform the aforementioned roles. If the amount of carbon structure is excessively high, the adhesion and insulating properties of the insulating coating may be poor. More specifically, the insulating coating composition for electrical steel sheets may contain 0.1 to 1 part by weight of carbon structure per 100 parts by weight of solid content.

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

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

[0044] Figure 1 shows a schematic cross-section of an electrical steel sheet 100 according to one embodiment of the present invention. As shown in Figure 1, the electrical steel sheet 100 according to one 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] The electromagnetic steel sheet substrate 10 may be any general non-oriented or oriented electromagnetic steel sheet without limitation. In one embodiment of the present invention, the main component is the formation of an insulating coating 20 with special components on the electromagnetic steel sheet substrate 10, so a specific description of the electromagnetic steel sheet substrate 10 will be omitted.

[0046] The thickness of the insulating film 20 may be 1 to 10 μm. If the thickness of the insulating film 20 is excessively thin, it is difficult to ensure adequate insulation. If the thickness of the insulating film 20 is excessively thick, the packing factor may be low. In one embodiment of the present invention, adequate insulation can be ensured even when an insulating film 20 of thinness is formed. More specifically, the thickness of the insulating film 20 may be 2 to 5 μm.

[0047] The insulating film 20 can maintain the solid content components and content ratios within the insulating film composition described above. Specifically, the insulating film 20 contains, per 100 parts by weight of the total insulating film, 30 to 60 parts by weight of a resin-based / inorganic composite in which inorganic nanoparticles are substituted, 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 composition of the insulating coating 20 has been explained in detail in relation to the insulating coating composition, so redundant explanations 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 the 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, prepare the electromagnetic steel sheet substrate. The electromagnetic steel sheet substrate 10 may be any general non-oriented or oriented electromagnetic steel sheet without limitation. In one embodiment of the present invention, the main component is the formation of an insulating coating 20 of special components on the electromagnetic steel sheet substrate 10, so a detailed explanation of the manufacturing method of the electromagnetic steel sheet substrate 10 will be omitted.

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

[0052] Next, the electromagnetic 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, film formation will take a long time and whitening may occur. If the temperature is too high, the heat resistance and bluing resistance due to cracking may decrease.

[0053] The following describes preferred embodiments of the present invention, comparative examples, and evaluation examples thereof. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to these embodiments.

[0054] Examples A blank specimen was prepared from a 0.27 mm thick non-oriented electrical steel sheet (150*50 mm) containing 3.15 wt% silicon (Si) by weight. The insulating coating solution, summarized in Table 1, was applied to the blank specimen using a bar coater and a roll coater to form a 6 μm film. The solution was then maintained in a drying oven at approximately 400°C for 30 seconds, and then slowly cooled in air. The insulating coating was evaluated using the method described below and summarized in Table 2.

[0055] The surface condition was evaluated by the surface stripe pattern and the degree of defect occurrence after coating and curing. When there are no surface stripe patterns and no defects, it is very excellent (◎); when there are almost no surface stripe patterns and no defects, it is excellent (○); when there are some surface stripe patterns and defects, it is normal (△); and when there are severe surface stripe patterns and defects, it is inferior (×).

[0056] The insulation was measured by a Franklin Insulation Tester, which is a single-plate test method device for measuring the surface insulation resistance of an electromagnetic steel sheet under a constant pressure and a constant voltage. The current range is 0 - 1,000 Amp. The insulation measurement method is as follows: after placing one measurement test piece on the plate so that the contacts of all electrodes touch it, apply pressure with a pressure device to reach 300 psi (20.4 atm). When the test pressure is reached, adjust the slip resistor and read the scale of the ammeter under a voltage of 0.5 V. Five pieces were evaluated for each test solution. When the insulation resistance value is 100 Ω·cm 2 / lamination or more, it is very excellent (◎); when it is 60 Ω·cm 2 / lamination or more, it is good (○); when it is 40 Ω·cm 2 / lamination or more, it is normal (△); when it is less than 40 Ω·cm 2 / lamination, it is poor (×).

[0057] The corrosion resistance was evaluated by immersing the sample in a 5%, 35°C, NaCl solution for 8 hours and checking for the presence of rust on the sample. When the rusted area is 2% or less, it is very excellent (◎); when it is 5% or less, it is excellent (○); when it is 30% or less, it is normal (△); and when it is 50% or less, it is poor (×).

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

[0059] Adhesion is defined as the minimum arc diameter at which the coating does not peel off when the tested specimen is bent 180° in contact with an arc of 5, 10, 20, 30, or 100 mm in diameter. Here, if the minimum arc diameter is 5 mmΦ or less, it is classified as excellent (◎), if it is 10 mmΦ or less, it is good (○), if it is 20 mmΦ or less, it is average (△), and if it exceeds 20 mmΦ, it is poor (×).

[0060] The recoating properties were evaluated by applying Comparative Example 1, a secondary coating solution, to the coating layer of a specimen coated with the solution of the example, drying it, and then assessing the surface condition of the secondary coating layer and its adhesion to the primary coating layer.

[0061] Solution stability was investigated by checking for precipitate formation while the solution was left standing for one week. No precipitate formation was indicated as good (O), and precipitate formation was indicated as poor (×).

[0062] The insulating properties were measured on the top of the coating using a Franklin measuring instrument, in accordance with the ASTM A717 international standard.

[0063] Carbon aggregates were analyzed by taking TEM images and carbon EDS mapping images of cross-sections perpendicular to the rolling direction. Aggregates containing one or more particles between 10 and 500 nm were identified as carbon aggregates, and empty spaces were identified as pores.

[0064] [Table 1]

[0065] [Table 2]

[0066] As shown in Tables 1 and 2, the examples containing appropriate amounts of inorganic / inorganic composites, metal phosphates, kaolin, inorganic dispersants, and carbon structures were found to be excellent in surface condition, insulation, corrosion resistance, high-temperature resistance, adhesion, and recoating properties. In contrast, the comparative examples that did not appropriately contain kaolin, inorganic dispersants, and carbon structures were found to be inferior in one or more of the following areas: surface condition, insulation, corrosion resistance, high-temperature resistance, adhesion, and recoating properties.

[0067] The present invention is not limited to the embodiments described herein and can be manufactured in a variety of different forms. Those with ordinary skill in the art to which the present invention pertains will understand that the invention can be implemented in other specific forms without altering the technical idea or essential features of the invention. Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects. [Explanation of symbols]

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

Claims

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

2. The insulating coating composition for electromagnetic steel sheets according to claim 1, characterized in that the resin-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.

3. The insulating coating composition for electrical steel sheets according to claim 1, characterized in that the resin comprises one or more selected from epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenolic resins, styrene resins, vinyl resins, ethylene resins, and urethane resins.

4. The insulating coating composition for electromagnetic steel sheets according to claim 1, characterized in that 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 The insulating coating composition for electromagnetic steel sheets according to claim 1, characterized by containing one or more of the following.

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

7. The insulating coating composition for electromagnetic steel sheets according to claim 1, characterized in that the metal phosphate comprises Al phosphate and one or more metal phosphates selected from Mg, Ca, Co, Mn, Zn, Zr, and Fe.

8. The inorganic dispersant is one or more selected from 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 O). The insulating coating composition for electromagnetic steel sheets according to claim 1 is characterized by containing one or more of them.

9. The insulating coating composition for electrical steel sheets according to claim 1, characterized in that the inorganic dispersant has an average particle size of 0.05 to 10 μm.

10. The insulating coating composition for electrical steel sheets according to claim 1, characterized in that the carbon structure comprises one or more of the following: natural graphite, artificial graphite, carbon black, carbon nanotubes, carbon fibers, and graphene.

11. Electrical steel sheet base material, The insulating coating located on the surface of the electromagnetic steel sheet substrate is included, The insulating coating is characterized by comprising 30 to 60 parts by weight of an inorganic / inorganic composite in which inorganic nanoparticles are substituted for the 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 electromagnetic steel sheet according to claim 11, characterized in that the insulating coating has a thickness of 1 to 10 μm.

13. The steps include preparing the electrical steel sheet substrate and The steps include applying the insulating coating composition according to any one of claims 1 to 10 to the surface of the electromagnetic steel sheet substrate, A method for manufacturing an electrical steel sheet, comprising the step of heat-treating an electrical steel sheet substrate to which the insulating coating composition has been applied.

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