Insulating coating composition for electrical steel sheet, electrical steel sheet, and manufacturing method thereof

Abstract

Provided are an insulating coating composition for electrical steel sheets, electrical steel sheets, and methods for producing the same. The insulating coating composition for electrical steel sheets of the present invention is characterized by containing 100 parts by weight of a resin containing two or more aromatic rings or aliphatic rings within a repeating unit structure and 20 to 150 parts by weight of zirconium phosphate. The electrical steel sheet of the present invention includes an electrical steel sheet substrate and an insulating coating located on the surface of the electrical steel sheet substrate, and is characterized in that the insulating coating contains 100 parts by weight of a resin containing two or more aromatic rings or aliphatic rings within its repeating unit structure and 20 to 150 parts by weight of zirconium phosphate.

Description

[Technical Field]

[0001] The present invention relates to an insulating coating composition for electrical steel sheets, electrical steel sheets, and a manufacturing method thereof, and more particularly to an insulating coating composition for electrical steel sheets, electrical steel sheets, and a manufacturing method thereof, which use a resin containing two or more aromatic or aliphatic rings in the repeating unit structure and zirconium phosphate to improve adhesion and insulation properties after stress relief annealing (SRA). [Background technology]

[0002] The insulating coating of non-oriented electrical steel sheets used in motors, transformers, etc. requires not only interlaminar resistance but also various other properties, such as ease of processing and forming, and stability during storage and use. Since non-oriented electrical steel sheets are used in a wide variety of applications, various insulating coating forms have been developed to suit each application. For example, when non-oriented electrical steel sheets are subjected to punching, shearing, bending, etc., residual deformation can cause deterioration of their magnetic properties, so they are often subjected to stress relief annealing (SRA) at high temperatures to restore the deteriorated magnetic properties. Here, the insulating coating must have heat resistance to maintain its inherent electrical insulation properties so that it does not peel off during stress relief annealing.

[0003] Conventionally, corrosion resistance and insulation properties have been improved by using a mixture of chromic anhydride, magnesium oxide, acrylic resin, or acrylic-styrene copolymer resin, but there are limitations to satisfying the level of stress relief annealing properties recently required for non-oriented electrical steel sheets. In addition, a method has been proposed to improve adhesion during stress relief annealing by using metal phosphate as the main component of the insulating coating. However, this method has the problem that whitening defects occur on the surface due to the strong absorption resistance of phosphate, which generates dust during processing at customer companies. In addition, the areas with whitening defects have poor heat resistance. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides an insulating coating composition for electrical steel sheets, an electrical steel sheet, and a method for producing the same. Specifically, the invention provides an insulating coating composition for electrical steel sheets, an electrical steel sheet, and a method for producing the same, which use a resin containing two or more aromatic or aliphatic rings in the repeating unit structure and zirconium phosphate, and which have improved adhesion and insulating properties after stress relief annealing. [Means for solving the problem]

[0005] The insulating coating composition for electrical steel sheets of the present invention is characterized by containing 100 parts by weight of a resin containing two or more aromatic or aliphatic rings in its repeating unit structure and 20 to 150 parts by weight of zirconium phosphate.

[0006] The resin is preferably an epoxy resin. The repeating unit structure can be represented by the following chemical formula 1. TIFF0007829042000001.tif55128 (In the above chemical formula 1, X is a divalent organic group containing two or more aromatic rings or aliphatic rings, and R 1 represents hydrogen, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, a heterocyclic group, an alkoxy group, a carboxy group, or a halogen. In Chemical Formula 1, X may include one or more of a bisphenol structure, a biphenyl structure, a naphthalene structure, an anthracene structure, and a dicyclopentadiene structure. The zirconium phosphate preferably has a crystalline phase of 5% by mass or less.

[0007] The insulating coating composition for electrical steel sheets according to an embodiment of the present invention may further contain 0.1 to 100 parts by weight of magnesium phosphate. The insulating coating composition for electrical steel sheets of the present invention may further include 0.1 to 100 parts by weight of inorganic nanoparticles. The inorganic nanoparticles can include one or more of SiO2, Al2O3, MgO, ZnO, ZrO2, TiO2, Mn2O3, and CaO. The inorganic nanoparticles may have an average particle size of 1 to 100 nm.

[0008] An electrical steel sheet according to one embodiment of the present invention includes an electrical steel sheet substrate and an insulating coating located on the surface of the electrical steel sheet substrate, the insulating coating including 100 parts by weight of a resin including two or more aromatic rings or aliphatic rings within a repeating unit structure and 20 to 150 parts by weight of zirconium phosphate. The insulating coating contains, by weight, one or more elements selected from the group consisting of Zr: 6 to 60%, C: 7 to 70%, Si: 1 to 40%, Al: 1 to 40%, Mg: 1 to 45%, P: 1 to 70%, and B: 0.01 to 9%, with the remainder consisting of Fe and unavoidable impurities.

[0009] The electrical steel sheet substrate contains, by weight, one or more elements selected from the group consisting of 2.0 to 6.5% Si, 0.1 to 3.0% Mn, 0.1 to 7.5% Al, 0.1% or less B, 0.01 to 0.15% Sn, and 0.01 to 0.15% Sb, with the remainder consisting of Fe and unavoidable impurities.

[0010] A method for manufacturing an electrical steel sheet according to an embodiment of the present invention includes the steps of preparing an electrical steel sheet substrate and applying an insulating coating composition to a surface of the electrical steel sheet substrate to form an insulating coating. The insulating coating composition may include 100 parts by weight of a resin containing two or more aromatic rings or aliphatic rings within a repeating unit structure and 20 to 150 parts by weight of zirconium phosphate. [Effects of the Invention]

[0011] According to the present invention, the insulating coating composition for electrical steel sheet of the present invention contains an organic compound with a specific chemical structure and zirconium phosphate, thereby having the effect of improving adhesion and insulating properties after stress relief annealing. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a cross section of an electrical steel sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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. Therefore, 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 forms "a," "an," and "the" include the plural forms unless the phrase clearly dictates otherwise. As used in the specification, the term "comprising" embodies certain properties, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other properties, regions, integers, steps, operations, elements, and / or components.

[0014] When a part is referred to as being "on" or "above" 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. In the present specification, when a group (atomic group) is represented without specifying whether it is substituted or unsubstituted, it means that it includes both a group having a substituent and a group having no substituent. For example, the term "alkyl group" includes not only an alkyl group having no substituent (an unsubstituted alkyl group) but also an alkyl group having a substituent (a substituted alkyl group). In this specification, unless otherwise defined, the term "substituted" means that at least one hydrogen atom of the compound is replaced with a C1 to C30 alkyl group; a C2 to C30 alkenyl group, a C2 to C30 alkynyl group, a C1 to C10 alkylsilyl group; a C3 to C30 cycloalkyl group; a C6 to C30 aryl group; a C1 to C30 heteroaryl group; a C1 to C10 alkoxy group; a silane group; an alkylsilane group; an alkoxysilane group; an amine group; an alkylamine group; an arylamine group; an ethyleneoxyl group, or a halogen group. As used herein, "hetero" means an atom selected from the group consisting of N, O, S and P, unless otherwise defined.

[0015] As used herein, unless otherwise specified, the term "alkyl group" includes both "saturated alkyl groups" that do not contain any alkenyl or alkynyl groups, and "unsaturated alkyl groups" that contain at least one alkenyl or alkynyl group. The term "alkenyl group" refers to a substituent in which at least two carbon atoms form at least one carbon-carbon double bond, and the term "alkyne group" refers to a substituent in which at least two carbon atoms form at least one carbon-carbon triple bond. The alkyl group may be branched, straight-chain, or cyclic. The alkyl group may be a C1 to C20 alkyl group, specifically a C1 to C6 lower alkyl group, a C7 to C10 middle alkyl group, or a C11 to C20 higher alkyl group.

[0016] For example, a C1 to C4 alkyl group means that there are 1 to 4 carbon atoms in the alkyl chain and indicates that it is selected from the group consisting of methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl and t-butyl. Typical alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, ethenyl, propenyl, butenyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. The term "heterocyclic group" refers to a ring group containing a heteroatom selected from the group consisting of N, O, S, and P. The heterocyclic group may contain 1 to 3 heteroatoms in each ring. Heteroaryl groups are also included in the heterocyclic group.

[0017] Unless otherwise defined in this specification, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group means a substituted or unsubstituted alkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, alkoxy group, or aminoalkyl group. 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 pertains. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless otherwise defined.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily understand and practice the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments set forth herein. An insulating coating composition for electrical steel sheets according to one embodiment of the present invention includes 100 parts by weight of a resin containing two or more aromatic or aliphatic rings in its repeating unit structure and 20 to 150 parts by weight of zirconium phosphate. An insulating coating composition according to one embodiment of the present invention includes a resin compound and zirconium phosphate having a unique chemical structure to dramatically improve adhesion and insulating properties after stress relief annealing.

[0019] Hereinafter, each component of an insulating coating composition for electrical steel sheets according to one embodiment of the present invention will be described in detail. First, the present invention includes a resin containing two or more aromatic rings or aliphatic rings within the repeating unit structure of an insulating coating for electrical steel sheets. Resins containing two or more aromatic or aliphatic rings in their repeating unit structure have excellent heat resistance due to the presence of two or more aromatic or aliphatic ring structures. Resins containing only one or no aromatic or aliphatic rings can cause coating peeling problems during heat treatment at the customer's company. More specifically, resins preferably contain two to five aromatic or aliphatic rings in their repeating unit structure. Two or more resins may be included in the composition. In this case, the number of rings can be calculated as the number average of the resins in the composition. All resins in the composition may contain two or more aromatic or aliphatic rings in their repeating unit structure. The resin is preferably an epoxy resin. Epoxy resins have a chemical structure derived from an epoxy structure within a repeating unit structure. Epoxy resins are advantageous in terms of solution stability when mixed with zirconium and inorganic nanoparticles compared to other resins such as urethane resins.

[0020] More specifically, a resin containing two or more aromatic rings or aliphatic rings in the repeating unit structure can be represented by the following chemical formula 1. TIFF0007829042000002.tif55128 (in the above chemical formula 1, X is a divalent organic group containing two or more aromatic rings or aliphatic rings, R 1 represents hydrogen, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, a heterocyclic group, an alkoxy group, a carboxy group, or a halogen.

[0021] More specifically, in Formula 1, X may include at least one of a bisphenol structure, a biphenyl structure, a naphthalene structure, an anthracene structure, and a dicyclopentadiene structure. More specifically, R 1represents hydrogen, an alkyl group, an aryl group, a carboxy group, or a halogen. More specifically, examples of resins containing two or more aromatic or aliphatic rings in the repeating unit structure include bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novolac epoxy resin, and cresol novolac epoxy resin. More specifically, Bisphenol A propoxylate diglycidyl ether (product number 475750) and Poly[(phenyl glycidyl ether)-co-formaldehyde] (product numbers 406775 and 406767) can be used.

[0022] An insulating coating composition for electrical steel sheets according to one embodiment of the present invention contains 20 to 150 parts by weight of zirconium phosphate per 100 parts by weight of resin. The zirconium phosphate serves to impart insulating and adhesive properties to the coating. A variety of metal phosphates are known, including those containing Al, Mg, Ni, Mn, Sr, Br, Ca, Co, and Zn.

[0023] In one embodiment of the present invention, zirconium phosphate is used, which reacts more stably at high temperatures with resins containing two or more aromatic or aliphatic rings in the repeating unit structure than other phosphates, contributing to improved adhesion and insulating properties after stress relief annealing (SRA). The zirconium phosphate is contained in an amount of 20 to 150 parts by weight per 100 parts by weight of resin. If the amount of zirconium phosphate is too small, problems with coating peeling may occur. If the amount of zirconium phosphate is too large, the viscosity of the solution may increase rapidly, resulting in deviations in coating thickness. More specifically, the zirconium phosphate is preferably contained in an amount of 50 to 135 parts by weight per 100 parts by weight of resin. In the present invention, parts by weight refer to the weight ratio relative to the resin.

[0024] Zirconium phosphate should preferably have phosphate crystalline phases of 5% or less by mass out of 100% by mass of the zirconium phosphate. The phosphate crystalline phase refers to the regular arrangement of zirconium and phosphate particles, and can be analyzed using XRD measurement. The more phosphate crystalline phases are formed, the more pores are formed, which is disadvantageous in terms of high-temperature adhesion, so there is an upper limit. The amount of phosphate crystalline phase can be reduced by mixing it with a resin containing two or more aromatic or aliphatic rings to ensure chemical stability.

[0025] An insulating coating composition for electrical steel sheet according to one embodiment of the present invention may further include 0.1 to 100 parts by weight of magnesium phosphate per 100 parts by weight of resin. Along with the zirconium phosphate, magnesium phosphate also plays a role in supplementary improvement of adhesion. However, as mentioned above, if magnesium phosphate is included without including an appropriate amount of zirconium phosphate, the coating layer may absorb moisture, causing whitening defects and poor surface properties. More specifically, it is preferable to further include 1 to 50 parts by weight of magnesium phosphate per 100 parts by weight of resin.

[0026] The insulating coating composition for electrical steel sheets according to an embodiment of the present invention may further include 0.1 to 100 parts by weight of inorganic nanoparticles per 100 parts by weight of resin. The inorganic nanoparticles prevent the precipitation and agglomeration of the insulating coating composition and contribute to the development of better surface properties after stress relief annealing. It is preferable that the inorganic nanoparticles are chemically bonded to the resin substituent. If the inorganic nanoparticles are added alone without being bonded to the resin, the inorganic nanoparticles may aggregate and not be dispersed properly. The term "chemically bonded to the resin substituent" means that the inorganic particles are substituted and bonded to the substituent of the resin substituent.

[0027] The inorganic nanoparticles can include one or more of SiO2, Al2O3, MgO, ZnO, ZrO2, TiO2, Mn2O3, and CaO. The inorganic nanoparticles preferably have an average particle size of 1 to 100 nm. This range ensures appropriate dispersibility. More specifically, the average particle size is preferably 10 to 50 nm. When inorganic nanoparticles are further included, the inorganic nanoparticles may be further included in an amount of 0.1 to 100 parts by weight per 100 parts by weight of the resin. If too much inorganic nanoparticles are added, the resin content becomes relatively low, which can easily cause problems in terms of adhesion. More specifically, the inorganic nanoparticles may be further included in an amount of 10 to 80 parts by weight.

[0028] The insulating coating composition according to one embodiment of the present invention may further contain an antioxidant, such as sodium perborate (NaBO3·4H2O). The antioxidant may be present in an amount of 5 parts by weight or less per 100 parts by weight of the resin. In addition to the above components, the insulating coating composition may contain a solvent to facilitate application and uniformly disperse the components. Examples of the solvent include water and alcohol. The amount of solvent is not particularly limited, but may be 50 to 1,000 parts by weight per 100 parts by weight of the resin.

[0029] Fig. 1 shows a schematic cross-sectional view of an electrical steel sheet 100 according to one embodiment of the present invention. As shown in Fig. 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. The electrical steel sheet substrate 10 can be a general non-oriented or grain-oriented electrical steel sheet without any restrictions. In one embodiment of the present invention, the main component is forming an insulating coating 20 of a special composition on the electrical steel sheet substrate 10, so a detailed description of the electrical steel sheet substrate 10 will be omitted. In FIG. 1 , the insulating coating 20 is present on the top surface of the electrical steel sheet substrate 10, but this is not limiting, and the insulating coating 20 may also be present on the bottom surface of the electrical steel sheet substrate 10 or on both the top and bottom surfaces.

[0030] The insulating coating 20 contains 100 parts by weight of a resin containing two or more aromatic or aliphatic rings in its repeating unit structure and 20 to 150 parts by weight of zirconium phosphate. The insulating coating 20 of the electrical steel sheet 100 according to one embodiment of the present invention contains a specific resin and zirconium phosphate to dramatically improve adhesion and insulation properties after stress relief annealing. The components of the insulating coating 20 have been specifically described in relation to the insulating coating composition described above, so a repeated description will be omitted. While the chemical structure of some resins may change during the process of forming the insulating coating 20, most resins maintain their original chemical structure. Because volatile components such as solvents are removed during the process of forming the insulating coating 20, the ratio of components in the insulating coating 20 is substantially the same as the relative weight ratio of the resin to the insulating coating composition.

[0031] The insulating coating 20 preferably contains, by weight, one or more elements selected from the group consisting of 6 to 60% Zr, 7 to 70% C, 1 to 40% Si, 1 to 40% Al, 1 to 45% Mg, 1 to 70% P, and 0.01 to 9% B, with the balance being Fe and unavoidable impurities. More specifically, the insulating coating 20 contains 7 to 70% C, 6 to 60% Zr, and 1 to 70% P, and one or more elements selected from the group consisting of 1 to 40% Si, 1 to 40% Al, 1 to 45% Mg, and 0.01 to 9% B, with the balance being Fe and unavoidable impurities. More specifically, it may contain Zr: 6 to 60%, C: 7 to 70%, Si: 1 to 40%, Al: 1 to 40%, Mg: 1 to 45%, P: 1 to 70% and B: 0.01 to 9%, with the remainder being Fe and unavoidable impurities.

[0032] C may be derived from the resin in the insulation coating composition. Zr and P may be derived from zirconium phosphate in the insulation coating composition. The remaining Si, Al, Mg, B, etc. may be diffused from the electrical steel sheet substrate 10 or may originate from additional components of the insulating coating composition.

[0033] In addition to the elements mentioned above, the insulating coating 20 may also contain elements derived from the insulating coating composition and the electrical steel sheet substrate 10 . The thickness of the insulating coating 20 may be 0.05 to 10 μm. If the insulating coating 20 is too thin, heat resistance decreases, resulting in poor core loss after stress relief annealing. If the insulating coating 20 is too thick, the space factor decreases, resulting in poor motor performance. Therefore, it is preferable to adjust the thickness of the insulating coating 20 within the above-mentioned range. More specifically, the thickness of the insulating coating 20 is preferably 0.1 to 5 μm.

[0034] The electrical steel sheet substrate 10 may be either a non-oriented electrical steel sheet or a grain-oriented electrical steel sheet. Specifically, a non-oriented electrical steel sheet may be used. In one embodiment of the present invention, the insulating properties are generated by the components of the insulating coating 20, and may be unrelated to the alloy components of the electrical steel sheet. The alloy components of the electrical steel sheet will be described below as an example.

[0035] The electrical steel sheet substrate 10 contains, by weight, one or more elements selected from the group consisting of 2.0 to 6.5% Si, 0.1 to 3.0% Mn, 0.1 to 7.5% Al, 0.1% or less B, 0.01 to 0.15% Sn, and 0.01 to 0.15% Sb, with the balance consisting of Fe and unavoidable impurities. More specifically, the electrical steel sheet substrate 10 contains, by weight, 2.0 to 6.5% Si, 0.1 to 3.0% Mn, 0.1 to 7.5% Al, 0.1% or less B, 0.01 to 0.15% Sn, and 0.01 to 0.15% Sb, with the balance consisting of Fe and unavoidable impurities. The reasons for limiting the components of the electrical steel sheet substrate 10 will be explained below.

[0036] Si: 2.0 to 6.5 wt% Silicon (Si) is a component that increases the resistivity of steel and reduces eddy current loss in iron loss. If the Si content is too high, it increases brittleness, making cold rolling difficult. Therefore, it is preferable to limit the Si content to 6.5 wt% or less. More specifically, the Si content should be 2.5 to 4.5 wt%.

[0037] Mn: 0.1 to 3.0% by weight When manganese (Mn) is present at less than 0.1 wt%, fine MnS precipitates are formed, inhibiting grain growth and resulting in poor magnetic properties. Therefore, when present at 0.1 wt% or more, coarse MnS precipitates are formed, and the S component is prevented from precipitating into the finer CuS precipitates. However, since an increase in Mn content leads to a deterioration in magnetic properties, the Mn content is controlled to 3.0 wt% or less. More specifically, a content of 0.5 to 2.0 wt% is recommended.

[0038] Al: 0.1 to 7.5% by weight Al is an effective component for increasing resistivity and reducing eddy current loss. If it is less than 0.1 wt%, fine AlN precipitates, resulting in poor magnetic properties. If it exceeds 7.5 wt%, workability deteriorates, so it is preferable to limit it to 7.5 wt% or less. More specifically, it is recommended that it be included at 0.5 to 3.0 wt%.

[0039] B: 0.1% by weight or less Since B forms precipitates such as BN and deteriorates the magnetic properties, it is preferable that it be contained in an amount of 0.100% by weight or less, more specifically, 0.001 to 0.050% by weight.

[0040] Sb, Sn: 0.01 to 0.15% by weight each Sb and Sn are surface precipitate elements that concentrate in the surface layer of steel sheet, suppressing nitrogen adsorption and ultimately reducing iron loss by not interfering with grain growth. Excessive Sb and Sn content can cause severe grain segregation, increasing the brittleness of the steel sheet and resulting in sheet fracture during rolling. More specifically, the Sn and Sb content should be 0.05 to 0.10 wt.% each.

[0041] It is preferable that the composition further contains C: 0.01% by weight or less, P: 0.5% by weight or less, S: 0.005% by weight or less, N: 0.005% by weight or less, and Ti: 0.005% by weight or less.

[0042] 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 and applying an insulating coating composition to a surface of the electrical steel sheet substrate to form an insulating coating. First, in step (S10), an electromagnetic steel sheet substrate is manufactured. The alloy components of the electromagnetic steel sheet substrate have been specifically described, so a repeated description will be omitted. The steps of manufacturing the electrical steel sheet substrate include hot rolling a slab to manufacture a hot-rolled sheet, cold rolling the hot-rolled sheet to manufacture a cold-rolled sheet, and annealing the cold-rolled sheet. First, the slab is heated. At this time, the slab can be heated at 1,200°C or less. The heated slab is then hot rolled to produce a hot rolled sheet, which can then be hot roll annealed. The hot-rolled sheet is then cold-rolled to produce a cold-rolled sheet. Cold rolling can be performed once, or two or more times with intermediate annealing.

[0043] Next, the cold-rolled sheet is annealed. In this step, the cold-rolled sheet is degreased to remove rolling oil present therein, followed by a primary annealing in an atmosphere consisting of hydrogen and nitrogen. In addition, the final annealing can be performed at a dew point temperature of -5°C or less to prevent oxide formation on the surface and deterioration of magnetic properties. Returning to the description of the method for manufacturing an electrical steel sheet, in step S20, an insulating coating composition is applied to the surface of the electrical steel sheet substrate to form an insulating coating. The insulating coating composition is the same as that described above, so a repeated description will be omitted.

[0044] The step of forming the insulating coating may include heat treating the steel sheet coated with the insulating coating composition at a temperature of 100 to 680°C. If the heat treatment temperature is too low, the solvent may not be easily removed, making it difficult to form a clean insulating coating. If the heat treatment temperature is too high, problems such as poor adhesion may occur. More specifically, the heat treatment may be performed at a temperature of 350 to 650°C. The heat treatment time may be 5 to 200 seconds. After the step of forming the insulating coating, the method may further include a step of stress relief annealing at a temperature of 700 to 1000°C. In one embodiment of the present invention, the insulating coating can maintain excellent adhesion and surface properties even after stress relief annealing. If the stress relief annealing temperature is too low, the intended stress relief may not be achieved smoothly. If the stress relief annealing temperature is too high, the magnetic properties of the electrical steel sheet may be deteriorated.

[0045] The stress relief annealing step is preferably carried out in a nitrogen atmosphere for 1 to 5 hours. Preferred examples of the present invention, comparative examples, and evaluation examples thereof are described below. However, the following examples are merely preferred examples of the present invention, and the present invention is not limited to the following examples. Manufacturing example

[0046] Preparation of epoxy resins containing acrylate groups 20g of the starting epoxy resin of the following formula was added to 120ml of methylene chloride in a 500ml flask at room temperature and stirred. 9.88ml of diisopropylethylamine was added at 4°C, and immediately 9ml of acryloyl chloride was slowly added. After reacting for 5 hours at 4°C, the solvent was removed by evaporation under reduced pressure to obtain an epoxy resin with acrylate groups. JPEG0007829042000003.jpg22142

[0047] Preparation of epoxy resins containing side epoxy groups At room temperature, 1.6 g of NaH was placed in a flask, 40 ml of DMF was added, and 10 g of the starting epoxy resin (with the following formula) dissolved in 20 ml of DMF at 4°C was slowly added. After stirring for 10 minutes at 4°C, 4.5 ml of epichlorohydrin was slowly added and the mixture was allowed to react at room temperature for 24 hours. The organic layer was separated and evaporated under reduced pressure to remove the solvent, yielding an epoxy resin with side epoxy groups. JPEG0007829042000004.jpg16128JPEG0007829042000005.jpg136128Example 1

[0048] A slab was prepared containing 3.4 wt% silicon (Si), 0.80 wt% aluminum (Al), 0.17 wt% manganese (Mn), 0.0015 wt% titanium (Ti), 0.03 wt% tin (Sn), 0.01 wt% nickel (Ni), 0.003 wt% carbon (C), 0.0013 wt% nitrogen (N), 0.012 wt% phosphorus (P), 0.001 wt% sulfur (S), with the remainder being Fe and other unavoidable impurities. The slab was heated at 1130°C and then hot rolled to a thickness of 2.3 mm to produce a hot-rolled sheet. The hot-rolled sheet was coiled at 650°C, cooled in air, and hot-rolled at 1040°C for 2 minutes, then quenched in water, pickled, and cold-rolled to a thickness of 0.25 mm to produce a cold-rolled sheet.

[0049] The cold-rolled sheet was subjected to final annealing at 1040°C for 50 seconds in an atmosphere of 20% hydrogen and 80% nitrogen while adjusting the dew point temperature, to produce an annealed steel sheet. For the insulating coating composition, the resin, zirconium phosphate, SiO2, and magnesium phosphate prepared in Preparation Example were mixed with distilled water to prepare a slurry. The slurry was then applied to the final-annealed steel sheet using a roll, followed by heat treatment at 650°C for 30 seconds and cooling in air. The electrical steel sheet was then subjected to stress relief annealing (SRA) in a 100% nitrogen atmosphere at 750°C for 2 hours and cooling in air.

[0050] The resin, zirconium phosphate, SiO2, and magnesium phosphate contents in the insulating coating composition were changed as shown in Table 1. The properties of the electrical steel sheets manufactured in the examples and comparative examples were measured and are summarized in Table 1 below. In addition, the insulation properties were measured on the top of the insulation coating using a Franklin measuring instrument according to the ASTM A717 international standard. The adhesion was expressed as the minimum arc diameter at which the coating did not peel off when the test piece was bent 180° in contact with an arc of 10 to 100 mm.

[0051] In Comparative Example 1, 1,2-epoxy-3-phenoxypropane was used instead of the resin produced in the Production Example.

[0052] [Table 1]

[0053] As shown in Table 1, Examples 1 to 10, in which the ratio of resin to zirconium phosphate was appropriately adjusted, were found to have excellent insulation properties before and after SRA and adhesion after SRA. In contrast, it can be seen that Comparative Example 1, which does not use an appropriate resin, exhibits poor insulating properties and adhesion after SRA. It can be seen that Comparative Examples 2 and 3, which used small amounts of zirconium phosphate, were inferior in insulating properties and adhesion after SRA. It can be seen that Comparative Examples 4 and 5, which contained an excessive amount of zirconium phosphate, exhibited poor adhesion after SRA.

[0054] The present invention is not limited to the above-described embodiments, and can be manufactured in various different forms, and those skilled in the art will understand that the present invention can be embodied in other specific forms without changing the technical concept or essential characteristics of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not limiting. [Explanation of symbols]

[0055] 100:Electromagnetic steel plate 10:Electromagnetic steel plate base material 20: Insulating coating

Claims

1. 100 parts by weight of a resin containing a repeating unit represented by the following [Chemical Formula 1] An insulating coating composition for electrical steel sheets, comprising 20 to 150 parts by weight of zirconium phosphate. 【Chemistry 1】 (In the above [Chemical Formula 1], X contains a naphthalene structure, and R 1 represents hydrogen, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, a heterocyclic group, an alkoxy group, a carboxy group, or a halogen.)

2. 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein the resin comprises an epoxy resin.

3. 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein the zirconium phosphate has a crystalline phase of 5 mass % or less.

4. 2. The insulating coating composition for electrical steel sheets according to claim 1, further comprising 0.1 to 100 parts by weight of magnesium phosphate.

5. 2. The insulating coating composition for electrical steel sheets according to claim 1, further comprising 0.1 to 100 parts by weight of inorganic nanoparticles.

6. The inorganic nanoparticles are SiO ２ , Al ２ O ３ , MgO, ZnO, ZrO ２ , TiO ２ , Mn ２ O ３ 6. The insulating coating composition for electrical steel sheets according to claim 5, further comprising at least one of:

7. 6. The insulating coating composition for electrical steel sheets according to claim 5, wherein the inorganic nanoparticles have an average particle size of 1 to 100 nm.

8. an electromagnetic steel sheet substrate; an insulating coating located on the surface of the electrical steel sheet substrate, The electrical steel sheet, wherein the insulating coating contains 100 parts by weight of a resin containing a repeating unit represented by the following Chemical Formula 1 and 20 to 150 parts by weight of zirconium phosphate. 【Chemistry 1】 (In the above [Chemical Formula 1], X contains a naphthalene structure, and R 1 represents hydrogen, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, a heterocyclic group, an alkoxy group, a carboxy group, or a halogen.)

9. 9. The electrical steel sheet according to claim 8, wherein the insulating coating contains, by weight%, one or more elements selected from the group consisting of Zr: 6 to 60%, C: 7 to 70%, Si: 1 to 40%, Al: 1 to 40%, Mg: 1 to 45%, P: 1 to 70%, and B: 0.01 to 9%, with the remainder being Fe and unavoidable impurities.

10. 9. The electrical steel sheet according to claim 8, wherein the electrical steel sheet substrate contains, by weight%, one or more elements selected from the group consisting of C: 0.01% or less, Si: 2.0 to 6.5%, Mn: 0.1 to 3.0%, Al: 0.1 to 7.5%, B: 0.1% or less, Sn: 0.01 to 0.15%, and Sb: 0.01 to 0.15%, with the balance consisting of Fe and unavoidable impurities.

11. Preparing an electromagnetic steel sheet substrate; and applying an insulating coating composition to a surface of the electrical steel sheet substrate to form an insulating coating, The method for producing an electrical steel sheet, wherein the insulating coating composition comprises 100 parts by weight of a resin containing a repeating unit represented by the following Chemical Formula 1 and 20 to 150 parts by weight of zirconium phosphate: 【Chemistry 1】 (In the above [Chemical Formula 1], X contains a naphthalene structure, and R 1 represents hydrogen, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, a heterocyclic group, an alkoxy group, a carboxy group, or a halogen.)

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