KR20180083295A - Annealing separating agent composition for grain oriented electrical steel sheet, grain oriented electrical steel sheet, and method for manufacturing grain oriented electrical steel sheet - Google Patents

Abstract

The present invention provides an annealing separating agent composition for a grain-oriented electrical steel plate, a grain-oriented electrical steel plate, and a manufacturing method of a grain-oriented electrical steel plate. The annealing separating agent composition for a grain-oriented electrical steel plate according to one embodiment of the present invention comprises: 5-70 wt% of mullite with respect to the total weight percent basis of a solid annealing separating agent; and the remaining including magnesium oxide or magnesium hydroxide.

Description

TECHNICAL FIELD [0001] The present invention relates to an annealing separator composition for a directional electric steel sheet, a directional electric steel sheet and a method for manufacturing a directional electric steel sheet,

An annealing separator composition for a directional electric steel sheet, a directional electric steel sheet, and a method for producing a directional electric steel sheet.

Generally, a grain-oriented electrical steel sheet refers to an electrical steel sheet containing a Si component in a steel sheet and having an aggregate structure in which the grain orientations are aligned in the {100} < 001 > direction, and has extremely excellent magnetic properties in the rolling direction .

Generally known directional electric steel sheets are formed by forming an insulating film on a forsterite (Mg ₂ SiO ₄ ) base coat and applying a tensile stress to the steel sheet by using the difference in thermal expansion coefficient of the insulating film, And noise reduction effect due to magnetostriction is achieved, but there is a limit to satisfy the characteristic level in the advanced directional electric steel sheet which is recently required.

There has been proposed a method of improving the surface characteristics of TiO ₂ powder in MgO in the step of applying an anti-fusion agent containing MgO as a main component in order to improve the characteristics of the forsterite coating film in the conventional directional electric steel sheet manufacturing process.

In addition, the surface of the steel sheet, the decarburization-annealed sheet surface kaolinite to _{(Al 4 Si 4 O 10 (} OH) 8) the solution is applied as the annealing separator is carried out to finish annealing to improve the film tension than the conventional forsterite, mullite and A method of forming a composite coating composed of silica has been proposed. However, this method is difficult to control in a high temperature annealing process and it is difficult to form a uniform quality because of the dual structure of a dual coating structure in which kaolinite is decomposed and the upper part is composed of mullite and the lower part is made of silica. There is a problem that the adhesion is heated.

Also known is a method for improving the iron loss of a grain-oriented electrical steel sheet by applying a mixture of alumina powder or colloidal silica and MgCl ₂ as a fusion preventive agent to remove the forsterite coating. However, such a method has a problem that the iron loss of the electrical steel sheet is rather disadvantageous due to the removal of the forsterite coating, and there is a problem that it is difficult to form an insulating film in a subsequent process.

An annealing separator composition for a directional electric steel sheet, a directional electric steel sheet and a method for producing a directional electric steel sheet. Specifically, the present invention provides an annealing separator composition for a directional electric steel sheet, a directional electric steel sheet and a method for producing a directional electric steel sheet, which are excellent in adhesion and film tension and capable of improving iron loss of a material.

An annealing separator for a directional electric steel sheet according to an embodiment of the present invention comprises 5 to 70% by weight of mullite, and the balance magnesium oxide or magnesium hydroxide based on 100% by weight of solids.

And 0.1 to 20% by weight of a metal hydroxide.

Hydroxide metal is _{Ni (OH) 2, Co (} OH) 2, Cu (OH) 2, Sr (OH) 2, Ba (OH) 2, Pd (OH) 2, In (OH) 3, Bi (OH) 3 And Sn (OH) ₂ .

And 0.5 to 10 parts by weight of a ceramic powder.

Ceramic powder may comprise at least one member selected from _{MnO, Al 2 O 3, SiO} 2, TiO 2 and ZrO _2.

_{Sb 2 (SO 4) 3,} SrSO 4, BaSO 4 , or may be one further comprising to 10% by weight of the combination of the two.

The directional electrical steel sheet according to an embodiment of the present invention is formed with a film including mullite and forsterite on one or both surfaces of the oriented electrical steel sheet substrate.

The coating may contain 0.5 to 50% by weight of Al.

The coating may further comprise 3 to 80% by weight of Mg, 3 to 80% by weight of Si, 3 to 80% by weight of O and Fe as the balance.

The coating may have a thickness of 0.1 to 10 mu m.

And a ceramic layer formed on the coating film.

The ceramic layer may comprise a ceramic powder.

Ceramic powder is _{Al 2 O 3, SiO 2,} TiO 2, ZrO 2, Al 2 O 3 · TiO 2, Y 2 O 3, 9Al 2 O 3 · B 2 O 3, BN, CrN, BaTiO 3, SiC and TiC And the like.

The ceramic layer may further comprise a metal phosphate.

The metal phosphate may include at least one selected from Mg, Ca, Ba, Sr, Zn, Al and Mn.

The directional electrical steel sheet base material is composed of 2.8 to 4.5 wt% of silicon (Si), 0.020 to 0.040 wt% of aluminum (Al), 0.01 to 0.20 wt% of manganese (Mn), and at least one of antimony (Sb) Ni) or a combination thereof in an amount of 0.01 to 0.15% by weight, the balance being Fe and other unavoidable impurities.

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes: preparing a steel slab; Heating the steel slab; Hot-rolling the heated steel slab to produce a hot-rolled steel sheet; Cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; A first recrystallization annealing of the cold rolled sheet; Applying an annealing separator on the surface of the primary recrystallized annealed steel sheet; And secondary annealing the steel sheet coated with the annealing separator.

The annealing separator comprises 5 to 70% by weight of mullite, based on 100% by weight of the total solid content, and the balance magnesium oxide or magnesium hydroxide.

After the step of secondary recrystallization annealing, a step of forming a ceramic layer on the film including mullite and forsterite may be further included.

The step of forming the ceramic layer may be a step of forming a ceramic layer by spraying a ceramic powder on the coating.

The step of forming the ceramic layer may be a step of forming a ceramic layer by applying a composition for forming a ceramic layer containing ceramic powder and metal phosphate on the coating.

The first recrystallization annealing step of the cold-rolled sheet may include decarburization annealing and nitriding annealing at the same time of the cold-rolled sheet, or nitriding annealing after decarburization annealing.

According to one embodiment of the present invention, it is possible to provide a grain-oriented electrical steel sheet having excellent iron loss and magnetic flux density and excellent adhesion and insulation of a film, and a method for producing the same.

1 is a schematic side cross-sectional view of a directional electric steel sheet according to an embodiment of the present invention.
2 is a flowchart of a method of manufacturing a directional electrical steel sheet according to an embodiment of the present invention.
3 is a scanning electron microscope (SEM) photograph of the film of the grain-oriented electrical steel sheet produced in Example 9. Fig.
4 is an X-ray diffraction (XRD) result of the film of the grain-oriented electrical steel sheet produced in Example 9. Fig.
5 is a scanning electron microscope (SEM) photograph of the film of the grain-oriented electric steel sheet produced in Comparative Example 2. Fig.

The terms first, second and third, etc. are used to describe various portions, components, regions, layers and / or sections, but are not limited thereto. These terms are only used to distinguish any moiety, element, region, layer or section from another moiety, moiety, region, layer or section. Thus, a first portion, component, region, layer or section described below may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified and that the presence or absence of other features, regions, integers, steps, operations, elements, and / It does not exclude addition.

When referring to a portion as being "on" or "on" another portion, it may be directly on or over another portion, or may involve another portion therebetween. In contrast, when referring to a part being "directly above" another part, no other part is interposed therebetween.

In the present invention, 1 ppm means 0.0001%.

In an embodiment of the present invention, the meaning further comprising additional components means that the additional components are replaced by additional amounts of the additional components.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

An annealing separator composition for a directional electric steel sheet according to an embodiment of the present invention comprises 5 to 70% by weight of mullite, and the balance magnesium oxide or magnesium hydroxide on a solid basis. Here, the solid content standard means that the solid content excluding the components such as solvent is set to 100% by weight.

Hereinafter, the annealing separator composition according to one embodiment of the present invention will be described in detail for each component.

The annealing separator composition according to an embodiment of the present invention is applied to a grain oriented electrical steel sheet substrate 10 to form a coating 20 containing mullite and forsterite.

Mullite was the only compound to be stabilized between the car and Silas alumina, it is 3Al ₂ O ₃ · 2SiO ₂ as the composition. Mullite has a small coefficient of thermal expansion (5 × 10 ^-6 / ° C), which makes it easy to improve iron loss by imparting the film tension. In addition, mullite has a relatively low modulus of elasticity, and therefore has excellent thermal shock resistance.

The existing primary coating, forsterite (Mg ₂ SiO ₄ ), is formed by the chemical reaction between the internal oxide layer (SiO ₂ ) present in the coil and magnesium oxide (MgO) in the annealing separator at high temperature annealing. Conventional forsterite coatings have an excellent function to prevent plate adhesion due to contact between coils during a high temperature annealing process, but there is a limit to open the film tension imparting ability and insulating property.

In one embodiment of the present invention, by adding mullite in addition to magnesium oxide or magnesium hydroxide, it is possible to dramatically improve the film-forming ability and the insulating property. However, when only mullite is used alone as the annealing separator, there is a problem that the difference in thermal expansion coefficient is extremely large during the secondary recrystallization annealing process and the peeled off is peeled off. In addition, the mullite component has a high specific gravity when it is used as an annealing separator and has a problem that it is not dispersed in a solvent and sinks, so that it may be difficult to uniformly coat the surface of an electric steel sheet. In one embodiment of the present invention, mullite is not used alone, but is used in combination with magnesium oxide or magnesium hydroxide.

Kaolinite _{(Al 4 Si 4 O 10 (} OH) 8) formed in the case, the bottom by a secondary recrystallization annealing process is difficult to control from the difficulty in forming a uniform quality, and degradation of the kaolinite comprising an annealing separator There is a problem in that the adhesion is heated due to the silica coating.

In one embodiment of the present invention, the annealing separator composition comprises mullite in an amount of 5 to 70 wt.% Solids. When mullite is included in a small amount, improvement of coating tension and insulation properties may not be sufficient. If too much mullite is included, there may be a problem in uniformly applying the annealing separator. And thus may include mullite in the aforementioned ranges.

The metal hydroxide acts to change the surface property from hydrophobic to hydrophilic by chemical reaction with the surface of mullite. Thus, it dramatically improves the dispersibility of mullite and helps to form a uniform fosterite coating. In addition, the metal hydroxide has a lowered melting point, so that the film-forming temperature is lowered in the secondary recrystallization annealing step, and surface characteristics of good quality can be secured. Further, the forsterite coating formed in the low temperature region has an effect of inhibiting the decomposition of the AlN system inhibitor, which has a decisive influence on the formation of the secondary recrystallization, and can ensure excellent magnetic quality.

In one embodiment of the present invention, the annealing separator composition may further contain 0.1 to 20% by weight of metal hydroxide. When the amount of the metal hydroxide is too small, there is a problem in sufficiently exhibiting the above-mentioned effect. If too much metal hydroxide is contained, the metal component diffuses into the inside to form a film, which may result in non-uniform poststellite formation behavior.

Here, the metal hydroxide means a metal hydroxide other than the above-mentioned magnesium hydroxide. Specifically, hydroxide, metal is _{Ni (OH) 2, Co (} OH) 2, Cu (OH) 2, Sr (OH) 2, Ba (OH) 2, Pd (OH) 2, In (OH) 3, Bi (OH ) ₃ and Sn (OH) ₂ .

Magnesium oxide (MgO) or magnesium hydroxide (Mg (OH) ₂ ) serves to supply Mg to the coating. In one embodiment of the present invention, the annealing separator composition may be present in the form of a slurry for easy application to the surface of the oriented electrical steel sheet substrate. When the slurry contains water as a solvent, the magnesium oxide is readily soluble in water and may be present in the form of magnesium hydroxide. Therefore, in one embodiment of the present invention, magnesium oxide and magnesium hydroxide are treated as one component.

The annealing separator composition according to an embodiment of the present invention may further include 0.5 to 10% by weight of a ceramic powder. Ceramic powder may comprise at least one member selected from _{MnO, Al 2 O 3, SiO} 2, TiO 2 and ZrO _2. When the ceramic powder further contains an appropriate amount, the insulating property of the formed film 20 can be further improved.

Annealing separator composition according to one embodiment of the present invention, _{Sb 2 (SO 4) 3,} SrSO 4, BaSO 4 , or may be one further comprising to 10% by weight of the combination of the two. _{Sb 2 (SO 4) 3,} SrSO 4, BaSO 4 , or by an appropriate amount more combinations thereof, surface gloss can be excellent and the roughness produced very aesthetic oriented electrical steel sheet.

The annealing separator composition may further comprise a solvent for even dispersion and easy application of the solids. As the solvent, water, alcohol and the like can be used, and 300 to 1000 parts by weight can be included relative to 100 parts by weight of the solid content. As such, the annealing separator composition may be in the form of a slurry.

The directional electrical steel sheet 100 according to an embodiment of the present invention is formed with a film 20 including mullite and forsterite on one or both sides of the oriented electrical steel sheet substrate 10. 1 is a schematic side cross-sectional view of a directional electrical steel sheet according to an embodiment of the present invention. 1 shows a case where a coating film 20 is formed on the upper surface of a grain-oriented electrical steel sheet substrate 10.

The film 20 including mullite and forsterite has excellent film-tension-imparting ability and insulation property compared to the conventional posterior film and has a low melting point, so that the temperature for forming the film 20 is lowered in the secondary recrystallization annealing process, It is possible to secure the surface characteristics of the substrate. In addition, the coating film 20 formed in the low temperature region has an effect of suppressing the decomposition of the AlN system inhibitor, which has a decisive influence on the formation of the secondary recrystallization, and can ensure excellent magnetic quality. Since this has been described above, redundant description will be omitted.

The coating 20 may further comprise an Al-Mg-Si composite in addition to mullite and forsterite.

The coating film 20 may contain 0.5 to 50% by weight of Al. If the Al content in the film 20 is too small, the iron loss of the grain-oriented electrical steel sheet may be deteriorated. If the Al content in the coating film 20 is too high, the corrosion resistance may become dull. Therefore, Al can be included in the above-mentioned range. Al can be derived from the annealing separator composition and the oriented electrical steel sheet substrate 10 described above.

The coating film 20 may further contain 3 to 80% by weight of Mg, 3 to 80% by weight of Si, 3 to 80% by weight of O and Fe as the balance. The Mg, Si and Fe element compositions are derived from the components in the substrate and the annealing separator component. In the case of O, it can be derived from the annealing separator component or can be infiltrated in the heat treatment process. And may further contain other impurity components such as carbon (C).

The coating 20 may have a thickness of 0.1 to 10 mu m. If the thickness of the film 20 is too small, the capacity of imparting the film tension may be lowered, which may cause a problem of heat loss. If the thickness of the coating film 20 is too large, the drop rate may be lowered and the problem of heat transfer characteristic may occur. Therefore, the thickness of the foresterite coating 20 can be adjusted to the above-mentioned range. More specifically, the thickness of the foresterite coating 20 may be 0.8 to 6 占 퐉.

The directional electrical steel sheet 100 according to an embodiment of the present invention may further include a ceramic layer 30 on the coating 20. 1 shows an example in which a ceramic layer 30 is further formed on the forsterite coating 20. [

The thickness of the ceramic layer 30 may be 0.5 to 5 占 퐉. If the thickness of the ceramic layer 30 is too small, the insulating effect of the ceramic layer 30 may be small. If the thickness of the ceramic layer 30 is too thick, the adhesion of the ceramic layer 30 becomes low, and peeling may occur. Therefore, the thickness of the ceramic layer 30 can be adjusted to the above-mentioned range. More specifically, the thickness of the ceramic layer 30 may be 0.8 to 3.2 占 퐉.

The ceramic layer 30 may comprise a ceramic powder. Ceramic powder is _{Al 2 O 3, SiO 2,} TiO 2, ZrO 2, Al 2 O 3 · TiO 2, Y 2 O 3, 9Al 2 O 3 · B 2 O 3, BN, CrN, BaTiO 3, SiC and TiC And the like. The particle size of the ceramic powder may be 2 to 900 nm. If the particle size of the ceramic powder is too small, the formation of the ceramic layer may become difficult. If the particle diameter of the ceramic powder is too large, the surface roughness may become coarse and surface defects may occur. Therefore, the particle diameter of the ceramic powder can be adjusted to the above-mentioned range.

The ceramic powder may be in the form of any one or more selected from the group including spherical, plate-like, and needle-shaped.

The ceramic layer 30 may further comprise a metal phosphate. The metal phosphate may include at least one selected from Mg, Ca, Ba, Sr, Zn, Al and Mn. When the metal phosphate further includes the metal oxide, the insulating property of the ceramic layer 30 is further improved.

The metal phosphate may be composed of a compound by chemical reaction of metal hydroxide and phosphoric acid (H ₃ PO ₄ ).

(OH) ₂ , Al (OH) ₃ , Mg (OH) ₂ , B (OH) ₂ and the like, and the metal hydroxide is a compound formed by a chemical reaction of metal hydroxide and phosphoric acid (H ₃ PO ₄ ) ₃ , Co (OH) ₂ and Cr (OH) ₃ .

Specifically, the metal atom of the metal hydroxide is formed by forming a single bond, a double bond, or a triple bond by a substitution reaction with phosphorus, and the amount of unreacted free phosphoric acid (H ₃ PO ₄ ) is 25 wt% or less .

The metal phosphate may be a compound formed by a chemical reaction between metal hydroxide and phosphoric acid (H ₃ PO ₄ ), and the weight ratio of metal hydroxide to phosphoric acid may be expressed by 1: 100 to 40: 100.

If the amount of the metal hydroxide is too much, the chemical reaction may not be completed and the problem of precipitate may occur. If the metal hydroxide is contained too much, the problem of corrosion resistance may occur. have.

In one embodiment of the present invention, the effects of the annealing separator composition and coating 20 are exhibited regardless of the composition of the grain-oriented electrical steel sheet substrate 10. Supplementally, the components of the oriented electrical steel sheet substrate 10 will be described as follows.

The grain-oriented electrical steel sheet substrate 10 is composed of 2.8 to 4.5% by weight of silicon (Si), 0.020 to 0.040% by weight of aluminum (Al), 0.01 to 0.20% by weight of manganese (Mn) , Nickel (Ni), or a combination thereof in an amount of 0.01 to 0.15% by weight, the balance being Fe and other unavoidable impurities.

The reason for limiting the components of the grain-oriented electrical steel sheet substrate 10 will be described below.

Si: 2.8 to 4.5 wt%

Silicon (Si) increases the resistivity of the steel to reduce iron loss. When the content of Si is too small, the resistivity of the steel becomes small and the iron loss characteristic deteriorates. In the high temperature annealing, Problems can arise. If the content of Si is too large, the brittleness is increased and cold rolling may become difficult. Therefore, the content of Si can be controlled within the above-mentioned range. More specifically, Si may be contained in an amount of 3.0 to 4.0% by weight.

Al: 0.020 to 0.040 wt%

Aluminum (Al) is finally a component that acts as an inhibitor by being made of nitride of (Al, Si, N), (Al, Si, Mn) N type. When the content of Al is too small, it is difficult to expect a sufficient effect as an inhibitor. When the content of Al is too large, the nitride of the Al system precipitates and grows too much, so that the effect as an inhibitor may become insufficient. Therefore, the content of Al can be controlled within the above-mentioned range.

Mn: 0.01 to 0.20 wt%

Manganese (Mn) has the effect of reducing the iron loss by increasing the resistivity as Si and reacting with the nitrogen introduced by the nitriding treatment together with Si to form precipitates of N (Al, Si, Mn) It is an important element for suppressing the growth of sizing and causing secondary recrystallization. However, when the content of Mn is too large, it accelerates the austenite phase transformation during hot rolling so that the size of the primary recrystallized grains is reduced to make the secondary recrystallization unstable. When the content of Mn is too small, the effect of increasing the austenite fraction during hot-rolling reheating as the austenite forming element to increase the amount of precipitates and thus to make the primary recrystallization through MnS formation not too much It can occur insufficiently. Therefore, the content of Mn can be controlled within the above-mentioned range.

Sb, Sn, Ni or a combination thereof: 0.01 to 0.15 wt%

Since antimony (Sb) and tin (Sn) nickel (Ni) are elements that interfere with grain boundary movement as grain boundary segregation elements, generation of goss grain in {110} < 001 & It is an important element for grain size control because it is well developed. If the content of Sb, Sn or Ni alone or in combination is too small, the effect may be deteriorated. If the content of Sb, Sn, or Ni alone or in combination is too large, crystal grain segregation occurs severely and the brittleness of the steel sheet becomes large, so that plate fracture may occur during rolling.

More specifically, it may contain 0.01 to 0.05% by weight of Sb, 0.01 to 0.12% by weight of Sn and 0.01 to 0.06% by weight of Ni.

C: not more than 0.01% by weight

C is a component which does not greatly contribute to the improvement of the magnetic properties of the grain-oriented electrical steel sheet in the embodiment of the present invention, and is preferably removed as much as possible. However, if it is contained above a certain level, the austenite transformation of the steel is promoted in the rolling process, and the hot rolled structure is miniaturized during hot rolling to help form uniform microstructure. Therefore, the C content in the slab is 0.03 weight % Or more. However, when the C content is excessive, coarse carbide is produced and it is difficult to remove the carbonaceous material during decarburization, so that it is preferably 0.08 wt% or less. The carbon is decarburized through the decarburization annealing process in the course of producing the grain-oriented electrical steel sheet, and C is contained in the grain-oriented electrical steel sheet to be produced at a final content of 0.01 wt% or less.

N: 0.005 to 0.05 wt%

N is an element that reacts with Al or the like to refine the crystal grains. When these elements are appropriately distributed, it is possible to appropriately finely structure the structure after cold rolling as described above, thereby assuring proper primary recrystallization grain size. However, if the content is excessive, the primary recrystallized grains are excessively refined, and as a result, the driving force causing crystal grain growth during the secondary recrystallization increases due to the fine crystal grains, so that the crystal grain can grow to an undesired orientation. Also, if the N content is excessive, it takes a long time to remove it in the final annealing process, which is not preferable. Therefore, the upper limit of the nitrogen content in the slab is 0.005 wt%, and the nitrogen content in the slab reheating should be 0.001 wt% or more, so that the lower limit of the nitrogen content in the slab is preferably 0.001 wt%. Nitrogen is partially penetrated through the steep annealing process in the production of the grain-oriented electrical steel sheet, and N is included in the final grain-oriented electrical steel sheet in an amount of 0.005 to 0.05% by weight.

Fig. 2 schematically shows a flowchart of a method of manufacturing a directional electrical steel sheet according to an embodiment of the present invention. The flowchart of the method of manufacturing the directional electrical steel sheet of Fig. 2 is for illustrating the present invention only, and the present invention is not limited thereto. Therefore, the manufacturing method of the directional electrical steel sheet can be variously modified.

As shown in Fig. 2, a method of manufacturing a grain-oriented electrical steel sheet comprises the steps of preparing a steel slab (S10); Heating the steel slab (S20); Hot rolling the heated steel slab to produce a hot rolled steel sheet (S30); A step (S40) of cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; A first recrystallization annealing step (S50) of the cold-rolled sheet; A step (S60) of applying an annealing separator on the surface of the primary recrystallized annealed steel sheet; And a second recrystallization annealing step (S70) of the steel sheet coated with the annealing separator. In addition, the manufacturing method of the directional electrical steel sheet may further include other steps.

First, in step S10, a steel slab is prepared. Since the components of the steel slab are described in detail with respect to the components of the grain-oriented electrical steel sheet described above, repeated description is omitted.

Next, in step S20, the steel slab is heated. At this time, the slab heating can be performed by the low-temperature slab method at 1,200 ° C or less.

Next, in step S30, the heated steel slab is hot-rolled to produce a hot-rolled steel sheet. After step S30, the produced hot-rolled sheet can be subjected to hot-rolled annealing.

Next, in step S40, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet. In step S40, cold rolling may be performed once, or cold rolling may be performed twice or more including intermediate annealing.

Next, in the step S50, the cold-rolled sheet is subjected to primary recrystallization annealing. At this time, the first recrystallization annealing step of the cold-rolled sheet may include decarburization annealing and nitriding annealing of the cold-rolled sheet at the same time, or nitriding annealing after decarburization annealing.

Next, in step S60, the annealing separator is coated on the surface of the steel sheet subjected to the primary recrystallization annealing. Since the annealing separator has been described above in detail, repeated description is omitted.

The application amount of the annealing separator may be 1 to 20 g / m ² . If the application amount of the annealing separator is too small, the film formation may not be smoothly performed. If the application amount of the annealing separator is too large, it may affect the secondary recrystallization. Therefore, the application amount of the annealing separator can be adjusted to the above-mentioned range.

Next, in step S70, the steel sheet coated with the annealing separator is subjected to secondary recrystallization annealing. During the secondary recrystallization annealing, the coating 20 including mullite and forsterite is formed.

The primary cracking temperature may be 650 to 750 占 폚 and the secondary cracking temperature may be 1100 to 1250 占 폚 in the secondary recrystallization annealing. And can be controlled at a temperature of 15 [deg.] C / hr in the temperature range of the temperature rising section. Further, the gas atmosphere is carried out in an atmosphere containing 20 to 30% by volume of nitrogen and 70 to 80% by volume of hydrogen until the first cracking step, maintained in a 100% hydrogen atmosphere for 15 hours in the second cracking step, (not shown). The coating film 20 can be smoothly formed through the above-described conditions.

And further forming the ceramic layer 30 after step S70. Since the ceramic layer 30 has been described above in detail, repeated description is omitted. As a method of forming the ceramic layer 30, a ceramic layer can be formed by spraying ceramic powder onto the coating film 20. [ Specifically, plasma spray coating, high velocity oxy fuel, aerosol deposition, and cold spray coating can be applied. More specifically, a plasma spray coating method may be used in which a ceramic powder is supplied to a heat source in which a gas containing Ar, H ₂ , N ₂ , or He is plasma-generated at an output of 20 to 300 kW to form a ceramic layer. As a plasma spray coating method, a gas containing Ar, H ₂ , N ₂ , or He is supplied in a suspension form of a mixture of a ceramic powder and a solvent to a heat source made by plasma at an output of 20 to 300 kW to form a ceramic layer 30, Can be formed. At this time, the solvent may be water or alcohol.

As a method for forming the ceramic layer 30, a method of forming a ceramic layer by applying a composition for forming a ceramic layer containing ceramic powder and metal phosphate may be used.

After formation of the ceramic layer 30, micro-miniaturization can be performed as required.

Hereinafter, the present invention will be described in more detail with reference to examples. However, these embodiments are only for illustrating the present invention, and the present invention is not limited thereto.

Experimental Example  1: annealing Separating agent  Ingredients and Ceramic layer  Characteristics by type

Example 1

, 0.04 wt% of antimony (Sb), 0.09 wt% of tin (Sn), and nickel (Ni) were added in an amount of 3.4 wt% of silicon (Si), 0.03 wt% of aluminum (Al) 0.02 wt% of carbon (C), 0.06 wt% of carbon (C) and 40 wt% of nitrogen (N), and the balance of Fe and other unavoidable impurities.

The slab was heated at 1150 占 폚 for 220 minutes and hot-rolled to a thickness of 2.3 mm to prepare a hot-rolled sheet.

The hot-rolled sheet was heated to 1120 占 폚, held at 920 占 폚 for 95 seconds, quenched in water and pickled, and then cold-rolled to a thickness of 0.23 mm to prepare a cold-rolled sheet.

The cold-rolled sheet was placed in a furnace maintained at 850 캜, maintained in a mixed atmosphere of 74% by volume of hydrogen, 25% by volume of nitrogen and 1% by volume of dry ammonia gas for 180 seconds, Annealing were simultaneously carried out to produce a primary recrystallized annealed steel sheet.

The annealing separator composition was mixed with 30 wt% of mullite, 3 wt% of cobalt hydroxide (Co (OH) ₂ ), 5 wt% of titanium oxide, 5 wt% of Sb ₂ (SO ₄ ) ₃ and magnesium oxide (MgO) The slurry was applied to a steel sheet subjected to primary recrystallization annealing using a roll, followed by secondary recrystallization annealing.

The primary and secondary cracking temperatures were set to 700 ° C and 1200 ° C, respectively, during the second recrystallization annealing, and to 15 ° C / hr during the temperature rise period. In addition, up to 1200 deg. C, a mixed gas atmosphere of 50 vol% nitrogen and 50 vol% hydrogen was set. After reaching 1200 deg. C, it was maintained in a hydrogen gas atmosphere of 100 vol% for 20 hours and then furnace cooled.

Thereafter, TiO ₂ was supplied as a ceramic powder to a heat source in which argon (Ar) gas was converted into plasma at an output of 250 kW to form a ceramic layer having a thickness of 0.9 탆 on the surface of the final annealed plate.

Examples 2 to 8

The procedure of Example 1 was repeated except that the mullite and metal hydroxide components in the annealing separator were changed as shown in Table 1 to form a film. The ceramic powders listed in Table 1 below were applied to the surface of the forsterite coating.

Example 9

The same procedure as in Example 1 was carried out except that no ceramic layer was formed.

Comparative Example 1

An annealing separator composition comprising 90 wt% magnesium oxide, 5 wt% titanium oxide, and 5 wt% Sb ₂ (SO ₄ ) ₃ was used in the same manner as in Example 1.

Comparative Example 2

The same procedure as in Example 1 was carried out except that the annealing separator composition containing 100 wt% of mullite was used.

Comparative Example 3

An annealing separator composition comprising 90% by weight of mullite, 5% by weight of titanium oxide and 5% by weight of Sb ₂ (SO ₄ ) ₃ was used in the same manner as in Example 1.

The magnetic steel sheets prepared in Examples and Comparative Examples were evaluated for magnetic properties and noise characteristics under the conditions of 1.7 T and 50 Hz, and the results are shown in Table 1 below.

Magnetic properties of the electrical steel sheet uses a conventional W _17/50 and B _8. W _17/50 refers to the power loss (W / kg) appears when sikyeoteul magnetized with the alternate current magnetic field frequency of 50Hz to 1.7Tesla. Here, Tesla is a unit of magnetic flux density, which means flux per unit area. B ₈ represents magnetic flux density (Tesla) flowing through an electric steel sheet when an electric current of 800 A / m is passed through a coil wound around the electric steel sheet.

In addition, the insulation properties were measured using a Franklin meter according to ASTM A717 international standard.

Further, the adhesion is represented by the minimum arc diameter without peeling of the film when the specimen is bent by 180 ° in contact with the arc of 10 to 100 mm.

In addition, the surface characteristics are the result of forming a uniform film and visually evaluating the degree of uniformity of color.

division Annealing Separator Component Type of ceramic layer Iron loss
_{(W 17/50, W /} kg) Magnetic flux density
(B ₈ , T) Isolation
(mA) Adhesiveness
(mmφ) Surface feature Mullite
(weight%) Metal hydroxide
(weight%) Comparative Example 1 - - - 0.981 1.910 982 30 Uniformity Comparative Example 2 100 - - 1.275 1.885 - 70 Surface peeling extreme Comparative Example 3 90 - - 1.223 1.890 - 70 Surface peeling extreme Example 1 30 Co
(1.2) TiO ₂ 0.690 1.925 35 20 Uniformity Example 2 5 Cu
(20) Al ₂ O ₃ 0.751 1.918 415 20 Uniformity Example 3 15 Sr
(11) _{9Al 2 O 3 · B 2 O} 3 0.735 1.915 330 15 Uniformity Example 4 20 Ba
(0.1) BN 0.775 1.931 245 20 Uniformity Example 5 30 Pd
(0.5) SiC 0.801 1.911 120 20 Uniformity Example 6 50 In
(3.3) Al ₂ O ₃ 0.650 1.942 130 15 Uniformity Example 7 70 Bi
(2.7) Al ₂ O ₃ 0.675 1.934 15 15 Uniformity Example 8 45 Sn
(8.5) TiO ₂ 0.664 1.928 32 25 Uniformity Example 9 30 Ni
(1.5) - 0.820 1.920 610 20 Uniformity

As shown in Table 1, it can be confirmed that the properties of Examples 1 to 9 are superior to those of Comparative Examples 1 to 3. Also, in Comparative Example 2 in which mullite is used alone, peeling of the film is extremely caused and it can be confirmed that the magnetic properties are heated.

3 is a scanning electron microscope (SEM) photograph of the film of the directional electrical steel sheet produced in Example 9. Fig. It can be confirmed that a film is uniformly formed without defects. Fig. 4 shows X-ray diffraction (XRD) results of the film of the grain-oriented electrical steel sheet produced in Example 9. Fig. It can be confirmed that peaks corresponding to Al, Mg and Si are formed.

5 is a scanning electron microscope (SEM) photograph of the film of the grain-oriented electrical steel sheet produced in Comparative Example 2. Fig. It can be confirmed that a large number of cracks are formed, and as a result, surface peeling becomes severe.

Experimental Example  2: 1000 kVA  Magnetic characteristics of transformer, Dotting rate  And evaluation of noise characteristics

Example 10

(Al), 0.03 wt% of antimony (Sb), 0.05 wt% of tin (Sn), 0.02 wt% of nickel (Ni), carbon (C) of 3.3 wt% And 0.05 wt% of nitrogen and 30 wt% of nitrogen (N), and the balance of Fe and other unavoidable impurities.

The slab was heated at 1150 占 폚 for 220 minutes and hot-rolled to a thickness of 2.3 mm to prepare a hot-rolled sheet.

The hot-rolled sheet was heated to 1120 占 폚, held at 920 占 폚 for 95 seconds, quenched in water and pickled, and then cold-rolled to a thickness of 0.23 mm to prepare a cold-rolled sheet.

The cold-rolled sheet was placed in a furnace maintained at 850 캜, maintained in a mixed atmosphere of 74% by volume of hydrogen, 25% by volume of nitrogen and 1% by volume of dry ammonia gas for 180 seconds, Annealing were simultaneously carried out to produce a primary recrystallized annealed steel sheet.

18 wt% of mullite, 3.8 wt% of nickel hydroxide, 5 wt% of titanium oxide, 5 wt% of Sb ₂ (SO ₄ ) ₃ and magnesium oxide (MgO) were mixed with distilled water to prepare a slurry composition, The slurry was applied to a steel sheet subjected to primary recrystallization using a roll, and then subjected to secondary recrystallization annealing.

The primary and secondary cracking temperatures were set to 700 ° C and 1200 ° C, respectively, during the second recrystallization annealing, and to 15 ° C / hr during the temperature rise period. In addition, up to 1200 deg. C, a mixed gas atmosphere of 50 vol% nitrogen and 50 vol% hydrogen was set. After reaching 1200 deg. C, it was maintained in a hydrogen gas atmosphere of 100 vol% for 20 hours and then furnace cooled.

Thereafter, a composition for forming a ceramic layer mixed with 45% by weight of colloidal silica, 45% by weight of aluminum phosphate, 5% by weight of chromium oxide and 5% by weight of nickel hydroxide was stirred and a surface layer of 4.5 g / m ² And then processed in a drying furnace set at 860 ° C for 120 seconds and then subjected to a laser magnetic domain refining process and a 1000 kVA transformer was fabricated and evaluated at 60 Hz according to the design flux density as shown in Table 2 .

Comparative Example 4

An annealing separator composition comprising 90% by weight of magnesium oxide, 5% by weight of titanium oxide and 5% by weight of Sb ₂ (SO ₄ ) ₃ was used in the same manner as in Example 10.

The spot rate was measured using a measuring instrument according to JIS C2550 international standard. A uniform pressure of 1 MPa was applied to the surface after laminating a plurality of electric steel plate specimens, and then the practical ratio of the electric steel plate lamination was measured by dividing the ratio by the theoretical weight through the precision measurement of the height of the four faces of the specimen.

The noise evaluation method is evaluated in the same way as the international standard IEC61672-1, but the vibration (vibration) data of the electric steel sheet is obtained instead of the sound pressure and evaluated as the noise conversion value [dBA]. The vibration of the electric steel plate is measured by the non-contact type vibration pattern by using the laser Doppler method when the magnetic field of the frequency 60 Hz is magnetized to AC of 1.7 Tesla.

division film The iron loss _{(W 17/50, W /} kg) Magnetic flux density (B ₈ , T) Dotting rate (%) Noise (dBA) Example 10 Contains mullite and posterior 0.680 1.932 97.2 49.5 Comparative Example 4 Posterior Light 0.842 1.908 96.2 55.5

As shown in Table 2, it can be confirmed that the characteristics of Example 10 are far superior to those of Comparative Example 4.

It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. It will be understood that the invention may be practiced. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100: directional electric steel plate 10: directional electric steel plate
20: Coating 30: Ceramic layer

Claims (19)

5 to 70% by weight, based on 100% by weight of total solids, of mullite, and
The remainder comprising magnesium oxide or magnesium hydroxide
An annealing separator composition for a directional electric steel sheet. The method according to claim 1,
And further comprising 0.5 to 10% by weight of a ceramic powder. 3. The method of claim 2,
The ceramic powder is _{MnO, Al 2 O 3, SiO} 2, TiO 2 and ZrO ₂ grain-oriented electrical steel sheet annealing separation, including one or more selected from the composition. The method according to claim 1,
_{Sb 2 (SO 4) 3,} SrSO 4, BaSO 4 , or aromatic, which further comprises 1 to 10% by weight of a combination of the electrical steel sheet annealing separator composition. A directional electric steel sheet having a film containing mullite and forsterite formed on one or both sides of a grain oriented electrical steel sheet base material. 6. The method of claim 5,
Wherein the film contains 0.5 to 50 wt% of Al. The method according to claim 6,
Wherein the coating further comprises 3 to 80% by weight of Mg, 3 to 80% by weight of Si, 3 to 80% by weight of O and Fe as the balance. 6. The method of claim 5,
Wherein the coating has a thickness of 0.1 to 10 占 퐉. 6. The method of claim 5,
Further comprising a ceramic layer formed on the film. 10. The method of claim 9,
Wherein the ceramic layer comprises a ceramic powder. 11. The method of claim 10,
The ceramic powder is _{Al 2 O 3, SiO 2,} TiO 2, ZrO 2, Al 2 O 3 · TiO 2, Y 2 O 3, 9Al 2 O 3 · B 2 O 3, BN, CrN, BaTiO 3, SiC , and TiC, and the like. 11. The method of claim 10,
Wherein the ceramic layer further comprises a metal phosphate. 13. The method of claim 12,
Wherein the metal phosphate comprises at least one selected from Mg, Ca, Ba, Sr, Zn, Al and Mn. 6. The method of claim 5,
The directional electrical steel sheet base material may include 2.8 to 4.5 wt% of silicon (Si), 0.020 to 0.040 wt% of aluminum (Al), 0.01 to 0.20 wt% of manganese (Mn), and at least one of antimony (Sb), tin (Ni) or a combination thereof in an amount of 0.01 to 0.15% by weight, the balance being Fe and other unavoidable impurities. Preparing a steel slab;
Heating the steel slab;
Hot-rolling the heated steel slab to produce a hot-rolled steel sheet;
Cold-rolling the hot-rolled sheet to produce a cold-rolled sheet;
Subjecting the cold-rolled sheet to primary recrystallization annealing;
Applying an annealing separator on the surface of the primary recrystallized annealed steel sheet; And
And secondary recrystallization annealing the steel sheet coated with the annealing separator,
Wherein the annealing separator comprises 5 to 70% by weight of mullite, and the balance magnesium oxide or magnesium hydroxide, based on 100% by weight of the total solid content. 16. The method of claim 15,
Further comprising the step of forming a ceramic layer on the film including mullite and forsterite after the secondary recrystallization annealing step. 17. The method of claim 16,
Wherein forming the ceramic layer comprises:
And forming a ceramic layer by spraying a ceramic powder onto the coating. 17. The method of claim 16,
Wherein forming the ceramic layer comprises:
And forming a ceramic layer by applying a composition for forming a ceramic layer containing a ceramic powder and a metal phosphate on the coating. 16. The method of claim 15,
The primary recrystallization annealing of the cold-
And a step of performing decarburization annealing and nitriding annealing simultaneously on the cold-rolled sheet, or nitriding annealing after decarburization annealing.

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