KR102325747B1 - Composition for forming insulation film of oriented electrical steel sheet, grain oriented electrical steel sheet, and method for manufacturing grain oriented electrical steel sheet - Google Patents

Abstract

The present embodiments relate to a composition for forming an insulating film of a grain-oriented electrical steel sheet, a grain-oriented electrical steel sheet, and a method for manufacturing the same. According to one embodiment, it is possible to provide a composition for forming an insulating film of a grain-oriented electrical steel sheet comprising a compound represented by the following formula (1).
[Formula 1]
[Na] ⁺ [(SiO(OR) ₂ ) _n OR] ^-
In Formula 1,
(R is at least one of an alkyl group having 1 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 4 to 12 carbon atoms, an aralkyl group having 4 to 12 carbon atoms, and an alkaryl group having 4 to 12 carbon atoms, and n is 1 It is an integer from to 30.)

Description

A composition for forming an insulating film of a grain-oriented electrical steel sheet, a grain-oriented electrical steel sheet, and a method for manufacturing a grain-oriented electrical steel sheet

It relates to a composition for forming an insulating film of a grain-oriented electrical steel sheet, a grain-oriented electrical steel sheet, and a method for manufacturing a grain-oriented electrical steel sheet. More specifically, it relates to a composition for forming an insulating film of a grain-oriented electrical steel sheet having excellent film tension even after stress relief annealing by including a sodium-based silicate sol, a grain-oriented electrical steel sheet, and a method for manufacturing a grain-oriented electrical steel sheet.

The grain-oriented electrical steel sheet is an electrical steel sheet having a Si component content of 3.1 wt% in general, and has a texture in which the grain orientation is aligned in the (110) [001] direction, thereby exhibiting excellent magnetic properties in the rolling direction.

It is known that these magnetic properties are further improved when the insulation is improved by reducing the iron loss of the grain-oriented electrical steel sheet. Grain-oriented electrical steel sheets, which are currently commercialized, use the difference in thermal expansion coefficient between the steel sheet and the insulating film (secondary film) formed on the forsteritic base film (primary film), thereby reducing iron loss by adding tensile stress to the steel plate. are doing In this regard, as one of the methods for reducing iron loss of grain-oriented electrical steel sheets, a method of forming a high-tensile insulating film on the surface is being actively studied.

The coil formed up to the secondary film, tension coating, is slitted to the size desired by the transformer manufacturer and then supplied in the form of a hoop. In particular, in the case of wound iron cores used for pole transformers, the transformer manufacturer laminates the plate-shaped products and then shears and deforms them for copper winding, and then performs stress relief heat treatment to remove the stress caused by processing. . At this time, the heat treatment temperature and atmospheric conditions are different depending on the transformer manufacturer, and depending on the heat treatment conditions, the iron loss is rather deteriorated after stress annealing, thereby lowering the efficiency of the transformer. In particular, transformer manufacturers often treat the heat treatment temperature at a high temperature to reduce the time required to manufacture the transformer and to see the stress relief effect in a short time. .

Therefore, there is no deterioration in iron loss even after high-temperature stress relief annealing, and at the same time, a grain-oriented electrical steel sheet product with excellent insulation is required. Moreover, a non-phosphate-chrome-free coating agent commercialization technology has not been proposed.

In this embodiment, it is intended to provide a composition for an insulation coating of a grain-oriented electrical steel sheet, a grain-oriented electrical steel sheet, and a method for manufacturing a grain-oriented electrical steel sheet, which has excellent film tension even after stress relief annealing by including a sodium-based silicate sol.

The composition for forming an insulating film of a grain-oriented electrical steel sheet according to an embodiment may include a compound represented by the following formula (1).

[Formula 1]

[Na] ⁺ [(SiO(OR) ₂ ) _n OR] ^-

In Formula 1, R is at least one of an alkyl group having 1 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 4 to 12 carbon atoms, an aralkyl group having 4 to 12 carbon atoms, and an alkaryl group having 4 to 12 carbon atoms. and n is an integer from 1 to 30.

A grain-oriented electrical steel sheet according to another embodiment includes a grain-oriented electrical steel sheet substrate, and an insulating film positioned on at least one surface of the substrate, wherein the insulating film is in weight %, Si: 10 to 50%, Na: 0.5 to 10%, Fe: 0.1 to 10% and the balance may contain oxygen and unavoidable impurities.

A method of manufacturing a grain-oriented electrical steel sheet according to another embodiment includes the steps of applying the composition for forming an insulation film according to an embodiment on a substrate of an electrical steel sheet, and drying the steel sheet to which the composition for forming an insulation film is applied to form an insulation film It may include the step of forming

When an insulating film is formed on a grain-oriented electrical steel sheet by using the composition for an insulation film of a grain-oriented electrical steel sheet containing a sodium-based silicate sol according to an embodiment, an electric steel sheet having excellent film density and film tension can be realized. Accordingly, it is possible to secure the excellent corrosion resistance of the grain-oriented electrical steel sheet and to dramatically improve the iron loss.

1 shows the corrosion resistance evaluation results for the specimens of Example 1 and Comparative Example 7.
2 is a result of analyzing the insulating film component of the grain-oriented electrical steel sheet prepared in Example 1.

Terms such as first, second and third are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and includes the presence or absence of another characteristic, region, integer, step, operation, element and/or component. It does not exclude additions.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part, or the other part may be involved in between. In contrast, when a part refers to being "directly above" another part, the other part is not interposed therebetween.

In addition, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

In one embodiment of the present invention, the meaning of further including the additional element means that the remaining iron (Fe) or oxygen (O) is included by replacing the additional amount of the additional element.

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, they are not interpreted in an ideal or very formal meaning.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In one embodiment of the present invention, in the production of an insulating coating composition for grain-oriented electrical steel sheet, a conventional sol-gel coating agent containing no metal phosphate and not containing chromium oxide is used, thereby using a conventional metal phosphate and chromium oxide as main components. Compared to the insulating coating composition, it is characterized in that it produces a grain-oriented electrical steel sheet with excellent iron loss improvement by improving adhesion, corrosion resistance and film tension.

In this regard, if we first consider the main components of a general metal phosphate-chromium oxide tension coating agent, colloidal silica that gives film tension, metal phosphate that gives adhesion to the interface between the coating agent and steel plate, chromium oxide, and other functionalities are reinforced. It is composed of a trace amount of additives for However, when chromium oxide is excluded from such a configuration, the drying rate is typically reduced, which leads to a decrease in insulation and tensile strength by coating.

More specifically, when chromium oxide is excluded from the insulating coating composition, the most problematic physical property is a decrease in drying rate. In general, as described above, the main components of the metal phosphate-chromium oxide-based insulating coating composition are colloidal silica that imparts film tension, metal phosphate that imparts adhesion to the interface between the coating agent and the steel sheet, chromium oxide, and other functionalities for reinforcing the Contains trace amounts of additives.

At this time, colloidal silica serves to impart film tension to the tension coating agent, and metal phosphate is used as a binder for the tension coating agent to provide adhesion between the coating agent and the base material.

The metal phosphate providing adhesion in this way proceeds with a dehydration condensation reaction depending on the drying temperature and a film forming reaction proceeds as follows.

- Low temperature state (coating agent temperature, ≤ 550 ℃)

Phosphate: 2Al(H ₂ PO ₄ ) ₃ → Al ₂ (H ₂ P ₂ O ₇ ) ₃ + 3H ₂ O ↑ (1)

- High temperature condition (coating agent temperature, ≥ 650 ℃)

Phosphate: nAl ₂ (H ₂ P ₂ O ₇ ) ₃ → [Al(PO ₃ ) ₃ ] ₂ n + 3nH ₂ O ↑ (2)

At this time, when chromium oxide is present in the coating agent, the free phosphate present in the low temperature state as in Equation (1) can be made into a state capable of forming a film at a low temperature through the following reaction.

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

In the case of the insulating coating composition containing chromium oxide as described above, as shown in Equation (3), chromium oxide suppresses the generation of free phosphoric acid, which causes sticky defects after drying the film, and improves the reactivity of phosphate even at low temperatures.

In addition, when the film is dried, hexavalent chromium in chromium oxide reacts with water present in the coating agent to change _{into a H 2 CrO 4} compound, and again H ₂ CrO ₄ reacts with Fe present in the steel sheet to produce FeO to form FeO and metal phosphate. Create a state of being able to react. This action helps a lot in improving the adhesion between the steel sheet and the insulating coating composition, and as a result, it helps to improve the coating tension. In addition, hexavalent chromium is also reduced to trivalent chromium by reacting with the produced iron oxide (FeO), and it is possible to increase the film density by condensation polymerization of the reduced trivalent chromium, which greatly affects the improvement of the film tension.

However, it cannot have this effect if chromium is to be excluded. In particular, the water constituting the insulating coating composition is composed of the water of each component itself and the water added to give the overall specific gravity, but the analysis of their drying mechanism has not been done yet. In addition, in the tension coating agent excluding chromium oxide, the generation of free phosphoric acid generated from metal phosphate cannot be suppressed during drying of the coating agent, so the drying rate of the film is slowed and the adhesion of the film is significantly reduced.

In addition, when the metal phosphate-chromium oxide-based tension coating agent is used as a wound iron core transformer such as a columnar distribution transformer, a forming process is required to process the iron core cut in the shape of a hoop by applying a slight stress. It undergoes a process of heat treatment at high temperature to relieve stress. Here, the purpose of high-temperature heat treatment is to recover the iron loss that was damaged during forming, and after stress relief annealing, the iron loss was observed to increase. significantly lower it.

The reason for the deterioration of iron loss during high-temperature heat treatment in the coil to which the metal phosphate-chromium oxide-based insulating coating composition is applied is that the metal phosphate in the coating material undergoes a phase change from amorphous to crystalline, causing cracks in the coating, which leads to a rapid decrease in film strength. . As the basic role of the coating agent to protect the base material is weakened through the chemical change of the metal phosphate in the coating agent, the base material reacts sensitively according to the heat treatment conditions, thereby reducing iron loss. In addition, as the heat treatment time increases, the crystallization of the metal phosphate proceeds rapidly, which increases the electrical conductivity of the coating surface and reduces the insulation.

As described above, in the case of a conventional coating agent, metal phosphate and chromium oxide are inevitably used at the same time, thereby imparting film adhesion and corrosion resistance within the material. It becomes an unavoidable weakness. Therefore, in one embodiment of the present invention, unlike the conventional insulating coating composition, metal phosphate and chromium oxide are excluded, and the silica component, which is the main component, is modified at the molecular level, and when dried, the difference between silicate sol compared to conventional metal phosphate-chromium oxide tension coating agent. By forming a dense film by condensation reaction, it has excellent corrosion resistance, and by excluding phosphate in the film and silica as the main component, it is possible to increase the film tension by lowering the coefficient of thermal expansion compared to the conventional film.

Colloidal silica (-(HO-Si-OH-)n), one of the main components of a typical metal phosphate-chromium oxide tension coating agent, serves to impart film tension to the insulating film composition. In the above, the condensation reaction by the chain reaction of silica takes place and forms a network structure like -(HO-Si-O-Si)-n. However, an excessively uniform network structure is created using colloidal silica, which limits the film density. Therefore, there is a limit to providing adhesion or corrosion resistance between the material and the coating agent, and metal phosphate and chromium oxide are introduced to reinforce these insufficient physical properties.

-(HO-Si-OH-)n + -(HO-Si-OH-)n = -(HO-Si-O-Si)-n + H ₂ O (4)

As described above, an excessively uniform network occurs when silica having the same characteristics, ie, the same particle size, is introduced.

That is, by using a compound represented by the following formula (1) (hereinafter also referred to as sodium silicate), the above problem was solved.

[Formula 1]

[Na] ⁺ [(SiO(OR) ₂ ) _n OR] ^-

R is at least one of an alkyl group having 1 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 4 to 12 carbon atoms, an aralkyl group having 4 to 12 carbon atoms, and an alkaryl group having 4 to 12 carbon atoms, and n is 1 It is an integer of to 30.

Examples of the alkyl group include methyl, ethyl, n-propyl, iso-propyl, n-butyl, 2-butyl (sec-butyl), isobutyl and tert-butyl, for example C 1 -C 4 -alkyl. or n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2, 3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl and 1 -Ethyl-2-methylpropyl may be present. or n-heptyl, 1-methylhexyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5-methylhexyl, 1-ethylpentyl, 2-ethylpentyl, 3-ethylpentyl, n-octyl, 1 -Methyloctyl, 2-methylheptyl, 1-ethylhexyl, 2-ethylhexyl, 1,2-dimethylhexyl, 1-propyl pentyl, 2-propylpentyl, nonyl, decyl, 2-propylheptyl and 3-propylheptyl there may be More specifically, as the alkyl group, there may be methyl, ethyl, n-propyl, iso-propyl, n-butyl, 2-butyl (sec-butyl), isobutyl and tert-butyl.

An alkenyl group is a monounsaturated straight-chain or branched hydrocarbon radical having a double bond at any position, for example ethenyl, 1-propenyl, 2-propenyl, 1-methylethenyl, 1-butenyl, 2-part C2-C4-alkenyl such as tenyl, 3-butenyl, 1-methyl-1-propenyl, 2-methyl-1-propenyl, 1-methyl-2-propenyl or 2-methyl-2-propenyl ; Ethenyl, 1-propenyl, 2-propenyl, 1-methylethenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-1-propenyl, 2-methyl-1-prop Phenyl, 1-methyl-2-propenyl, 2-methyl-2-propenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-methyl-1-butenyl, 2 -Methyl-1-butenyl, 3-methyl-1-butenyl, 1-methyl-2-butenyl, 2-methyl-2-butenyl, 3-methyl-2-butenyl, 1-methyl-3- Butenyl, 2-methyl-3-butenyl, 3-methyl-3-butenyl, 1,1-dimethyl-2-propenyl, 1,2-dimethyl-1-propenyl, 1,2-dimethyl-2 -propenyl, 1-ethyl-1-propenyl, 1-ethyl-2-propenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, 1-methyl -1-pentenyl, 2-methyl-1-pentenyl, 3-methyl-1-pentenyl, 4-methyl-1-pentenyl, 1-methyl-2-pentenyl, 2-methyl-2-pentenyl , 3-methyl-2-pentenyl, 4-methyl-2-pentenyl, 1-methyl-3-pentenyl, 2-methyl-3-pentenyl, 3-methyl-3-pentenyl, 4-methyl- 3-pentenyl, 1-methyl-4-pentenyl, 2-methyl-4-pentenyl, 3-methyl-4-pentenyl, 4-methyl-4-pentenyl, 1,1-dimethyl-2-bu tenyl, 1,1-dimethyl-3-butenyl, 1,2-dimethyl-1-butenyl, 1,2-dimethyl-2-butenyl, 1,2-dimethyl-3-butenyl, 1,3- Dimethyl-1-butenyl, 1,3-dimethyl-2-butenyl, 1,3-dimethyl-3-butenyl, 2,2-dimethyl-3-butenyl, 2,3-dimethyl-1-butenyl , 2,3-dimethyl-2-butenyl, 2,3-dimethyl-3-butenyl, 3,3-dimethyl-1-butenyl, 3,3-dimethyl-2-butenyl, 1-ethyl-1 -Butenyl, 1-ethyl-2-butenyl, 1-ethyl-3-butenyl, 2-ethyl-1-butenyl, 2-ethyl-2-butenyl, 2-ethyl-3-butenyl, 1 ,1,2-trimethyl-2-propenyl, 1-ethyl-1-methyl-2-propenyl, 1-ethyl-2-methyl-1-propenyl, 1-ethyl-2-methyl-2-propenyl This can be.

By aryl group is meant a mono-, bi- or tricyclic aromatic hydrocarbon radical such as phenyl or naphthyl, in particular phenyl.

Aralkyl refers to a substituent including an alkyl group bonded through a bond to an alkyl atom in the alkyl group, and the alkyl group includes an aryl group. The aryl group includes a benzyl group.

Alkaryl refers to a substituent including an aryl group bonded through a bond to an aromatic atom in an aromatic group, and the aryl group includes an alkyl group. An example of an alkaryl group is a tolyl group.

R may have up to 12 carbon atoms. If the number of carbon atoms is higher than that, the compactness of the film may be deteriorated.

In Formula 1, n may be an integer of 1 to 30. More specifically, n may be 7 to 20. If n is too large, the molecular structure becomes large, the particle size of the resulting silicate sol becomes large, and the surface after film formation may not be beautiful.

More specifically, Chemical Formula 1 may be represented as follows.

In general, a common colloidal silica is to prepare a stable colloidal silica through a polymerization reaction of _{sodium oxide (Na 2} O) as a precursor and SiO _{2 in the form of a sol.} As described above, since the conventional colloidal silica uses sodium silicate as a raw material, it is common to contain a very small amount of sodium. Various factors are involved in the reactivity of colloidal silica, such as particle diameter, specific surface area, and the type and amount of anions added during manufacture. It is known that the higher the amount of sodium, the higher the reactivity of colloidal silica, but in reality, it is not easy to increase the amount of sodium.

Accordingly, in one embodiment of the present invention, sodium silicate of the form represented by formula 1 is prepared by reacting the silicate represented by formula 2 with sodium oxide or sodium hydroxide, unlike conventional colloidal silica production, and silicon and sodium in the molecule You can adjust the ratio.

That is, in an embodiment of the present invention, the compound represented by Chemical Formula 1 may be prepared by reacting silicate represented by Chemical Formula 2 and at least one of sodium oxide and sodium hydroxide.

[Formula 2]

Si(OR) ₄

In Formula 2, each R is hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 4 to 12 carbon atoms, an aralkyl group having 4 to 12 carbon atoms, and an alkaryl group having 4 to 12 carbon atoms. at least one

Descriptions of the alkyl group, aquinyl group, aryl group, aralkyl group, and alkaryl group are the same as those described above, and thus will be omitted herein.

Specifically, the atomic ratio (Si:Na) of silicon (Si) and sodium (Na) may be in the range of 20:1 to 7:1. If the silicon atomic ratio is too high, the hardness of the film is too high, resulting in poor workability. If the silicon atomic ratio is too low, the film tension effect by silica may be reduced. More specifically, the atomic ratio (Si:Na) of silicon (Si) and sodium (Na) may be in the range of 14:1 to 7:1.

In the composition for forming an insulating film including the compound represented by Formula 1 prepared in this way, the condensation reaction between silicate sols is continuously performed even during stress relief annealing, so that, unlike conventional products, the film tension is improved after heat treatment and, thereby, iron loss is improved. can have an effect.

In addition to the above components, the composition for forming an insulating film may further include a solvent.

The grain-oriented electrical steel sheet according to an embodiment of the present invention includes a grain-oriented electrical steel sheet substrate and an insulating film positioned on one or both sides of the substrate, and the insulating film is in weight %, Si: 10 to 50%, Na: 0.5 to 10%, Fe: 0.1 to 10% and balance oxygen and unavoidable impurities.

In one embodiment of the present invention, the effect is shown by the characteristics of the insulating film composition and the insulating film irrespective of the components of the grain-oriented electrical steel sheet substrate. Supplementally, the components of the grain-oriented electrical steel sheet are described as follows.

The grain-oriented electrical steel sheet substrate is silicon (Si): 2.0 to 7.0 wt%, aluminum (Al): 0.020 to 0.040 wt%, manganese (Mn): 0.01 to 0.20 wt%, phosphorus (P) 0.01 to 0.15 wt%, carbon ( C) 0.01% by weight or less (excluding 0%), N: 0.005 to 0.05% by weight and 0.01 to 0.15% by weight of antimony (Sb), tin (Sn), or a combination thereof, the balance being Fe and others It may contain unavoidable impurities. Since the description of each component of the grain-oriented electrical steel sheet substrate 10 is the same as the generally known content, a detailed description thereof will be omitted.

A metal oxide layer formed by reacting with the annealing separator and the oxide layer of the steel sheet in the secondary recrystallization process may exist between the grain-oriented electrical steel sheet substrate and the insulating film. An example of the metal oxide layer may be a forsterite layer. By suppressing the formation of the metal oxide layer or removing the metal oxide layer in the manufacturing process of the grain-oriented electrical steel sheet, it is also possible to contact the grain-oriented electrical steel sheet substrate and the insulating film.

The insulating film includes, by weight, Si: 10 to 50%, Na: 0.5 to 10%, Fe: 0.1 to 10%, and the remainder of oxygen and unavoidable impurities.

Silicon (Si) is included in the insulating film in an amount ranging from 10 to 50% by weight. Silicone may be derived from the compound represented by Formula 1 in the insulating coating composition, or may be diffused from the grain-oriented electrical steel sheet substrate. When the silicone ratio is too high, the hardness of the coating is too high, which leads to poor workability, and when the silicone ratio is too low, the coating tension effect by the silicone may be reduced. More specifically, it may contain 15 to 35% by weight of Si.

Sodium (Na) is included in the insulating film in an amount ranging from 0.5 to 10% by weight. Compared to other metal cations, such as Zr, Ge, Mg, Sb, Sn, Al, etc., the use of Na reacts with oxygen atoms, which are nucleophiles in silicate, better than other elements. The adhesion, corrosion resistance, and tension of the film can be improved. Sodium may be derived from the compound represented by Formula 1 in the insulating coating composition. If the sodium ratio is too high, on the contrary, the silicone ratio may be lowered and the film tension effect may be lowered. If the sodium ratio is too low, on the contrary, the silicone ratio may be high and processability may be deteriorated. More specifically, the insulating film may include sodium in an amount ranging from 1 to 5 wt%.

Iron (Fe) is included in the insulating film in an amount ranging from 0.1 to 10% by weight. Iron may be diffused from the grain-oriented electrical steel sheet substrate during the formation of the insulating film.

The remainder contains oxygen (O). In addition to the aforementioned Si, K, and Fe, it may further include an element, and in this case, it is included in place of oxygen (O). Specifically, oxygen may include 10 to 50% by weight.

The insulating film may further include one or more of Mg: 0.1 wt% or less, Al: 0.1 wt% or less, and Cr: 0.1 wt% or less.

Mg, Al, Cr, etc. may be diffused from the primary film or the electrical steel sheet substrate. Since these elements adversely affect the physical properties of the insulating film, when they are unavoidably included, they may be further included in the above-described range. More specifically, Mg: 0.01 wt % or less, Al: 0.01 wt % or less, and Cr: 0.01 wt % or less may further include one or more.

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises: applying a composition for forming an insulating film on an electrical steel sheet substrate; and drying the steel sheet coated with the composition for forming an insulating film to form an insulating film.

First, a composition for forming an insulating film is applied on an electrical steel sheet substrate.

Since the composition for forming the electrical steel sheet substrate and the insulating film is the same as that described above, repeated descriptions will be omitted.

The composition for forming an insulating film before application may be managed at a temperature of 15 to 25°C. If it is lower than the above range, the viscosity may increase, making it difficult to manage a uniform application amount. When the temperature is too high, the gelation phenomenon of the composition for forming an insulating film is accelerated, and the surface quality may be deteriorated.

When the composition for forming an insulating film is applied, the application amount may be in the range of 0.1 to 6.0 g/m ² , more specifically 0.5 to 3.0 g/m ² , of the dried insulating film on the surface of the grain-oriented electrical steel sheet. When the application amount is too large, the insulating film becomes too thick, and the adhesion with the steel sheet and the space factor of the electrical steel sheet product may be inferior. When the amount applied is too small, the tension imparted by the insulating film may be weakened.

In the drying step, it may be dried by heating at 350 to 900° C. for 50 to 1200 seconds.

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

Experimental example: Check the characteristics according to the type of metal

Example 1

A grain-oriented electrical steel sheet (300*60mm) with a primary film containing a Si: 3.1% by weight ratio and finish annealing with a plate thickness of 0.23mm was prepared as a test material.

Si[CH ₃ OH] ₄ was reacted with sodium hydroxide, and 100 g of a compound in the form of a sol was used as an insulating coating agent.

^{After 4 g/m 2} of the insulating coating composition was applied to the test material, the specimen was dried at 800° C. for 30 to 120 seconds, and the basic physical properties were measured with the thus-prepared specimen.

When measuring physical properties, assuming stress relief annealing, 100% N ₂ , 95% N ₂ , 5% H _{2 In} each gas atmosphere, 850 ° C., after heat treatment for more than 2 hours, the measurement was divided into before/after heat treatment. measured.

(1) Adhesion measurement method: When the specimen is bent by 180° in contact with an arc of 10, 20, 30, or 100 mmφ, it is expressed as the minimum arc diameter without film peeling.

(2) Corrosion resistance measurement method: 5% by weight, 35 ℃, NaCl solution for 8 hours to evaluate the presence or absence of rust on the specimen. If the area of rust occurrence is 5% or less, it is excellent, if it is 20% or less, it is good, 20-50% is slightly bad, and if it is 50% or more, it is bad.

(3) Method of measuring iron loss improvement rate: It was measured based on iron loss (W17/50). W17/50 measures the power loss that occurs when a magnetic field with a frequency of 50Hz is magnetized to 1.7Tesla with alternating current. In Table 1, the iron loss improvement rate was calculated as {(core loss before coating - iron loss after coating)/core loss before coating} × 100, and in Table 2, the iron loss improvement rate was {(core loss before SRA - iron loss after SRA) / iron loss before SRA} × 100 was saved.

Comparative Examples 1 to 7

It was carried out in the same manner as in Example 1, but as an insulating coating composition, it was prepared by reacting a silicate represented by _{Si[CH 3} OH] _{4 with the metal hydroxides listed in Table 1 below, not sodium hydroxide.}

In Comparative Example 7, an insulating film was formed using a conventionally known phosphate-based insulating film composition.

division metal after coating
(Before SRA)
adhesion
(mmΦ) after coating
(Before SRA)
corrosion resistance after coating
(Before SRA)
iron loss improvement rate
(%) After SRA
adhesion
(mmΦ) After SRA
iron loss
improvement rate
(%) Comparative Example 1 Al 20 Good 6.2 30 -0.5 Comparative Example 2 Zr 30 Good 4.8 35 -1.1 Comparative Example 3 Ge 30 slightly bad 4.2 30 -0.2 Comparative Example 4 Mg 35 slightly bad 3.8 35 -0.1 Comparative Example 5 Sb 35 slightly bad 4.0 30 -0.6 Comparative Example 6 Sn 35 slightly bad 4.5 30 -0.9 Example 1 Na 15 Great 7.5 20 +0.5 Comparative Example 7 Phosphate-based
tension coating agent 25 Good 3.3 30 -2.0

Referring to Table 1, it can be seen that when a sodium compound is used, both film adhesion and corrosion resistance after coating are excellent. Based on these physical properties, it can be predicted that when the sodium silicate sol is formed in a gel form through the drying process, the film is very dense and the adhesion between the material and the film is excellent. In addition, it can be confirmed that the film tension of the potassium silicate sol is very excellent from the improvement of iron loss before/after coating by more than 2 times compared to normal.

1 shows the corrosion resistance evaluation results for the specimens of Example 1 and Comparative Example 7. Referring to FIG. 1 , it can be seen that the corrosion resistance of the embodiment according to the present invention is particularly excellent when compared with the case of using the phosphate-based insulating coating composition.

In addition, it can be confirmed that the film adhesion after SRA is at least 1.5 times superior to that of Comparative Examples 1 to 7 when the sodium silicate sol is coated as in Example 1.

2 shows the results of analyzing the insulating film components of the grain-oriented electrical steel sheet prepared in Example 1.

As a result of the analysis, Si: 25% by weight, Na: 2.5% by weight, Fe: 4.8% by weight and O ₂ : It was analyzed to contain 20.5% by weight, and it can be confirmed that the film tension and iron loss improvement rate is the best due to the appropriate element content.

The present invention is not limited to the above embodiments, but can be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (9)

A composition for forming an insulating film of a grain-oriented electrical steel sheet comprising a compound represented by the following formula (1).
[Formula 1]
[Na] ⁺ [(SiO(OR) ₂ ) _n OR] ^-
In Formula 1,
(R each is at least one of an alkyl group having 1 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 4 to 12 carbon atoms, an aralkyl group having 4 to 12 carbon atoms, and an alkaryl group having 4 to 12 carbon atoms,
n is an integer from 1 to 30.) According to claim 1,
The atomic ratio of silicon (Si) and sodium (Na) in the compound represented by Formula 1 is in the range of 20:1 to 7:1, a composition for forming an insulating film of a grain-oriented electrical steel sheet. delete grain-oriented electrical steel sheet substrate; and
Including an insulating film located on at least one surface of the substrate,
The insulating film includes, by weight, Si: 10 to 50%, Na: 0.5 to 10%, Fe: 0.1 to 10%, and the remainder of oxygen and unavoidable impurities,
The insulating film is a grain-oriented electrical steel sheet comprising a compound represented by the following formula (1).
[Formula 1]
[Na] ⁺ [(SiO(OR) ₂ ) _n OR] ^-
(In Formula 1,
R is at least one of an alkyl group having 1 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 4 to 12 carbon atoms, an aralkyl group having 4 to 12 carbon atoms, and an alkaryl group having 4 to 12 carbon atoms,
n is an integer from 1 to 30.) delete 5. The method of claim 4,
The insulating film is a grain-oriented electrical steel sheet further comprising at least one of Mg: 0.1 wt% or less, Al: 0.1 wt% or less, and Cr: 0.1 wt% or less. Applying the composition for forming an insulating film according to any one of claims 1 to 2 on the electrical steel sheet substrate; and
A method of manufacturing a grain-oriented electrical steel sheet comprising the step of forming an insulating film by drying the steel sheet coated with the composition for forming an insulating film. 8. The method of claim 7,
A method of manufacturing a grain-oriented electrical steel sheet in which the composition for forming an insulating film in the applying step is applied so that an application amount of the dried insulating film on the surface of the grain-oriented electrical steel sheet is in the ^{range of 0.1 to 6.0 g/m 2 .} 8. The method of claim 7,
A method of manufacturing a grain-oriented electrical steel sheet by heating and drying at 350 to 900° C. for 50 to 1200 seconds in the drying step.

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