KR20220089112A - Insulation coating composition and method for manufacturing the same, and electrical steel sheet using the same - Google Patents

Abstract

Disclosed are an insulating coating composition prepared by adding metal nitrate and/or metal nitrite, a method for manufacturing the same, and a high weather resistance electrical steel sheet using the same.
Insulation coating composition according to the present invention is a metal phosphate (M _{x = 1-3} (H ₃ PO ₄ ) _y = _1-3 ); and an organic-inorganic composite in which the functional group contained in the organic resin is substituted with inorganic nanoparticles; and, when calculated as the integral value of the energy peak during energy dispersive X-ray spectroscopy (EDS) analysis of the insulating coating composition, phosphorus (P) With respect to the content of the element 100%, the element ratio of the metal (M) element is 100 to 250%.

Description

Insulation coating composition, manufacturing method thereof, and electrical steel sheet using the same

The present invention relates to an insulating coating composition, a method for manufacturing the same, and a high weather resistance electrical steel sheet using the same.

Electrical steel sheet is used as a material for transformers, motors, and electric machines.

Electrical steel sheet is a functional material that emphasizes electrical properties, unlike general carbon steel, which emphasizes workability such as mechanical properties.

Electrical properties required for the electrical steel sheet include low core loss, high magnetic flux density, magnetic permeability and space factor.

Electrical steel sheet is divided into grain-oriented electrical steel sheet and non-oriented electrical steel sheet.

Grain-oriented electrical steel sheet is an electrical steel sheet with excellent magnetic properties in the rolling direction by forming a Goss texture ({110}<001> texture) throughout the steel sheet by using an abnormal grain growth phenomenon called secondary recrystallization.

Non-oriented electrical steel sheet is an electrical steel sheet with uniform magnetic properties in all directions on the rolled sheet.

In order to improve magnetic properties after punching, electrical steel sheet must be subjected to Stress Relieving Annealing (SRA) to remove machining stress, and cost due to heat treatment rather than the effect of magnetic properties caused by stress relief annealing. If the loss is large, the stress relief annealing is omitted and used separately.

On the other hand, forming an insulating film on the surface of the electrical steel sheet is a process corresponding to the final manufacturing process of the product.

The insulating film has the main purpose of interlayer insulation between a plurality of laminated electrical steel sheets.

In the insulating film forming step, in addition to the electrical properties of suppressing the generation of eddy currents, continuous punching is required to suppress the wear of the mold when a plurality of electrical steel sheets are laminated to form an iron core after punching into a predetermined shape.

In addition, in the insulating film forming step, after the stress relief annealing process of the electrical steel sheet, sticking resistance and surface adhesion are required so that the steel sheets do not adhere to each other in the iron core.

Furthermore, in the insulating film forming step, in addition to the above basic characteristics, excellent coating workability of the coating solution and stability of the solution that can be used for a long time after mixing are also required.

As the use of small electric devices is gradually expanding, there is a trend to evaluate the film performance advantageous in not only insulation but also workability, weldability, and corrosion resistance as major properties.

In recent years, as the quality of the surface of the electrical steel sheet also affects the characteristics of use, an electrical steel sheet with excellent surface quality is required.

On the other hand, non-oriented electrical steel sheet is riding a wave of luxury due to the development of high-efficiency motors.

However, as it progresses toward higher quality, the surface of electrical steel sheet requires high functionality (high insulation, high heat resistance, high corrosion resistance).

In particular, insulation is essential for maximizing the performance of the motor by minimizing the eddy current loss.

In order to secure excellent insulation, a method of increasing the thickness of the insulating film is generally used.

However, when the thickness of the insulating film increases, the properties such as weather resistance, weldability, heat resistance, adhesion before and after stress relief annealing and stacking factor required for non-oriented electrical steel sheet are inferior.

An object of the present invention is to provide an insulating coating composition capable of dramatically reducing the amount of unreacted free phosphoric acid by promoting the reaction between phosphoric acid and the surface of an electrical steel sheet.

Another object of the present invention is to provide a method for preparing a coating composition for solving the sticky properties of the coating surface turning white due to moisture absorption.

It is also an object of the present invention to provide a method for preparing an insulating coating composition for improving the deterioration and deformation of the pressure pad.

Another object of the present invention is to provide an electrical steel sheet with improved insulation properties before and after stress relief annealing (SRA).

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention not mentioned may be understood by the following description, and will be more clearly understood by the examples of the present invention. It will also be readily apparent that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the appended claims.

Insulation coating composition according to the present invention is a metal phosphate (M _{x = 1-3} (H ₃ PO ₄ ) _y = _1-3 ); and an organic-inorganic composite in which the functional group contained in the organic resin is substituted with inorganic nanoparticles; and, when calculated as the integral value of the energy peak during energy dispersive X-ray spectroscopy (EDS) analysis of the insulating coating composition, phosphorus (P) With respect to the content of the element 100%, the element ratio of the metal (M) element is 100 to 250%.

The manufacturing method of the insulating coating composition according to the present invention comprises (a) a metal hydroxide (M(OH) _{x = 1 to 3} ), a nitric acid compound, and a phosphoric acid (H ₃ PO ₄ ) aqueous solution by mixing a metal phosphate (M _{x = 1 to 3} (H ₃ PO ₄ ) _y=1-3 ) to prepare; and (b) preparing an insulating coating composition by mixing the metal phosphate and an organic-inorganic composite in which the functional groups contained in the organic resin are substituted with inorganic nanoparticles; including, energy-dispersive X-ray spectroscopy of the insulating coating composition When calculated as an integral value of the energy peak during (EDS) analysis, the element ratio of the metal (M) element is 100 to 250% with respect to 100% of the phosphorus (P) element content.

The electrical steel sheet according to the present invention includes an electrical steel sheet substrate; and an insulating film disposed on the surface of the electrical steel sheet substrate, wherein the insulating film includes a metal phosphate (M _{x = 1-3} (H ₃ PO ₄ ) _y = _1-3 ); and an organic-inorganic composite in which the functional groups contained in the organic resin are substituted with inorganic nanoparticles; and, when calculated as the integral value of the energy peak during energy dispersive X-ray spectroscopy (EDS) analysis of the insulating film, phosphorus (P) With respect to the content of the element 100%, the element ratio of the metal (M) element is 100 to 250%.

The insulating coating composition according to the present invention is prepared by mixing a nitrate compound such as a metal nitrate and/or a metal nitrite with a metal hydroxide and then reacting it with phosphoric acid when preparing a metal nitrate, thereby dramatically reducing the number of unreacted free phosphoric acid has the effect of making

In addition, as the insulating coating composition according to the present invention utilizes a metal nitrate and/or a metal nitrite, there is an effect that the element ratio of the metal (M) element to 100% of the phosphorus (P) element content in the EDS spectrum is 100% or more .

In addition, the surface of the insulating film formed from the insulating film composition of the present invention turns white due to water absorption, and there is an effect of improving stickiness.

In addition, the insulating film has an effect of improving the problem of deterioration and deformation of the pressure pad.

Furthermore, the electrical steel sheet using the insulating coating composition according to the present invention can secure excellent weather resistance and surface properties.

In addition to the above-described effects, the specific effects of the present invention will be described together while describing specific details for carrying out the invention below.

1 is a flowchart illustrating a method for manufacturing an insulating coating composition according to the present invention.
2 is a cross-sectional view of an electrical steel sheet on which an insulating film according to the present invention is disposed.
3 is a photograph of the surface of an electrical steel sheet before and after forming an insulating film using aluminum hydroxide in Comparative Example 1. Referring to FIG.
4 is a photograph of the surface of the electrical steel sheet before and after forming an insulating film by adding 50% of aluminum nitrate compared to 100% of aluminum hydroxide in Example 1.
5 is a photograph of the surface of an electrical steel sheet before and after forming an insulating film by adding 400% of aluminum nitrate compared to 100% of aluminum hydroxide in Example 2;
6 is a photograph of the surface of the electrical steel sheet before and after forming an insulating film by adding 100% of aluminum nitrate compared to 100% of aluminum hydroxide in Example 3;
7 is a photograph of the surface of the electrical steel sheet before and after forming an insulating film by adding 200% of aluminum nitrate compared to 100% of aluminum hydroxide in Example 4.
8 is a graph showing the EDS composition ratio of the insulating film of Comparative Example 1.
9 is a graph showing the EDS composition ratio of the insulating film of Example 1.
10 is a graph showing the EDS composition ratio of the insulating film of Example 2.
11 is a graph showing the EDS composition ratio of the insulating film of Example 3;
12 is a graph showing the EDS composition ratio of the insulating film of Example 4;

The above-described objects, features and advantages will be described below in detail with reference to the accompanying drawings, and accordingly, those of ordinary skill in the art to which the present invention pertains will be able to easily implement the technical idea of the present invention. In describing the present invention, if it is determined that a detailed description of a known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

In the following, that an arbitrary component is disposed on the "upper (or lower)" of a component or "upper (or below)" of a component means that any component is disposed in contact with the upper surface (or lower surface) of the component. Furthermore, it may mean that other components may be interposed between the component and any component disposed on (or under) the component.

In addition, when it is described that a component is “connected”, “coupled” or “connected” to another component, the components may be directly connected or connected to each other, but other components are “interposed” between each component. It should be understood that “or, each component may be “connected,” “coupled,” or “connected,” through another component.

Hereinafter, an insulation coating composition according to some embodiments of the present invention, a method for manufacturing the same, and an electrical steel sheet using the same will be described.

The manufacturing method of the insulating coating composition of this invention is as follows.

1 is a flowchart illustrating a method for manufacturing an insulating coating composition according to the present invention.

Referring to FIG. 1 , the method for preparing the insulating coating composition of the present invention includes a metal hydroxide (M(OH) _{x = 1 to 3} ), a metal nitrate (M(NO ₃ ) _{x = 1 to 3} ) and/or a metal nitrite ( By mixing a nitric acid compound containing M(NO ₂ ) _x=1~3 , and an aqueous solution of phosphoric acid (H ₃ PO ₄ ), a metal phosphate (M _x=1~3 (H ₃ PO ₄ ) _y=1~3 ) It includes the step of preparing (S110) and mixing the metal phosphate and the organic-inorganic composite material to prepare an insulating coating composition (S120).

In the present invention, in the process of preparing a metal phosphate (M _{x = 1 ~ 3} (H ₃ PO ₄ ) _{y = 1 ~ 3} ), a metal hydroxide (M(OH) _{x = 1 ~ 3} ) and a metal nitrate (M(NO ₃ ) ) _x=1~3 ) and/or metal nitrite (M(NO ₂ ) _x=1~3 ) are mixed, and then reacted with an aqueous solution of phosphoric acid (H ₃ PO ₄ ) to form a metal phosphate (M _x=1~3 ( H ₃ PO ₄ ) _{y=1 to 3} ) is prepared.

The aqueous phosphoric acid solution is prepared by mixing 10 to 20% by weight of distilled water and 80 to 90% by weight of phosphoric acid (H ₃ PO ₄ ).

With respect to 100 parts by weight of the aqueous phosphoric acid solution, a nitric acid compound comprising a metal hydroxide, a metal nitrate (M(NO ₃ ) _{x = 1 to 3} ) and/or a metal nitrite (M(NO ₂ ) _{x = 1 to 3} ) A metal phosphate is prepared by mixing 15 to 120 parts by weight and reacting at 80 to 90° C. for 6 to 10 hours. At this time, the metal hydroxide and the nitric acid compound may be mixed in a weight ratio of 1: 0.5 to 4. In other words, 50 to 400% by weight of a nitric acid compound may be added based on 100% by weight of the metal hydroxide.

For example, 10 to 40 g of metal hydroxide and 5 to 80 g of metal nitrate may be added and reacted based on 100 g of aqueous phosphoric acid solution.

With respect to the metal hydroxide, when the content of the nitric acid compound including the metal nitrate and/or the metal nitrite is less than 0.5, the effect of improving the weather resistance may not be significantly exhibited. Conversely, when the content exceeds 4, the reactivity between the electrical steel sheet and the composition becomes excessively large, and powdering may occur.

When the reaction conditions are out of 80 to 90° C. and 6 to 10 hours, the reaction between the metal phosphate and the surface of the steel sheet may not be sufficiently performed.

The metal may include at least one of Al, Co, Ca, Sr, Zn, Mg, and Mn, and preferably, at least one of Al and Co.

Metal nitrates (M(NO ₃ ) _x=1~3 ) are 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 ), and magnesium nitrate (Mg(NO ₃ ) ₂ ).

Metal nitrite (M(NO ₂ ) _x=1~3 ) is expressed as calcium nitrite (Ca(NO ₂ ) ₂ ), zinc nitrite (Zn(NO ₂ ) ₂ ), magnesium nitrite (Mg(NO ₂ ) ₂ ), etc. can be

Metal phosphate (M _x=1~3 (H ₃ PO ₄ ) _y=1~3 ) is the metal hydroxide (M(OH) _x=1~3 ) and metal nitrate (M(NO ₃ ) _x=1~3 ) and/or a metal nitrite (M(NO ₂ ) _{x=1 to 3} ) is mixed and then reacted with an aqueous phosphoric acid solution, and may include a derivative thereof.

In general, when an insulating coating composition containing a large amount of metal phosphate is coated on the surface of an electrical steel sheet, unreacted free phosphoric acid is precipitated and hygroscopicity or surface powdering caused by free phosphoric acid may appear.

Therefore, in order to reduce surface defects caused by free phosphoric acid and increase stability in the composition, phosphoric acid and metal hydroxide must be prepared in a controlled ratio, and reactivity between the insulating coating composition and the electrical steel sheet material is very important.

However, in the present invention, in a more robust method, metal hydroxide (M(OH) _{x=1 to 3} ) is mixed with metal nitrate (M(NO ₃ ) _{x=1 to 3} ) and/or metal nitrite (M(NO ₂ ) _{x= 1-3} ) is added.

Accordingly, it is possible to dramatically reduce the number of unreacted free phosphoric acid that may occur during the surface reaction of phosphoric acid with the electrical steel sheet, thereby reducing the precipitation of free phosphoric acid, or dramatically increasing the reactivity with the electrical steel sheet material.

More specifically, when the surface of the electrical steel sheet and the phosphate react at a certain temperature or higher, the phosphate that did not participate in the reaction is precipitated as free phosphoric acid.

That is, the amount of free phosphoric acid precipitated varies depending on the reactivity of the surface of the material such as the surface oxide layer of the electrical steel sheet.

Phosphoric acid (H ₃ PO ₄ ) exists in solution as H ₂ PO ₄ ^- , HPO ₄ ^2- , PO ₄ ^3- .

When phosphoric acid (H ₃ PO ₄ ) and metal hydroxide (M(OH) _x=1~3 ) react at a high temperature, phosphoric acid (H ₃ PO ₄ ) and metal (M) form a metal hydroxide (M(OH) _{x=1 ~3} ), 20-70% of single bonds (MP), double bonds (M=P) and triple bonds (M≡P) are formed depending on the injection amount. And the remaining about 30% that does not form bonds exists as unreacted free phosphoric acid.

Phosphoric acid, which is an anion trivalent, forms a single bond with a single metal, but due to its weak bonding strength, it easily reacts with moisture in the air and has hygroscopicity.

As such, the primary phosphoric acid reacted with one metal or the unreacted free phosphoric acid is a cause of inferior weather resistance due to its unique hygroscopicity.

That is, only phosphoric acid reacted with at least two or more metals has low hygroscopicity to have strong weather resistance.

Therefore, it is important to reduce the ratio of single bonds between phosphoric acid (H ₃ PO ₄ ) and metal phosphates (M _x=1~3 (H ₃ PO ₄ ) _y=1~3 ) and increase the ratio of double bonds and triple bonds.

And increasing the amount of metal ions in the insulating coating composition is advantageous to increase the weather resistance of the electrical steel sheet.

However, the more the metal hydroxide (M(OH) _{x=1 to 3} ) is injected into the insulation coating composition, the lower the acidity of the composition and the lower the stability, so there is a limit to the amount of addition.

In addition, the pKa of phosphoric acid has a low activity of about 2.2, so the reactivity is affected by the condition of the surface of the electrical steel sheet.

On the other hand, when a nitrate compound containing metal nitrate (M(NO ₃ ) _{x=1 to 3} ) and/or metal nitrite (M(NO ₂ ) _{x=1 to 3} ) is injected, the insulation coating composition, that is, the acidity of the solution Since it does not decrease, the effect on stability is small, and there is an advantage that there is little limit to the amount of addition.

In addition, when the phosphate reacts with the electrical steel sheet material, nitrate ions (NO ₃ ^- ) and/or nitrite ions (NO ₂ ^- ) present in the insulating coating composition adhere to the material surface and generate H ₂ that slows the reaction rate. Control reaction (1).

Accordingly, it is possible to promote the reaction between phosphoric acid and the surface of the material to minimize the influence of the surface oxide layer as in (2) and (3).

Fe(s) + H ₃ PO ₄ → H ₂ (g) + HFePO ₄ -------- (1)

NO ₃ ^- + 3H ⁺ + 2e ^- → HNO ₃ + H ₂ O -------- (2)

2NO ₂ ^- + 8H ⁺ + 6e ^- → N ₂ + 4H ₂ O -------- (3)

As described above, nitrate ions (NO ₃ ^- ) and/or nitrite ions (NO ₂ ^- ) contained in the insulating coating composition promote the reaction of phosphoric acid and the surface of the electrical steel sheet while controlling the hydrogen gas generation reaction to remove unreacted free phosphoric acid. It has the effect of remarkably reducing precipitation.

The nitrate compound including metal nitrate and/or metal nitrite may be added in an amount of 50 to 400% based on 100% by weight of the metal hydroxide to dramatically increase the amount of the metal phosphate.

The concentration of nitrate ions (NO ₃ ⁻ ) and/or nitrite ions (NO ₂ ⁻ ) present in an ionic state in the insulating coating composition may be about 0.01 to 100 ppm (weight/weight) based on the weight of the metal phosphate, but, It is not limited.

Next, an insulating coating composition is prepared by mixing the metal phosphate and the organic-inorganic composite in which the functional groups included in the organic resin are substituted with inorganic nanoparticles.

The organic-inorganic composite material is modified by replacing the functional group of an organic resin with inorganic nanoparticles or bonding inorganic nanoparticles, and provides appropriate adhesion and dispersibility of the insulating coating composition.

In the organic-inorganic composite, the organic resin does not undergo thermal decomposition even at high temperatures, and as a part remains, it provides adhesion even after the stress relief annealing process.

The organic resin includes an aromatic hydrocarbon, and may include at least one of an epoxy-based resin, an ester-based resin, an acrylic resin, a styrene-based resin, a urethane-based resin, and an ethylene-based resin.

Preferably, the organic resin may include an acid-based epoxy-based resin.

The inorganic nanoparticles may include one or more of SiO ₂ , Al ₂ O ₃ , TiO ₂ , MgO, ZnO, CaO, and ZrO ₂ .

Preferably, the inorganic nanoparticles may include SiO ₂ .

The diameter of the inorganic nanoparticles may be about 5-50 nm.

When the diameter is less than 5 nm, the surface area of the particles increases and the insulating properties can be improved by maximizing the barrier effect, but there is a disadvantage in that the price of the coating composition increases.

Conversely, when the diameter exceeds 50 nm, the surface area of the particles decreases, resulting in inferior insulating properties.

The solid content of the organic-inorganic composite may be 30 to 70 wt%, and the ratio of inorganic nanoparticles: organic resin in the solid content may be 0.3 to 0.6: 1 by weight.

When the ratio is out of the above ratio, it is difficult to secure adhesion, dispersibility, and surface properties depending on the content of the inorganic nanoparticles, or there is a problem in that the inorganic nanoparticles aggregate with each other.

The insulating coating composition may include 30 to 200 parts by weight of the organic/inorganic composite material based on 100 parts by weight of the metal phosphate, but is not limited thereto.

In the step of mixing the metal phosphate and the organic-inorganic composite, a sodium-based oxidation promoter may be further added to prepare an insulating coating composition.

A trace amount of free phosphoric acid remains in the insulating film due to the introduction of phosphate, which may cause problems with hygroscopicity or adhesion during annealing.

To solve this, in the present invention, sodium perborate (NaBO ₃ .4H ₂ O) is applied, focusing on the fact that sodium (Na) cation promotes the reaction of iron (Fe)-based oxide and free phosphoric acid remaining in the composition. did

The oxidation promoter may be a sodium-based material, including sodium carbonate (Na ₂ CO ₃ ), sodium perborate (NaBO ₃ ·4H ₂ O), and the like.

In particular, sodium perborate readily dissociates in aqueous solution.

In addition, when sodium perborate is added to the insulating coating composition, the solution stability is not adversely affected, and surface properties including corrosion resistance are not impaired.

The insulating coating composition may include 0.001 to 0.05 parts by weight of an oxidation promoter based on 100 parts by weight of the metal phosphate, but is not limited thereto.

The insulating coating composition prepared according to the manufacturing method of the present invention is a metal phosphate (M _{x = 1-3} (H ₃ PO ₄ ) _y = _1-3 ); and an organic-inorganic composite in which a functional group included in the organic resin is substituted with inorganic nanoparticles.

In addition, the insulating coating composition includes nitrate ions (NO ₃ ⁻ ) and/or nitrite ions (NO ₂ ⁻ ) ionized from a nitric acid compound added during preparation of a metal phosphate.

And the insulating coating composition may further include a sodium-based oxidation promoter.

Since the description of the metal phosphate and the organic-inorganic composite is the same as that described in the manufacturing method, it will be omitted.

As described above, the insulating coating composition of the present invention uses a nitrate compound such as metal nitrate and metal nitrite, and thus exhibits a composition ratio different from that of the conventional insulating coating composition using only metal hydroxide.

The insulating coating composition has a relatively high content of metal elements due to metal nitrate and metal nitrite.

Accordingly, in the EDS spectrum, the insulation coating composition shows a result in which the content of the metal element is 100 to 250% based on 100% of the phosphorus (P) element content when calculated as the integral value of the energy peak.

In Energy Dispersive X-Ray Spectroscope (EDS) analysis, an electron beam is irradiated to a sample to detect X-rays generated from the sample, and the element of the sample can be identified by characteristic X-rays.

The ratio of elements in the EDS spectrum can be measured through energy dispersive X-ray spectroscopy (SEM-EDS) under scanning electron microscopy. At this time, the accelerating voltage can be adjusted from 5 to 20 kV.

The ratio of elements through the EDS spectrum is an element ratio, not a weight ratio, and is expressed through the integration of the corresponding energy peaks.

The content of the element means an integral value of the energy peak of the element. It always has a relative value because the ratio of the element varies depending on the type of measured element.

Accordingly, it is possible to determine a standard for an element and calculate a ratio with respect to the reference value.

For example, when the integral value of the energy peak of the phosphorus (P) element is 100%, the integral value of the energy peak of the metal element is 100 to 250%.

An insulating coating composition exhibiting such an element ratio and a specific peak can provide an insulating coating having low hygroscopicity and excellent weather resistance.

Therefore, when the electrical steel sheet coated with the insulating coating composition of the present invention is used, excellent weather resistance can be ensured regardless of the coating thickness and the type of the electrical steel sheet.

Furthermore, after applying the insulation coating composition, there is almost no change in gloss of the insulation coating and little change in surface stickiness even after being left for 3 days in a temperature range of 20 to 70° C. and a humidity of 99% atmosphere.

In addition, it is possible to solve the hygroscopicity problem caused by the introduction of phosphate before the stress relief annealing of the electrical steel sheet.

2 is a cross-sectional view of an electrical steel sheet on which an insulating film according to the present invention is disposed.

Referring to FIG. 2 , the electrical steel sheet 100 according to the present invention includes an electrical steel sheet substrate 10 and an insulating film 20 disposed on the surface of the electrical steel sheet substrate 10 .

The electrical steel sheet base 10 is a non-oriented or grain-oriented electrical steel sheet, preferably a non-oriented electrical steel sheet.

The insulating film 20 is formed by applying an insulating film composition and then drying it.

After the insulation coating composition is applied to the surface of the electrical steel sheet substrate 10 to a thickness of 0.5 to 1 μm, and then heat-treated for 10 to 30 seconds in a temperature range of 300 to 750 ° C. And it is possible to provide an electrical steel sheet having excellent adhesion before/after SRA, as well as excellent insulation.

The insulating film 20 formed by heat treatment is an organic-inorganic composite in which metal phosphate (M _{x = 1 to 3} (H ₃ PO ₄ ) _y = _{1 to 3} ), and functional groups contained in organic resins are substituted with inorganic nanoparticles. include

The insulating film 20 is present in the form of metal phosphate rather than in the form of metal ions.

In addition, the insulating film 20 may contain a small amount of a compound produced by reacting nitrate ions and/or nitrite ions, metal nitrates and/or metal nitrites present in the insulating film composition with each other.

Descriptions of the metal, organic resin, and inorganic nanoparticles are the same as those described in the manufacturing method, and thus will be omitted.

When calculated as the integral value of the energy peak during energy dispersive X-ray spectroscopy (EDS) analysis of the insulating film 20, for 100% of the phosphorus (P) element content, the elemental ratio of the metal (M) element is 100 ~250%.

In the present invention, as a metal nitrate and/or a metal nitrite is used, the ratio of the metal element increases compared to 100% of the phosphorus (P) element content in the EDS spectrum.

The ratio of the elemental metal may increase from 50 to 90% to 100 to 250% when only metal hydroxide is used.

The metal phosphate with the increased amount of metal can improve the inferiority of adhesion between the insulating film (coating layer) and the steel sheet material, and the hygroscopicity and precipitation of free phosphoric acid due to the introduction of phosphate in the reaction with the electrical steel sheet substrate.

As described above, specific examples of the insulating coating composition, a method for manufacturing the same, and an electrical steel sheet using the same will be described as follows.

1. Manufacture of electrical steel sheet

Comparative Example 1

A high-grade non-oriented electrical steel sheet (150*50 mm) containing 3.15 wt% of silicon (Si) in a weight ratio and thickness of 0.27 mm was prepared as a specimen.

Then, the insulating coating composition prepared as shown in Table 1 was applied to each prepared specimen in a certain thickness using a bar coater and a roll coater, and then in a drying furnace at a temperature range of 300 to 750 ° C. After holding for 10 to 30 seconds, it was cooled slowly in air.

In the process of preparing the insulating coating composition, first, 40 g of aluminum hydroxide was mixed with 100 g of a phosphoric acid aqueous solution to prepare a metal phosphate.

Thereafter, with respect to 100 g of the metal phosphate, 100 g of an organic-inorganic composite substituted with silica nanoparticles was mixed with an epoxy resin to prepare an insulating coating composition.

Comparative Example 2

An electrical steel sheet was manufactured under the same conditions as in Comparative Example 1, except that a metal phosphate was prepared by mixing 60 g of aluminum hydroxide with 100 g of an aqueous solution of phosphoric acid during the manufacturing process of the insulating coating composition.

Example 1

A high-grade non-oriented electrical steel sheet (150*50 mm) containing 3.15 wt% of silicon (Si) in a weight ratio and thickness of 0.27 mm was prepared as a specimen.

Thereafter, the insulating coating composition prepared as shown in Table 1 was applied to each prepared specimen to a certain thickness using a bar coater and a roll coater, and then maintained in a drying furnace at a temperature range of 300 to 750° C. for 10 to 30 seconds. It was cooled slowly in

In the process of preparing the insulating coating composition, first, 40 g of aluminum hydroxide and 20 g of aluminum nitrate were mixed with 100 g of an aqueous phosphoric acid solution to prepare a metal phosphate.

Thereafter, with respect to 100 g of the metal phosphate, 100 g of an organic-inorganic composite substituted with silica nanoparticles was mixed with an epoxy resin to prepare an insulating coating composition.

Example 2

An electrical steel sheet was manufactured under the same conditions as in Example 1, except that metal phosphate was prepared by mixing 20 g of aluminum hydroxide and 80 g of aluminum nitrate with respect to 100 g of an aqueous solution of phosphoric acid during the manufacturing process of the insulating coating composition.

Example 3

An electrical steel sheet was manufactured under the same conditions as in Example 1, except that a metal phosphate was prepared by mixing 40 g of aluminum hydroxide and 40 g of aluminum nitrate with respect to 100 g of an aqueous solution of phosphoric acid during the preparation of the insulating coating composition.

Example 4

An electrical steel sheet was manufactured under the same conditions as in Example 1, except that metal phosphate was prepared by mixing 40 g of aluminum hydroxide and 80 g of aluminum nitrate with respect to 100 g of an aqueous solution of phosphoric acid during the manufacturing process of the insulating coating composition.

2. Methods for evaluating physical properties and their results

Table 1 below is a constant temperature and humidity test result of the plate according to the addition ratio of aluminum nitrate.

Solution stability: After synthesizing the coating solutions of Comparative Examples and Examples, and storing them at room temperature for 3 days, the occurrence of precipitation was visually determined. If precipitation did not occur, it was marked as “good”, and if precipitation did occur, it was marked as “not synthesized”.

Weather resistance: Changes in glossiness (60 degrees) were investigated after maintaining 25-90 ℃, 99% humidity, and 96 hours. Physical property determination was indicated by "X" when the absorbance decreased by more than 50%, "Δ" when the absorbance was 10 to 50%, and "○" when the absorbance was less than 10%.

[Table 1]

Referring to Table 1, Examples 2, 3, and 4 in which 50 to 400% of aluminum nitrate were added showed excellent weather resistance, and Example 1 showed good weather resistance.

On the other hand, in Comparative Examples 1 and 2 in which aluminum nitrate was not added, the absorbance was reduced by 50% or more.

In Comparative Example 2, when aluminum hydroxide was added in excess, aluminum hydroxide in an appropriate amount or more remained in a precipitated state, so synthesis was impossible, and coating was also impossible.

Comparing the solution stability, in Comparative Example 2, the acidity of the insulating coating composition decreased due to the aluminum hydroxide in the precipitated state, and the solution stability was decreased.

The pH of the solution of Comparative Example 2 is expected to be relatively high compared to the pH of the solutions of Comparative Examples 1 and 1-4.

Table 2 below shows the EDS spectrum results of the insulating film according to the addition ratio of aluminum nitrate. In Table 2, the EDS spectrum was observed with SEM-EDS (acceleration voltage: 15 kV).

[Table 2]

3 is a photograph of the surface of an electrical steel sheet before and after forming an insulating film using aluminum hydroxide in Comparative Example 1. Referring to FIG.

Referring to Table 2 and FIG. 3 , in Comparative Example 1 using aluminum hydroxide as a metal phosphate, the ratio of the metal element to the content of the P element in the insulating film was low. This causes the insulating film to absorb moisture, causing the surface of the film to turn white.

In Comparative Example 2, although 60 g of aluminum hydroxide was added, the ratio of metal elements was 100% or less. When aluminum hydroxide is injected in excess, it can be expected that this is because the aluminum hydroxide does not react with phosphoric acid anymore and exists as a precipitate.

4 is a photograph of the surface of the electrical steel sheet before and after forming an insulating film by adding 50% of aluminum nitrate compared to 100% of aluminum hydroxide in Example 1.

5 is a photograph of the surface of an electrical steel sheet before and after forming an insulating film by adding 400% of aluminum nitrate compared to 100% of aluminum hydroxide in Example 2;

6 is a photograph of the surface of the electrical steel sheet before and after forming an insulating film by adding 100% of aluminum nitrate compared to 100% of aluminum hydroxide in Example 3;

7 is a photograph of the surface of an electrical steel sheet before and after forming an insulating film by adding 200% of aluminum nitrate compared to 100% of aluminum hydroxide in Example 4.

Referring to Table 2 and FIGS. 4 to 7, in the case of Examples 1 to 4 in which 50% to 400% of aluminum nitrate was added to the metal phosphate, the ratio of the metal element to the content of the P element in the insulating film was high. .

As the ratio of metal elements in the insulating film is increased, the surface of the insulating film is modified, so that weather resistance and excellent surface properties can be secured.

8 is a graph showing the EDS composition ratio of the insulating film of Comparative Example 1.

9 is a graph showing the EDS composition ratio of the insulating film of Example 1, FIG. 10 is the EDS composition ratio of the insulating film of Example 2, FIG. 11 is the EDS composition ratio of the insulating film of Example 3, and FIG. It is a graph showing the EDS composition ratio of the insulating film.

Referring to FIG. 8 , it can be confirmed that the energy peak of P element is higher than that of other metal elements.

On the other hand, compared to the energy peak of the metal element of FIG. 8 , it can be seen that the ratio of the energy peak of the metal element in FIGS. 9 to 12 is significantly increased.

As described above, the present invention has been described with reference to the illustrated drawings, but the present invention is not limited by the embodiments and drawings disclosed in this specification, and various methods can be obtained by those skilled in the art within the scope of the technical spirit of the present invention. It is obvious that variations can be made. In addition, although the effects according to the configuration of the present invention have not been explicitly described and described while describing the embodiments of the present invention, it is natural that the effects predictable by the configuration should also be recognized.

10: electrical steel plate substrate
20: insulation film
100: electrical steel sheet

Claims (17)

metal phosphate (M _x=1-3 (H ₃ PO ₄ ) _y = _1-3 ); and
Including; an organic-inorganic composite in which the functional group contained in the organic resin is substituted with inorganic nanoparticles;
When calculated as the integral value of the energy peak during energy dispersive X-ray spectroscopy (EDS) analysis of the insulating coating composition, the element ratio of the metal (M) element is 100 to 250% with respect to 100% of the phosphorus (P) element content Phosphorus insulating coating composition.
According to claim 1,
The metal is an insulating coating composition comprising at least one of Al, Co, Ca, Sr, Zn, Mg and Mn.
According to claim 1,
The organic resin is an insulating coating composition comprising at least one of an epoxy-based resin, an ester-based resin, an acrylic resin, a styrene-based resin, a urethane-based resin, and an ethylene-based resin.
According to claim 1,
The inorganic nanoparticles are SiO ₂ , Al ₂ O ₃ , TiO ₂ , MgO, ZnO, CaO, and ZrO ₂ Insulation coating composition comprising at least one of.
According to claim 1,
The insulation coating composition includes nitrate ions (NO ₃ ⁻ ) and/or nitrite ions (NO ₂ ⁻ ).
According to claim 1,
The insulation coating composition further comprises a sodium-based oxidation promoter.
(a) metal hydroxide (M(OH) _x=1~3 ), a nitric acid compound and an aqueous solution of phosphoric acid (H ₃ PO ₄ ) are mixed to form a metal phosphate (M _x=1~3 (H ₃ PO ₄ ) _{y=1~ 3} ) preparing; and
(b) preparing an insulating coating composition by mixing the metal phosphate and an organic-inorganic composite in which the functional groups contained in the organic resin are substituted with inorganic nanoparticles;
When calculated as the integral value of the energy peak during energy dispersive X-ray spectroscopy (EDS) analysis of the insulating coating composition, the element ratio of the metal (M) element is 100 to 250% with respect to 100% of the phosphorus (P) element content A method for preparing a phosphorus insulating coating composition.
8. The method of claim 7,
The nitric acid compound is a metal nitrate (M(NO ₃ ) _{x=1 to 3} ) and/or a metal nitrite (M(NO ₂ ) _{x=1 to 3} ).
8. The method of claim 7,
In the step (a), with respect to 100 parts by weight of the phosphoric acid (H ₃ PO ₄ ) aqueous solution, 15 to 120 parts by weight of a metal hydroxide and a nitric acid compound are mixed in a method of manufacturing an insulating coating composition.
8. The method of claim 7,
In the step (a), a method for producing an insulating coating composition in which the metal hydroxide and the nitric acid compound are mixed in a weight ratio of 1: 0.5-4.
8. The method of claim 7,
The insulation coating composition is a method of manufacturing an insulation coating composition comprising nitrate ions (NO ₃ ^- ) and/or nitrite ions (NO ₂ ^- ).
8. The method of claim 7,
In the step (b), a method for producing an insulating coating composition further adding a sodium-based oxidation promoter.
electrical steel plate substrate; and
Including; an insulating film disposed on the surface of the electrical steel sheet substrate;
The insulating film is
metal phosphate (M _x=1-3 (H ₃ PO ₄ ) _y = _1-3 ); and
Including; an organic-inorganic composite in which the functional group contained in the organic resin is substituted with inorganic nanoparticles;
When calculated as the integral value of the energy peak during energy dispersive X-ray spectroscopy (EDS) analysis of the insulating film, the element ratio of the metal (M) element is 100 to 250% with respect to 100% of the phosphorus (P) element content phosphorus electrical steel sheet.
14. The method of claim 13,
The metal is an electrical steel sheet comprising at least one of Al, Co, Ca, Sr, Zn, Mg and Mn.
14. The method of claim 13,
The organic resin is an electrical steel sheet comprising at least one of an epoxy-based resin, an ester-based resin, an acrylic resin, a styrene-based resin, a urethane-based resin, and an ethylene-based resin.
14. The method of claim 13,
The inorganic nanoparticles are SiO ₂ , Al ₂ O ₃ , TiO ₂ , MgO, ZnO, CaO, and ZrO ₂ Electrical steel sheet comprising at least one of.
14. The method of claim 13,
The thickness of the insulating film is 0.5 ~ 1㎛ electrical steel sheet.

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