Composition for forming insulating film of electrical steel sheet, electrical steel sheet, and method for manufacturing electrical steel sheet

Abstract

A composition for forming an insulating film of an electrical steel sheet, according to an embodiment of the present invention, includes 100 parts by weight of a resin and 70-500 parts by weight of a metal phosphate as solids. The resin has a carbonization temperature of 210-270° C, and the metal phosphate includes at least two of Mg, Ca, Ba, Sr, Zn, Co, and Al.

Description

Composition for forming an insulating film on an electrical steel sheet, electrical steel sheet, and method for manufacturing an electrical steel sheet

[0001] One embodiment of the present invention relates to a composition for forming an insulating film on an electrical steel sheet, an electrical steel sheet, and a method for manufacturing an electrical steel sheet. More specifically, one embodiment of the present invention relates to a coating composition for forming an insulating film on an electrical steel sheet, an electrical steel sheet, and a method for manufacturing an electrical steel sheet, wherein the composition comprises a resin and a metal phosphate as main components, and the carbonization temperature of the resin and the type of metal phosphate are varied to ensure excellent glossiness of the insulating film and adhesion even after heat treatment.

[0002] Electrical steel sheets are products used as materials for transformers, motors, and electrical equipment. Unlike general carbon steel, which prioritizes processability such as mechanical properties, electrical steel is a functional product that places importance on electrical characteristics. Required electrical properties include low iron loss and high magnetic flux density, permeability, and stacking density.

[0003] Electrical steel sheets are further classified into oriented electrical steel sheets and non-oriented electrical steel sheets. Oriented electrical steel sheets utilize an abnormal grain growth phenomenon called secondary recrystallization to form a Goss texture ({110} <001> It is an electrical steel sheet with excellent magnetic properties in the rolling direction, formed by creating a texture throughout the entire sheet. Non-oriented electrical steel is an electrical steel sheet in which magnetic properties are uniform in all directions on the rolled sheet.

[0004] Electrical steel sheets are used in two forms: one that requires stress relief annealing (SRA) to improve magnetic properties after stamping, and another that omits SRA when the cost loss due to heat treatment outweighs the effect on magnetic properties provided by SRA.

[0005] Meanwhile, the formation of an insulating film is a process corresponding to the final manufacturing process of a product. In addition to electrical properties that suppress the generation of eddy currents, it typically requires continuous stamping processability to suppress mold wear when multiple sheets are stacked to form a core after stamping into a predetermined shape, as well as anti-sticking properties and surface adhesion to prevent adhesion between core sheets after the SRA process, which removes processing stress from the steel sheets and restores magnetic properties. In addition to these basic properties, excellent application workability of the coating solution and solution stability that allows for long-term use after mixing are also required. Coating solutions used for this purpose include chromium coatings based on chromic acid and phosphate coatings based on phosphate.

[0006] Insulating films are primarily intended for interlayer insulation between laminated steel plates. However, with the expansion of small electric motors, film performance that is advantageous for processability, weldability, and corrosion resistance, in addition to insulation, has come to be evaluated as a major physical property. Recently, as the surface quality of the steel plates also affects usage characteristics, there has been a demand for electrical steel plates with excellent surface quality.

[0007] As mentioned earlier, non-oriented electrical steel is currently riding the wave of premiumization driven by the development of high-efficiency motors in line with global low-carbon policies. As premiumization progresses, the surface of the electrical steel requires high functionality (high insulation, high heat resistance, and high corrosion resistance). In particular, excellent insulation, which can maximize motor performance by minimizing eddy current loss, is an essential requirement. The most common method to secure excellent insulation is to increase the coating thickness. However, increasing the coating thickness has the disadvantage of degrading characteristics required for non-oriented electrical steel, such as weather resistance, weldability, heat resistance, adhesion before and after SRA, and stacking factor.

[0008] In one embodiment of the present invention, a composition for forming an insulating film on an electrical steel sheet, an electrical steel sheet, and a method for manufacturing an electrical steel sheet are provided. Specifically, in one embodiment of the present invention, a coating composition for forming an insulating film on an electrical steel sheet, an electrical steel sheet, and a method for manufacturing an electrical steel sheet are provided, wherein the resin and a metal phosphate are main components, and the carbonization temperature of the resin and the type of metal phosphate are varied, resulting in excellent glossiness of the insulating film and adhesion even after heat treatment.

[0009] A composition for forming an insulating film on an electrical steel sheet according to one embodiment of the present invention comprises, as a solid content, 100 parts by weight of resin and 70 to 500 parts by weight of metal phosphate.

[0010] The resin has a carbonization temperature of 210 to 270°C, and the metal phosphate contains two or more of Mg, Ca, Ba, Sr, Zn, Co, and Al.

[0011] The resin may include one or more of epoxy resins, ester resins, acrylic resins, styrene resins, urethane resins, and ethylene resins.

[0012] The resin may have a glass transition temperature of 25 to 75°C.

[0013] The resin may include one or more of epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenolic resins, styrene resins, vinyl resins, ethylene resins, and urethane resins.

[0014] The resin can be an emulsion resin.

[0015] One type of metal phosphate may be included in an amount of 75% by weight or less relative to 100% by weight of metal phosphate.

[0016] The metal phosphate may include three or more of Mg, Ca, Ba, Sr, Zn, Co, and Al, and may include one type of metal phosphate in an amount of 50% by weight or less relative to 100% by weight of the metal phosphate.

[0017] The metal phosphate may contain 25 to 75 weight% of Al phosphate and 25 to 75 weight% of one metal phosphate selected from Mg, Ca, Ba, Sr, Zn, and Co.

[0018] The metal phosphate may contain 15 to 35 weight% of Al phosphate and may contain 65 to 85 weight% of two or more metal phosphates selected from Mg, Ca, Ba, Sr, Zn, and Co.

[0019] An electrical steel sheet according to one embodiment of the present invention comprises an electrical steel sheet substrate and an insulating film located on the surface of the electrical steel sheet substrate, and the insulating film and the electrical steel sheet substrate may have a glossiness difference rate of 0.15 to 0.45.

[0020] After annealing an electrical steel sheet at 800°C for 1 hour in a reducing or non-reactive atmosphere, the adhesion between the insulating film and the electrical steel sheet substrate may be 5B or higher.

[0021] The insulating film comprises 100 parts by weight of resin and 70 to 500 parts by weight of metal phosphate, the resin has a carbonization temperature of 210 to 270°C, and the metal phosphate may comprise two or more of Mg, Ca, Ba, Sr, Zn, Co, and Al.

[0022] A method for manufacturing an electrical steel sheet according to one embodiment of the present invention comprises the steps of: preparing an electrical steel sheet substrate; applying an insulating film composition to the surface of the electrical steel sheet substrate; and heat-treating the electrical steel sheet substrate.

[0023] The insulating film composition comprises 100 parts by weight of resin and 70 to 500 parts by weight of metal phosphate as solids, the resin has a carbonization temperature of 210 to 270°C, and the metal phosphate comprises two or more of Mg, Ca, Ba, Sr, Zn, Co, and Al.

[0024] The heat treatment step can be performed at a temperature of 400 to 700°C for 5 to 100 seconds.

[0025] A composition for forming an insulating film on an electrical steel sheet according to one embodiment of the present invention utilizes a resin having an appropriate carbonization temperature and uses two or more types of phosphates to suppress the carbonization of the resin and the growth of phosphate crystals during stress relief annealing (SRA) heat treatment, thereby suppressing the increase in film tension of the insulating film and improving film adhesion even after stress relief annealing. When an emulsion resin is used, a constant difference in glossiness is observed before and after coating removal due to changes in surface glossiness.

[0026] FIG. 1 is a schematic diagram of a cross-section of an electrical steel sheet according to one embodiment of the present invention.

[0027] 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 solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0028] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0029] When it is stated that one part is "on" or "on" another part, it may be directly on or on the other part, or another part may be involved in between. In contrast, when it is stated that one part is "directly on" another part, no other part is interposed in between.

[0030] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0031] In one embodiment of the present invention, the meaning of including additional elements is that the remainder of iron (Fe) or oxygen (O) is replaced by an amount of the additional element.

[0032] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0033] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0034]

[0035] A composition for forming an insulating film on an electrical steel sheet according to one embodiment of the present invention comprises, as a solid content, 100 parts by weight of resin and 70 to 500 parts by weight of metal phosphate.

[0036] Each component is described in detail below. In one embodiment of the present invention, the weight part refers to a relative weight ratio based on 100 weight parts of resin, and is based on the solid content of each component. Solid content refers to the weight when each component is dried in a state free of volatile substances such as solvents. Specifically, assuming a heat treatment process when forming an insulating film, it refers to the weight remaining after heat treatment.

[0037]

[0038] Resin refers to a polymer compound and is a concept contrasted with monomer. In compositions for forming insulating films, resin acts as a binder and also plays a role in ensuring insulation properties.

[0039] The resin may include one or more of epoxy resins, ester resins, melamine resins, siloxane resins, acrylic resins, phenolic resins, styrene resins, vinyl resins, ethylene resins, and urethane resins. More specifically, the resin may include one or more of epoxy resins, ester resins, acrylic resins, styrene resins, urethane resins, and ethylene resins. More specifically, it may include acrylic resins.

[0040] The resin may have a carbonization temperature of 210 to 270°C. If the carbonization temperature of the resin is too low, carbonization of the resin may occur in a motor operating environment, which may degrade motor performance. During stress relief annealing (SRA), stress is generated due to the difference in the coefficient of thermal expansion between the phosphate and the substrate steel, and if the oxidizing atmosphere intensifies, the bonding strength between the substrate steel and the phosphate interface may weaken, leading to coating delamination. Therefore, by limiting the upper limit of the resin's carbonization temperature, carbonization can be induced to occur easily during SRA, thereby improving the adhesion between the steel sheet substrate and the insulating film. If the resin's carbonization temperature is too high, it is difficult to ensure sufficient adhesion between the steel sheet substrate and the insulating film. More specifically, the resin's carbonization temperature may be 220 to 260°C.

[0041] To control the carbonization temperature of the resin, a method can be used in which monomers containing benzene rings are not used during the resin manufacturing process, and the molecular weight of the resin is controlled to be low.

[0042] The carbonization temperature of the resin can be confirmed by raising the material's temperature using TGA and measuring the temperature at the point where the weight decreases rapidly.

[0043] The resin may have a glass transition temperature (Tg) of 25 to 75°C. If the glass transition temperature is too low, the heat resistance of the coating may be low, which may be problematic. If the glass transition temperature is too high, the viscosity of the solution may be high, which may be problematic in terms of coating properties. More specifically, the resin may have a glass transition temperature (Tg) of 30 to 70°C. The glass transition temperature can be measured by DSC.

[0044] The resin may be an emulsion resin. It is possible to coat the domains by introducing an emulsion resin. Emulsion resins and dispersion resins can be distinguished by whether C-enriched particles are observed when analyzing the solution phase (emulsion resin) and the semi-transparent solution (dispulsion resin) or the coating layer using TEM-EDS.

[0045] Metal phosphates serve as a binder and a cushion during stamping within the composition for forming an insulating film. Metal phosphates may be included in an amount of 70 to 500 parts by weight per 100 parts by weight of resin. If too little metal phosphate is included, a problem with dust may occur during stress relief heat treatment annealing. If too much metal phosphate is included, problems with poor stamping performance and corrosion resistance may occur. More specifically, metal phosphates may be included in an amount of 80 to 300 parts by weight per 100 parts by weight of resin.

[0046] Metal phosphates may include two or more of Mg, Ca, Ba, Sr, Zn, Co, and Al. Including two or more metal phosphates can mitigate the progression of crystallization of the metal phosphates, thereby improving the adhesion between the steel sheet substrate and the insulating film.

[0047] One type of metal phosphate may be included in an amount of 75% by weight or less relative to 100% by weight of the metal phosphate. If a large amount of one type of metal phosphate is included, it may not be of much help in mitigating the aforementioned crystallization progress. More specifically, one type of metal phosphate may be included in an amount of 15 to 75% by weight.

[0048] When the metal phosphate comprises three or more types of metal phosphates, one type of metal phosphate may be included in an amount of 50% by weight or less relative to 100% by weight of the metal phosphate. In addition, as previously mentioned, if a large amount of one type of metal phosphate is included, it may not significantly help in mitigating the aforementioned crystallization progress. More specifically, one type of metal phosphate may be included in an amount of 15 to 35% by weight.

[0049] More specifically, the metal phosphate may contain 25 to 75 weight% of Al phosphate and 25 to 75 weight% of one metal phosphate selected from Mg, Ca, Ba, Sr, Zn, and Co. Al phosphate may be included as an essential component because its low hygroscopicity is advantageous in terms of the stability of the coating layer. The remainder may include other phosphates in addition to Al phosphate. The content ratio among the phosphates may be limited because including a large amount of one type of metal phosphate does not significantly help in mitigating the crystallization process described above. More specifically, it may contain 30 to 70 weight% of Al phosphate and 30 to 70 weight% of one metal phosphate selected from Mg, Ca, Ba, Sr, Zn, and Co.

[0050] In addition, when including three or more types of metal phosphates, it may include 15 to 35 weight% of Al phosphate and 65 to 85 weight% of two or more metal phosphates selected from Mg, Ca, Ba, Sr, Zn, and Co. Al phosphate is advantageous in terms of the stability of the coating layer due to its low hygroscopicity, so it may be included as a necessity. The remainder may include other phosphates in addition to Al phosphate. The content ratio among the phosphates may be limited because including a large amount of a single type of metal phosphate does not significantly help in mitigating the aforementioned crystallization process. More specifically, it may include 20 to 30 weight% of Al phosphate and 70 to 80 weight% of two or more metal phosphates selected from Mg, Ca, Ba, Sr, Zn, and Co.

[0051] In addition to the aforementioned components, the composition for forming an insulating film may further include a solvent. The solvent serves to facilitate the application of the composition and to uniformly disperse the components. The amount of solvent is not particularly limited, but may be included in an amount of 100 to 1,000 parts by weight per 100 parts by weight of resin.

[0052]

[0053] 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 film (20) located on the electrical steel sheet substrate (10).

[0054] The electrical steel substrate (10) can be any general non-oriented or oriented electrical steel without limitation. In one embodiment of the present invention, since the main configuration is to form an insulating film (20) of a special component on the electrical steel substrate (10), a detailed description of the electrical steel substrate (10) is omitted.

[0055] Additionally, the composition of the non-oriented electrical steel substrate is explained as follows.

[0056] The non-oriented electrical steel substrate comprises silicon (Si): 2.0 to 7.0 wt%, aluminum (Al): 0.010 to 3.000 wt%, manganese (Mn): 0.010 to 3.00 wt%, phosphorus (P) 0.15 wt% or less (excluding 0%), carbon (C) 0.01 wt% or less (excluding 0%), N: 0.01 wt% or less (excluding 0%), sulfur (S) 0.01 wt% or less (excluding 0%), and the remainder may include Fe and other unavoidable impurities. Since the description of each component of the non-oriented electrical steel substrate (10) is the same as generally known, a detailed description is omitted.

[0057] The thickness of the insulating film (20) can be 1 to 10 μm. If the thickness of the insulating film (20) is too thin, it is difficult to secure adequate insulation. If the thickness of the insulating film (20) is too thick, the packing density may be reduced. In one embodiment of the present invention, adequate insulation can be secured even when forming an insulating film (20) of thin thickness. More specifically, the thickness of the insulating film (20) can be 2 to 5 μm.

[0058] The insulating film (20) may maintain the solid component and content ratio within the composition of the insulating film described above. Specifically, the insulating film (20) may include 100 parts by weight of resin and 70 to 500 parts by weight of metal phosphate. Since the reasons for limiting each component and its content are the same as those explained in the composition described above, redundant explanations are omitted.

[0059] When applying an insulating film with improved heat resistance after stress relief heat treatment annealing, the insulating film (20) and the electrical steel substrate (10) may have a glossiness difference rate of 0.15 to 0.45. Glossiness can be calculated by comparing the difference in glossiness of the material before and after removing the insulating film using an NaOH solution. Glossiness can be measured in the vertical direction (C direction) of rolling using 60° glossiness. The glossiness difference rate can be calculated as [(glossiness before removing insulating film) - (glossiness after removing insulating film)] / (glossiness before removing insulating film). More specifically, the glossiness difference rate may be 0.20 to 0.40.

[0060] In one embodiment of the present invention, adhesion after annealing heat treatment can be improved by controlling the components described above. Specifically, after annealing an electrical steel sheet at 800°C for 1 hour in a reducing or non-reactive atmosphere, the adhesion between the insulating film (20) and the electrical steel sheet substrate (10) can be 5B or higher. Adhesion can be measured by ASTM D3359.

[0061] A method for manufacturing an electrical steel sheet according to one embodiment of the present invention comprises the steps of: preparing an electrical steel sheet substrate; applying an insulating film composition to the surface of the electrical steel sheet substrate; and heat-treating the electrical steel sheet substrate.

[0062] First, an insulating film-forming composition is applied to an electrical steel substrate.

[0063] As the electrical steel sheet substrate and the composition for forming the insulating film are the same as those previously described, a repetitive explanation is omitted.

[0064] The composition for forming an insulating film before application can be maintained at a temperature of 10 to 30°C. If the temperature is lower than the aforementioned range, the viscosity increases, making it difficult to manage a uniform application amount. If the temperature is too high, the gelation phenomenon of the composition for forming an insulating film is accelerated, which may degrade the surface quality. More specifically, the composition for forming an insulating film before application can be maintained at a temperature of 15 to 25°C.

[0065] When applying a composition for forming an insulating film, the application amount is 0.5 to 6.0 g / m² 2 It can be applied within a specified range. If the application amount is too high, the insulating film becomes too thick, and the adhesion to the steel sheet and the packing density of the electrical steel product may be compromised. If the application amount is too low, the tensile strength imparted by the insulating film may be weakened. More specifically, the application amount is 1.0 to 5.0 g / m² 2 It could be.

[0066] The heat treatment step can be performed at a temperature of 400 to 700°C for 5 to 100 seconds.

[0067]

[0068] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0069]

[0070] Examples

[0071] A non-oriented electrical steel sheet (300*60mm) containing 3.1% Si by weight and having a primary film finished annealed with a thickness of 0.23mm was prepared as a test material.

[0072] An insulating film-forming composition was prepared comprising 100 parts by weight of resin, 100 parts by weight of metal phosphate, and 800 parts by weight of water as summarized in Table 1 below. The insulating film-forming composition was applied to the test material at a rate of 4 g / m² 2 After coating, specimens were prepared by heat-treating at 600°C for 30 seconds. The physical properties of the specimens prepared in this way were measured and are shown in Table 2 below.

[0073] Method for measuring adhesion after annealing heat treatment: Assuming stress relief annealing, the adhesion between the insulating film and the steel sheet substrate was measured according to ASTM D3359 after heat treatment at 800°C for 1 hour in an N2 atmosphere.

[0074] Gloss difference: Calculated by comparing the difference in material gloss before and after coating removal using an NaOH solution. Gloss was measured in the vertical direction (C direction) of rolling using a 60° gloss level. The gloss difference rate was calculated as [(Gloss before insulation film removal) - (Gloss after insulation film removal)] / (Gloss before insulation film removal).

[0075] Phosphate Component Ratio (Ratio to 100 wt% of phosphate) Resin Characteristics Al-Phosphate Mg-Phosphate Ca-Phosphate Co-Phosphate Type Tg (°C) Carbonization Temperature (°C) 150 50--Emulsion Resin 50 240 270 30--Emulsion Resin 50 240 330 70--Emulsion Resin 50 240 450--50-Emulsion Resin 50 240 550--50 Emulsion Resin 50 240 630 30 20 20 Emulsion Resin 50 240 720 30 30 20 Emulsion Resin 50 240 850 50--Emulsion Resin 30 230 950 50--Emulsion Resin 70 260 10 50 50--Emulsion Resin 40 230 11 50 50--Emulsion Resin 60 250 12 100---Emulsion Resin 50240132080--Emulsion Resin 50240148020--Emulsion Resin 50240155050--Dispersion Resin 50240165050--Emulsion Resin 90300175050--Emulsion Resin 80280185050--Emulsion Resin 20200195050--Emulsion Resin 10180

[0076] Product Characteristics Adhesion after Annealing Heat Treatment Gloss Difference Rate between Insulating Film / Steel Substrate Remarks Classification 15B0.3-Example 25B0.3-Example 35B0.3-Example 45B0.3-Example 55B0.3-Example 65B0.3-Example 75B0.3-Example 85B0.2-Example 95B0.4-Example 105B0.25-Example 115B0.4-Example 122B0.3-Comparative Example 133B0.3-Comparative Example 144B0.3-Comparative Example 150B0.5-Comparative Example 160B0.5-Comparative Example 170B0.4-Comparative Example 185B0.1 Carbonization Occurrence during Motor Operation Comparative Example 195B0.1 Comparative Example

[0077]

[0078] As can be seen in Tables 1 and 2, when metal phosphate and resin are appropriately combined, it can be confirmed that the adhesion after annealing heat treatment is excellent and the glossiness between the insulating film and the steel sheet substrate is also appropriately controlled.

[0079] On the other hand, if metal phosphate is not used properly or if a suitable resin is not used, it can be observed that the adhesion after annealing heat treatment is inferior, and the glossiness between the insulating film and the steel sheet substrate is too small or too large. In particular, in the case of specimens 18 and 19, it can be observed that the difference in glossiness is too small and carbonization occurs during motor operation.

[0080] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

[0081] [Explanation of the symbol]

[0082] 100: Electrical steel sheet, 10: Electrical steel sheet substrate,

[0083] 20: Insulating film

Claims

1. As a solid content, it comprises 100 parts by weight of resin and 70 to 500 parts by weight of metal phosphate, and The above resin has a carbonization temperature of 210 to 270℃, and The above metal phosphate is an insulating film composition for electrical steel sheets comprising two or more of Mg, Ca, Ba, Sr, Zn, Co, and Al.

2. In Paragraph 1, The above resin is an insulating film composition for electrical steel sheets comprising one or more of epoxy resin, ester resin, acrylic resin, styrene resin, urethane resin, and ethylene resin.

3. In Paragraph 1, The above resin is an insulating film composition for electrical steel sheets having a glass transition temperature of 25 to 75°C.

4. In Paragraph 1, The above resin is an insulating film composition for electrical steel sheets comprising one or more of epoxy resin, ester resin, melamine resin, siloxane resin, acrylic resin, phenolic resin, styrene resin, vinyl resin, ethylene resin, and urethane resin.

5. In Paragraph 1, The above resin is an emulsion resin, an insulating film composition for electrical steel sheets.

6. In Paragraph 1, An insulating film composition for electrical steel sheets comprising 75 weight% or less of one type of metal phosphate with respect to 100 weight% of the above metal phosphate.

7. In Paragraph 1, The above metal phosphate comprises three or more of Mg, Ca, Ba, Sr, Zn, Co, and Al, and An insulating film composition for electrical steel sheets comprising 50 weight% or less of one type of metal phosphate with respect to 100 weight% of the above metal phosphate.

8. In Paragraph 1, An insulating film composition for electrical steel sheets comprising 25 to 75 weight% of Al phosphate and 25 to 75 weight% of one metal phosphate selected from Mg, Ca, Ba, Sr, Zn, and Co.

9. In Paragraph 1, An insulating film composition for electrical steel sheets comprising 15 to 35 weight% of Al phosphate and 65 to 85 weight% of two or more metal phosphates selected from Mg, Ca, Ba, Sr, Zn, and Co.

10. Electrical steel sheet substrate and It includes an insulating film located on the surface of the electrical steel sheet substrate, and The above insulating film and the above electrical steel sheet substrate are electrical steel sheets having a glossiness difference rate of 0.15 to 0.

45.

11. In Paragraph 10, After annealing the above electrical steel sheet at 800°C for 1 hour in a reducing or non-reactive atmosphere, An electrical steel sheet having an adhesion of 5B or higher between the insulating film and the electrical steel sheet substrate.

12. In Paragraph 10, The above insulating film comprises 100 parts by weight of resin and 70 to 500 parts by weight of metal phosphate, and The above resin has a carbonization temperature of 210 to 270℃, and The above metal phosphate is an electrical steel sheet comprising two or more of Mg, Ca, Ba, Sr, Zn, Co, and Al.

13. Step of preparing the electrical steel sheet substrate; A step of applying an insulating film composition to the surface of the above electrical steel sheet substrate and The method includes a step of heat-treating the above electrical steel sheet substrate, and The above insulating film composition comprises, as a solid content, 100 parts by weight of resin and 70 to 500 parts by weight of metal phosphate, and The above resin has a carbonization temperature of 210 to 270℃, and A method for manufacturing an electrical steel sheet in which the above metal phosphate comprises two or more of Mg, Ca, Ba, Sr, Zn, Co, and Al.

14. In Paragraph 13, A method for manufacturing an electrical steel sheet in which the heat treatment step is performed at a temperature of 400 to 700°C for 5 to 100 seconds.

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