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

Abstract

The present invention provides an insulating coating composition for grain-oriented electrical steel sheets, which contains a coating substance that prevents separation of the film from the substrate even in a high-temperature and high-humidity environment, and a method for producing the grain-oriented electrical steel sheets. [Solution] The present invention relates to a coating composition for grain-oriented electrical steel sheet, a grain-oriented electrical steel sheet containing the same, and a method for manufacturing grain-oriented electrical steel sheet. According to one embodiment of the present invention, the coating composition for grain-oriented electrical steel sheet contains a phosphate, silica, a nitrate, and an oxidizer, wherein the silica contains 50 to 400 parts by weight of solid content per 100 parts by weight of the phosphate, the blending ratio of the solid content of the silica to the solid content of the phosphate is 0.3 to 3.9, and the oxidizer contains 0.5 to 10.0 parts by weight of solid content per 100 parts by weight of the phosphate.

Description

[Technical Field]

[0001] The present invention relates to an electrical steel sheet, and more particularly to an insulating coating composition, a grain-oriented electrical steel sheet including the same, and a method for manufacturing the same. [Background technology]

[0002] Electrical steel sheets are used as materials for transformers, motors, and electrical equipment, and unlike general carbon steels, which emphasize workability such as mechanical properties, they are functional products that emphasize electrical properties, such as low iron loss, high magnetic flux density, high magnetic permeability, and high space factor.

[0003] The electrical steel sheets are further divided into grain-oriented electrical steel sheets and non-oriented electrical steel sheets. The grain-oriented electrical steel sheets are formed by utilizing the phenomenon of abnormal grain growth called secondary recrystallization to form a Goss structure ({110} <001> In contrast to this, non-oriented electrical steel sheets have uniform magnetic properties in all directions on the rolled sheet.

[0004] To ensure stability over time in grain-oriented electrical steel sheets, it is important to ensure physical properties such as surface roughness, gloss, color, and coating uniformity of the insulating coating after insulation coating. For example, grain-oriented electrical steel sheets must be durable in extremely high-temperature and humid environments, such as during SRA processing, and be more effective than existing products in extreme corrosion-resistant environments, while also ensuring heat resistance at high temperatures.

[0005] The grain-oriented electrical steel sheet generally has a coating structure consisting of an MgO coating on the base material and an insulating coating on the upper surface, which is generally made of phosphate, silica, and nitrate.

[0006] The general conditions for existing corrosion resistance are 5% NaCl, 60°C, and 8 hours. For automotive accessories that are used for long periods of time, the extreme conditions for corrosion resistance are 5% NaCl, 65°C, and 100 hours in salt spray. The general conditions for weather resistance are 98% moisture, 60°C, and 72 hours, but the extreme conditions for weather resistance are 98% moisture, 65°C, and 100 hours.

[0007] Although the general insulating coating has excellent corrosion resistance, it has the disadvantages of being weak in weather resistance and having a sticky surface, which can cause problems with adhesion when winding the wound coil.

[0008] Therefore, there is a current need to develop a chromium-free phosphate coating for grain-oriented electrical steel sheets that will not separate from the substrate even in humid environments, and an insulating coating composition that will solve the problem of the surface becoming sticky due to phosphate, making it vulnerable to humid environments. Summary of the Invention [Problem to be solved by the invention]

[0009] The technical problem to be solved by the present invention is to provide an insulating coating composition for grain-oriented electrical steel sheets, which contains a coating material that prevents separation of the film from the substrate even in a high-temperature and high-humidity environment.

[0010] Another technical problem to be solved by the present invention is to provide a grain-oriented electrical steel sheet coated with an insulating coating composition having the above-mentioned advantages.

[0011] Yet another technical problem to be solved by the present invention is to provide a method for manufacturing a grain-oriented electrical steel sheet having the above-mentioned advantages. [Means for solving the problem]

[0012] The insulating coating composition for grain-oriented electrical steel sheet of the present invention comprises a phosphate, silica, a nitrate, and an oxidizing agent, wherein the silica has a solid content of 50 to 400 parts by weight based on 100 parts by weight of the phosphate, the blending ratio of the solid content of the silica to the solid content of the phosphate is 0.3 to 3.9, and the oxidizing agent has a solid content of 0.5 to 10.0 parts by weight based on 100 parts by weight of the phosphate.

[0013] The nitrate may include at least one of aluminum nitrate (Al(NO3)3), cobalt nitrate (Co(NO3)2), calcium nitrate (Ca(NO3)2), strontium nitrate (Sr(NO3)2), zinc nitrate (Zn(NO3)2), manganese nitrate (Mn(NO3)2), magnesium nitrate (Mg(NO3)2), and silver nitrate (AgNO3).

[0014] The nitrates can include at least two of aluminum nitrate (Al(NO3)3), cobalt nitrate (Co(NO3)2), calcium nitrate (Ca(NO3)2), strontium nitrate (Sr(NO3)2), zinc nitrate (Zn(NO3)2), manganese nitrate (Mn(NO3)2), magnesium nitrate (Mg(NO3)2), and silver nitrate (AgNO3).

[0015] The nitrate may contain 5 to 100 parts by weight of solids based on 100 parts by weight of the phosphate. In one embodiment, the oxidizing agent may contain at least one of HClO4, NaClO, NaClO4, KMnO4, NaIO4, OsO4, H2O2, and Ca(ClO)2.

[0016] The grain-oriented electrical steel sheet of the present invention comprises an electrical steel sheet substrate and an insulating coating located on a surface of the electrical steel sheet substrate, the insulating coating comprising a phosphate, silica, a nitrate, and an oxidizing agent, the silica having a solid content of 50 to 400 parts by weight based on 100 parts by weight of phosphate, the blending ratio of the solid content of the silica to the solid content of the phosphate being 0.3 to 3.9, and the oxidizing agent having a solid content of 0.5 to 10.0 parts by weight based on 100 parts by weight of the phosphate.

[0017] The method for producing a grain-oriented electrical steel sheet of the present invention includes the steps of preparing an electrical steel sheet substrate, applying an insulating coating composition to a surface of the electrical steel sheet substrate, and curing the insulating coating composition, wherein the insulating coating composition includes a phosphate, silica, a nitrate, and an oxidizing agent, the silica having a solid content of 50 to 400 parts by weight based on 100 parts by weight of phosphate, the blending ratio of the solid content of the silica to the solid content of the phosphate being 0.3 to 3.9, and the oxidizing agent having a solid content of 0.5 to 10.0 parts by weight based on 100 parts by weight of the phosphate, and the step of curing the insulating coating composition is performed at a temperature in the range of 800 to 900°C for 30 to 180 seconds.

[0018] The step of applying the insulating coating composition to the surface of the electrical steel sheet substrate may include the steps of adding and mixing a phosphate and silica, adding a nitrate to the mixed solution, and then adding an oxidizer.

[0019] The step of preparing an electrical steel sheet substrate may include the steps of preparing a steel slab, heating the steel slab, hot-rolling the heated steel slab to manufacture a hot-rolled steel sheet, cold-rolling the hot-rolled steel sheet to manufacture a cold-rolled steel sheet, performing primary recrystallization annealing on the cold-rolled sheet, applying an annealing separator to the steel sheet that has been primarily recrystallized annealed, and performing secondary recrystallization annealing.

[0020] The step of applying the annealing separator to the steel sheet that has been subjected to the primary recrystallization annealing is carried out by applying the annealing separator in an amount of 1 to 5 g / m 2 The method may include applying the coating in a range of

[0021] The secondary recrystallization annealing step may include a soaking step and a temperature-raising step, the soaking step being performed in a range of 650 to 750°C, and the temperature-raising step being performed in a range of 1,100 to 1,250°C.

[0022] The temperature increasing step may be performed at a temperature increasing rate in the range of 10 to 20° C. / hr. The soaking step may be performed in an atmosphere of two or more gases selected from hydrogen gas, nitrogen gas, and an inert gas.

[0023] The temperature increase step may be carried out in a hydrogen atmosphere. [Effects of the Invention]

[0024] By adding an oxidizing agent to grain-oriented electrical steel sheet to remove hydrogen groups from phosphates, it is possible to provide an insulating coating composition for grain-oriented electrical steel sheet that has excellent durability in high-temperature, high-humidity environments, extreme corrosion resistance, and excellent heat resistance at temperatures that are extremely high in workability, such as SRA.

[0025] The grain-oriented electrical steel sheet of the present invention can be provided as a grain-oriented electrical steel sheet coated with the above-described insulating coating composition.

[0026] Furthermore, it is possible to provide a method for producing a grain-oriented electrical steel sheet having the above-mentioned advantages. DETAILED DESCRIPTION OF THE INVENTION

[0027] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight.

[0032] 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.

[0033] While the present invention may be embodied in various different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein, and that the invention may be embodied in various different forms, without departing from the spirit or scope of the present invention.

[0034] An insulating coating composition for grain-oriented electrical steel sheet according to one embodiment of the present invention may include a phosphate, silica, a nitrate, and an oxidizer. The phosphate is a metal phosphate and may satisfy M(H2PO4) or M(HPO4). M may include Mg, Al, Zn, Ca, or a combination thereof. For example, M may be a phosphate containing Mg and Al.

[0035] Silica is a necessary component for applying tension to the steel sheet and reducing iron loss. Phosphate acts as a binder for silica, improving the film-forming properties of the coating and improving the film adhesion. In one embodiment, silica may be a basic or acidic substance.

[0036] In one embodiment, the silica may contain 50 to 400 parts by weight of solids based on 100 parts by weight of the phosphate, specifically 80 to 200 parts by weight of the silica, more specifically 135 to 180 parts by weight, and even more specifically 145 to 160 parts by weight of the silica based on 100 parts by weight of the phosphate.

[0037] If the silica content exceeds the upper limit, it may be found to have poor stickiness or poor solution stability, whereas if the silica content exceeds the lower limit, it may be found to have insufficient tensioning effect on the steel sheet.

[0038] In one embodiment, the silica may have an average particle size in the range of 5 to 20 nm. If the average particle size of the silica exceeds the upper limit of this range, the surface area per unit mass decreases, slowing the condensation reaction rate. To increase the reaction rate, the heat treatment temperature must be increased, which is uneconomical. If the average particle size of the silica exceeds the lower limit of this range, the condensation reaction rate increases, causing aggregation, which can lead to color deviation defects on the surface.

[0039] In one embodiment, the 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 or more silica nanoparticles having different average particle sizes in order to form an insulating coating having excellent coating properties.

[0040] In one embodiment, the compounding ratio of the silica solid content to the phosphate solid content may be 0.3 to 3.9. Specifically, the compounding ratio may be 0.5 to 2.0. By compounding silica and phosphate at this compounding ratio, excellent adhesion to the base material can be achieved during the production of electrical steel sheets, and the advantages of excellent heat resistance, weather resistance, and corrosion resistance can be achieved.

[0041] In terms of the compounding ratio, if the ratio of phosphate is too high, there is a problem that durability decreases in hot and humid environments, and if the ratio of silica is too high, there is a problem that adhesive strength to the base material decreases.

[0042] The nitrate may be responsible for corrosion resistance and weather resistance. In one embodiment, the nitrate may be any one of aluminum nitrate (Al(NO3)3), cobalt nitrate (Co(NO3)2), calcium nitrate (Ca(NO3)2), strontium nitrate (Sr(NO3)2), zinc nitrate (Zn(NO3)2), manganese nitrate (Mn(NO3)2), magnesium nitrate (Mg(NO3)2), and silver nitrate (AgNO3).

[0043] In one embodiment, the nitrate may contain 5 to 100 parts by weight of solids based on 100 parts by weight of the phosphate. Specifically, the nitrate may contain 15 to 80 parts by weight of solids based on 100 parts by weight of the phosphate, more specifically 20 to 60 parts by weight of solids, even more specifically 22 to 51 parts by weight of solids, and even more specifically 22 to 28 parts by weight of solids.

[0044] If the nitrate content exceeds the upper limit of the range, there is a fire hazard. If the nitrate content exceeds the lower limit of the range, there is a weathering problem.

[0045] The oxidizing agent can function as an additive for removing hydrogen groups (H) from phosphates such as M(H2PO4) or M(HPO4). By removing hydrogen groups from phosphates, the oxidizing agent can remove H from sticky phosphates such as M(H2PO4) or M(HPO4) and allow them to react with non-sticky M(PO4).

[0046] In one embodiment, the oxidizing agent can include at least one of HClO, NaClO, NaClO, KMnO, NaIO, OsO, H2O, and Ca(ClO). The oxidizing agent can include oxidizing phosphate to remove hydrogen groups, as described above.

[0047] In one embodiment, the oxidizing agent may contain 0.5 to 10.0 parts by weight of solids based on 100 parts by weight of the phosphate. The oxidizing agent may contain 0.8 to 5.0 parts by weight, more specifically 1.0 to 3.0 parts by weight, based on 100 parts by weight of the phosphate. By including the oxidizing agent in the above range, there is an advantage that the stickiness caused by the phosphate is reduced.

[0048] If the oxidizing agent content exceeds the upper limit of the range, the anti-stickiness and solution stability may be deteriorated, whereas if the oxidizing agent content exceeds the lower limit of the range, the advantage of adding the oxidizing agent, i.e., reducing stickiness, may not be realized.

[0049] In one embodiment, the silica may be an acidic material. If a basic material is used as the silica, the phosphate and nitrate may not be stable and may gel.

[0050] According to another embodiment of the present invention, a grain-oriented electrical steel sheet includes an electrical steel sheet substrate and an insulating coating disposed on the surface of the electrical steel sheet substrate. The insulating coating includes phosphate, silica, nitrate, and an oxidizer. The detailed descriptions of the phosphate, silica, nitrate, and oxidizer are the same as those of the insulating coating composition described above to the extent that they do not contradict.

[0051] According to yet another embodiment of the present invention, a method for manufacturing a grain-oriented electrical steel sheet includes the steps of preparing an electrical steel sheet substrate, applying an insulating coating composition to a surface of the electrical steel sheet substrate, and curing the insulating coating composition.

[0052] The step of preparing an electrical steel sheet substrate may include the steps of preparing a steel slab, heating the steel slab, hot-rolling the heated steel slab to manufacture a hot-rolled steel sheet, cold-rolling the hot-rolled steel sheet to manufacture a cold-rolled steel sheet, performing primary recrystallization annealing on the cold-rolled sheet, applying an annealing separator to the steel sheet that has been primarily recrystallized annealed, and performing secondary recrystallization annealing.

[0053] In the step of heating the steel slab, the steel slab may be heated at a temperature of 1,300°C or less. When the steel slab is heated within the above temperature range, the columnar crystal structure of the slab is prevented from growing coarsely, thereby preventing cracks from occurring in the plate during the hot rolling process. Specifically, the step of heating the steel slab may be heated at a temperature of 1,050 to 1,300°C.

[0054] The heated steel slab can then be hot-rolled to produce a hot-rolled steel sheet. The hot-rolling temperature is not limited, and in one example, the hot-rolling can be completed at a temperature of 950°C or less.

[0055] In one embodiment, after the step of producing the hot-rolled steel sheet, a step of annealing the hot-rolled steel sheet may be performed. The step of annealing the hot-rolled steel sheet may homogenize the non-uniform microstructure and precipitates of the hot-rolled steel sheet. Specifically, the step of annealing the hot-rolled steel sheet may be performed at a temperature in the range of 800 to 1,300°C.

[0056] Thereafter, the hot-rolled steel sheet may be cold-rolled to produce a cold-rolled steel sheet. The cold-rolling may be performed in one cold rolling step or in two or more cold rolling steps including intermediate annealing.

[0057] Thereafter, the cold-rolled steel sheet may be subjected to primary recrystallization annealing. At this time, the primary recrystallization annealing may include a decarburization step and a nitriding step. The decarburization step and the nitriding step may be performed in any order. For example, the decarburization step may be followed by the nitriding step, or the decarburization step may be performed after the nitriding step.

[0058] In one embodiment, the cold-rolled steel sheet obtained by cold rolling may be subjected to decarburization annealing and nitriding simultaneously to cause primary recrystallization. Specifically, the decarburization and nitriding steps may be performed simultaneously. The nitriding step is for nitriding within the steel sheet, and is a step of introducing nitrogen ions into the steel sheet, thereby precipitating precipitates such as (Al, Si, Mn)N or AlN, which act as grain growth inhibitors. After the nitriding step, the grain-oriented electrical steel sheet may be nitrided to have a nitrogen content of 0.01% or less.

[0059] In the primary recrystallization annealing step, the annealing temperature can be within the range of 800 to 950°C. If the annealing temperature exceeds the upper limit of the range, the recrystallized grains grow coarsely, reducing the driving force for crystal growth and preventing stable secondary recrystallization. If the annealing temperature exceeds the lower limit of the range, the decarburization takes an excessively long time.

[0060] The primary recrystallization annealing may be performed in a nitrogen, hydrogen, or mixed gas atmosphere. For example, the gas atmosphere may be an ammonia gas atmosphere. The gas atmosphere may be a wet atmosphere or a dry atmosphere.

[0061] After the step of primary recrystallization annealing, an annealing separator may be applied to the steel sheet. For example, an annealing separator containing MgO as a main component may be used. In one embodiment, in the step of applying the annealing separator, the amount of the annealing separator applied is 1 to 5 g / m. 2 may be carried out within the range of

[0062] If the amount of annealing separator applied exceeds the upper limit of the range, secondary recrystallization may be adversely affected, whereas if the amount of annealing separator applied exceeds the lower limit of the range, a coating may not be formed smoothly.

[0063] The stage where secondary recrystallization annealing is performed is the {110} <001> The formation of a texture and the formation of a glassy film by the reaction between the oxide layer formed during primary recrystallization annealing and MgO provide insulation and remove impurities that impair magnetic properties.

[0064] In one embodiment, the secondary recrystallization annealing step may include a soaking step and a temperature-raising step. The soaking step may be performed in a range of 650 to 750°C, and the temperature-raising step may be performed in a range of 1,100 to 1,250°C. If the temperature exceeds this range, it may be difficult to form an appropriate coating.

[0065] In one embodiment, the temperature-raising step may be carried out at a temperature-raising rate in the range of 10 to 20° C. / hr. Specifically, the temperature-raising rate may be in the range of 13 to 17° C. / hr.

[0066] If the heating rate exceeds the upper limit of the range, there is a problem that the coating film is decomposed due to decomposition of the phosphate, and if the heating rate exceeds the lower limit of the range, there is a problem that the silica is not cured, resulting in deterioration of corrosion resistance and weather resistance.

[0067] In one embodiment, the soaking step may be performed in an atmosphere of at least two gases selected from the group consisting of hydrogen gas, nitrogen gas, and an inert gas. In another embodiment, the heating step may be performed in a hydrogen gas atmosphere. Specifically, in a method of secondary recrystallization annealing, a heating step before secondary recrystallization occurs is performed in a mixed gas of nitrogen and hydrogen to protect nitrides, which act as grain growth inhibitors, and thereby promote the development of secondary recrystallization. After secondary recrystallization is completed, the soaking step is performed in a 100% hydrogen atmosphere for a long period of time to remove impurities.

[0068] In one embodiment, the step of applying an insulating coating composition to a surface of an electrical steel sheet substrate includes the steps of adding and mixing a phosphate and silica, adding a nitrate to the mixed solution, and then adding an oxidizer. The phosphate, silica, nitrate, and oxidizer may be the same as those described above for the insulating coating composition to the extent that they are consistent.

[0069] In one embodiment, the step of curing the insulating coating may be performed at a temperature in the range of 800 to 900°C. If the temperature exceeds the upper limit of the temperature range, the weather resistance and corrosion resistance of the insulating coating may be reduced. If the temperature exceeds the lower limit of the temperature range, the silica sol may not harden, resulting in problems with corrosion resistance and weather resistance.

[0070] In one embodiment, the step of curing the insulating coating may be performed for a time period of 30 to 240 seconds, specifically, for a time period of 45 to 180 seconds.

[0071] If the time exceeds the upper limit, the phosphate may be decomposed, whereas if the time exceeds the lower limit, the corrosion resistance and weather resistance may be deteriorated due to the remaining uncured.

[0072] 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]

[0073] Experimental Examples 1-8 To prepare an insulating coating composition for grain-oriented electrical steel sheet according to the present invention, an aluminum and magnesium phosphate solution containing 67% phosphate solids and having the contents shown in Table 1 below was prepared, and then a colloidal silica solution containing 30% solids and having the contents shown in Table 1 below was added and mixed.

[0074] Next, a nitrate solution with a 50% solids content, such as aluminum nitrate or magnesium nitrate, corresponding to the conversion coating material, having the contents shown in Table 1 below, was added, followed by an oxidizer with a 50% solids content, such as HClO, NaClO, or NaClO, having the contents shown in Table 1 below, to prepare an insulating coating composition solution with the composition shown in Table 1 below. The prepared insulating coating composition was applied to an MgO-treated steel sheet. The solution was then dried at 700 to 950°C for 30 to 240 seconds, and the stickiness, weather resistance, heat resistance, corrosion resistance, and solution stability were evaluated.

[0075] The stickiness, weather resistance, heat resistance, corrosion resistance, and solution stability were evaluated by the following methods.

[0076] <Evaluation method> Anti-sticky rating Anti-stickiness is evaluated to assess the degree of stickiness. Test 1 was conducted using a ball diameter of 12.7 mm, a pressure load of 50 N, a rotation speed of 50 rpm, a rotation radius of 15 mm, and a slip distance of 200 m. To compare the amount of wear according to the slip distance, the same load and rotation speed as Test 1 were used, but the rotation radius was changed to 10 mm and the slip distance was changed to 10 m. Stickiness was evaluated as the coefficient of friction. The coefficient of friction was calculated as the friction force against the normal load (friction force / normal load). A coefficient of friction of less than 0.4 was considered good, and a coefficient of friction of 0.4 or higher was considered bad, and an "NG" was displayed.

[0077] Coating evaluation The evaluation was carried out with the naked eye, and if there were no stains and the product was in good condition, it was marked as "OK", and if there were stains and the product was poor, it was marked as "NG".

[0078] Weather resistance evaluation Weather resistance was evaluated under conditions of 98% moisture, 60°C, and 72 hours, with good results indicated as "OK" and poor results indicated as "NG."

[0079] Heat resistance evaluation For heat resistance evaluation, the specimen was heated at 560°C under conditions of 20% hydrogen and 80% nitrogen for 2 hours. After that, a CROSS-HATCH CUT test confirmed that the specimen had a hardness of 5B or higher.

[0080] If the test result was 5B or higher, it was deemed good and was marked as "OK," and if it was less than 5B, it was deemed bad and was marked as "NG."

[0081] Corrosion resistance evaluation A salt spray test was conducted using 5% NaCl, 100 RH, 65°C, and 8 hours.

[0082] Solution stability evaluation

[0083] Dissolve a 2x2cm coated plate in 100ml of 10% NaOH, then filter. The undissolved powder is PO4. Measure the weight of the powder remaining in the filter. If powder is present, it means that the HPO4 has been removed by the oxidizer.

[0084] Cl tracking method: After dissolving a 2x2cm coating in 100mL of 10% NaOH, if Cl components are present in the solution, it is considered that Cl has been added.

[0085] [Table 1]

[0086] As shown in Table 1 above, comparing Experimental Examples 1 and 2 to 4, it was confirmed that when an oxidizing agent such as HClO4, NaClO, or NaClO4 was additionally added, the stickiness resistance, weather resistance, corrosion resistance, and solution stability were good, while when no oxidizing agent was added, the stickiness resistance, weather resistance, and corrosion resistance were poor.

[0087] Furthermore, in Experimental Examples 5 to 8, there is a difference compared to Experimental Examples 1 to 4 in that magnesium nitrate was used as the nitrate instead of aluminum nitrate, and it was confirmed that the same effect was obtained even when magnesium nitrate was used as the nitrate instead of aluminum nitrate.

[0088] Specifically, by adding an oxidizing agent, a hydrogen group can be removed from the oxidizing agent such as M(H2PO4) or M(HPO4) according to the following reaction formula:

[0089] [Reaction scheme] 2M X (HPO4) Y +NaClO→H2O+NaCl+M X (PO4) Y

[0090] The reaction formula confirmed that removal of hydrogen groups from phosphate salts improves anti-stickiness.

[0091] Experimental Examples 9-17 Insulation coating compositions were produced and evaluated in the same manner as in Experimental Examples 1 to 8, except that the composition of the insulation coating composition for grain-oriented electrical steel sheet was controlled within the content ranges shown in Table 2 below, and aluminum nitrate was used as the nitrate and HClO was used as the oxidizing agent.

[0092] [Table 2]

[0093] As shown in Table 2 above, it was confirmed that when an oxidizing agent, HClO4, was added as in Experimental Examples 9 to 12, the anti-stickiness was improved and the stickiness was not observed compared to Experimental Example 13, in which no oxidizing agent was added. In addition, it was confirmed that when an excessive amount of oxidizing agent was added, the solution stability was poor, as in Experimental Example 12. Furthermore, by comparing Experimental Examples 9 to 11 with Experimental Examples 14 to 17, it was confirmed that when the silica content was excessively high and the compounding ratio of phosphate to silica exceeded the target compounding ratio of the present invention, the anti-stickiness or solution stability was poor.

[0094] Experimental Examples 18-26 In Experimental Examples 18 to 26, insulating coating compositions for grain-oriented electrical steel sheets were produced and evaluated in the same manner as in Experimental Examples 1 to 8, except that the composition of the insulating coating compositions was controlled to fall within the content ranges shown in Table 3 below.

[0095] [Table 3]

[0096] As shown in Table 3 above, when comparing Experimental Examples 18 to 20, in which an oxidizing agent, HClO4, was added, with Experimental Example 22, in which no oxidizing agent was added, it was confirmed that Experimental Example 22 had anti-stickiness and was not sticky. Furthermore, it was confirmed that when an excessive amount of oxidizing agent was added, exceeding the compounding ratio of phosphate to silica according to the present invention, as in Experimental Examples 23 to 26, the anti-stickiness or solution stability was poor.

[0097] Experimental Examples 27-36 In Experimental Examples 27 to 36, insulating coating compositions for grain-oriented electrical steel sheets were produced and evaluated in the same manner as in Experimental Examples 1 to 9, except that the composition of the insulating coating composition for grain-oriented electrical steel sheets was controlled within the content ranges shown in Table 4 below, magnesium nitrate was added in addition to aluminum nitrate as the nitrate, and HClO was used as the oxidizing agent.

[0098] [Table 4]

[0099] As shown in Table 4 above, in Experimental Examples 29, 31, 32, 34, and 35, when magnesium nitrate and aluminum nitrate were added simultaneously as nitrates and HClO4 was included as an oxidizing agent, it was confirmed that the anti-stick properties were better than those of Experimental Example 33, which did not include an oxidizing agent.

[0100] In addition, it was confirmed that when the content of the oxidizing agent was too high or too low, as in Experimental Examples 27 and 28, the anti-stickiness or solution stability was poor.

[0101] In addition, Experimental Example 30 confirmed that when the total amount of magnesium nitrate and aluminum nitrate was 1 g and the content of nitrate was too low, the anti-stickiness was poor.

[0102] In addition, it was confirmed that when the content of the oxidizing agent was too high, as in Experimental Example 36, the anti-stickiness and solution stability were poor.

[0103] Experimental Examples 37-47 - Curing Temperature Test Table 5 below shows the evaluation of the stickiness resistance, weather resistance, and corrosion resistance of insulating coating compositions for grain-oriented electrical steel sheets of the same composition when the curing temperature and curing time were adjusted as shown in Table 4 below.

[0104] [Table 5]

[0105] As shown in Table 5 above, it was confirmed that Experimental Examples 38 to 40, in which the curing temperature was within the range of the present invention under the curing conditions, had better stickiness resistance, weather resistance, and corrosion resistance than Experimental Examples 37 and 41, in which the curing temperature exceeded the range of the present invention. Looking at Experimental Examples 42 to 47, it was confirmed that Experimental Examples 42 to 45, in which the curing time was within the range of the present invention under the curing conditions, had good stickiness resistance, weather resistance, and corrosion resistance, but Experimental Examples 46 and 47, in which the curing time exceeded the range of the present invention, were poor in at least one of stickiness resistance, weather resistance, and corrosion resistance.

[0106] 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.

Claims

1. phosphates, silica, Nitrates, and Contains an oxidizing agent, The silica contains 50 to 400 parts by weight of a solid content based on 100 parts by weight of the phosphate, a blending ratio of the solid content of the silica to the solid content of the phosphate is 0.3 to 3.9; The insulating coating composition for grain-oriented electrical steel sheets is characterized in that the oxidizing agent contains 0.5 to 10.0 parts by weight of solid content based on 100 parts by weight of the phosphate.

2. The nitrate is aluminum nitrate (Al(NO ３ ) ３ ), cobalt nitrate (Co(NO ３ ) ２ ), calcium nitrate (Ca(NO ３ ) ２ ), strontium nitrate (Sr(NO ３ ) ２ ), zinc nitrate (Zn(NO ３ ) ２ ), manganese nitrate (Mn(NO ３ ) ２ ), magnesium nitrate (Mg(NO ３ ) ２ ), and silver nitrate (AgNO ３ 2. The insulating coating composition for grain-oriented electrical steel sheet according to claim 1, further comprising at least one of the following:

3. The nitrate is aluminum nitrate (Al(NO ３ ) ３ ), cobalt nitrate (Co(NO ３ ) ２ ), calcium nitrate (Ca(NO ３ ) ２ ), strontium nitrate (Sr(NO ３ ) ２ ), zinc nitrate (Zn(NO ３ ) ２ ), manganese nitrate (Mn(NO ３ ) ２ ), magnesium nitrate (Mg(NO ３ ) ２ ), and silver nitrate (AgNO ３ 3. The insulating coating composition for grain-oriented electrical steel sheet according to claim 2, wherein the insulating coating composition contains at least two of the following:

4. 2. The insulating coating composition for grain-oriented electrical steel sheet according to claim 1, wherein the nitrate contains 5 to 100 parts by weight of solid content based on 100 parts by weight of the phosphate.

5. The oxidizing agent is HClO ４ , NaClO, NaClO ４ , KMnO ４ , NaIO ４ , OsO ４ , H ２ O ２ , Ca(ClO) ２ 2. The insulating coating composition for grain-oriented electrical steel sheet according to claim 1, comprising at least one of the following:

6. an electromagnetic steel sheet substrate; an insulating coating located on a surface of the electrical steel sheet substrate, the insulating coating includes a phosphate, a silica, a nitrate, and an oxidizer; The silica contains 50 to 400 parts by weight of solids based on 100 parts by weight of phosphate, a blending ratio of the solid content of the silica to the solid content of the phosphate is 0.3 to 3.9; The oxidizing agent contains 0.5 to 10.0 parts by weight of solid content based on 100 parts by weight of the phosphate.

7. Providing an electromagnetic steel sheet substrate; applying an insulating coating composition to a surface of the electrical steel sheet substrate; and curing the insulating coating composition. the insulating coating composition comprises a phosphate, silica, a nitrate, and an oxidizer; the silica contains 50 to 400 parts by weight of solid content based on 100 parts by weight of the phosphate, the blending ratio of the solid content of the silica to the solid content of the phosphate is 0.3 to 3.9, and the oxidizing agent contains 0.5 to 10.0 parts by weight of solid content based on 100 parts by weight of the phosphate, The method for manufacturing a grain-oriented electrical steel sheet, wherein the step of curing the insulating coating composition is carried out at a temperature of 800 to 900° C. for 30 to 180 seconds.

8. 8. The method for manufacturing a grain-oriented electrical steel sheet according to claim 7, wherein the step of applying the insulating coating composition to the surface of the electrical steel sheet substrate comprises the steps of adding and mixing a phosphate and silica, adding a nitrate to the mixed solution, and then adding an oxidizer.

9. The step of preparing an electromagnetic steel sheet substrate includes: preparing a steel slab; heating the steel slab; hot rolling the heated steel slab to produce a hot-rolled steel sheet; cold-rolling the hot-rolled steel sheet to produce a cold-rolled steel sheet; A step of subjecting the cold-rolled sheet to primary recrystallization annealing; Applying an annealing separator to the steel sheet that has been subjected to primary recrystallization annealing; The method for manufacturing a grain-oriented electrical steel sheet according to claim 7, further comprising the step of performing secondary recrystallization annealing.

10. The step of applying the annealing separator to the steel sheet that has been subjected to the primary recrystallization annealing includes applying the annealing separator in an amount of 1 to 5 g / m ２ The method for manufacturing a grain-oriented electrical steel sheet according to claim 9, further comprising the step of applying the coating material in a range of

11. The secondary recrystallization annealing step includes a soaking step and a temperature rising step, 10. The method of claim 9, wherein the soaking step is performed in a temperature range of 650 to 750°C, and the heating step is performed in a temperature range of 1,100 to 1,250°C.

12. The method for manufacturing a grain-oriented electrical steel sheet according to claim 11, wherein the temperature increasing step is performed at a temperature increasing rate in the range of 10 to 20° C. / hr.

13. The method of manufacturing a grain-oriented electrical steel sheet according to claim 11, wherein the soaking step is performed in an atmosphere of two or more gases selected from the group consisting of hydrogen gas, nitrogen gas, and an inert gas.

14. The method for manufacturing a grain-oriented electrical steel sheet according to claim 11, wherein the temperature increasing step is performed in a hydrogen atmosphere.

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