KR100762466B1 - Coating solution for forming insulating film with excellent film close adhesion property and film intensity without cr and a method for making the insulation film on non-oriented electrical steel sheet by using it - Google Patents

Abstract

A chrome-free coating composition for forming a dielectric film is provided to form an eco-friendly coating layer on a non-oriented electric steel sheet, and to obtain improved adhesion and strength of a coating layer before and after stress relief annealing(SRA). A chrome-free coating composition for forming a dielectric film having excellent anticorrosive property and adhesion after SRA comprises: a phosphate solution containing aluminum phosphate and zinc phosphate mixed in a ratio of 1:1 and having a solid content of 60 wt%; and based on 100g of the phosphate solution, 0.5-5g of a solid material containing cobalt hydroxide and strontium hydroxide mixed in a ratio of 1:1; 100-300g of an epoxy emulsion resin having a solid content of 20 wt%; 3-10g of aluminum having a solid content of 20%; and 0.1-6g of a Ti-based chelating agent.

Description

COSTING SOLUTION FOR FORMING INSULATING FILM WITH EXCELLENT FILM CLOSE ADHESION PROPERTY AND FILM INTENSITY WITHOUT Cr AND A METHOD FOR MAKING THE INSULATION FILM ON NON-ORIENTED ELECTRICAL STEEL SHEET BY USING IT}

1 is a chemical formula of colloidal silica-aluminum phosphate for explaining the present invention.

The present invention relates to the production of non-oriented electrical steel sheet, and in particular, it does not contain chromium, it is excellent in film adhesion after the formation of the insulation coating, and also excellent in film strength after stress relief annealing (SRA), punchability, weldability And a coating composition for forming an insulating film having excellent coating adhesiveness and film strength before and after stress relief annealing, which also improves coating properties such as adhesion, adhesion ratio, appearance, and the like, and a method of forming an insulating coating of a non-oriented electrical steel sheet using the same. .

Generally, non-oriented electrical steel sheet is used for iron core of electric motor or generator, and it is necessary to perform SRA to improve magnetic characteristics after punching, and SRA when cost loss due to heat treatment is greater than magnetic characteristics effect by SRA. It is divided into two forms that omit.

In this case, forming an insulating film on the non-oriented electrical steel sheet corresponds to the finishing manufacturing process of the product, and in addition to the electrical properties that suppress the generation of eddy currents, wear of the mold when forming a core by laminating a large number after punching into a predetermined shape. After the SRA process to restore the magnetic properties by removing the processing stress of the steel sheet and removing the processing stress of the steel sheet, the basic characteristics such as sticky property, which does not adhere to the steel cores, and the excellent coating workability of the coating agent Stability that can be used for a long time is also required.

However, as the use of small electric motors has been expanded, the coating performance, which is more favorable for workability, weldability, and corrosion resistance than insulation, has been evaluated as the main physical properties. Asked.

As a result, in order to reinforce the heat resistance and insulation of the insulating film for non-oriented electrical steel sheet, an organic-inorganic composite coating material having been developed to compensate for the inorganic defects such as phosphate and chromate was developed. No. 31208 and US Pat. Nos. 4,316,751, 4,498,936 and the like.

In addition, Japanese Patent No. 50-15013 discloses a high viscosity ratio and excellent adhesion by forming an insulating coating using a treatment liquid containing a dichromate, an organic resin emulsion such as vinyl acetate, butadiene-styrene copolymer, and an acrylic resin as a main component. A method of forming an insulating coating, which protects the coating properties such as the punching property, and the like, and in which good coating properties are obtained even after SRA, has been proposed.

However, the conventional coating liquid (coating solution) exemplified above is essential in that chromium oxide is contained, and thus its use is limited in view of the fact that environmental regulations are being strengthened.

Therefore, the chromium-free coating of electrical steel sheet coating material (coating agent) is actively progressed, and a method of introducing phosphate to reinforce corrosion resistance and weakening of adhesion due to lack of chromate and a method of inducing a barrier effect by introducing colloidal silica. It can be divided into.

As described in Japanese Patent Laid-Open No. 2004-322079, the adhesion and corrosion resistance are improved by using a phosphate mixed with Al, Ca, and Zn phosphates properly, or the free phosphate present in the metal phosphate when metal phosphate is used. It can cause stickyness of the film, but Japanese Patent Laid-Open No. 11-131250, Korean Patent No. 1999-26912 discloses a technique of adding an organic acid and a silane coupling agent to prevent the stickyness of such free phosphoric acid. .

On the other hand, as a representative example of the increase in the barrier effect by the addition of the latter colloidal silica, as shown in Korean Patent No. 1999-26911, Japanese Patent No. 3370235, colloidal silica, alumina sol, zirconium oxide one kind or a mixture of two or more kinds It has been proposed a technique to secure corrosion resistance, adhesion and smoothness after SRA by using the prepared inorganic material, and to improve adhesion and solvent resistance by adding a silane coupling agent or the like.

In addition, when the ratio of the surface area of the resin and the silica is appropriate, a technique of improving adhesion and corrosion resistance due to the formation of a fine dispersed film structure has been introduced through Japanese Patent No. 3320983.

However, the Cr-free coatings mainly based on the phosphate or colloidal silica described above have limitations on the stickyness of the phosphate and the corrosion resistance improvement of the colloidal silica, respectively. Is still difficult to commercialize.

In addition, when a non-oriented electrical steel sheet is used for the iron core of a motor or a transformer, the product is punched according to the standard, and then a certain amount of sheets are stacked and welded or bonded to become the iron core.

In such work, SRA may be performed in some cases, and in the case where the SRA process is involved, adhesion, insulation, corrosion resistance, etc., after annealing become important.

In general, non-oriented electrical steel sheet insulation contains chromium, in which case it helps a lot to improve the film properties after SRA.

However, in the case of the coating material which does not contain chromium, phosphate is introduced as a substitute for chromium. At this time, there is a problem of hygroscopicity due to the trace amount of free phosphoric acid remaining in the coating or adhesion during annealing.

The present invention was created in view of the limitations of the prior art as described above, and it was created to solve this problem. Also, it was found to be in the compatibility problem between epoxy resin and metal phosphate, which is the main component of the coating material, as a cause of the decrease in film strength after SRA, and included chromium oxide, which is the main component of the insulation coating agent (coating agent) of non-oriented electrical steel sheet. Instead of phosphate, water-soluble epoxy resins, and metal oxides, the organic-inorganic mixed composition is advantageous in terms of environment, and chromium-free stress relief annealing can improve the film adhesion and film strength before and after SRA. Coating composition for insulating film formation with excellent front and back film adhesion and film strength The main purpose is to provide a method for forming an insulating film of the non-oriented electrical steel sheet used.

The present invention relates to 100g of a phosphate solution having a solid content of 60% by weight in which the first aluminum phosphate and the first zinc phosphate are mixed 1: 1 in order to achieve the above technical problem; Solid mixed with cobalt hydroxide and strontium hydroxide in a ratio of 1: 1: 0.5 to 5 g, epoxy emulsion resin having a solid content of 20% by weight: 100 to 300 g, aluminum silicate having a solid content of 20% by weight: 3 to 10 g , Ti-based chelating additives: The technical characteristics of the coating composition for forming an insulating film excellent in the film adhesion and film strength before and after the stress relief annealing, which is added by adding 0.1 ~ 6g.

At this time, the first zinc phosphate has a solid content of 2.75M, 52.5%; The viscosity of the liquid mixture of the first aluminum phosphate and zinc phosphate is 30 to 70 cp, and the solid fraction (solid content ratio) is 60% by weight; The said epoxy resin has the characteristics that the molecular weight is 1-20,000, Tg (glass transition temperature) is 50-60 degreeC, and a solid fraction is 20 weight%.

In addition, the chelating additive of the Ti system is Triethanolamine titanate (triethanolamine titanate), Titanium 2,2,2-nitrilotrisethanolate (2-2-2 titanium nitrilotricetanolate), Mixture organic titanate and inorganic phophrous compounds (organic and inorganic) Titanate-porous composites).

In addition, the epoxy emulsion resin is characterized in that a part of the combined structural formula of bisphenol and epoxide is substituted with an acrylic group and kept in an emulsion state.

In addition, when the coating composition is applied to the surface of the non-oriented electrical steel sheet, the coating amount is applied so that the coating amount is in the range of 0.5 ~ 6.0 g / m ² per one side and then heat-treated for 10 to 50 seconds in the temperature range of 350 ~ 700 ℃ The technical features are also present in forming a film.

Hereinafter, a preferred embodiment according to the present invention will be described in more detail.

According to the present invention, the corrosion resistance of the coating agent (coating agent) and the decrease in adhesiveness after SRA are present in the coating as a free phosphoric acid after drying the film, and this free phosphoric acid absorbs moisture after forming the film to reduce corrosion resistance. Of course, due to the compatibility problem between the emulsion organic resin and the phosphate, the main component of the coating agent as a cause of the decrease in film adhesion after SRA, the first monophosphate (Al (H ₂ PO ₄ ) ₃ ) and the first zinc phosphate (Zn) (H ₂ PO ₄ ) ₂ ) Chromium is added to the coating (coating agent) by adding cobalt hydroxide (cobalt hydroxide) and strontium hydroxide (strontium hydroxide) to the mixed phosphate. It is to overcome the corrosion and adhesion that can occur when excluded and to improve the film adhesion after SRA.

For example, with respect to 100 g of the mixed phosphate (60% by weight of solids), 100-300 g of an epoxy emulsion resin having 20% by weight of solids, 3-10g of aluminum silicate having a 20% by weight of solids, and a chelate of the Ti system A coating agent (coating agent) containing 0.1 to 6 g of an additive was prepared, and the coating agent thus prepared was coated so as to be in a range of 0.5 to 6.0 g / m ² per side of the non-oriented electrical steel sheet, and then 350 to 700 ° C. Heat treatment for 10 to 30 seconds in the temperature range to form an insulating film can improve the corrosion resistance and film adhesion.

Here, the epoxy resin in an emulsion state, the molecular weight of 1 to 20,000, Tg (glass transition temperature) of 50 to 60 ℃, and the solid fraction of 20% by weight of the material is preferable, in particular of bisphenol and epoxide Although it is composed of a combination form, it is preferable that a part of the structural formula is substituted with an acryl group in order to exist in a water-soluble emulsion, and when the weight of the solid is less than 100 g, the fraction of phosphate is relatively high, which is advantageous for corrosion resistance, but it is sticky resistance and powder. There is a risk of precipitation, and when 300 g is used, corrosion resistance and compatibility are remarkably lowered, so it is preferably added in the above range.

In addition, the aluminum silicate is preferably using an aqueous alumina colloidal silica having a solid fraction of 20% by weight having a chemical formula as shown in Figure 1, which is improved in corrosion resistance due to the barrier effect by the crosslinking reaction of silica during drying When the aluminum phosphate functional group present in the silica increases the compatibility with the metal phosphate, which is the main component of the coating agent, when the solid content is less than 3 g, the film formation and corrosion resistance of the film decreases. It is preferable to add in the above range value because it causes.

In addition, the chelating additive of the Ti system is present in the coating material and serves as a crosslinking agent that ultimately connects the metal phosphate and the epoxy resin during drying of the coating material. In the above, since it shows the same reaction characteristic, it is preferable to add in the said range value.

At this time, in the present invention, a chelate additive of Ti system was introduced to improve the film adhesion after SRA. As the chelate additive of the Ti system used, Triethanolamine titanate (Tethanolamine titanate), Titanium 2 , 2,2-nitrilotrisethanolate (2-2-2 titanium nitrilotricetanolate), Mixture organic titanate and inorganic phophrous compounds.

Thus, when drying the coating containing metal phosphate and epoxy resin, the Ti chelate additive causes a special reaction between the metal phosphate and the epoxy resin to form a more rigid coating, and no foreign matter such as black ash remains after the SRA. Will not.

The chelate additive of the Ti system has the chemical structure shown in (A) of (Formula 1) below, and when (B) of epoxy resin (Formula 1) is present in the coating agent, it is shown in (Formula 1). As such, special chemical reactions occur.

In addition, the chelate additive of the Ti system will induce a chemical reaction such as (Formula 2) or (Formula 3) with one of the main components in the coating.

(Equation 1)

Ti (OR) ₄ [A] + (CH ₂ OCHCH ₃ ) _n [B] → Ti (OR) _3- (O-CH ₂ -CH-OR-CH ₃ ) _n

(Equation 2)

Ti (OR) ₄ + Al (OH ₂ PO ₃ ) ₃ → Ti (OR) ₃ -O-CH ₂ -O-Al (OH ₂ PO ₃ ) ₂ + H ₃ PO ₄

(Equation 3)

Ti (OR) ₄ + Zn (OH ₂ PO ₃ ) ₂ → Ti (OR) ₃ -O-CH ₂ -O-Zn (OH ₂ PO ₃ ) + H ₃ PO ₄

In summary, the present invention is to improve the corrosion resistance and film adhesion after SRA inferior when chromium oxide is excluded through the following method.

First, the first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and the first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) are preferably in a mixed form of 1: 1. Cobalt hydroxide (cobalt hydoroxide) and strontium hydroxide (strontium hydroxide) were added to ensure the heat resistance and compactness of the film, thereby improving the corrosion resistance.

At this time, the metal phosphate, as is well known, when introduced as a component of the coating agent (coating agent) serves as a binder of the coating material composed of an organic-inorganic composite component and the base steel sheet to improve the adhesion of the coating material as well as heat resistance It has an important role as an excellent film forming agent.

In addition, the phosphate solutions used in the coating material of the present invention have a 2.75 M, 52.5% solids in the case of the first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ), in addition to the first aluminum phosphate (Al (H ₂ PO ₄ )). The production method of ₃ ) is not limited, but the mixing ratio between them is very closely related to the viscosity related to the adhesion, and the solution viscosity according to the mixing ratio is shown in Table 1 below.

In addition, the phosphoric acid used in the preparation of the mixed hydrogen phosphate salt of the first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and the first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) is not particularly limited. It can be used in the concentration range, but the total solid content of the mixed solution is about 60% by weight.

Second, the surface hygroscopicity and post-SRA stickyness that can occur when using coatings containing phosphate were overcome by optimizing the mixing ratio of phosphate and resin and introducing cobalt hydroxide and strontium hydroxide. .

In other words, after surface coating using a coating agent (coating agent) containing a large amount of phosphate, the hygroscopicity or powdering by free phosphoric acid may appear.

Therefore, in order to reduce the surface defects caused by free phosphoric acid, pure phosphate and metal oxides must be prepared in an appropriate molar ratio, and the component ratio of phosphate in the coating material (coating agent) is very important.

In the present invention, as described above, the mixed solution (solid fraction) in which the first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and the first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) are mixed 1: 1. 60% by weight) based on the weight of the solid part with respect to 100g of cobalt hydroxide (cobalt hydroxide) and strontium hydroxide (strontium hydroxide) is added based on about 2% by weight.

As shown in Equation 4, cobalt hydroxide and strontium hydroxide replace the inhibitory function of free phosphoric acid by the reaction between chromium oxide and phosphoric acid. In addition, it contributes to improving the corrosion resistance by improving the compactness of the film.

(Equation 4)

CrO ₃ + 2H ₃ PO ₄ → Cr (PO ₄ ) ₂ + 6H ₂ O

Third, a chelate additive of Ti system was introduced to improve the film adhesion after SRA.

Usually, post SRA film strength is related to the compatibility of organic resins with metal phosphates. That is, if the compatibility between the organic resin and the metal phosphate is poor immediately after the coating agent (coating agent) production, fine phase separation or entanglement between the two components may occur.

After forming the film using the coating agent prepared in this way, the SRA process for about 2 hours at about 750 ℃, it can be observed that the foreign material such as black ash remains on the surface of the specimen. When manufacturing a motor or a compressor using the product, as well as clogging the water supply line of the cooling oil, as well as can have a fatal effect on the life of the product, in the present invention to solve this problem, the main coating of the coating agent using the chelate of the Ti system To solve the above problems by improving the compatibility of the organic resin and metal phosphate components and the adhesion between the coating agent and the material.

In general, the surface treatment method of the electrical steel sheet is greatly affected by the base material, in particular, the smaller the silicon content tends to lower the adhesion, this tendency is more pronounced for the film peeling after SRA.

On the other hand, chromium oxide is usually contained as a medicament for the insulation coating treatment to impart the required properties of the coating such as corrosion resistance. It is ideal to exclude use from the beginning of manufacturing insulation coating liquid since wastewater discharge may cause environmental problems and shortening of life due to abnormal wear of mold during punching due to residual chromium hexavalent.

In addition, metal phosphate is essential in the present invention in order to prevent corrosion and film denseness due to the exclusion of chromium oxide, for example, monobasic aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and zinc phosphate monobasic (Zn). (H ₂ PO ₄ ) ₂ ) mixed hydrogen phosphate salts.

At this time, in the present invention, various metal phosphates, that is, the first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and the first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ), and the first magnesium phosphate (Mg (H ₂ Various combinations are prepared for various metal phosphates such as PO ₄ ) ₂ ), mixed with epoxy resins, and subjected to corrosion resistance tests to test aluminum monophosphate (Al (H ₂ PO ₄ ) ₃ and zinc monophosphate (Zn (H)). ₂ PO ₄ ) ₂ ) is a mixed solution of 50/50, that is, a ratio of 1: 1, and the solid content at this time is 60% by weight, the viscosity of 30-70 cp is used, which is the best for corrosion resistance This is because it exhibits characteristics.

The reason for limiting the viscosity in this manner is that when the monoaluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) is high, the proper viscosity cannot be maintained and the sticky property after drying is exhibited; If the ratio of zinc monophosphate (Zn (H ₂ PO ₄ ) ₂ ) is high, the corrosion resistance is reduced and the desired purpose cannot be achieved, and thus the range of the viscosity is preferable, and particularly about 50 cp is most preferred.

However, when the phosphate is used in the coating agent, as mentioned above, surface sticky or powdery precipitation by free phosphoric acid is a problem.

Therefore, in the present invention, to solve this problem and to find a substance that substitutes the reaction of chromium oxide and free phosphoric acid as in the above (Equation 4), the effect was verified by applying a wide range of metal oxides or hydroxides, and as a result cobalt hydroxide The best efficiency was obtained by adding 0.5 ~ 5g, especially 2g, of a solid mixed with cobalt hydoroxide and strontium hydroxide in a solid weight ratio to about 0.5 g.

At this time, the reason for mixing the cobalt hydroxide (strobalium hydroxide) and strontium hydroxide (strontium hydroxide) in a ratio of 1: 1, while the increase in the ratio of cobalt hydroxide (cobalt hydoroxide) increases the corrosion resistance, Increasing the viscosity of the metal phosphate reduces the compatibility with the epoxy resin, another major component of the coating.Increasing the ratio of strontium hydroxide limits the corrosion resistance. Is added to 0.5 ~ 5g, especially 2g in the solid weight ratio to 100g of phosphate solution of 30-70 cp, especially 50 cp to improve the surface sticky (sticky), powder precipitation prevention and corrosion resistance.

In addition, the method for forming an insulating coating according to the present invention is applied to the coating composition, that is, the treatment liquid as described above on the surface of the non-oriented electrical steel sheet, so that the dry coating thickness, that is, the coating amount is in the range of 0.5 ~ 6.0 g / m ² per one side After heat treatment for 10 to 50 seconds in the temperature range of 350 ~ 700 ℃.

Here, the application amount is 0.5 g / m ² or less in insulation is a function of insulating coatings insignificant decrease, and 6.0 g / m ² or more when it is difficult to form a solid film to cracking due to the film drying problems and film weight of the excessive fabric.

In addition, the drying temperature of 350 ℃ or less is suspected that the drying of the phosphate in the component is suspected, and relatively above 700 ℃ is based on drying under the above temperature conditions due to the film color change due to deterioration of the organic emulsion in the component.

As a result, an insulation coating having excellent adhesion and corrosion resistance that the non-oriented electrical steel sheet insulation coating agent should have is formed.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

Si: 0.1% by weight, 0.50mm non-oriented electrical steel sheet (120 × 60 mm) as a test material, and various treatment liquids are applied thereon in a range of 0.5 to 6.0 g / m ² using a coating bar. It was.

In addition, the applied specimen was dried at 650 ° C. for several seconds and then air cooled.

Then, for evaluation, SRA was heat treated for 2 hours at 750 ° C under a dry 100% N ₂ gas atmosphere, and insulation was measured by the received current value when a current of 0.5 V and 1.0 A was input under 300 PSI pressure. The specimens before and after the SRA were measured with a minimum arc diameter without film peeling when they were bent 180 ° by contact with an arc of 10, 20, 30 ~ 100mm, and the appearance of the film was evaluated by visual observation of streaks and gloss.

In addition, the corrosion resistance was evaluated for 5 hours at 35 ℃, NaCl solution for 8 hours in the presence of rust generation in the present embodiment, the rust generation area is excellent when 5% or less, good when 20% or less, 20-50% days In case of a slight defect, more than 50% was marked as defective.

In addition, the film strength after SRA was quantified (%) using the image processing technique to determine the adhesion of the film peeling powder and the degree of contamination of the tape, which appeared when a certain amount of adhesive tape was attached to the film after the SRA.

For example, 0 means that there is no film peeling from the film surface after SRA, and 100 means that the entire tape area is contaminated with film peeling. Therefore, the higher this number, the poorer the film strength.

Table 1 below shows cobalt hydroxide and strontium hydroxide in 100 g of a mixture of aluminum monophosphate and zinc monophosphate having a solid content of 60% by weight in a 50/50 mixture (viscosity 30 to 70 cp, especially 50 cp). When a 50/50 mixed solid is added in a weight ratio of about 2 g, the coating agent is prepared by varying the amount of Ti chelate additive and colloidal silica, and the weight ratio of phosphate, solution, and epoxy resin is the stability of the mutual component. At 1: 2.1 level. In addition, Table 2 shows the characteristics of the coating after coating and drying the coating material thus prepared 2.5g / m ² .

Wherein Co.hy + St.hy means cobalt hydroxide + strontium hydroxide

In particular, Table 2 shows the coating (coating agent) prepared in the present invention, that is, the first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ added with cobalt hydroxide and strontium hydroxide) ) And 100 g of phosphate in a mixed form of zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) (60 wt% solids), 210 g of an epoxy emulsion resin having a 20 wt% solids ratio, and 0.5 to 5.0 g of aluminum silicate. , Ti-chelate (chelate) additive of 0.05 ~ 8.0g when the addition amount is different shows the change in corrosion resistance and film properties.

As shown in Table 2, mono-phosphate monophosphate having 60% by weight of solid content added with cobalt hydroxide and strontium hydroxide as in test materials 11-8 and 11-9 100 g of phosphate mixed with (Al (H ₂ PO ₄ ) ₃ ) and monophosphate (Zn (H ₂ PO ₄ ) ₂ ), 1.0 to 3.0 g of aluminum silicate, and 0.1 to 0.5 of a chelate additive of Ti system When g was added, it was confirmed that the corrosion resistance and the film adhesion were improved, which had an equivalent level or higher than that of the coating material (coating agent) of the conventional chromium-containing type.

As described in detail above, the present invention is a mixture of aluminum silicate and Ti-based phosphate of cobalt hydroxide and strontium hydroxide added phosphate in the mixed form of the first aluminum phosphate and zinc phosphate When a non-oriented electrical steel sheet insulating film is formed using a coating agent (coating agent) based on a chelating additive, it is possible to form a non-oriented electrical steel sheet insulating film without chromium having excellent film adhesion and film strength before and after SRA.

Claims (6)

To 100 g of a phosphate solution in which monobasic aluminum phosphate and zinc monophosphate are mixed 1: 1 and having a solid content of 60% by weight; Solid mixed with cobalt hydroxide and strontium hydroxide in a ratio of 1: 1: 0.5-5 g, Epoxy emulsion resin with solid content of 20% by weight: 100-300 g, Aluminum silicate with 20% solids: 3 ~ 10g, Ti-based chelate additive: A coating composition for forming an insulating film having excellent film adhesion and film strength before and after stress relief annealing excluding chromium, characterized in that 0.1 ~ 6g is added. The method according to claim 1; The first zinc phosphate has a solid content of 2.75 M, 52.5%; Solid content ratio of the liquid mixture of aluminum monophosphate and zinc phosphate monobasic is 60% by weight, and the viscosity is 30-70 cps; The epoxy resin has a molecular weight of 1 ~ 20,000, Tg is 50 ~ 60 ℃, solid content is 20% by weight, characterized in that the coating composition for forming an insulating film excellent before and after the film removal stress removal annealing, characterized in that the stress removal annealing. . The method according to claim 2; The chelating additives of the Ti system include Triethanolamine titanate, Titanium 2,2,2-nitrilotrisethanolate (2-2-2 titanium nitrilotricetanolate), Mixture organic titanate and inorganic phophrous compounds Porous composites) coating composition for forming an insulating coating having excellent corrosion resistance after chromium-free corrosion resistance and the film adhesion after stress annealing characterized in any one selected from. The method according to claim 1; The epoxy resin is a coating composition for forming an insulating film having excellent coating adhesion after corrosion resistance and stress relief annealing, which is chromium-excluded, characterized in that one part of the combined structural formula of bisphenol and epoxide is substituted with an acryl group and kept in an emulsion state. . The method according to claim 1; The chelating additives of the Ti system include Triethanolamine titanate, Titanium 2,2,2-nitrilotrisethanolate (2-2-2 titanium nitrilotricetanolate), Mixture organic titanate and inorganic phophrous compounds Porous composites) coating composition for forming an insulating coating having excellent corrosion resistance after chromium-free corrosion resistance and the film adhesion after stress annealing characterized in any one selected from. When applying the coating composition of any one of claims 1 to 5 on the surface of the non-oriented electrical steel sheet, The coating amount was applied so as to be in the range of 0.5 to 6.0 g / m ² per side, and then heat-treated for 10 to 50 seconds at a temperature range of 350 to 700 ° C. to form an insulating coating. A method of forming an insulating film of a non-oriented electrical steel sheet using a coating composition for forming an insulating film having excellent after-film adhesion.

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