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

Abstract

The present invention provides an insulating coating composition that can improve the weldability of electrical steel sheets, an electrical steel sheet including a coating layer composition having the above advantages, and a method for producing an insulating coating composition having the above advantages. [Solution] The method includes the steps of mixing a resin containing an organic substance with at least one metal phosphate selected from Mg, Al, Ca, Sr, Mn, and Zn in a ratio of the resin to the metal phosphate of 1 / 9 to 1 / 1 based on solid content, and adding at least one metal chloride selected from Al, Ca, Mg, Sr, Zn, and Fe to the mixture that has undergone the mixing step in an amount of 1 to less than 40 parts by weight based on solid content per 100 parts by weight of the mixture, wherein the metal chloride includes at least one of iron sulfate (FeSO4), aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate, and the metal phosphate includes at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, and zinc phosphate.

Description

[Technical Field]

[0001] The present invention relates to an insulating coating composition for electrical steel sheets, an electrical steel sheet including the same, and a manufacturing method thereof. More particularly, the present invention relates to an insulating coating composition for electrical steel sheets that can improve weldability in electrical steel sheets, and an electrical steel sheet including a coating layer composition having the above advantages, an electrical steel sheet including the same, and a manufacturing method thereof. [Background technology]

[0002] Electrical steel sheets are used as materials for transformers, motors, and electronic devices. Unlike ordinary carbon steel, which emphasizes workability such as mechanical properties, electrical properties are emphasized. The electrical properties include iron loss, magnetic flux density, magnetic permeability, and space factor. Electrical steel sheets are characterized by low iron loss and high magnetic flux density, magnetic permeability, and space factor.

[0003] The electrical steel sheets are broadly divided into grain-oriented electrical steel sheets and non-oriented electrical steel sheets. The grain-oriented electrical steel sheets utilize the phenomenon of abnormal grain growth called secondary recrystallization to form a Goos texture {100} <001> The non-oriented electrical steel sheet has a texture formed throughout the entire steel sheet, and has excellent magnetic properties in the rolling direction. The non-oriented electrical steel sheet has uniform magnetic properties in all directions on the rolled sheet.

[0004] The formation of the insulating coating on non-oriented electrical steel sheet is a process equivalent to the finishing process of the product, and typically requires electrical properties to suppress eddy currents. It also requires continuous punching processability to suppress die wear when punching into a desired shape and laminating multiple sheets to form an iron core. It also requires good sticking resistance and surface adhesion to prevent adhesion between the steel sheets in the iron core after stress relief annealing (SRA), which removes processing stress from the steel sheet and restores magnetic properties. It also requires good weldability when side-welding to secure the laminated core. In addition to these basic properties, the coating also requires excellent application properties for the coating solution and solution stability to ensure long-term use after mixing.

[0005] Among these, welding is performed to secure the laminated core, but due to the characteristics of welding that takes place at high temperatures, organic matter in the coating layer may evaporate and be trapped in the welding liquid, leaving holes where the organic matter escapes.Recently, with the development of high-efficiency motors, materials have become thinner to reduce eddy current loss, and as the thickness of the coating layer increases, the number of defects increases. As described above, the current situation is that measures are needed to improve the weldability of the above defects that appear due to the reduction in space factor associated with the thinning of the material while maintaining the thickness of the coating layer. Summary of the Invention [Problem to be solved by the invention]

[0006] The technical problem to be solved by the present invention is to provide an insulating coating composition that can improve the weldability of electrical steel sheets. Another technical problem to be solved by the present invention is to provide an electrical steel sheet including a coating layer composition having the above advantages. A further technical problem to be solved by the present invention is to provide a method for producing an insulating coating composition having the above advantages. [Means for solving the problem]

[0007] The insulating coating composition of the present invention is characterized in that it contains a resin having an average particle size of 50 to 250 nm, at least one metal phosphate of Mg, Al, Ca, Sr, Mn, and Zn, and a metal chloride, and the metal chloride is contained in an amount of 1 to less than 40 parts by weight, based on the solid content, per 100 parts by weight of the total insulating coating composition.

[0008] The metal chloride may be at least one of Al, Ca, Mg, Sr, Zn, and Fe. The metal chloride may include at least one of iron sulfate (FeSO4), aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

[0009] The ratio of the resin to the metal phosphate may be, on a solids basis, 1 / 9 to 1. The metal phosphate may include at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, and zinc phosphate.

[0010] The electrical steel sheet of the present invention comprises an electrical steel sheet substrate and an insulating coating layer applied to the electrical steel sheet substrate, wherein the insulating coating layer comprises a resin, at least one metal phosphate selected from Mg, Al, Ca, Sr, Mn, and Zn, and at least one metal chloride selected from Al, Ca, Mg, Sr, Zn, and Fe, the metal chloride being present in an amount of 1 to less than 40 parts by weight on a solids content basis per 100 parts by weight of the total insulating coating composition, and the coating thickness difference rate of the insulating coating layer satisfies the following formula 1:

[0011] <Expression 1> 10≦((Coating thickness of thickest part - Coating thickness of thinnest part) / Average coating thickness)×100≦40 At least one of the metal chlorides may contain iron sulfate (FeSO4). The gloss of the electrical steel sheet may be 60 GU or more. The surface roughness of the electrical steel sheet may be 0.28 to 0.51 μm.

[0012] The method for producing an insulating coating composition of the present invention includes the steps of mixing a resin containing an organic substance with at least one metal phosphate selected from Mg, Al, Ca, Sr, Mn, and Zn in a ratio of the resin to the metal phosphate of 1 / 9 to 1 / 1 based on solid content, and adding to the mixture resulting from the mixing step at least one metal chloride selected from Al, Ca, Mg, Sr, Zn, and Fe in an amount of 1 to less than 40 parts by weight based on solid content per 100 parts by weight of the mixture. The metal chloride is characterized by including at least one of iron sulfate (FeSO4), aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

[0013] The metal phosphate can include at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, and zinc phosphate. [Effects of the Invention]

[0014] The insulating coating composition of the present invention contains a resin, a metal phosphate, and a metal sulfate, which imparts surface roughness when coated onto electrical steel sheets and ensures gas channels between the materials, thereby preventing blow-hole defects that occur during the welding process. The electrical steel sheet of the present invention contains an insulating coating composition having the above-described advantages, and thus can provide an electrical steel sheet with surface roughness and good weldability. Furthermore, the method for producing an insulating coating composition of the present invention can produce an insulating coating composition having the above-mentioned advantages. [Brief explanation of the drawings]

[0015] [Figure 1] 1 shows an electrical steel sheet according to the present invention. [Figure 2A] 1 shows cross-sectional SEM (Scanning Electron Microscope) images of insulating coatings according to the amount of metal sulfate added according to the present invention. [Figure 2B] 1 shows cross-sectional SEM (Scanning Electron Microscope) images of insulating coatings according to the amount of metal sulfate added according to the present invention. [Figure 2C] 1 shows cross-sectional SEM (Scanning Electron Microscope) images of insulating coatings according to the amount of metal sulfate added according to the present invention. [Figure 2D] 1 shows cross-sectional SEM (Scanning Electron Microscope) images of insulating coatings according to the amount of metal sulfate added according to the present invention. [Figure 3A] 1 shows cross-sectional images of welds of electrical steel sheets coated with insulating coatings according to the amount of metal sulfate added according to the present invention. [Figure 3B] 1 shows cross-sectional images of welds of electrical steel sheets coated with insulating coatings according to the amount of metal sulfate added according to the present invention. [Figure 3C] 1 shows cross-sectional images of welds of electrical steel sheets coated with insulating coatings according to the amount of metal sulfate added according to the present invention. [Figure 3D] 1 shows cross-sectional images of welds of electrical steel sheets coated with insulating coatings according to the amount of metal sulfate added according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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 form includes the plural form unless the context clearly dictates otherwise. As used in the specification, the meaning of "comprising" embodies certain features, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components. When a part is referred to as being "on" another part, it may be directly on top of the other part, or there may be other parts between them. In contrast, when a part is referred to as being "directly on top" of another part, there are no other parts between them.

[0017] 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 to have 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. Unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight. In one embodiment of the present invention, the term "additionally containing an additional element" means that the remaining iron (Fe) is replaced by the additional amount of the additional element.

[0018] DETAILED DESCRIPTION OF THE INVENTION The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The insulating coating composition of the present invention includes at least one of a resin, a metal phosphate, and a metal chloride. Specifically, the insulating coating composition is an insulating coating composition for electrical steel sheets, and may be applied to electrical steel sheets to improve properties such as substrate adhesion, corrosion resistance, and punchability. The resin may be contained in the insulating coating composition and function as a binder. The resin may be an acrylic resin, an epoxy resin, a polyester resin, a styrene resin, a phenolic resin, a urethane resin, a melamine resin, a vinyl acetate resin, or a mixture of two or more of these, specifically an acrylic emulsion resin. The resin may be an emulsion or a water-soluble resin, specifically an emulsion resin.

[0019] As the acrylic resin, a monomer such as methyl methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, n-octyl acrylate, i-octyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, n-decyl acrylate, or n-dodecyl acrylate can be used, and further, a copolymer of a monomer having a functional group such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, or itaconic acid, or a monomer having a hydroxyl group such as 2-hydroxylethyl (meth)acrylate, 2-hydroxylpropyl (meth)acrylate, 3-hydroxylbutyl (meth)acrylate, or 2-hydroxylethyl (meth)aryl ether can be more preferably used.

[0020] The epoxy resin may be an amine-modified epoxy resin reacted with a carboxylic acid anhydride. For example, an epoxy resin such as bisphenol A diglycidyl ether, a caprolactone ring-opening adduct of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, novolac glycidyl ether, or dimer acid glycidyl ether may be modified with an amine such as isopropanolamine, monopropanolamine, monobutanolamine, monoethanolamine, diethylenetriamine, ethylenediamine, butylamine, propylamine, isophoronediamine, tetrahydrofurfurylamine, xylenediamine, hexylamine, nonylamine, triethylenetetramine, tetramethylenepentamine, or diaminodiphenylsulfone, and then reacted with a carboxylic acid anhydride such as succinic anhydride, itaconic anhydride, maleic anhydride, citraconic anhydride, phthalic anhydride, or trimellitic anhydride.

[0021] Suitable polyester resins include those obtained by reacting a dicarboxylic acid such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, succinic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, or citraconic acid with a glycol such as ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyldiol, 1,6-hexanediol, triethylene glycol, dipropylene glycol, or polyethylene glycol. Also, graft polymerized polyester resins such as those described above with acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, or methacrylic anhydride may be used.

[0022] The resin may have an average particle size in the range of 50 to 250 nm. Specifically, if the average particle size of the resin exceeds the upper limit of the range, there is a problem of reduced coating wetting performance. If the average particle size of the resin exceeds the lower limit of the range, there is a problem of reduced solution stability.

[0023] The metal phosphate may be a solid content obtained by drying an aqueous solution containing phosphoric acid and metal ions as its main components, and may function as a binder in the insulating coating. The metal phosphate may be one or more metal phosphates selected from magnesium (Mg), aluminum (Al), calcium (Ca), strontium (Sr), manganese (Mn), and zinc (Zn). Specifically, the metal phosphate may be at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, and zinc phosphate.

[0024] The ratio of the resin to the metal phosphate may be 1 / 9 to 1 based on the solid content. Specifically, the ratio of the metal phosphate to the resin may be 9:1 to 5:5 based on the solid content. If the ratio of the metal phosphate is too high compared to the ratio of the resin, there is a problem of mold deterioration occurring during the punching process. If the ratio of the resin is too high, there is a problem of peeling of the coating layer including the insulating coating composition after stress relief annealing.

[0025] Metal chlorides can be added to facilitate the aggregation of resins. Resins generally do not distribute uniformly throughout the coating layer during the heat drying or curing process, imparting surface roughness and making it difficult to improve weldability. Adding metal sulfates or metal chlorides to resins can increase the ionic strength of the solution used to form the insulating coating composition. Therefore, when the metal chloride reacts with the surface of the substrate during the heating and drying or curing process of the solution for forming the insulating coating composition to release iron ions, the ionic strength increases, and this can impart surface roughness to the insulating coating composition due to the aggregation of resin particles.

[0026] Metal chlorides can be substances that can dissolve in water to form ions and can form insoluble coatings by salt formation after heat curing or drying. Metal chlorides can include metal sulfates and metal nitrates. Metal chlorides can include nitrites (-NO3), sulfides (-SO4), chlorides (-Cl), or carbonates (-CO3) to form salts. The metal chloride may include at least one of aluminum (Al), calcium (Ca), magnesium (Mg), strontium (Sr), zinc (Zn), and iron (Fe). Specifically, the metal chloride may include iron, and may be iron sulfate (FeSO4), aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, or zinc sulfate. The metal chloride can be added in an amount of 1 to less than 40 parts by weight based on 100 parts by weight of the total insulating coating composition on a solids basis, specifically 10 to 30 parts by weight.

[0027] If the upper limit of the range is exceeded, the stability of the solution will decrease, the coefficient of surface friction will increase, which may cause workability problems such as slitting, and the boiling point of the coating layer will increase, which may cause an increase in blow-holes during weldability evaluation.If the lower limit of the range is exceeded, it will be difficult to expect an improvement in weldability.

[0028] FIG. 1 shows an electrical steel sheet 10 . 1, an electrical steel sheet 10 of the present invention can include an electrical steel sheet substrate 100 and an insulating coating layer 200. By applying the insulating coating layer 200 to the electrical steel sheet substrate 100, which is the surface of a non-oriented electrical steel sheet, for example, the electrical steel sheet 10 can improve properties such as material adhesion, corrosion resistance, punchability, insulation, and weldability.

[0029] The electrical steel sheet substrate 100 is formed by utilizing the phenomenon of abnormal grain growth called secondary recrystallization, which results in a Goos texture {100} <001> The electrical steel sheet substrate 100 of the present invention may be a grain-oriented electrical steel sheet having excellent magnetic properties in the rolling direction by forming a texture throughout the steel sheet, or a non-oriented electrical steel sheet having uniform magnetic properties in all directions on the rolled sheet. Specifically, the electrical steel sheet substrate 100 of the present invention may be a non-oriented electrical steel sheet.

[0030] The insulating coating layer 200 is applied to the electrical steel sheet substrate 100 and is formed by applying the above-described insulating coating composition to the electrical steel sheet substrate 100 and then drying it. The insulating coating composition is the same as that described above to the extent that it is not inconsistent. The insulating coating layer 200 may include a resin, a metal phosphate, and a metal chloride. The resin, the metal phosphate, and the metal chloride are the same as those described above to the extent that they are not inconsistent, and therefore detailed descriptions thereof will be omitted.

[0031] The insulating coating layer 200 is applied onto the surface of the electromagnetic steel sheet substrate 100 and may be located from the surface of the electromagnetic steel sheet substrate 100 toward the outside of the electromagnetic steel sheet 10 . The insulating coating layer 200 may be formed by applying a coating solution for the insulating coating composition, and then drying the coating solution, which reacts with the electrical steel sheet 10, causing some of the Fe component contained in the substrate to dissolve into the solution in the form of ions. After the insulating coating layer 200 is formed, the insulating coating layer 200 of the electrical steel sheet 10 may have a coating thickness difference rate, and the coating thickness difference rate may satisfy the following formula 1:

[0032] <Expression 1> 10≦((Coating thickness of thickest part - Coating thickness of thinnest part) / Average coating thickness)×100≦40

[0033] According to the above formula 1, the coating thickness difference ratio is the difference between the thickness of the thickest part of the coated portion and the thickness of the thinnest part of the coated portion relative to the average coating thickness, expressed as a percentage. The coating thickness difference ratio may be in the range of 10 to 40. If the coating thickness difference ratio is too high, gloss may be reduced, and if the coating thickness difference ratio is too low, weldability may be reduced.

[0034] The glossiness of the electrical steel sheet 10 may be 60 GU or more. The glossiness is measured at a measurement angle of 60°, and if the glossiness is lower than 60, the external appearance of the electrical steel sheet 10 may not be attractive.

[0035] The surface roughness (Ra) of the electrical steel sheet 10 may be in the range of 0.28 to 0.51 μm. If the surface roughness exceeds the upper limit of the range, there are problems such as a decrease in space factor and a decrease in weldability. If the surface roughness exceeds the lower limit of the range, there are problems such as an increase in costs during the cold rolling process and a decrease in weldability.

[0036] A method for producing an insulating coating composition of the present invention can include the steps of mixing a resin containing an organic substance with at least one metal phosphate selected from Mg, Al, Ca, Sr, Mn, and Zn in a ratio of resin to metal phosphate of 1 / 9 to 1 / 1 based on solid content, and adding at least one metal chloride selected from Mg, Al, Fe, Co, Mn, and Zn to the mixture resulting from the mixing step in an amount of 1 to less than 40 parts by weight based on solid content per 100 parts by weight of the mixture. The resin, metal phosphate, and metal chloride are the same as those described above to the extent that they are not inconsistent, and therefore detailed description thereof will be omitted.

[0037] In the step of mixing an organic resin with at least one metal phosphate selected from Mg, Al, Ca, Sr, Mn, and Zn at a ratio of resin to metal phosphate of 1 / 9 to 1 based on solid content, the resin and the metal phosphate are mixed to synthesize a solution for forming an insulating coating composition. Specifically, the resin may be an acrylic emulsion resin, and the metal phosphate may be specifically aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, or zinc phosphate. For a detailed description of this, please refer to the above description of the insulating coating composition to the extent that it does not contradict.

[0038] In the step of adding at least one metal chloride selected from Mg, Al, Fe, Co, Mn, and Zn to the mixture after the mixing step in an amount of 1 to less than 40 parts by weight based on the solid content per 100 parts by weight of the mixture, the metal chloride may be added to facilitate aggregation of the resin in the solution for forming the insulating coating composition. Specifically, the metal chloride may be iron sulfate (FeSO4), aluminum sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, or zinc sulfate, and the detailed description thereof may refer to the description of the insulating coating composition described above to the extent that it does not contradict the description.

[0039] Hereinafter, specific examples of the present invention will be described, but the following examples are merely specific examples of the present invention and the present invention is not limited to the following examples. [Example]

[0040] A non-oriented electrical steel sheet (150 x 50 mm) containing 3.15 wt % silicon (Si) and having a thickness of 0.27 mm was used as a test piece. A solution prepared according to the components in Table 1 below was applied to the non-oriented electrical steel sheet to a thickness of 0.4 to 0.6 μm using a bar coater and a roll coater. The test piece was then maintained in a drying oven at 300 to 750°C for 10 to 30 seconds and then slowly cooled in air. The solution for forming the insulating coating composition was prepared by mixing acrylic emulsion resin and aluminum phosphate (AlPO4, Al(H2PO4)3, Al2(HPO4)3) in a ratio of 3:7, and 1% of iron sulfate (FeSO4) was added as an additive when preparing the solution. [Example]

[0041] The same procedure as in Example 1 was carried out except that 10% of the iron sulfate (FeSO4) was added. [Example]

[0042] The same procedure as in Example 1 was carried out except that 30% of the iron sulfate (FeSO4) was added. [Example]

[0043] The same procedure as in Example 1 was carried out, except that the emulsion used had an average particle size of 50 μm. [Example]

[0044] The same procedure as in Example 1 was carried out, except that the emulsion used had an average particle size of 100 μm. [Example]

[0045] The same procedure as in Example 1 was carried out, except that the emulsion used had an average particle size of 250 μm. [Example]

[0046] The same procedure as in Example 1 was carried out, except that magnesium phosphate (Mg3(PO4)2, Mg(HPO4, Mg(H2PO4)2) was used instead of aluminum phosphate as the type of phosphate. [Example]

[0047] The same procedure as in Example 1 was carried out, except that calcium phosphates (Ca3(PO4)2, Ca(HPO4, Ca(H2PO4)2) were used instead of aluminum phosphate as the type of phosphate. [Example]

[0048] The same procedure as in Example 1 was carried out, except that strontium phosphate (Sr3(PO4)2, Sr(HPO4, Sr(H2PO4)2) was used instead of aluminum phosphate as the type of phosphate. [Example]

[0049] The same procedure as in Example 1 was carried out, except that manganese phosphate (Mn3(PO4)2, Mn(HPO4, Mn(H2PO4)2) was used instead of aluminum phosphate as the type of phosphate. [Example]

[0050] The same procedure as in Example 1 was carried out, except that zinc phosphate (Zn3(PO4)2, Zn(HPO4, Zn(H2PO4)2) was used instead of aluminum phosphate as the type of phosphate. [Example]

[0051] The same procedure as in Example 1 was carried out, except that aluminum sulfate (Al2(SO4)3) was used instead of iron sulfate as the inorganic additive. [Example]

[0052] The same procedure as in Example 1 was carried out, except that calcium sulfate (CaSO4) was used instead of iron sulfate as the inorganic additive. [Example]

[0053] The same procedure as in Example 1 was carried out, except that magnesium sulfate (MgSO4) was used instead of iron sulfate as the inorganic additive. [Example]

[0054] The same procedure as in Example 1 was carried out, except that manganese sulfate (MnSO4) was used instead of iron sulfate as the inorganic additive. [Example]

[0055] The same procedure as in Example 1 was carried out, except that strontium sulfate (SrSO4) was used instead of iron sulfate as the inorganic additive.

[0056] Comparative Example 1 The same procedure as in Example 1 was carried out except that the iron sulfate (FeSO4) was not added. Comparative Example 2 The same procedure as in Example 1 was carried out except that 40% of the iron sulfate (FeSO4) was added. Comparative Example 3 The same procedure as in Example 1 was carried out except that the iron sulfate (FeSO4) was added in an amount of 50%. Comparative Example 4 The same procedure as in Example 1 was carried out, except that the emulsion used had an average particle size of 30 μm. Comparative Example 5 The same procedure as in Example 1 was carried out, except that the emulsion used had an average particle size of 300 μm.

[0057] The following formula 1 is used to evaluate the effects of the present invention based on the above-mentioned examples and comparative examples. Specifically, solution stability, gloss, material roughness, surface roughness, thickness difference ratio, weldability, and adhesion after heat treatment were evaluated. Solution stability was measured using a DLS Turbiscan, glossiness was measured using a glossmeter, and material and surface roughness were measured using a roughness meter. The thickness difference ratio was calculated by measuring the thickness difference between the thickest and thinnest parts within a 40 μm range using SEM cross-sectional analysis. Weldability was evaluated in a laboratory experiment using visual inspection and cross-sectional inspection after TIG welding. The adhesion after heat treatment was evaluated according to ASTM D3359 after heat treatment at 750°C in a N2 atmosphere.

[0058] The weldability and adhesion were evaluated as excellent (◎), good (◯), average (△), and poor (×). For weldability, excellent was evaluated when there were no blowholes during the visual inspection and the diameter of the blowholes was 0.1 mm or less during the cross-sectional inspection, good was evaluated when there were no blowholes during the visual inspection and the diameter of the blowholes was 0.2 mm or less during the cross-sectional inspection, average was evaluated when there were no blowholes during the visual inspection but the diameter of the blowholes was more than 0.2 mm during the cross-sectional inspection, and poor was evaluated when blowholes were observed during the visual inspection. The adhesion after the heat treatment was evaluated as excellent if it was 5B or higher, good if it was 4B, fair if it was 3B, and poor if it was 2B or lower.

[0059] [Table 1]

[0060] As shown in Table 1, it can be seen that there are differences in weldability and adhesion after heat treatment between Examples 1 to 3 and Comparative Examples 1 to 3. It was confirmed that, when the average particle size of the resin emulsion satisfies the range of the present invention, Examples 4 to 6 are superior in weldability and adhesion after heat treatment to Comparative Examples 4 and 5, in which the average particle size of the resin emulsion does not satisfy the range of the present invention.

[0061] In Examples 7 to 11, it was confirmed that when magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, or zinc phosphate was used as the type of phosphate in addition to aluminum phosphate, very good effects were obtained in terms of weldability and adhesion after heat treatment.

[0062] In Examples 12 to 17, it was confirmed that when aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, or zinc sulfate was used as the inorganic additive in addition to iron sulfate, very good effects were observed in terms of weldability and adhesion after heat treatment.

[0063] 2A to 2D are cross-sectional SEM (Scanning Electron Microscope) images of insulating coatings according to the amount of metal sulfate added according to the present invention. Specifically, Fig. 2A is a cross-sectional SEM image of the insulating coating for Comparative Example 1, where no iron sulfate was added, Fig. 2B is an SEM image of Example 1, Fig. 2C is an SEM image of Example 2, and Fig. 2D is an SEM image of Example 3.

[0064] 3A to 3D are images of welded cross sections of electrical steel sheets coated with insulating coatings according to the amount of metal sulfate added according to the present invention. Specifically, Fig. 3A is an image of a welded cross section of electrical steel sheets coated with insulating coatings for Comparative Example 1, in which no iron sulfate was added, Fig. 3B is an image of an example 1, Fig. 3C is an example 2, and Fig. 3D is an example 3.

[0065] As shown in FIGS. 2A to 2D and Table 1, Examples 1 to 3 have superior glossiness compared to Comparative Examples 2 and 3, and compared to Comparative Examples 1 to 3, the surface roughness is also within the range targeted by the present invention, and the percentage value of the difference between the thickest and thinnest parts of the coating layer relative to the average coating layer thickness is also within the range targeted by the present invention.

[0066] As shown in Table 1, the weldability of Examples 1 to 3 was evaluated, and it can be seen that Example 1 is good (◯), and Examples 2 and 3 are very good (◎). Compared to Examples 1 to 3, it can be seen that Comparative Example 1 has poor weldability (X), Comparative Example 2 is fair (△), and Comparative Example 3 is unmeasurable (-).

[0067] The present invention is not limited to the above-described embodiments and / or examples, 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 spirit or essential characteristics of the present invention. Therefore, it should be understood that the above-described embodiments and / or examples are illustrative in all respects and not limiting. [Explanation of symbols]

[0068] 10 Electrical steel sheet 100 Electromagnetic steel sheet base material 200 insulating coating layer

Claims

1. a resin having an average particle size of 50 to 250 nm; a metal phosphate of at least one of Mg, Al, Ca, Sr, Mn, and Zn; a metal chloride; The insulating coating composition is characterized in that the metal chloride is contained in an amount of 1 to less than 40 parts by weight on a solids basis relative to 100 parts by weight of the entire insulating coating composition.

2. 2. The insulating coating composition according to claim 1, wherein the metal chloride is at least one of Al, Ca, Mg, Sr, Zn, and Fe.

3. The metal chloride is iron sulfate (FeSO ４ 2. The insulating coating composition of claim 1, further comprising at least one of aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

4. 2. The insulating coating composition according to claim 1, wherein the ratio of the resin to the metal phosphate is 1 / 9 to 1 on a solids basis.

5. 2. The insulating coating composition of claim 1, wherein the metal phosphate comprises at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, and zinc phosphate.

6. an electromagnetic steel sheet substrate; an insulating coating layer applied to the electrical steel sheet substrate, the insulating coating layer includes at least one of a resin, a metal phosphate of at least one of Mg, Al, Ca, Sr, Mn, and Zn, and a metal chloride of at least one of Al, Ca, Mg, Sr, Zn, and Fe; the metal chloride is present in an amount of 1 to less than 40 parts by weight, based on the solid content, relative to 100 parts by weight of the total insulating coating composition; The electrical steel sheet is characterized in that the coating thickness difference rate of the insulating coating layer satisfies the following formula 1: <Formula 1> 10≦((coating thickness of thickest part−coating thickness of thinnest part) / average coating thickness)×100≦40

7. At least one of the metal chlorides is iron sulfate (FeSO ４ 6. The electrical steel sheet according to claim 5, further comprising at least one of aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

8. The electrical steel sheet according to claim 5, wherein the glossiness is 60 GU or more.

9. The electrical steel sheet according to claim 5, wherein the surface roughness is 0.28 to 0.51 μm.

10. mixing a resin containing an organic substance with at least one metal phosphate of Mg, Al, Ca, Sr, Mn, and Zn in a ratio of the resin to the metal phosphate of 1 / 9 to 1 on a solid content basis; and adding to the mixture that has undergone the mixing step at least one metal chloride selected from Al, Ca, Mg, Sr, Zn, and Fe in an amount of 1 to less than 40 parts by weight based on the solid content per 100 parts by weight of the mixture.

11. The metal chloride is iron sulfate (FeSO ４ 11. The method for producing an insulating coating composition according to claim 10, wherein the composition contains at least one of aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

12. 11. The method for producing an insulating coating composition according to claim 10, wherein the metal phosphate includes at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, and zinc phosphate.

Images