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

Abstract

An insulating coating composition for an electrical steel sheet, according to an embodiment of the present invention, comprises: 100 parts by weight of a metal phosphate; 30 to 350 parts by weight of silica; 30 to 350 parts by weight of chromium nitrate; 30 to 350 parts by weight of at least one shielding agent among dolomite, talc, carbonate, and feldspar; and 1 to 100 parts by weight of a carbon structure.

Description

Electrical steel sheet insulation film composition, electrical steel sheet, and method of manufacturing the same

[0001] One embodiment of the present invention relates to an electrical steel sheet insulating film composition, an electrical steel sheet, and a method for manufacturing the same. Specifically, by appropriately combining the components of the insulating film composition, the invention relates to an electrical steel sheet insulating film composition, an electrical steel sheet, and a method for manufacturing the same, wherein the film does not separate even in high-temperature and high-humidity environments, exhibits excellent insulation properties in the high-frequency range, and can shield Fe-mound defects.

[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] 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 to restore 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.

[0005] These coatings have excellent corrosion resistance. However, they have the disadvantages of being weak in weather resistance and sticky. If weather resistance is poor and they are sticky, problems arise where the coatings adhere to each other when the wound coil is unwound. Additionally, stains may occur on the surface due to defects in various steel sheets.

[0006] In one embodiment of the present invention, an electrical steel sheet insulating film composition, an electrical steel sheet, and a method for manufacturing the same are provided. Specifically, by appropriately combining the components of the insulating film composition, the present invention aims to provide an electrical steel sheet insulating film composition, an electrical steel sheet, and a method for manufacturing the same, wherein the film does not separate even in high-temperature and high-humidity environments, exhibits excellent insulation properties in the high-frequency range, and can shield Fe-mound defects.

[0007] An insulating film composition for electrical steel sheets according to one embodiment of the present invention comprises 100 parts by weight of metal phosphate, 30 to 350 parts by weight of silica, 30 to 350 parts by weight of chromium nitrate, 30 to 350 parts by weight of one or more shielding agents selected from dolomite, talc, carbonate and feldspar, and 1 to 100 parts by weight of a carbon structure.

[0008] An insulating film composition for electrical steel sheets according to one embodiment of the present invention may further include 30 to 350 parts by weight of one or more of Sn oxide or Zr oxide.

[0009] Metal phosphates may include one or more of Mg, Ca, Ba, Sr, Zn, and Al.

[0010] Silica can have a pH of 8 to 12.

[0011] The carbon structure may include one or more of carbon black, carbon nanotubes, graphene, and fullerene.

[0012] 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, wherein the insulating film comprises 100 parts by weight of metal phosphate, 30 to 350 parts by weight of silica, 30 to 350 parts by weight of chromium nitrate, 30 to 350 parts by weight of one or more shielding agents selected from dolomite, talc, carbonate and feldspar, and 1 to 100 parts by weight of a carbon structure.

[0013] 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, wherein the insulating film composition comprises 100 parts by weight of a metal phosphate, 30 to 350 parts by weight of silica, 30 to 350 parts by weight of chromium nitrate, 30 to 350 parts by weight of one or more shielding agents selected from dolomite, talc, carbonate and feldspar, and 1 to 100 parts by weight of a carbon structure.

[0014] The heat treatment step can be performed at a temperature of 750 to 1000°C for 10 to 300 seconds.

[0015] According to one embodiment of the present invention, it has excellent durability and extreme corrosion resistance in high-temperature and high-humidity environments, and excellent heat resistance at very high processability temperatures such as stress relief annealing (SRA).

[0016] According to one embodiment of the present invention, it has a very excellent insulation effect in a high-frequency magnetic field environment.

[0017] According to one embodiment of the present invention, Fe-mound defects occurring during final annealing can be shielded.

[0018] According to one embodiment of the present invention, a working environment that is not harmful to workers can be provided by replacing a hexavalent chromium coating, which is harmful to the environment and workers, with a trivalent chromium coating.

[0019] FIG. 1 is a schematic diagram of a cross-section of an electrical steel sheet according to one embodiment of the present 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 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.

[0021] 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.

[0022] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0023] 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.

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0025]

[0026] An insulating film composition for electrical steel sheets according to one embodiment of the present invention comprises 100 parts by weight of metal phosphate, 30 to 350 parts by weight of silica, 30 to 350 parts by weight of chromium nitrate, 30 to 350 parts by weight of one or more shielding agents selected from dolomite, talc, carbonate and feldspar, and 1 to 100 parts by weight of a carbon structure.

[0027] 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 metal phosphate, 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.

[0028]

[0029] Metal phosphates act as binders within the insulating film composition. If an appropriate amount of metal phosphate is not included, the adhesion of the insulating film is compromised, or sufficient tensile strength cannot be obtained. Metal phosphates can be produced through a manufacturing process in which a metal oxide is added to pure phosphoric acid (H3PO4) and reacted. To improve the adhesion of the metal phosphate, a condensation reaction between the metal phosphate and boric acid can be induced by additionally adding boric acid during the reaction process and maintaining it for at least 3 hours; it is also possible to use this condensed product instead of the metal phosphate. In one embodiment of the present invention, the metal phosphate comprises not only the metal phosphate but also the condensed product of the metal phosphate and boric acid. The produced metal phosphate exhibits strong acidity.

[0030] Metal phosphates can be added to the composition using a solution having a solid content of 50 to 70 weight%. At this time, if the solid content in the solution is too low, the amount of free phosphoric acid in the metal phosphate increases, which may cause surface moisture absorption after the production of the metal phosphate; if the solid content is too high, the excess of solid content relative to pure phosphoric acid may result in poor reaction and precipitation.

[0031] Metal phosphates and metal oxides may include various metals without limitation. Specifically, the metals of the metal phosphates and metal oxides may include one or more of Mg, Ca, Ba, Sr, Zn, and Al. More specifically, the metal phosphate may include one or more of magnesium dihydrogen phosphate (Mg(H2PO4)2) and aluminum dihydrogen phosphate (Al(H2PO4)3). More specifically, it may include magnesium dihydrogen phosphate (Mg(H2PO4)2) and aluminum dihydrogen phosphate (Al(H2PO4)3). In this case, the metal phosphate may include 10 to 60 parts by weight of aluminum dihydrogen phosphate and 40 to 90 parts by weight of magnesium dihydrogen phosphate, based on solid content, per 100 parts by weight of the total. If too little aluminum dihydrogen phosphate is included, the tensile strength enhancement effect due to the addition of aluminum dihydrogen phosphate may not be sufficient. If too much aluminum diphosphate is added, the Al component may increase the crystallization of silica, causing cracks in the insulating film. Specifically, the metal phosphate may comprise 15 to 55 parts by weight of aluminum diphosphate and 45 to 85 parts by weight of magnesium diphosphate based on solid content, with respect to 100 parts by weight of the total, and more specifically, may comprise 20 to 50 parts by weight of aluminum diphosphate and 50 to 80 parts by weight of magnesium diphosphate.

[0032] An insulating film composition for electrical steel sheets according to one embodiment of the present invention comprises 30 to 350 parts by weight of silica per 100 parts by weight of metal phosphate.

[0033] Silica is a necessary component to impart weather resistance and corrosion resistance to the insulating film. If too little silica is included, it is difficult to sufficiently obtain the effect of imparting weather resistance and corrosion resistance to the insulating film. If too much silica is included, problems may arise regarding stickiness or solution stability, and also problems may arise regarding coating properties. More specifically, 100 to 300 parts by weight of silica may be included per 100 parts by weight of metal phosphate. More specifically, 150 to 250 parts by weight may be included.

[0034] Silica may include basic and acidic properties, and more specifically, may include basic properties. When basic silica is included, it is advantageous in terms of the stability of the insulating film composition, and the storage stability of the solution may be improved. The basic silica may have a pH of 8 to 12. The pH of the silica can be measured in sol form.

[0035] The silica may have an average particle size in the range of 5 to 20 nm. If the average particle size of the silica is too small, the condensation reaction rate is fast, causing aggregation and potentially inducing color deviation defects on the surface. If the average particle size is too large, the surface area per unit mass decreases, slowing down the condensation reaction rate and potentially causing defects. More specifically, the silica may have an average particle size in the range of 10 to 15 nm. In one embodiment of the present invention, the particle size can be measured using a particle size meter called Zeta Potential, and the average particle size is the arithmetic mean.

[0036] Silica may be composed of at least one nanoparticle having a different average particle size. Specifically, the silica may be used by mixing at least one silica nanoparticle having a different average particle size to form an insulating film having excellent film properties.

[0037] An insulating film composition for electrical steel sheets according to one embodiment of the present invention comprises 30 to 350 parts by weight of chromium nitrate per 100 parts by weight of metal phosphate.

[0038] Chromium nitrate is represented as Cr(NO3)3 and contributes to the improvement of corrosion resistance and weather resistance. In addition, it also serves as a dispersant that stably disperses the shielding agent described later within the insulating film composition. Particularly when used as an insulating film for grain-oriented electrical steel sheets, the use of organic dispersants is difficult, and chromium nitrate takes on the role of a dispersant. If too little chromium nitrate is included, it is difficult to sufficiently achieve the aforementioned roles, which may result in inferior weather resistance and corrosion resistance. If too much chromium nitrate is included, there is a risk of fire, and problems may arise regarding solution stability and coating properties. More specifically, 70 to 250 parts by weight of chromium nitrate may be included per 100 parts by weight of metal phosphate. More specifically, 100 to 200 parts by weight of chromium nitrate may be included. More specifically, 130 to 170 parts by weight of chromium nitrate may be included.

[0039] In addition, chromium nitrate is trivalent chromium and does not pose the same health risks to the human body as hexavalent chromium. In other words, chromium nitrate is an environmentally friendly substance that is not harmful to the human body. However, if trivalent chromium is added without adding hexavalent chromium, the stability of the solution decreases, making it prone to gelation, and there is a problem with the surface becoming sticky during coating. In one embodiment of the present invention, chromium nitrate is used among various trivalent chromiums, and by appropriately adjusting the combination and ratio of the components of chromium nitrate and the remaining insulating film composition, a film that does not separate and is not sticky can be manufactured even in high-temperature and high-humidity environments. For example, in addition to chromium nitrate, chromium compounds such as Cr(PO4)3, Cr2O3, Cr(H2O)6Cl3, CrBr3, and CrCl3 exist, but if these are used, the solution stability may decrease, or problems may arise in terms of corrosion resistance and weather resistance.

[0040] An insulating film composition for electrical steel sheets according to one embodiment of the present invention comprises 30 to 350 parts by weight of a shielding agent per 100 parts by weight of metal phosphate.

[0041] In one embodiment of the present invention, the shielding agent plays a role in improving insulation in an ultra-high frequency environment, and additionally, also exhibits the effect of making the surface color uniform. If too little of the shielding agent is included, the aforementioned role cannot be properly performed, and problems may arise in terms of corrosion resistance. If too much of the shielding agent is added, the lifespan of the solution is shortened, and problems may arise regarding solution stability, coating properties, etc. More specifically, the shielding agent may be included in an amount of 100 to 300 parts by weight. More specifically, the shielding agent may be included in an amount of 150 to 250 parts by weight.

[0042] The shielding agent may include one or more of dolomite, talc, carbonate, and feldspar. These materials are known to be applied in the cosmetics, paint, and ceramics industries. Additionally, they provide surface roughness and play a role in uniformizing surface color differences by scattering and blocking light through their crystal structure. However, these materials have the problem of being difficult to apply uniformly without using organic polymers or organic dispersants. In one embodiment of the present invention, the aforementioned nitrate is added together to enable the shielding agent to be applied uniformly.

[0043] Dolomite, also known as paleofossil, is chemically represented as CaMg(CO3)2. Talc (talcum) is a magnesium-containing silicate mineral, H2Mg3(SiO3)4 or Mg3Si4O 10 It is represented as (OH)2. Carbonates are carbonate ions CO3 2-It is a salt of carbonate present therein. Specifically, it may include one or more of magnesium carbonate, barium carbonate, and calcium carbonate. Feldspar is a network-structured silicate mineral, and more specifically, it may include Albite (soda feldspar) and Orthoclase (potassium feldspar). More specifically, it may include feldspar as a shielding agent.

[0044] An insulating film composition for electrical steel sheets according to one embodiment of the present invention comprises 1 to 100 parts by weight of a carbon structure per 100 parts by weight of a metal phosphate. The carbon structure acts as a dye within the insulating film composition. If too little of the carbon structure is included, it may not sufficiently perform the aforementioned role, and weather resistance and corrosion resistance may be inferior. If too much of the carbon structure is included, the solution lifespan is shortened, and issues regarding solution stability and coating properties may arise. More specifically, the carbon structure may be included in 3 to 50 parts by weight. More specifically, it may be included in 5 to 30 parts by weight. More specifically, it may be included in 7 to 15 parts by weight.

[0045] The carbon structure may include one or more of carbon black, carbon nanotubes, graphene, and fullerene. More specifically, it may include carbon black.

[0046] An insulating film composition for electrical steel sheets according to one embodiment of the present invention may further include 30 to 350 parts by weight of one or more of Sn oxide or Zr oxide per 100 parts by weight of metal phosphate. Sn oxide or Zr oxide acts as a shielding agent within the insulating film composition. If too little Sn oxide or Zr oxide is included, it may not sufficiently perform the aforementioned role, and weather resistance and corrosion resistance may be inferior. If too much Sn oxide or Zr oxide is included, the solution lifespan is shortened, and issues regarding solution stability and coating properties may arise. More specifically, 50 to 200 parts by weight of Sn oxide or Zr oxide may be included. More specifically, 80 to 150 parts by weight of Sn oxide or Zr oxide may be included. Sn oxide and Zn oxide may be included simultaneously, in which case the total amount may be 30 to 350 parts by weight. More specifically, 50 to 150 parts by weight of Sn oxide and 50 to 150 parts by weight of Zr oxide may be included. More specifically, it may contain 80 to 120 parts by weight of Sn oxide and 80 to 120 parts by weight of Zr oxide.

[0047] 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 metal phosphate.

[0048] The method of manufacturing the insulating film composition is not particularly limited and can be manufactured by mixing the aforementioned components. Specifically, it can be manufactured by mixing a metal phosphate and silica to prepare a mixed composition, adding chromium nitride to the mixed composition, and then mixing in the order of adding a shielding agent and a carbon structure.

[0049]

[0050] 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).

[0051] 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.

[0052] Additionally, the composition of the grain-oriented electrical steel substrate is explained as follows.

[0053] The oriented electrical steel substrate comprises silicon (Si): 2.0 to 7.0 wt%, aluminum (Al): 0.020 to 0.040 wt%, manganese (Mn): 0.01 to 0.20 wt%, phosphorus (P) 0.01 to 0.15 wt%, carbon (C) 0.01 wt% or less (excluding 0%), N: 0.005 to 0.05 wt%, and antimony (Sb), tin (Sn), or a combination thereof 0.01 to 0.15 wt%, and the remainder may comprise Fe and other unavoidable impurities. Since the description of each component of the oriented electrical steel substrate (10) is the same as generally known, a detailed description is omitted.

[0054] Between the grain-oriented electrical steel substrate and the insulating film, a metal oxide layer (base coating layer, primary film) formed by reacting with an annealing separator and the oxide layer of the steel sheet during the secondary recrystallization process may exist. An example of the metal oxide layer may be a forsterite layer. It is also possible to suppress the formation of the metal oxide layer or remove the metal oxide layer during the manufacturing process of the grain-oriented electrical steel so that the grain-oriented electrical steel substrate and the insulating film come into contact.

[0055] The thickness of the insulating film (20) can be 0.5 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 1 to 5 μm.

[0056] The insulating film (20) comprises 100 parts by weight of metal phosphate, 30 to 350 parts by weight of silica, 30 to 350 parts by weight of chromium nitrate, 30 to 350 parts by weight of one or more shielding agents selected from dolomite, talc, carbonate and feldspar, and 1 to 100 parts by weight of a carbon structure. The insulating film may be substantially the same as the solid component in the aforementioned insulating film composition.

[0057]

[0058] 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 performing heat treatment.

[0059] As detailed information regarding the electrical steel substrate and the insulating film composition has been provided previously, redundant explanations will be omitted.

[0060] For example, the substrate of an electrical steel sheet can be manufactured as follows.

[0061] A steel slab is prepared. In the next step, the steel slab is heated. At this time, the slab may be heated using the low-temperature slab method at 1,200°C or lower. Next, the heated steel slab is hot-rolled to produce a hot-rolled plate. Subsequently, the produced hot-rolled plate may be hot-rolled and annealed. Next, the hot-rolled plate is cold-rolled to produce a cold-rolled plate. Cold rolling may be performed once, or two or more cold-rolling steps including intermediate annealing may be performed. Next, the cold-rolled plate is subjected to primary recrystallization annealing. At this time, the step of primary recrystallizing annealing of the cold-rolled plate may include a step of simultaneously decarburizing and nitriding the cold-rolled plate, or a step of nitriding annealing after decarburizing annealing. Next, an annealing separating agent is applied to the surface of the recrystallized steel plate. The application amount of the annealing separating agent is 1 to 5 g / m² 2 If the amount of annealing separator applied is too small, film formation may not proceed smoothly. If the amount of annealing separator applied is too large, it may affect secondary recrystallization. Therefore, the amount of annealing separator applied can be controlled within the aforementioned range. Next, the steel plate coated with the annealing separator is subjected to secondary recrystallization annealing. During secondary recrystallization annealing, the primary cracking temperature can be set to 650 to 750 ℃, and the secondary cracking temperature to 1100 to 1250 ℃. The temperature range of the heating section can be controlled at a condition of 15 ℃ / hr. In addition, the gas atmosphere can be performed in an atmosphere containing 20 to 30 volume% nitrogen and 70 to 80 volume% hydrogen up to the primary cracking stage, and in the secondary cracking stage, it can be maintained in a 100% hydrogen atmosphere for 15 hours and then furnace cooling.

[0062] Next, an insulating film composition is applied to the surface of the electrical steel substrate. Since the details of the insulating film composition have been previously described, a redundant explanation is omitted. The insulating film composition is applied to one or both surfaces at a concentration of 1.0 to 10.0 g / mm 2It can be applied in large quantities.

[0063] In the heat treatment step, the heat treatment temperature may be 750 to 1000°C. If the temperature is too low, the time required to form the insulating film may be too long, which may result in poor continuous processing performance. If the temperature is too high, heat resistance and bluening resistance may be reduced due to cracking. More specifically, the heat treatment temperature may be 800 to 950°C. The heat treatment time may be 10 to 300 seconds. More specifically, it may be 30 to 180 seconds.

[0064] The atmosphere during heat treatment may be a nitrogen atmosphere.

[0065]

[0066] Preferred embodiments of the present invention, comparative examples, and evaluation examples thereof are described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0067]

[0068] Example 1

[0069] A 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.

[0070] An insulating film composition was prepared by mixing the components in the weight ratios summarized in Table 1 below. First, basic colloidal silica (average particle size 15 nm, pH 10) was added to and mixed with a phosphate solution containing 50 parts by weight of aluminum phosphate and 50 parts by weight of magnesium phosphate. Subsequently, a chromium nitrate solution was added and mixed, and then carbon black (manufactured by Aldrich) was added as a shielding agent and a carbon structure to finally prepare the insulating film composition.

[0071] Apply the prepared solution to both sides of the electrical steel sheet at 3.1 g / mm 2An insulating film with a thickness of 1 μm was formed by applying and heat treating at 850°C for 45 seconds.

[0072] Weather resistance, corrosion resistance, solution stability, coating properties, and heat adhesion were evaluated using the following methods and summarized in Table 2.

[0073]

[0074] Weather resistance evaluation

[0075] Weather resistance was evaluated under conditions of 98% moisture, 60°C, and 72 hours, and was marked as “OK” if good and “NG” if poor.

[0076]

[0077] Corrosion resistance evaluation

[0078] A salt spray test was conducted at 5% NaCl, 100 RH, 65 ℃, for 8 hours. It was marked “OK” if good and “NG” if poor.

[0079]

[0080] Solution stability evaluation

[0081] After storing the solution at 30℃ for 72 hours, the viscosity was measured using a Brook Field viscometer. It was marked as OK if 10 cp or less, and NG if it exceeded 10 cp.

[0082]

[0083] Coating performance evaluation

[0084] Upon visual evaluation, it was marked “OK” if there were no stains and it was in good condition, and “NG” if there were stains and it was defective.

[0085]

[0086] Heat adhesion evaluation

[0087] For the heat adhesion evaluation, heating was performed for 2 hours under conditions of 560°C, 20% hydrogen, and 80% nitrogen. Subsequently, it was confirmed to be 5B or higher through a CROSS-HATCH CUT test.

[0088] If the result of the above test is 5B or higher, it is indicated as “OK” as good, and if it is less than 5B, it is indicated as “NG” as poor.

[0089]

[0090] Silica Cr(NO3) Trifeldspar SnO2 ZrO2 Carbon Black 1200 150 2000 100 102 200 150 20000 103 20 150 2000 100 104 400 150 2000 100 105 200 10 2000 100 106 200 400 2000 100 107 200 150 100 100 108 200 150 4000 100 109 200 150 200 2000 10 10 200 150 2000 10 10 11 200 150 2000 400 10 12 200 150 200 100 100 100 113 200 150 200 100 100 200

[0091] Weather resistance, corrosion resistance, solution stability, coating properties, heat resistance, adhesion, shielding properties. Remarks 1 OK OK OK OK OK OK Example 2 OK OK OK OK OK NG Comparative Example 3 NG NG OK OK OK OK Comparative Example 4 OK OK NG NG OK OK Comparative Example 5 NG NG OK OK OK OK Comparative Example 6 OK OK NG NG NG OK Comparative Example 7 OK NG OK OK OK OK Comparative Example 8 OK OK NG NG OK OK Comparative Example 9 NG NG OK OK OK Comparative Example 10 NG NG OK OK OK Comparative Example 11 OK OK NG NG NG OK Comparative Example 12 NG NG OK OK OK Comparative Example 13 OK OK NG NG NG OK Comparative Example

[0092] As shown in Tables 1 and 2, when the components of the insulating film composition are included in appropriate amounts, it can be confirmed that weather resistance, corrosion resistance, solution stability, coating properties, and heat adhesion are all excellent. On the other hand, when the components of the insulating film composition are not included in appropriate amounts, it can be confirmed that some properties are inferior.

[0093]

[0094] 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.

[0095] [Explanation of the symbol]

[0096] 100 : Electrical steel sheet 10 : Electrical steel sheet material

[0097] 20: Insulating film

Claims

1. 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 is an electrical steel sheet comprising 100 parts by weight of metal phosphate, 30 to 350 parts by weight of silica, 30 to 350 parts by weight of chromium nitrate, 30 to 350 parts by weight of one or more shielding agents selected from dolomite, talc, carbonate and feldspar, and 1 to 100 parts by weight of a carbon structure.

2. In Paragraph 1, The above insulating film is an electrical steel sheet further comprising 30 to 350 parts by weight of one or more of Sn oxide or Zr oxide.

3. In Paragraph 1, The above metal phosphate is an electrical steel sheet comprising one or more of Mg, Ca, Ba, Sr, Zn, and Al.

4. In Paragraph 1, The above silica is an electrical steel sheet having a pH of 8 to 12.

5. In Paragraph 1, The above carbon structure is an electrical steel sheet comprising one or more of carbon black, carbon nanotubes, graphene, and fullerene.

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