KR102009391B1 - Oriented electrical steel sheet formed insulation coating and forming method of insulation coating for oriented electrical steel sheet - Google Patents

Abstract

Preparing a grain-oriented electrical steel sheet; Passing the oriented electrical steel sheet between a pair of first rolls to form a first insulating coating layer on the surface of the oriented electrical steel sheet; And forming a second insulating coating layer on the surface of the first insulating coating layer by passing the oriented electrical steel sheet on which the first insulating coating layer is formed between a pair of second rolls. On the other hand, a method for forming a grain-oriented electrical steel sheet is formed by rotating the first roll in the forward direction and rotating the second roll in the reverse direction.

Description

ORIENTED ELECTRICAL STEEL SHEET FORMED INSULATION COATING AND FORMING METHOD OF INSULATION COATING FOR ORIENTED ELECTRICAL STEEL SHEET}

The present invention relates to a grain-oriented electrical steel sheet and a grain-oriented electrical steel sheet insulating film formed method.

A grain-oriented electrical steel sheet is a soft magnetic material having excellent magnetic properties in the rolling direction composed of grains having a Goss orientation, which has a crystal orientation of {110} <001>.

The oriented electrical steel sheet is rolled to a final thickness through hot rolling, hot rolled sheet annealing, cold rolling after slab heating, and then manufactured through high temperature annealing for primary recrystallization annealing and secondary recrystallization.

An insulating coating is formed on the surface of the electrical steel sheet for the purpose of minimizing the power loss of the oriented electrical steel sheet. Insulation coating should basically have high electric insulation, good adhesion with material, and uniform color without any defect in appearance. In addition, due to the strengthening of international standards and competition in the transformer noise, the need for noise reduction of the insulating film has emerged.

When a magnetic field is applied to an electrical steel sheet used as a transformer core, contraction and expansion are repeated to cause tremor. This phenomenon is called magnetostriction or magnetostriction. This tremor causes vibration and noise in the transformer.

In the current commercialized oriented electrical steel sheet to form an insulating film by passing the directional electrical steel sheet with a base coating layer between the rolls, the roll is rotated in the same direction as the traveling direction of the steel sheet to finish with a forward insulation coating in one coating .

In the conventional method, the surface of the insulating film becomes rough, which causes problems in eddy current loss due to noise and heat generation when used after lamination.

Forming two insulating coating layers on the grain-oriented electrical steel sheet, by increasing the density of the insulating coating layer is finally coated can provide a grain-oriented electrical steel sheet to reduce the degree of surface roughness, and prevent eddy current loss in advance.

Method for forming a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises the steps of preparing a grain-oriented electrical steel sheet; Passing the oriented electrical steel sheet between a pair of first rolls to form a first insulating coating layer on the surface of the oriented electrical steel sheet; And forming a second insulating coating layer on the surface of the first insulating coating layer by passing the oriented electrical steel sheet on which the first insulating coating layer is formed between a pair of second rolls. The first roll is rotated in the forward direction, and the second roll is rotated in the reverse direction.

The forming of the first insulating coating layer may include: coating the insulating coating composition on the surface of the oriented electrical steel sheet by passing the oriented electrical steel sheet between a pair of first rolls; And drying the grain-oriented electrical steel sheet passed between the first rolls to form the first insulating coating layer.

In the step of coating the insulating coating composition on the surface of the grain-oriented electrical steel sheet, the coating amount of the insulation coating composition may be 0.5 to 1.0 g / m ² per one side of the grain-oriented electrical steel sheet.

In the forming of the first insulating coating layer, it may be dried at 830 to 860 ° C. for 35 to 48 seconds and cooled.

The forming of the second insulating coating layer may include coating an insulating coating composition on the surface of the first insulating coating layer by passing the oriented electrical steel sheet on which the first insulating coating layer is formed between a pair of second rolls; And drying the grain-oriented electrical steel sheet passed between the second rolls to form the second insulating coating layer.

In the step of coating the insulating coating composition on the surface of the first insulating coating layer, the coating amount of the insulating coating composition may be 1.5 to 3.0 g / m ² per one side of the grain-oriented electrical steel sheet.

In the step of forming the second insulating coating layer, it may be dried and cooled to give a tension to the grain-oriented electrical steel sheet for 25 to 40 seconds at 850 to 900 ℃.

In the step of forming the second insulating coating layer, the tension applied to the grain-oriented electrical steel sheet may be 0.5 to 2.5kg / cm ² .

After preparing the grain-oriented electrical steel sheet, the step of scarfing the base coating layer located on the surface of the grain-oriented electrical steel sheet; may further include.

After the forming of the second insulating coating layer, the step of stress-relieving annealing the oriented electrical steel sheet on which the first insulating coating layer and the second insulating coating layer is formed.

Directional electrical steel sheet formed with an insulating coating according to an embodiment of the present invention is a directional electrical steel sheet; A first insulating coating layer on the surface of the oriented electrical steel sheet; And a second insulating coating layer disposed on a surface of the first insulating coating layer and having a higher density than the first insulating coating layer.

The first insulation coating layer and the second insulation coating layer may include 0.05 to 70 wt% of inorganic nanoparticles and 30 to 99.5 wt% of metal phosphate.

The grain-oriented electrical steel sheet, in weight percent, Si: 2.8 to 4.5%, Al: 0.02 to 0.04%, Mn: 0.01 to 0.20%, at least one of Sb, Sn and Ni: 0.01 to 0.15%, balance Fe and inevitable It may contain impurities.

A base coating layer disposed between the oriented electrical steel sheet and the first insulating coating layer; further comprising a plurality of grooves formed on the surface of the base coating layer may be filled by the first insulating coating layer.

In the method for forming a grain-oriented electrical steel sheet according to an embodiment of the present invention, two layers of insulating coating layers are formed on the grain-oriented electrical steel sheet. It is possible to prevent eddy current loss by increasing the density of the insulating coating layer and drastically reducing the surface roughness.

1 is a view showing a method for forming an oriented electrical steel sheet insulating film according to an embodiment of the present invention.
FIG. 2 is a diagram schematically illustrating a grain-oriented electrical steel sheet having an insulating coating according to an embodiment of the present invention.
3 is a photograph showing an enlarged cross-sectional view of a grain-oriented electrical steel sheet having an insulating coating according to an embodiment of the present invention.
4 is a photograph showing the surface of Comparative Example 1 (left) and a photograph showing the surface of Example 1 (right).

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

The terminology used herein is for reference only to specific embodiments and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” include plural forms as well, unless the phrases clearly indicate the opposite. As used in the specification, the meaning of “comprising” embodies a particular characteristic, region, integer, step, operation, element and / or component, and the presence of another characteristic, region, integer, step, operation, element and / or component or It does not exclude the addition.

When a portion is referred to as being "on" or "on" another portion, it may be directly on or on the other portion or may be accompanied by another portion in between. In contrast, when a portion is referred to as "directly above" another portion, no other portion is intervened in between.

Unless defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Commonly defined terms used are additionally interpreted to have a meaning consistent with the related technical literature and the presently disclosed contents, and are not interpreted in an ideal or very formal sense unless defined.

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

In an embodiment of the present invention, the meaning of further including an additional element means to include iron (Fe), which is the balance by an additional amount of the additional element.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Oriented electrical steel sheet Insulation film  Forming method

In one embodiment of the present invention to form a double-layered insulating film on the oriented electrical steel sheet, when forming an insulating coating layer is finally coated to increase the density of the insulating coating layer by driving the roll in the reverse direction of the direction of the oriented electrical steel sheet In addition, it is possible to provide a method for forming a grain-oriented electrical steel sheet to prevent eddy current loss in advance by dramatically reducing the degree of surface roughness.

As can be seen in Figures 1 and 2, the method for forming a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises the steps of preparing a grain-oriented electrical steel sheet 100, a pair of directional electrical steel sheet 100 Passing through one roll 10 to form a first insulating coating layer 200 on the surface of the oriented electrical steel sheet 100 and a pair of second oriented electrical steel sheet 100 having the first insulating coating layer 200 formed thereon. Passing between the rolls 20 to form a second insulating coating layer 300 on the surface of the first insulating coating layer 200, the first roll 10 with respect to the traveling direction of the oriented electrical steel sheet 100 Rotate in the forward direction, and rotate the second roll 20 in the reverse direction.

The forward direction means a direction in which the tangential direction at the contact point of the first roll 10 in contact with the upper and lower surfaces of the grain-oriented electrical steel sheet 100 is the same as the advancing direction of the grain-oriented electrical steel sheet 100.

On the contrary, the reverse direction means a direction in which the tangential direction at the contact point of the second roll 20 in contact with the upper and lower surfaces of the grain-oriented electrical steel sheet 100 is opposite to the traveling direction of the grain-oriented electrical steel sheet 100.

After preparing the grain-oriented electrical steel sheet 100, the method may further include scarfing the base coating layer on the surface of the grain-oriented electrical steel sheet 100.

First, a grain-oriented electrical steel sheet 100 is prepared. Specifically, the grain-oriented electrical steel sheet 100 is a step of preparing a slab, heating, hot rolling the heated slab to produce a hot rolled sheet, cold rolled hot rolled sheet to prepare a cold rolled sheet, cold rolled sheet 1 The first recrystallization annealing and the first recrystallization annealing on the surface of the steel sheet may be prepared by applying an annealing separator and a second recrystallization annealing of the steel sheet coated with the annealing separator. Primary recrystallization annealing may include decarburization annealing and nitriding annealing.

The base coating layer including forsterite (Mg ₂ SiO ₄ ) may be formed through chemical reaction of the oxide layer and the MgO slurry produced in the step of applying the annealing separator inevitably produced in the decarburization annealing step.

Therefore, the roughness may be lowered by scarfing the base coating layer. Roughness can be lowered to 4 to 5 μm before scarfing, after scarfing at Ra 7 to 8 μm.

The directional electrical steel sheet 100 prepared through the above steps is passed between the pair of first rolls 10 to form a first insulating coating layer 200 on the directional electrical steel sheet 100. Specifically, the first insulating coating layer 200 may be formed on the base coating layer formed on the surface of the grain-oriented electrical steel sheet 100.

Specifically, the forming of the first insulating coating layer 200 includes passing the oriented electrical steel sheet 100 between the pair of first rolls 10 to coat the insulating coating composition on the surface of the oriented electrical steel sheet 100 and It may include the step of forming a first insulating coating layer 200 by drying the grain-oriented electrical steel sheet 100 passed between the first roll (10).

The first insulating coating layer 200 is formed on the upper and lower surfaces of the electrical steel sheet while passing between the pair of first rolls 10 rotating in opposite directions. The insulating coating composition supplied through the first roll 10 is applied to the upper and lower surfaces of the electrical steel sheet passing between the first rolls 10.

The insulation coating composition may include 0.05 to 70 wt% of inorganic nanoparticles and 30 to 99.5 wt% of metal phosphate.

When the base coating layer is scarfed on the upper and lower surfaces of the electrical steel sheet, the insulating coating composition may be filled between the plurality of grooves formed on the surface of the base coating layer.

Specifically, the coating amount of the insulating coating composition by the first roll 10 may be 0.5 to 1.0 g / m ² per one side of the grain-oriented electrical steel sheet (100). If the coating amount is less than 0.5g / m ² , it may be insufficient to fill a plurality of grooves formed on the surface of the base coating layer, and if it exceeds 1.0g / m ² , cracking may occur due to the weight of the first insulating coating layer 200. .

Thereafter, in the step of forming the first insulating coating layer 200, the drying may be performed through the first dryer 11 at 830 to 860 ° C. for 35 to 48 seconds, and then rapidly cooled through the quench cooler 12. The drying temperature and time may be adjusted as described above in order to prevent a poor film hardness due to incomplete drying of the first insulating coating layer 200. Specifically, it may be dried for 40 to 45 seconds.

The directional electrical steel sheet 100 on which the first insulating coating layer 200 is formed is passed between the pair of second rolls 20 to form a second insulating coating layer 300 on the first insulating coating layer 200.

Specifically, the forming of the second insulating coating layer 300 passes the oriented electrical steel sheet 100 on which the first insulating coating layer 200 is formed between the pair of second rolls 20 to pass the insulating coating composition to the first insulating layer. The method may include coating the surface of the coating layer 200 and drying the oriented electrical steel sheet 100 passed between the second rolls 20 to form the second insulating coating layer 300.

The second insulating coating layer 300 is formed on the upper and lower surfaces of the first insulating coating layer 200 while passing between the pair of second rolls 20 rotating in opposite directions. The insulating coating composition supplied through the second roll 20 is applied to the upper and lower surfaces of the electrical steel sheet passing between the second rolls 20.

Since the second roll 20 rotates in the reverse direction with respect to the advancing direction of the electrical steel sheet, it is possible to apply the insulating coating composition in a dense manner. Accordingly, the density of the second insulating coating layer 300 may be formed relatively higher than that of the first insulating coating layer 200. Due to the high density, the interplate adhesion and spot rate can be increased. In addition, it is possible to secure the beauty, insulation and corrosion resistance of the surface of the second insulating coating layer (300).

Specifically, the coating amount of the insulating coating composition by the second roll 20 may be 1.5 to 3.0 g / m ² per one side of the grain-oriented electrical steel sheet (100). The amount of the insulating coating composition applied to form the first insulating coating layer 200 is greater than that. If the coating amount is less than 1.5g / m ² , an excessively thin film is formed, so that the effect of improving adhesion may be insignificant. When the coating amount is more than 3.0g / m ² , the crack may be caused by the weight of the second insulating coating layer 300. have.

Subsequently, in the step of forming the second insulating coating layer 300, the tension is applied to the grain-oriented electrical steel sheet 100 through the second dryer 21 for 25 to 40 seconds at 850 to 900 ° C., and cooled by slow cooling. Can be. The drying temperature and time may be adjusted as described above in order to prevent poor coating hardness due to incomplete drying of the second insulating coating layer 300. Specifically, it may be dried for 30 to 35 seconds.

Tension imparted to the grain-oriented electrical steel sheet (100) there between 0.5 and 2.5kg / cm ² il may be limited if the 0.5 kg / cm ² below, the iron loss reducing effect. On the other hand, when it exceeds 2.5 kg / cm ² , the tension is excessively high may cause the separation of the second insulating coating layer 300. Specifically, the tension applied to the grain-oriented electrical steel sheet 100 may be 1 to 2kg / cm ² .

After the forming of the second insulating coating layer 300, the method may further include stress reducing annealing of the oriented electrical steel sheet 100 on which the first insulating coating layer 200 and the second insulating coating layer 300 are formed. Insulation, corrosion resistance and magnetic properties may be improved through stress relief annealing at 700 to 800 ° C. for 30 minutes to two hours.

Oriented electrical steel sheet Insulation film  Formed directional electrical steel sheet

As can be seen in Figures 2 and 3, the directional electrical steel sheet formed with an insulating coating according to an embodiment of the present invention is a directional electrical steel sheet 100, the first insulating coating layer located on the surface of the directional electrical steel sheet 100 ( 200 and a second insulating coating layer 300 disposed on the surface of the first insulating coating layer 200 and having a higher density than the first insulating coating layer 200.

The first insulating coating layer 200 is formed on the surface of the electrical steel sheet, the second insulating coating layer 300 is formed on the surface of the first insulating coating layer 200. As described in the method for forming the oriented electrical steel sheet, the first insulating coating layer 200 is coated using a first roll that rotates in the forward direction, and the second insulating coating layer 300 is rotated in the reverse direction. The coating is performed using a roll, and the coating amount of the insulating coating composition is greater than that of the first insulating coating layer 200, and the density is higher than that of the first insulating coating layer 200. Specifically, the thickness of the first insulating coating layer 200 is 1 to 10㎛, the density by dividing the height of the first insulating coating layer 200 by the coating amount of the insulating coating composition per area applied to the first insulating coating layer 200 Can be calculated. The thickness of the second insulating coating layer 300 is 1 to 10 μm, and the density is similarly calculated by dividing the height of the second insulating coating layer 300 by the application amount of the insulating coating composition per area applied to the second insulating coating layer 300. Can be.

As can be seen in FIG. 4, the second insulating coating layer 300 can be expected to have an effect of preventing eddy current loss due to its beautiful surface, and has high insulation and corrosion resistance. In detail, the surface roughness Ra of the second insulating coating layer 300 may be 0.1 to 0.6 μm.

Specifically, the grain-oriented electrical steel sheet by weight, Si: 2.8 to 4.5%, Al: 0.02 to 0.04%, Mn: 0.01 to 0.20%, at least one of Sb, Sn and Ni: 0.01 to 0.15%, balance Fe and It may contain unavoidable impurities.

Hereinafter, the reason for component limitation of the grain-oriented electrical steel sheet will be described.

Si: 2.8 to 4.5 wt%

Silicon (Si) plays a role of reducing iron loss by increasing the specific resistance of steel. If the content of silicon (Si) is too small, the specific resistance of steel is reduced, and the iron loss characteristics are deteriorated. Recrystallization may become unstable. When the content of silicon (Si) is too large, a problem may occur that the brittleness becomes large and cold rolling becomes difficult. Therefore, it is possible to control the content of silicon (Si) in the above range.

Al: 0.020 to 0.040 wt%

Aluminum (Al) is finally a nitride in the form of AlN, (Al, Si) N, (Al, Si, Mn) N and acts as an inhibitor. If the content of aluminum (Al) is too small, it is difficult to expect a sufficient effect as an inhibitor. If the content of aluminum (Al) is too high, the Al-based nitride precipitates and grows so coarsely that the effect as an inhibitor may be insufficient. Therefore, the content of aluminum (Al) can be adjusted in the above-described range.

Mn: 0.01 to 0.20 wt%

Manganese (Mn) has the effect of reducing the iron loss by increasing the specific resistance similar to that of silicon (Si), and precipitates of (Al, Si, Mn) N by reacting with nitrogen introduced by nitriding treatment with silicon (Si). To form. When the content of manganese (Mn) is too small, the austenite-forming element, when reheating hot rolled, increases the austenite fraction to increase the high capacity of precipitates, and when re-precipitation, the primary recrystallization through the refinement of precipitates and MnS formation is not excessive. Ineffective effects may occur. When the content of manganese (Mn) is too high, it promotes austenite phase transformation during hot rolling, thereby reducing the size of the primary recrystallized grains, thereby destabilizing the secondary recrystallization. Therefore, the content of manganese (Mn) can be adjusted in the above-described range.

At least one of Sb, Sn and Ni: 0.01 to 0.15 wt%

Antimony (Sb) and tin (Sn) Nickel (Ni) is a grain boundary segregation element and is an element that hinders the movement of grain boundaries. It is an important element in controlling the grain size because it promotes the generation of goth grains in the {110} <001> direction so that secondary recrystallization is well developed. If the content of one or more of the antimony (Sb), tin (Sn) and nickel (Ni) is too small, the effect may be reduced. If the content of at least one of antimony (Sb), tin (Sn) and nickel (Ni) is added too much, grain boundary segregation may occur severely, leading to brittleness of the steel sheet, which may cause plate breakage during rolling.

Specifically, the first insulation coating layer 200 and the second insulation coating layer 300 may include 0.05 to 70 wt% of inorganic nanoparticles and 30 to 99.5 wt% of metal phosphate.

If too little inorganic nanoparticles are included, the ceramic layer may not be formed, thereby causing a problem of imparting sufficient tensile stress to the grain-oriented electrical steel sheet. If too much inorganic nanoparticles are included, there is a problem in that the solid content is increased and the quality of the surface of the grain-oriented electrical steel sheet is degraded. Therefore, the addition amount of the inorganic nanoparticles can be adjusted in the above-described range.

When too little metal phosphate is included, the adhesive strength of the insulating coating composition forming the first insulating coating layer 200 and the second insulating coating layer 300 may be lowered, which may cause a problem of deterioration of the film tension and adhesion. If too much metal phosphate is included, insulation properties may be degraded. Therefore, the addition amount of the metal phosphate can be adjusted in the above-described range.

Inorganic nanoparticles include mullite (Al ₆ Si ₂ O ₁₃ ), cordierite ((Mg, Fe) ₂ Al ₄ Si ₅ O ₁₈ ), zircon (ZrSiO ₄ ), spinel (MgAl ₂ O ₄ ), montiselite (CaMgSiO ₄ ), olinite (Al ₂ Si ₂ O ₅ (OH) ₄ ), sapphire ((Mg, Al) ₈ (Al, Si) ₆ O ₂ ), aluminum titanate (Al ₂ TiO ₅ ), zinc It may include one or more of titanate (ZnTiO ₃ ), lithium aluminate (LiAlO ₂ ), titanium silicon oxide (TiSiO ₄ ) and tepropite (Mn ₂ SiO ₄ ).

The average particle diameter of the inorganic nanoparticles may be 0.01 to 0.30 μm. Accordingly, the stability of the insulating coating composition forming the first insulating coating layer 200 and the second insulating coating layer 300 can be maintained for a long time, the surface filling properties can be improved, and the insulating properties can be improved.

The metal phosphate may include one or more of Al, Mg, Ca, Ni, Co, and Mn.

Specifically, the metal phosphate may be aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₃ ), calcium hydroxide (Ca (OH) ₂ ), nickel hydroxide (Ni (OH) ₂ ), cobalt hydroxide (Co ( OH) ₂ ) and manganese hydroxide (Mn (OH) ₂ ) may be formed by the reaction of at least one hydroxide with phosphoric acid (H ₃ PO ₄ ).

Hereinafter, specific examples of the present invention will be described. However, the following examples are only specific examples of the present invention, and the present invention is not limited to the following examples.

Example

Silicon (Si): 3.4 wt%, Aluminum (Al): 0.03 wt%, Manganese (Mn): 0.05 wt% Antimony (Sb): 0.04 wt%, Tin (Sn): 0.09 wt%, and Nickel (Ni): 0.02% by weight, balance: A grain-oriented electrical steel sheet made of iron (Fe) and unavoidable impurities was prepared.

The insulation coating composition was prepared with a component containing 35% by weight of inorganic nanoparticles and 65% by weight of metal phosphate.

Then, as shown in Table 1, in the case of Examples 1, 2, and 3, the first insulating coating layer is formed by passing through primary rolls that rotate in the forward direction with respect to the advancing direction of the grain-oriented electrical steel sheet. It was. The second insulating coating layer was coated by passing through the rolls continuously rotating in the reverse direction to coat the second insulating layer, and then subjected to stress relief annealing (SRA) at 750 ° C.

In the case of Comparative Example 1, without forming the primary coating layer, only the secondary coating layer was passed through the roll rotating in the reverse direction to form a coating layer. The subsequent process was performed in the same manner as in the embodiment.

Iron loss, magnetic flux density, insulation property, etc. of Example 1, Example 2, Example 3, and Comparative Example 1 were evaluated and compared.

Magnetic properties of oriented electrical steel sheets are usually W _17/50 and B ₈ used. W _17/50 means when sikyeoteul magnetized with the alternate current magnetic field frequency of 50Hz to 1.7Tesla, the power loss (W / kg) appears. Tesla is the unit of magnetic flux density, which means flux per unit area. B ₈ represents the magnetic flux density value Tesla flowing in the grain-oriented electrical steel sheet when a current amount of 800 A / m flows through the winding wound around the electrical steel sheet.

Drying tension refers to the tension applied to the grain-oriented electrical steel sheet during drying.

Insulation was also measured using a Franklin meter in accordance with ASTM A717 International Standard.

division Application amount
(g / m ² ) Drying temperature
(℃) Retention time
(second) Drying tension
(kg / m ² ) Primary
coating Secondary
coating Primary
coating Secondary
coating Primary
coating Secondary
coating Secondary
coating Comparative Example 1 0 One - 800 - 20 0 Example 1 0.5 1.5 830 850 40 30 One Example 2 One 2 860 900 45 35 2 Example 3 3 4 900 950 50 45 3

division Iron loss
(W _17/50 , W / kg) Magnetic flux density
(B ₈ , T) Insulation
(mA) Insulation after SRA
(mA) Iron loss after SRA
(W _17/50 , W / kg) Comparative Example 1 0.820 1.920 170 240 0.800 Example 1 0.790 1.954 50 0 0.770 Example 2 0.780 1.952 50 0 0.756 Example 3 0.810 1.925 150 120 0.830

As shown in Table 2 above, it can be confirmed that the characteristics of Examples 1 to 3 are superior to Comparative Example 1. In addition, it can be confirmed that the properties are more excellent when the stress relief annealing (SRA) after coating.

In addition, it can be confirmed that the characteristics of Examples 1 and 2, which satisfy the coating amount, drying temperature, holding time and drying tension than Example 3 is excellent.

As can be seen through Figure 4, the stripe occurs on the surface of the oriented electrical steel sheet formed with an insulating coating according to Comparative Example 1, but the stripe does not occur on the surface of the oriented electrical steel sheet formed with an insulating coating according to Example 1 more beautiful surface It can be confirmed that has.

The present invention is not limited to the above embodiments and / or embodiments, but may be manufactured in various forms, and a person of ordinary skill in the art to which the present invention pertains may change the technical spirit or essential features of the present invention. It will be appreciated that it can be practiced in other specific forms without doing so. Therefore, it is to be understood that the embodiments and / or embodiments described above are illustrative in all respects and not restrictive.

10: first roll 11: first dryer
12: quenching machine 20: second roll
21: second dryer
100: grain-oriented electrical steel 200: first insulating coating layer
300: second insulating coating layer

Claims (14)

Preparing a grain-oriented electrical steel sheet;
Passing the oriented electrical steel sheet between a pair of first rolls to apply an insulating coating composition by 0.5 to 1.0 g / m ² per one side of the oriented electrical steel sheet to coat the surface of the oriented electrical steel sheet;
Drying the grain-oriented electrical steel sheet passed between the first rolls to form a first insulating coating layer;
Passing the oriented electrical steel sheet formed with the first insulating coating layer between a pair of second rolls to apply an insulating coating composition by 1.5 to 3.0g / m ² per one side of the oriented electrical steel sheet to coat the surface of the first insulating coating layer step; And
And drying the oriented electrical steel sheet passed between the second rolls to form a second insulating coating layer.
The method of claim 1, wherein the first roll is rotated in the forward direction and the second roll is rotated in the reverse direction with respect to the traveling direction of the oriented electrical steel sheet. delete delete The method of claim 1,
In the step of forming the first insulating coating layer,
Method for forming a grain-oriented electrical steel sheet to dry at 830 to 860 ℃ for 35 to 48 seconds, and to cool. delete delete The method of claim 1,
In the step of forming the second insulating coating layer,
Method for forming a grain-oriented electrical steel sheet insulation film to dry and cool to give a tension to the grain-oriented electrical steel sheet for 25 to 40 seconds at 850 to 900 ℃. The method of claim 7, wherein
In the step of forming the second insulating coating layer,
The tension applied to the grain-oriented electrical steel sheet is 0.5 to 2.5kg / cm ^{2 The} method of forming an oriented electrical steel sheet insulation film. The method of claim 1,
After preparing the grain-oriented electrical steel sheet,
Scarping the base coating layer located on the surface of the grain-oriented electrical steel sheet; further comprising a. The method of claim 1,
After forming the second insulating coating layer,
Stress-treating annealing of the oriented electrical steel sheet having the first insulating coating layer and the second insulating coating layer; The method of claim 1, further comprising a. By weight%, Si: 2.8 to 4.5%, Al: 0.02 to 0.04%, Mn: 0.01 to 0.20%, at least one of Sb, Sn and Ni: 0.01 to 0.15%, directional electricity containing residual Fe and unavoidable impurities Steel plate;
A first insulating coating layer on the surface of the oriented electrical steel sheet; And
And a second insulating coating layer disposed on a surface of the first insulating coating layer and having a higher density than the first insulating coating layer. The method of claim 11,
The first insulating coating layer and the second insulating coating layer,
A grain-oriented electrical steel sheet having an insulating coating comprising 0.05 to 70% by weight of inorganic nanoparticles and 30 to 99.5% by weight of metal phosphate. delete The method of claim 11,
And a base coating layer positioned between the directional electrical steel sheet and the first insulating coating layer.
The grain-oriented electrical steel sheet having an insulating coating is formed by filling the plurality of grooves formed on the surface of the base coating layer by the first insulating coating layer.

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