KR100918642B1 - Methode for measuring coating strength of tention insulting coationg layer of oriented electric steel - Google Patents

Abstract

The present invention relates to a method for measuring the coating force of the tension insulating film of a grain-oriented electrical steel sheet, and more specifically, to a metal salt solution, a colloidal ceramic material, a transition metal oxide, and an acid having a pH of 6.2 or less by mixing in the presence of a resin Preparing a coating composition; Applying the insulating coating composition to both sides of the grain-oriented electrical steel sheet, followed by heat treatment to prepare a specimen having a tension insulating coating formed thereon; Coating the coated paper on one surface of the specimen and then immersing the specimen in an elution solution prepared by mixing an alkali metal hydroxide and water to elute the tension insulating film on one surface of the coated paper; And cooling the specimen and then rapidly drying and removing the coated paper to measure the degree of warpage of the specimen.

The method of measuring the coating force of the tension insulating film of the grain-oriented electrical steel sheet according to the present invention has the advantage of accurately measuring the coating force of the tension insulating film by improving the characteristics of the insulating film.

Directional, insulating film, electrical steel sheet, film, measuring method

Description

METHODE FOR MEASURING COATING STRENGTH OF TENTION INSULTING COATIONG LAYER OF ORIENTED ELECTRIC STEEL}

The present invention relates to a method for measuring the coating force of the tension insulating film of the grain-oriented electrical steel sheet, and more particularly to a method of accurately measuring the coating force of the tension insulation film formed on the grain-oriented electrical steel sheet.

Usually, oriented electrical steel sheet is characterized by containing 3.1% of Si component. It has an aggregate structure in which the grain orientation is aligned in the (110) (001) direction, and this product has very excellent magnetic properties in the rolling direction. It is used as a core material for transformers, electric motors, generators and other electronic devices.

These oriented electrical steel sheets are generally (hot rolled) (pre-annealed) (once or two cold rolls subjected to annealing) (decarburization) using steel containing 2 to 4% Si and AlN and MnS as grain growth inhibitors. Annealed) (MgO main component annealing separator applied) (hot finish annealing) (insulation coating and planarization annealing), etc., where the 'insulation coating and planarization annealing' is recoated on the primary coating of oriented electrical steel sheet It refers to the process of annealing after implementation, and it improves the magnetic properties of the material by the tensile stress added by the thermal expansion coefficient difference between the film and the material in the cooling process after annealing.

Excellent insulation coating should basically have a uniform color without defects in appearance, but the technique was mainly used to improve the electrical insulation and enhance the adhesion of the film by incorporating various techniques to give functionality. However, with the recent commercialization of high magnetic flux density oriented electrical steel sheets, the high tensile strength of the final insulating film has been pursued, and it has been confirmed that the high tensile insulating film contributes to the improvement of the magnetic properties of the final product.

The manufacturing process of oriented electrical steel sheet is usually made of steel in steelmaking, continuous casting slab production, reheating and hot rolling, thickness adjustment by hot roll annealing and cold pressure, decarburization and nitride annealing, and high temperature for secondary recrystallization. It is manufactured by annealing and final insulation coating process. This manufacturing process is aimed at mass production, and the high temperature annealing process is an important factor of the mass production system.

In recent years, the production of high magnetic flux oriented electrical steel sheet has become the center of oriented electrical steel sheet production, and as the center of production cost is shifted due to the production of thin products, securing more excellent magnetic properties is a key technology. New functional role of the improvement of the magnetic by the is added.

However, the evaluation method for the tension insulating film has not been developed and the problem that the reproducibility of the data and the accuracy of the evaluation results are inferior because the tension value for the tension insulating film is simply replaced by the tension coating force.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily and accurately measuring the coating force of a tension insulating film applied to a surface of a oriented electrical steel sheet having a high tensile stress due to the tension insulating film while having an excellent insulating film.

However, technical problems to be achieved by the present invention are not limited to the above-mentioned problems, and other technical problems will be clearly understood by the average technician from the following description.

In order to achieve the above object, an embodiment of the present invention comprises the steps of preparing a dielectric coating composition by mixing a metal salt solution, a colloidal ceramic material, a transition metal oxide, and an acid having a pH of 6.2 or less in the presence of a resin; Applying the insulating coating composition to both sides of the grain-oriented electrical steel sheet, followed by heat treatment to prepare a specimen having a tension insulating coating formed thereon; Coating the coated paper on one surface of the specimen and immersing the specimen in an elution solution prepared by mixing hydroxide of alkali metal and water to elute the tension insulating film on one surface of the coated paper; And cooling the specimen and then rapidly drying and removing the coated paper to provide a method for measuring the coating force of the tension insulating film, the method comprising measuring the bending degree of the specimen.

Other specific details of embodiments of the present invention are included in the following detailed description.

The method for measuring the coating force of the tension insulating film of the grain-oriented electrical steel sheet according to the present invention has the advantage of accurately measuring the coating force of the tension insulating film that can improve the characteristics of the insulating film.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is provided by way of example, and the present invention is not limited thereto, and the present invention is defined only by the scope of the claims to be described later.

Method for measuring the coating force of the tension insulating film of the grain-oriented electrical steel sheet according to an embodiment of the present invention is a dielectric film composition by mixing a metal salt solution, a colloidal ceramic material, a transition metal oxide, and an acid having a pH of 6.2 or less in the presence of a resin Preparing a; Applying the insulating coating composition to both sides of the grain-oriented electrical steel sheet, followed by heat treatment to prepare a specimen having a tension insulating coating formed thereon; Coating the coated paper on one surface of the specimen and then immersing the specimen in an elution solution prepared by mixing an alkali metal hydroxide and water to elute the tension insulating film on one surface of the coated paper; And cooling the specimen and then rapidly drying and removing the coated paper to measure the degree of warpage of the specimen.

Hereinafter, the coating force measuring method will be described for each step.

First, a colloidal ceramic material, a transition metal oxide, and an acid having a pH of 6.2 or less are mixed with a metal salt solution in the presence of a resin to prepare an insulating coating composition.

Phosphates, sulfates, nitrates, etc. may be used as the metal salt of the metal salt solution, and specific examples thereof include magnesium phosphate ((Mg (H ₂ PO ₄ ) ₂ ), aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ), And metal salts selected from the group consisting of silver (AgNO ₃ ), copper sulfate (CuSO ₄ ), magnesium sulfate (MgSO ₄ ), zinc sulfate (ZnSO ₄ ), and combinations thereof.

The metal salt solution may be prepared by adding the above-described metal salt to water that is commonly used.

As the colloidal ceramic material, silica, alumina, zirconia, titania, or a mixture thereof may be used.

The colloidal ceramic material is used in an amount of 10 to 50 parts by weight (solid content) based on 100 parts by weight of the metal salt. When the content of the colloidal ceramic material is in the above range, it is preferable to improve the adhesion of the insulating film.

In addition, specific examples of the transition metal oxide include chromium oxide, copper oxide, titanium oxide, and manganese oxide. The content of the transition metal oxide is 5 to 15 parts by weight based on 100 parts by weight of the metal salt. When the content of the transition metal oxide is in the above range can improve the physical properties of the insulating film.

In addition, examples of the acid having a pH of 6.2 or less include boric acid. The acid content of the pH of 6.2 or less is 10 to 50 parts by weight based on 100 parts by weight of the metal salt. When the acid content of the pH is less than 6.2 is in the above range can improve the physical properties of the insulating film. More preferably, the acid pH range is between 4.5 and 6.0.

The insulating coating composition is prepared by mixing a metal salt solution, a colloidal ceramic material, a transition metal oxide, and an acid having a pH of 6.2 or less in the presence of a resin. As the resin, a thermosetting resin, a phenol resin, urea resin, melamine resin, furan resin, alkyd resin, unsaturated polyester, diaryl phthalate resin, epoxy resin, silicon resin, polyurethane and the like can be preferably used. Of these, phenol resins and unsaturated polyesters can be preferably used.

The manufacturing process of the insulating coating composition may be prepared by stirring at a rotation speed of 60 or more times per minute using a stirrer, but is not limited thereto .

Subsequently, the insulating coating composition is applied to the grain-oriented electrical steel sheet, and then heated to prepare a specimen having a tensile insulating coating.

The insulating coating composition is applied to a thickness of 2 to 7㎛ on both sides of the grain-oriented electrical steel sheet. If the thickness of the insulating film composition is within the above range does not peel off, there is an advantage to endure high heat.

The coating process may use a conventional method, for example, a doctor blade method, a roller coating method, a roll type coating method and the like. The roll type coating method is well known in the art in that the insulating coating composition transferred through the roll to pick up is finally applied to the electrical steel sheet .

The heat treatment step is performed for 10 to 50 seconds in the temperature range of 550 to 900 ℃ or less. When the heat treatment is performed at a temperature of 550 ° C. or lower or for a shorter time than 10 seconds, the film is not completely dried, resulting in deterioration of the film. If it is a problem that the insulating film burns.

In general, when the tensile insulating film is coated in a very small amount compared to the electrical steel sheet, the residual stress RD in the rolling direction can be expressed by the following equation (AJMoses and JE Thompson, Proc. IEEE, 119). , 1222 [1972]).

[Equation 1]

(Mean value of the above formula, △ T = temperature difference (℃), αsi-Re = Si-Fe thermal expansion coefficient, α _C = coefficient of thermal expansion of the insulating _{film, E C = △ T Young's} Modulus of the insulating film in the region of the alloy, δ = Thickness ratio of material and insulating film, ν _RD = Poisson's ratio in rolling direction.)

As the tensile stress improvement coefficient by the tension insulating film from Equation 1, the difference of the coefficient of thermal expansion between the electrical steel sheet and the insulating film can be mentioned, and by increasing this value, the effect of improving the tensile stress can be obtained.

1 and 2 show the reaction occurring on the surface of the electrical steel sheet when using aluminum phosphate or magnesium phosphate as the metal salt in the preparation of the insulating coating composition and boric acid as the acid having a pH of 6.2 or less. 1 is a reaction equation showing the reaction between the oxide layer and phosphoric acid present on the surface of the electrical steel sheet, Figure 2 is a reaction equation showing the reaction of aluminum phosphate or magnesium phosphate with boric acid which is a phosphate.

As shown in FIG. 1, the free phosphoric acid contained in an excessive amount in the insulating coating composition at a low baking temperature is present in the state indicated by A of FIG. 1 in combination with an oxidizing material present on the surface of the electrical steel sheet.

Meanwhile, as shown in FIG. 2, magnesium phosphate and aluminum phosphate exist in the form of A ′ of FIG. 2 through a condensation reaction with boric acid. Therefore, as the tension insulation film is formed, the reaction between A and A 'formed at the beginning of the insulation film formation can be expected (for example, AA reaction, A-A' reaction, or A'-A 'reaction). The AA reaction, the A-A 'reaction, or the A'-A' composite product induces another condensation reaction with the OH groups present in the ceramic layer produced by the colloidal ceramic material at temperatures above 800 ° C at the end of the insulating film formation. A complex product is formed that could not be derived by conventional methods.

Therefore, the composite material produced by the chemical reactions shown in FIGS. 1 and 2 plays an important role in improving the adhesion of the tension insulating film.

Subsequently, the coated paper is applied to one surface of the specimen to maintain airtightness. At this time, in order to apply a coated paper on one surface of the specimen may be further carried out a step of cutting the specimen to a size of 60 X 300mm.

The coating step may be carried out in the same manner as described above, the coating step is further carried out a step of pressing the coated paper about 5 to 25mm, preferably 10 to 15mm of the edge of the specimen. In this way, the coating paper coating process is performed to ensure the airtightness between the specimen and the coating paper.

The coated paper is not particularly limited, and any coated paper generally used may be used.

On the other hand, an alkali metal hydroxide and water are mixed to prepare an elution solution. Specific examples of the hydroxide of the alkali metal include, but are not limited to, potassium hydroxide, sodium hydroxide, and the like. The elution solution is prepared by mixing a hydroxide of alkali metal and water in a weight ratio of 10:90 to 50:50, preferably 20:80 to 30:70. When the content of the hydroxide of the alkali metal is less than 10% by weight may increase the insulating film dissolution time and the residual amount of the insulating film, when the content of the hydroxide of the alkali metal exceeds 50% by weight the viscosity of the elution solution is increased There is a problem that the melt output is lowered and the use of sodium hydroxide more than necessary increases the raw material cost and increase the processing cost, as well as significantly lower workability.

Subsequently, the specimen is immersed in the prepared elution solution to elute the tension insulating film on one surface.

The elution process is carried out for 5 to 25 minutes, preferably 10 to 15 minutes in the temperature range of 70 to 110 ℃, preferably 80 to 90 ℃. When the elution process is carried out under the above conditions, the elution process may be easily performed, and when the elution temperature or elution time is long, a problem may occur due to melting of the coated paper attached to the other surface.

After the specimen is cooled and rapidly dried, the coated paper is removed to measure the degree of warpage of the specimen. When the coated paper is removed, as shown in FIG. 3, the tension insulating film 20 is formed only on one surface of the oriented electrical steel sheet 10, and the shrinkage of the electrical steel sheet 10 is larger than that of the tension insulating film 20. The furnace specimen is bent toward the side where no insulating film is formed. The greater the deflection (H) of the specimen, the greater the coating strength of the electrical steel sheet . High coating power means less loss of steel sheet.

The cooling step is preferably carried out in a temperature range of 30 to 40 ℃. The rapid drying step can be carried out by a conventional method, specifically, using a dryer or the like.

Hereinafter, specific embodiments of the present invention are presented. However, the embodiments described below are merely for illustrating or explaining the present invention in detail, and thus the present invention is not limited thereto.

(Examples 1 and 2, and Comparative Example 1)

100 g of magnesium phosphate ((Mg (H ₂ PO ₄ ) ₂ ) was added to water to prepare a phosphate solution, and this phosphate solution, colloidal silica 30 g, chromium oxide 10 g, and boric acid 30 g were mixed in the presence of a phenol resin to insulate The coating composition was prepared.

The insulating coating composition thus prepared was coated on both sides of a grain-oriented electrical steel sheet (300X60 mm) containing 3.1% of Si to be 5.0 ± 0.5 g / m ² , and then baked at 750 ° C. for 30 seconds to be 0.23 mm thick. A grain-oriented electrical steel sheet (sample) having a finished annealed insulating film was prepared. The coated paper was pressed on one surface of the prepared specimen, and immersed in the elution solution prepared by mixing sodium hydroxide and water under the conditions shown in Table 1 below.

tension Insulation film  Characterization

When one surface of the specimens according to Examples 1 and 2 and Comparative Example 1 obtained as described above were eluted and dried, the surface was bent in one direction as shown in FIG. 3 with the addition of tensile stress caused by the insulating film remaining on the other surface. (H) was measured to evaluate the tension by the coating. The specimens according to Examples 1 and 2 were found to have a degree of warpage of 4 mm or more. On the contrary, the degree of warpage of the specimen of Comparative Example 1 was hardly shown.

The application amount deviation and workability of the specimens obtained according to Examples 1 and 2 and Comparative Example 1 are shown in Table 2 below.

In the case of Comparative Example 1, the width of the coated paper, which is attached to one side of the specimen but separately pressurized to secure airtightness at both edges, is too narrow in the case of Comparative Example 1, so that some of the elution solution is submerged and the tension insulating film to be protected is peeled off. However, in Examples 1 and 2, the elution solution did not penetrate through the edges at all, and it was found that the removal after the elution was also easily performed.

In addition, Comparative Example 1 results in a time delay in dissolution of the tension insulating film using only water in the mixing ratio of the aqueous sodium hydroxide solution and water.

On the other hand, when the elution temperature is maintained at 60 to 70 ℃ as in Comparative Example 1, the elution time is delayed, there is a problem that some tension insulating film remains because it is not completely dissolved.

The settling time (precipitation time) of the specimen in the elution solution has a problem that the tension insulating film is not sufficiently eluted from the surface of the specimen when maintained for 1 to 5 minutes as in Comparative Example 1.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

1 is a chemical formula showing a reaction between an oxide layer present on a surface of an electrical steel sheet and phosphoric acid.

2 is a chemical formula showing the reaction of aluminum phosphate or magnesium phosphate with boric acid.

3 is a view schematically showing the film tension measurement using the radius of curvature.

Claims (8)

Preparing a dielectric coating composition by mixing a metal salt solution, a colloidal ceramic material, a transition metal oxide, and an acid having a pH of 6.2 or less in the presence of a resin; Applying the insulating coating composition to a grain-oriented electrical steel sheet, followed by heating to prepare a specimen having a tension insulating coating formed thereon; Coating the coated paper on one surface of the specimen and immersing the specimen in an elution solution prepared by mixing hydroxide of alkali metal and water to elute the tension insulating film on one surface of the coated paper; And After cooling the specimen and drying it to remove the coated paper to measure the degree of warpage of the specimen Method for measuring the coating force of the tension insulating film comprising a. The method of claim 1, The metal salt solution is a method of measuring the coating force of the tension insulating film will include a metal salt selected from the group consisting of phosphate, sulfate, nitrate and combinations thereof. The method of claim 2, The metal salt includes magnesium phosphate ((Mg (H ₂ PO ₄ ) ₂ ), aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ), silver nitrate (AgNO ₃ ), copper sulfate (CuSO ₄ ), magnesium sulfate (MgSO ₄ ), sulfuric acid Zinc (ZnSO ₄ ), and a method for measuring the coating force of the tension insulating film comprising a metal salt selected from the group consisting of a combination thereof. The method of claim 1, The insulating coating composition is prepared by adding 10 to 50 parts by weight (solid content) of colloidal ceramic material, 5 to 15 parts by weight of transition metal oxide, and 3 to 7 parts by weight of acid having a pH of 6.2 or less based on 100 parts by weight of a metal salt. Method of measuring coating force of tension insulating film. The method of claim 1, The tension insulating film is a method of measuring the coating force of the tension insulating film is formed on the oriented electrical steel sheet to a thickness of 2 to 7㎛. The method of claim 1, The method of measuring the coating force of the tension insulating film is the step of preparing a specimen in which the tensile insulating film is formed by heat treatment is performed for 10 to 50 seconds in the temperature range of 550 to 900 ℃. The method of claim 1, The elution solution is a method for measuring the coating force of the tension insulating film is prepared by mixing a hydroxide of alkali metal and water in a weight ratio of 10:90 to 50:50. The method of claim 1, The eluting of the specimen in the elution solution to elute the tension insulating film on one surface is not coated coated paper to measure the coating force of the tension insulating film to be carried out for 5 to 25 minutes in the temperature range of 70 to 110 ℃ Way.

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