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

Abstract

An insulating coating composition according to one embodiment of the present invention comprises: a resin having an average particle diameter of 50 to 250 nm; a metal phosphate of at least one of Mg, Al, Ca, Sr, Mn and Zn; and a metal chloride in an amount of 1 to less than 40 parts by weight in terms of solid content with respect to 100 parts by weight of the total insulating coating composition.

Description

Technical Field

[0001] The present invention relates to an electrical steel sheet. More specifically, the present invention relates to an insulating coating composition for an electrical steel sheet, an electrical steel sheet containing the composition, and a method for producing the same. Background Art

[0002] Electrical steel sheets are products used as materials for transformers, motors, and electronic devices. Different from ordinary carbon steels that emphasize workability such as mechanical properties, electrical steel sheets are functional products that emphasize electrical properties. The electrical properties include properties such as iron loss, magnetic flux density, magnetic permeability, and duty ratio. The characteristics of the electrical steel sheet are low iron loss and high magnetic flux density, magnetic permeability, and duty ratio.

[0003] The electrical steel sheets are roughly divided into grain-oriented electrical steel sheets and non-oriented electrical steel sheets. The grain-oriented electrical steel sheet forms a {100}<001> texture as a Goss texture on the entire steel sheet by using an abnormal grain growth phenomenon called secondary recrystallization, so as to have good magnetic properties in the rolling direction. The non-oriented electrical steel sheet is an electrical steel sheet having uniform magnetic properties in all directions of the rolled sheet.

[0004] In the non-oriented electrical steel sheet, the formation of the insulating coating is a process equivalent to the final production process of the product. In addition to the electrical property of usually suppressing the generation of eddy currents, the following good properties are also required: continuous punching processability, suppressing die wear when punching into a predetermined shape and then stacking multiple layers to prepare a core; anti-sticking, after performing Stress Relief Annealing (SRA) to remove the processing stress of the steel sheet to restore the magnetic properties, the core steel sheets will not be closely adhered to each other; and surface adhesion; weldability during side welding, which is used to fix the laminated core. In addition to these basic properties, excellent coating operability of the coating solution and solution stability that can be used for a long time after batching are also required.

[0005] The welding is performed to fix the laminated core. Due to the characteristic of welding at high temperature, the organic substances in the coating will vaporize and part of them will be trapped by the welding liquid or there will also be traces left by escaping to form blow-hole defects such as holes. Recently, with the development of high-efficiency motors and the thinning of materials to reduce eddy current losses, the amount of the coating has relatively increased, so the defects will also increase.

[0006] As described above, with the thinning of the material, due to the defects caused by the decrease in the duty ratio, there is an urgent need for a solution to improve the weldability while maintaining the coating thickness. Summary of the Invention

[0007] (I) Technical Problems to be Solved

[0008] The technical problem to be solved by the present invention is to provide an insulating coating composition that can improve the weldability in electrical steel sheets.

[0009] Another technical problem to be solved by the present invention is to provide an electrical steel sheet that includes a coating composition having the above advantages.

[0010] Still another technical problem to be solved by the present invention is to provide a method for preparing an insulating coating composition that has the above advantages.

[0011] (II) Technical Solution

[0012] An insulating coating composition according to an embodiment of the present invention includes: 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; and a metal chloride, which, based on 100 parts by weight of the total insulating coating composition and on a solids basis, can be 1 to less than 40 parts by weight. In one embodiment, the metal chloride can be at least one of Al, Ca, Mg, Sr, Zn, and Fe. In one embodiment, the metal chloride can include at least one of iron sulfate (FeSO4), aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

[0013] In one embodiment, based on a solids basis, the ratio of the resin to the metal phosphate can be 1 / 9 to 1. In one embodiment, the metal phosphate can include at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, and zinc phosphate.

[0014] An electrical steel sheet according to another embodiment of the present invention includes an electrical steel sheet substrate; and an insulating coating layer coated on the electrical steel sheet substrate, the insulating coating layer including 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, which, based on 100 parts by weight of the total insulating coating composition and on a solids basis, is 1 to less than 40 parts by weight, and the coating thickness difference rate of the insulating coating layer can satisfy the following formula 1.

[0015] <Formula 1>

[0016] 10 ≤ ((coating thickness of the thickest part - coating thickness of the thinnest part) / average coating thickness) × 100 ≤ 40

[0017] In one embodiment, at least one of the metal chlorides may include iron sulfate (FeSO4). In one embodiment, the glossiness of the electrical steel sheet may be 60 GU or more. In one embodiment, the surface roughness of the electrical steel sheet may be 0.28 to 0.51 μm.

[0018] A method for preparing an insulating coating composition according to another embodiment of the present invention may include: mixing a resin containing an organic substance with a metal phosphate of at least one of Mg, Al, Ca, Sr, Mn, and Zn such that the ratio of the resin to the metal phosphate is 1 / 9 to 1 by solids; and adding, to 100 parts by weight of the mixture obtained through the mixing step, at least one metal chloride of Al, Ca, Mg, Sr, Zn, and Fe in an amount of 1 to less than 40 parts by weight by solids. In one embodiment, 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. In one embodiment, the metal phosphate may include at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, and zinc phosphate.

[0019] (III) Advantageous Effects

[0020] An insulating coating composition according to an embodiment of the present invention includes a resin, a metal phosphate, and a metal sulfate. Thus, when coating an electrical steel sheet, it imparts surface roughness and ensures a gas channel (GasChannel) between materials, and can prevent blow-hole defects generated during the welding process.

[0021] An electrical steel sheet according to another embodiment of the present invention includes an insulating coating composition having the above advantages, thus imparting surface roughness and providing an electrical steel sheet with good weldability.

[0022] A method for preparing an insulating coating composition according to still another embodiment of the present invention can prepare an insulating coating composition having the above advantages. Brief Description of the Drawings

[0023] Figure 1 Shows an electrical steel sheet according to an embodiment of the present invention.

[0024] Figures 2a to 2d Is a cross-sectional scanning electron microscope (Scanning Electron Microscope, SEM) image of an insulating coating based on the amount of metal sulfate added according to an embodiment of the present invention.

[0025] Figures 3a to 3dIt is a welded cross-sectional image of an electrical steel sheet coated with an insulating film based on the addition amount of metal sulfate according to an embodiment of the present invention. Detailed Description of the Invention

[0026] The terms first, second, third, etc. are used to describe various parts, components, regions, layers, and / or segments, but these parts, components, regions, layers, and / or segments should not be limited by these terms. These terms are only used to distinguish one part, component, region, layer, or segment from another part, component, region, layer, or segment. Therefore, without departing from the scope of the present invention, the first part, component, region, layer, or segment described below can also be described as the second part, component, region, layer, or segment.

[0027] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. Unless otherwise clearly indicated to the contrary in the context, the singular forms used herein are also intended to include the plural forms. The term "comprising" used in the specification can specifically refer to a certain property, field, integer, step, action, element, and / or component, but does not exclude the existence or addition of other properties, fields, integers, steps, actions, elements, and / or components.

[0028] If a part is described as being above another part, there may be other parts directly above the other part or there may be other parts in between. When a part is described as being directly above another part, there are no other parts in between.

[0029] Although not otherwise defined, the meanings of all terms (including technical terms and scientific terms) used herein are the same as those commonly understood by those of ordinary skill in the art to which the present invention pertains. For terms defined in a dictionary, they should be interpreted as having a meaning consistent with the relevant technical literature and the content disclosed herein, and should not be interpreted in an idealized or overly formal sense.

[0030] In addition, unless otherwise specifically stated, % represents weight %, and 1 ppm is 0.0001 weight %.

[0031] In an embodiment of the present invention, further including an additional element means that the additional element replaces the remaining iron (Fe), and the replacement amount is equivalent to the addition amount of the additional element.

[0032] Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement the present invention. However, the present invention can be implemented in various different ways and is not limited to the embodiments described herein.

[0033] An insulating film composition according to an embodiment of the present invention includes at least one of a resin, a metal phosphate, and a metal chloride. Specifically, the insulating film composition is for an electrical steel sheet, and by coating it on the electrical steel sheet, properties such as material adhesion, corrosion resistance, and punching properties can be improved.

[0034] The resin contained in the insulating film composition can function as an adhesive. In one embodiment, the resin may be an acrylic resin, an epoxy resin, a polyester resin, a styrene resin, a phenolic resin, a polyurethane resin, a melanin resin, a vinyl acetate resin, or a mixture of two or more thereof, and specifically may be an acrylic emulsion resin. The resin may be an emulsion resin or a water-soluble resin, and specifically may be an emulsion resin.

[0035] As the acrylic resin, methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, n-decyl acrylate, or n-dodecyl acrylate, etc. can be used as monomers, and copolymers of monomers having functional groups such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, or itaconic acid, or monomers having hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, or 2-hydroxyethyl (meth)aryl ether can be more suitably used.

[0036] As the epoxy resin, an epoxy resin obtained by reacting an amine-modified epoxy resin with a carboxylic anhydride can be used. For example, an epoxy resin obtained by modifying 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, and dimer acid glycidyl ether with an amine such as isopropanolamine, monopropanolamine, monobutanolamine, monoethanolamine, diethylenetriamine, ethylenediamine, butylamine, propylamine, isophoronediamine, tetrahydrofurfurylamine, xylenediamine, hexylamine, nonylamine, triethylenetetramine, tetramethylenepentamine, or diaminodiphenyl sulfone and reacting it with a carboxylic anhydride such as succinic anhydride, itaconic anhydride, maleic anhydride, citraconic anhydride, phthalic anhydride, or trimellitic anhydride can be suitably used.

[0037] As the polyester resin, for example, a polyester resin obtained by reacting a dicarboxylic acid such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, succinic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid or citraconic acid with a diol such as ethylene glycol, 1,2 - propanediol, 1,3 - propanediol, 1,4 - butanediol, 1,5 - pentanediol, neopentyl glycol, 1,6 - hexanediol, triethylene glycol, dipropylene glycol or polyethylene glycol can be suitably used. In addition, a polyester resin obtained by graft polymerization of the above - mentioned polyester resin with acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid or methacrylic anhydride can also be used.

[0038] The resin may be a resin having an average particle size of 50 to 250 nm. Specifically, if the average particle size of the resin exceeds the upper limit value of the range, there is a problem of deterioration of the coating wetting performance. If the average particle size of the resin exceeds the lower limit value of the range, there is a problem of deterioration of the stability of the solution.

[0039] The metal phosphate may be a solid formed when an aqueous solution mainly composed of phosphoric acid and metal ions is dried, and can function as an adhesive in the insulating coating film. In one embodiment, the metal phosphate may be a metal phosphate of any one or more of 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.

[0040] In one embodiment, based on solids, the ratio of the resin to the metal phosphate may be from 1 / 9 to 1. Specifically, based on solids, the ratio of the metal phosphate to the resin may be from 9:1 to 5:5. If the ratio of the metal phosphate is too high relative to the ratio of the resin, there is a problem of deterioration of the mold in the punching process. If the ratio of the resin is too high, there is a problem of peeling of the coating containing the insulating coating composition after stress relief annealing.

[0041] The metal chloride can be added to cause the resin to coagulate. The resin is usually uniformly distributed in the coating during the heat - drying or curing process, so that it does not impart roughness to the surface, and there is a problem that it is difficult to improve the weldability. By adding the metal sulfate or the metal chloride to the resin, the ionic strength of the solution for forming the insulating coating composition can be increased.

[0042] Therefore, for the metal chloride, during the heating and drying or curing process of the solution used to form the insulating coating composition, when iron ions are released through reaction with the material surface, the ionic strength becomes high, and thus surface roughness can be imparted to the insulating coating composition through the aggregation of the resin particles.

[0043] In one embodiment, the metal chloride may be a substance that can dissolve in water to form ions and can form an insoluble coating by forming a salt after heating and curing or drying. In one embodiment, the metal chloride may include metal sulfates and metal nitrates. To form a salt, the metal chloride may include nitrate (-NO3), sulfide (-SO4), chloride (-Cl), or carbonate (-CO3).

[0044] In one embodiment, the metal chloride may include at least one of aluminum (Al), calcium (Ca), magnesium (Mg), strontium (Sr), zinc (Zn), and iron (Fe). Specifically, when the metal chloride contains the iron, it may be ferrous sulfate (FeSO4) or aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, or zinc sulfate.

[0045] In one embodiment, relative to 100 parts by weight of the total insulating coating composition, the metal chloride may be added in an amount in the range of 1 to less than 40 parts by weight based on solids. Specifically, the range may be in the range of 10 to 30 parts by weight.

[0046] If it exceeds the upper limit value of the range, the stability of the solution decreases, or the surface friction coefficient increases, and processing problems such as slit processing may occur. Moreover, the boiling point of the coating increases, and there is a problem of an increase in blow-holes when evaluating weldability. If it exceeds the lower limit value of the range, there is a problem that the improvement effect of weldability is difficult to expect.

[0047] Figure 1 An electrical steel sheet 100 according to an embodiment of the present invention is shown.

[0048] See Figure 1 , an electrical steel sheet 10 according to an embodiment of the present invention may include an electrical steel sheet substrate 100 and an insulating coating layer 200. For the electrical steel sheet 10, for example, the insulating coating layer 200 is coated on the electrical steel sheet substrate 100 on the surface of the non-oriented electrical steel sheet, so that characteristics such as material adhesion, corrosion resistance, punching property, insulation property, and weldability can be improved.

[0049] The base 100 of the electrical steel sheet can be a grain-oriented electrical steel sheet, on which a {100}<001> texture as a Goss texture is formed by an abnormal grain growth phenomenon called secondary recrystallization, so as to have good magnetic properties in the rolling direction, or it can be a non-grain-oriented electrical steel sheet, having uniform magnetic properties in all directions of the rolled sheet. Specifically, the base 100 of the electrical steel sheet according to an embodiment of the present invention can be a non-grain-oriented electrical steel sheet.

[0050] The insulating coating layer 200 is coated on the base 100 of the electrical steel sheet, and is formed by coating the aforementioned insulating coating composition on the base 100 of the electrical steel sheet and then drying. The insulating coating composition is the same within the scope not conflicting with the foregoing content.

[0051] In one embodiment, 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 within the scope not conflicting with the foregoing description, so the detailed description is omitted.

[0052] In one embodiment, the insulating coating layer 200 is coated on the surface of the base 100 of the electrical steel sheet and can be located in the direction from the surface of the base 100 of the electrical steel sheet to the outside of the electrical steel sheet 10. For the insulating coating layer 200, when a coating solution for forming the insulating coating is coated and in the drying step, when the coating solution reacts with the electrical steel sheet 10, a part of the Fe component contained in the base dissolves in the solution in an ionic form to form it.

[0053] 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.

[0054] <Formula 1>

[0055] 10 ≤ ((Coating thickness of the thickest part - Coating thickness of the thinnest part) / Average coating thickness) × 100≤ 40

[0056] According to Formula 1, the coating thickness difference rate represents, in percentage, the thickness difference between the thickest part and the thinnest part in the coating part with respect to the average coating thickness. The coating thickness difference rate may be in the range of 10 to 40.

[0057] If the range of the coating thickness difference rate exceeds the upper limit value too much, there is a problem of reduced gloss. If the range of the coating thickness difference rate exceeds the lower limit value too much, there is a problem of reduced weldability.

[0058] In one embodiment, the glossiness of the electrical steel sheet 10 may be 60 GU or more. The glossiness is measured at a measurement angle of 60°. If the glossiness is less than 60, there is a problem that the appearance of the electrical steel sheet 10 is not aesthetically pleasing.

[0059] In one embodiment, 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 value of the range, there are problems of a decrease in duty ratio and a decrease in weldability. If the surface roughness exceeds the lower limit value of the range, the cost has an upward trend during the cold rolling process, and there is also a problem of a decrease in weldability.

[0060] The method for preparing an insulating coating composition according to an embodiment of the present invention may include: mixing a resin containing an organic substance with a metal phosphate of at least one of Mg, Al, Ca, Sr, Mn, and Zn so that the ratio of the resin to the metal phosphate is 1 / 9 to 1 by solids content; and for the mixture obtained through the mixing step, adding, per 100 parts by weight of the mixture, a metal chloride of at least one of Mg, Al, Fe, Co, Mn, and Zn in an amount of 1 to less than 40 parts by weight by solids content. The resin, the metal phosphate, and the metal chloride are the same within the range not conflicting with the foregoing description, and thus detailed description thereof is omitted.

[0061] In the step of mixing a resin containing an organic substance with a metal phosphate of at least one of Mg, Al, Ca, Sr, Mn, and Zn so that the ratio of the resin to the metal phosphate is 1 / 9 to 1 by solids 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. Specifically, the metal phosphate may be aluminum phosphate, magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, or zinc phosphate. A detailed description thereof may be referred to the foregoing description of the insulating coating composition within the non-conflicting range.

[0062] In the step of adding, per 100 parts by weight of the mixture obtained through the mixing step, a metal chloride of at least one of Mg, Al, Fe, Co, Mn, and Zn in an amount of 1 to less than 40 parts by weight by solids content, the metal chloride may be added to cause coagulation of the specific 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. A detailed description thereof may be referred to the foregoing description of the insulating coating composition within the non-conflicting range.

[0063] Hereinafter, specific embodiments of the present invention will be described. However, the following embodiments are merely specific embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0064] Example 1

[0065] An non-oriented electrical steel sheet (150 50 mm) with a silicon (Si) content of 3.15 wt% and a plate thickness of 0.27 mm was used as a sample. A solution having the composition shown in Table 1 below was applied to the separately prepared samples using a bar coater and a roll coater, with a coating thickness of 0.4 to 0.6 μm. Then, it was kept in a drying furnace at 300 to 750 °C for 10 to 30 seconds, and then slowly cooled in air.

[0066] At this time, for the solution, an acrylic emulsion resin and aluminum phosphate (AlPO4, Al(H2PO4)3, Al2(HPO4)3) were mixed in a ratio of 3:7 to synthesize a solution for forming an insulating coating composition. When synthesizing the solution, 1% of ferrous sulfate (FeSO4) was added as an additive.

[0067] Example 2

[0068] 10% of ferrous sulfate (FeSO4) was added, and except for this, the implementation method was the same as that of Example 1.

[0069] Example 3

[0070] 30% of ferrous sulfate (FeSO4) was added, and except for this, the implementation method was the same as that of Example 1.

[0071] Example 4

[0072] The average particle size of the emulsion used was 50 μm, and except for this, the implementation method was the same as that of Example 1.

[0073] Example 5

[0074] The average particle size of the emulsion used was 100 μm, and except for this, the implementation method was the same as that of Example 1.

[0075] Example 6

[0076] The average particle size of the emulsion used was 250 μm, and except for this, the implementation method was the same as that of Example 1.

[0077] Example 7

[0078] As the type of the phosphate, magnesium phosphate (Mg3(PO4)2, Mg(HPO4), Mg(H2PO4)2) is used instead of aluminum phosphate, and the implementation is the same as that of Example 1 except for this.

[0079] Example 8

[0080] As the type of the phosphate, calcium phosphate (Ca3(PO4)2, Ca(HPO4), Ca(H2PO4)2) is used instead of aluminum phosphate, and the implementation is the same as that of Example 1 except for this.

[0081] Example 9

[0082] As the type of the phosphate, strontium phosphate (Sr3(PO4)2, Sr(HPO4), Sr(H2PO4)2) is used instead of aluminum phosphate, and the implementation is the same as that of Example 1 except for this.

[0083] Example 10

[0084] As the type of the phosphate, manganese phosphate (Mn3(PO4)2, Mn(HPO4), Mn(H2PO4)2) is used instead of aluminum phosphate, and the implementation is the same as that of Example 1 except for this.

[0085] Example 11

[0086] As the type of the phosphate, zinc phosphate (Zn3(PO4)2, Zn(HPO4), Zn(H2PO4)2) is used instead of aluminum phosphate, and the implementation is the same as that of Example 1 except for this.

[0087] Example 12

[0088] As the type of the inorganic additive, aluminum sulfate (Al2(SO4)3) is used instead of iron sulfate, and the implementation is the same as that of Example 1 except for this.

[0089] Example 13

[0090] As the type of the inorganic additive, calcium sulfate (CaSO4) is used instead of iron sulfate, and the implementation is the same as that of Example 1 except for this.

[0091] Example 14

[0092] As the type of the inorganic additive, magnesium sulfate (MgSO4) is used instead of iron sulfate, and the implementation is the same as that of Example 1 except for this.

[0093] Example 15

[0094] As the type of the inorganic additive, manganese sulfate (MnSO4) was used instead of iron sulfate, and except for this, the implementation was the same as that of Example 1.

[0095] Example 16

[0096] As the type of the inorganic additive, strontium sulfate (SrSO4) was used instead of iron sulfate, and except for this, the implementation was the same as that of Example 1.

[0097] Comparative Example 1

[0098] The iron sulfate (FeSO4) was not added, and except for this, the implementation was the same as that of Example 1.

[0099] Comparative Example 2

[0100] 40% of the iron sulfate (FeSO4) was added, and except for this, the implementation was the same as that of Example 1.

[0101] Comparative Example 3

[0102] 50% of the iron sulfate (FeSO4) was added, and except for this, the implementation was the same as that of Example 1.

[0103] Comparative Example 4

[0104] The average particle size of the emulsion used was 30 μm, and except for this, the implementation was the same as that of Example 1.

[0105] Comparative Example 5

[0106] The average particle size of the emulsion used was 300 μm, and except for this, the implementation was the same as that of Example 1.

[0107] For the following formula 1, the effects of the present invention were evaluated according to the foregoing examples and comparative examples. Specifically, solution stability, glossiness, material roughness, surface roughness, thickness difference rate, weldability, and adhesion after heat treatment were evaluated respectively.

[0108] The solution stability was measured by DLS Turbiscan, the glossiness was measured by a gloss meter, and the material roughness and surface roughness were measured by a roughness meter. For the thickness difference rate, the thickness difference between the thickest part and the thinnest part within 40 μm was proportionalized through SEM cross-section analysis. For the weldability, it was evaluated by visual inspection and cross-section inspection after TIG welding through a Lab experiment.

[0109] For the adhesion after heat treatment, the adhesion was evaluated using ASTM D3359 after heat treatment at 750 °C in a N2 atmosphere.

[0110] The evaluations of the weldability and the adhesion are expressed as excellent ( ) Excellent (○), Good (△), Ordinary (△), and Poor (×). For the weldability, when there are no blow holes during visual inspection and the diameter of blow holes in cross-section inspection is 0.1 mm or less, it is rated as excellent; when there are no blow holes during visual inspection and the diameter of blow holes in cross-section inspection is 0.2 mm or less, it is rated as good; when there are no blow holes during visual inspection and the diameter of blow holes in cross-section inspection exceeds 0.2 mm, it is rated as ordinary; when blow holes are observed during visual inspection, it is rated as poor.

[0111] For the adhesion after heat treatment, a rating of 5B or above is considered excellent, 4B is good, 3B is ordinary, and 2B or below is poor.

[0112]

Table 1

[0113]

[0114] As can be seen from Table 1 above, for Examples 1 to 3, there are differences in weldability and adhesion after heat treatment compared with Comparative Examples 1 to 3. For Examples 4 to 6, when the average particle size of the resin emulsion meets the scope of the present invention, the weldability and adhesion after heat treatment are excellent compared with Comparative Examples 4 and 5 where the average particle size of the resin emulsion does not meet the scope of the present invention. For Examples 7 to 11, when using magnesium phosphate, calcium phosphate, strontium phosphate, manganese phosphate, or zinc phosphate as the type of phosphate in addition to aluminum phosphate, very good effects are also achieved in terms of weldability and adhesion after heat treatment.

[0115] For Examples 12 to 17, when using aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, or zinc sulfate as the type of inorganic additive in addition to iron sulfate, very good effects are also achieved in terms of weldability and adhesion after heat treatment.

[0116] Figures 2a to 2d is a cross-sectional scanning electron microscope (SEM) image of an insulating coating based on the addition amount of metal sulfate according to an embodiment of the present invention. Specifically, Figure 2a is for Comparative Example 1 without the addition of iron sulfate, Figure 2b is for Example 1, Figure 2c is for Example 2, Figure 2d is a cross-sectional SEM image of the insulating coating for Example 3.

[0117] Figures 3a to 3d is a welded cross-sectional image of an electrical steel sheet coated with an insulating coating based on the addition amount of metal sulfate according to an embodiment of the present invention. Specifically, Figure 3ais Comparative Example 1 without the addition of iron sulfate, Figure 3b is Example 1, Figure 3c is Example 2, Figure 3d is a cross-sectional image of the welded portion of the electrical steel sheet coated with an insulating coating film in Example 3.

[0118] See Figures 2a to 2d and Table 1. For Examples 1 to 3, compared with Comparative Examples 2 and 3, the glossiness is excellent. Compared with Comparative Examples 1 to 3, the surface roughness also falls within the target range of the present invention. The percentage value of the difference between the thickest part and the thinnest part of the coating relative to the average coating thickness falls within the target range of the present invention.

[0119] Referring again to Table 1 above, regarding the results of evaluating the weldability of Examples 1 to 3, it can be confirmed that Example 1 is good (○), and Examples 2 and 3 are very good ( ). Compared with Examples 1 to 3, Comparative Example 1 has poor weldability (X), Comparative Example 2 is normal (△), and Comparative Example 3 is unmeasurable (-).

[0120] The present invention is not limited to the above-described embodiments and / or examples and can be prepared in various different ways. Those of ordinary skill in the technical field to which the present invention pertains can understand that the present invention can be implemented in other specific ways without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the above-described embodiments and / or examples are exemplary in all aspects and not restrictive.

[0121] Description of Reference Numerals

[0122] 10: Electrical steel sheet

[0123] 100: Electrical steel sheet substrate

[0124] 200: Insulating coating film layer

Claims

1. An insulating film coating composition, comprising: 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; and a metal chloride, wherein, based on 100 parts by weight of the total insulating film coating composition and on a solids basis, the metal chloride is 1 to less than 40 parts by weight.

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

3. The insulating film coating composition according to claim 1, wherein the metal chloride comprises at least one of iron sulfate (FeSO4), aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

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

5. The insulating film coating composition according to 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 electrical steel sheet, comprising: an electrical steel sheet substrate; and an insulating film coating layer coated on the electrical steel sheet substrate, wherein the insulating film coating layer comprises a resin; a metal phosphate of at least one of Mg, Al, Ca, Sr, Mn, and Zn; and at least one of a metal chloride of at least one of Al, Ca, Mg, Sr, Zn, and Fe, wherein, based on 100 parts by weight of the total insulating film coating composition and on a solids basis, the metal chloride is 1 to less than 40 parts by weight, and the coating thickness difference rate of the insulating film coating layer satisfies the following formula 1, <Formula 1> 10 ≤ ((coating thickness of the thickest part - coating thickness of the thinnest part) / average coating thickness) × 100 ≤ 40.

7. The electrical steel sheet according to claim 5, wherein at least one of the metal chlorides comprises at least one of iron sulfate (FeSO4), aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

8. The electrical steel sheet according to claim 5, having a glossiness of 60 GU or more.

9. The electrical steel sheet according to claim 5, having a surface roughness of 0.28 to 0.51 μm.

10. A method for preparing an insulating film coating composition, comprising: a step of mixing a resin containing an organic substance with a metal phosphate of at least one of Mg, Al, Ca, Sr, Mn, and Zn so that, based on a solids basis, the ratio of the resin to the metal phosphate is 1 / 9 to 1; and a step of adding, to the mixture obtained in the mixing step, 1 to less than 40 parts by weight, based on a solids basis, of a metal chloride of at least one of Al, Ca, Mg, Sr, Zn, and Fe, relative to 100 parts by weight of the mixture.

11. The method for preparing an insulating film coating composition according to claim 10, wherein the metal chloride comprises at least one of iron sulfate (FeSO4), aluminum sulfate, calcium sulfate, magnesium sulfate, manganese sulfate, strontium sulfate, and zinc sulfate.

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

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