Title of Invention: Annealing separator composition for grain-oriented electrical steel sheet, grain-oriented electrical steel sheet and method for manufacturing grain-oriented electrical steel sheet
technical field
[One]
It relates to an annealing separator composition for 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 an annealing separator composition for grain-oriented electrical steel sheet having improved adhesion and magnetic properties by adding γ-aluminum oxide, grain-oriented electrical steel sheet, and a method for manufacturing grain-oriented electrical steel sheet.
background
[2]
Grain-oriented electrical steel sheet is an electrical steel sheet containing Si component in the steel sheet, has a grain orientation aligned in the {110} <001> direction, and has extremely excellent magnetic properties in the rolling direction.
[3]
Recently, as grain-oriented electrical steel sheets of high magnetic flux density have been commercialized, materials with low iron loss are required. The improvement of iron loss in electrical steel sheet can be approached by four technical methods. First, the {110}<001> grain orientation including the easy magnetization axis of grain-oriented electrical steel sheet is accurately oriented in the rolling direction, and secondly, the thinness of the material. Third, there is a magnetic domain refinement method that refines the magnetic domain through chemical and physical methods, and finally, there are surface properties improvement or surface tension application by chemical methods such as surface treatment and coating.
[4]
In particular, for improving surface properties or imparting surface tension, a method of forming a primary film and an insulating film has been proposed. As a primary film, a forsterite (2MgO·SiO2) layer formed by the reaction of silicon oxide (SiO 2 ) generated on the surface of the material during the primary recrystallization annealing process of the electrical steel sheet material and magnesium oxide (MgO) used as an annealing separator. This is known In this way, the primary film formed during the secondary recrystallization annealing should have a uniform color without defects in appearance, and functionally prevent fusion between the plate and the plate in the coil state, and the difference in the coefficient of thermal expansion between the material and the primary film By applying tensile stress, it is possible to bring about the effect of improving the iron loss of the material.
[5]
Recently, as the demand for low iron loss grain-oriented electrical steel sheet has increased, high tension of the primary coating has been pursued. A method of controlling factors is being tried. If the film tension due to the primary film is improved, not only the iron loss of the material can be improved, but also the transformer efficiency can be improved.
[6]
In contrast, a method for obtaining a high-tensile film by introducing a halogen compound into an annealing separator has been proposed. In addition, a technique for forming a mullite film with a low coefficient of thermal expansion by applying an annealing separator containing kaolinite as the main component has been proposed. In addition, methods for enhancing interfacial adhesion by introducing rare elements Ce, La, Pr, Nd, Sc, Y, etc. have been proposed. However, the annealing separator additive suggested by these methods is very expensive and has a problem in that workability is significantly lowered to be applied to the actual production process. In particular, when a material such as kaolinite is prepared as a slurry for use as an annealing separator, its applicability is poor, so it is very insufficient as an annealing separator.
[7]
Also, a method of adding aluminum oxide (α-aluminum oxide) or aluminum hydroxide to the annealing separator has been proposed. However, in the case of aluminum oxide (α-aluminum oxide), since no crystal phase change occurs during annealing after introduction into the annealing separator, iron loss improvement by reduction of the coefficient of thermal expansion cannot be expected. A high-tensile primary film can be expected, but in order to generate a complex reactant, it is very difficult to uniformly produce a powder particle size that controls the diffusion of aluminum hydroxide, so it is not suitable for actual mass production process.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[8]
An annealing separator composition for a grain-oriented electrical steel sheet, a grain-oriented electrical steel sheet, and a method for manufacturing a grain-oriented electrical steel sheet are provided. More specifically, it provides an annealing separator composition for grain-oriented electrical steel sheet having improved adhesion and magnetism by adding γ-aluminum oxide, grain-oriented electrical steel sheet, and a method of manufacturing grain-oriented electrical steel sheet.
means of solving the problem
[9]
The grain-oriented electrical steel sheet according to an embodiment of the present invention includes a base tissue, an Al permeation layer positioned on the base tissue, and a film positioned on the Al permeation layer.
[10]
The Al permeation layer contains 0.5 to 5% by weight of Al, and the film includes an Al-Mg composite.
[11]
The film may contain 0.1 to 10% by weight of Al, 5 to 30% by weight of Mg, 0.1 to 20% by weight of Si, 10 to 55% by weight of O, and Fe as the balance.
[12]
The film may have a thickness of 0.1 to 10 μm.
[13]
The Al permeation layer may include α-aluminum oxide.
[14]
With respect to the cross section in the thickness direction of the steel sheet, the area occupied by the α-aluminum oxide with respect to the area of ​​the Al permeation layer may be 0.1 to 50%.
[15]
The Al penetration layer may have a thickness of 0.1 to 10 μm.
[16]
The matrix structure 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 wt% or less (excluding 0%), N: 0.005 to 0.05 wt% and antimony (Sb), tin (Sn), or a combination thereof in 0.01 to 0.15 wt%, the balance being Fe and other unavoidable impurities may include
[17]
The annealing separator composition for grain-oriented electrical steel sheet according to an embodiment of the present invention includes 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide and 5 to 200 parts by weight of γ-aluminum oxide.
[18]
The γ-aluminum oxide may have an average particle size of 3 to 1000 nm.
[19]
1 to 10 parts by weight of the ceramic powder may be further included.
[20]
The ceramic powder may be at least one selected from SiO 2 , TiO 2 and ZrO 2 .
[21]
50 to 500 parts by weight of a solvent may be further included.
[22]
A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises the steps of preparing a steel slab; heating the steel slab; Hot rolling the heated steel slab to manufacture a hot-rolled sheet; cold-rolling the hot-rolled sheet to manufacture a cold-rolled sheet; primary recrystallization annealing the cold-rolled sheet; applying an annealing separator on the surface of the steel sheet subjected to the primary recrystallization annealing; and performing secondary recrystallization annealing of the steel sheet coated with the annealing separator.
[23]
The annealing separator includes 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide and 5 to 200 parts by weight of γ-aluminum oxide.
Effects of the Invention
[24]
According to an embodiment of the present invention, Al permeates a large amount into the matrix tissue to form an Al permeation layer, thereby improving adhesion and magnetism between the film and the matrix tissue.
Brief description of the drawing
[25]
1 is a schematic side cross-sectional view of a grain-oriented electrical steel sheet according to an embodiment of the present invention.
[26]
2 is a GDS analysis result for the grain-oriented electrical steel sheet prepared in Example 4.
[27]
3 is a GDS analysis result of the grain-oriented electrical steel sheet prepared in Comparative Example 2.
[28]
4 is a focused ion beam-scanning electron microscope (FIB-SEM) analysis results for the grain-oriented electrical steel sheet prepared in Example 4.
[29]
5 is an aluminum-magnesium composite crystal (Al2MgO4, FCC) analysis result for 1 in FIG.
[30]
6 is an α-aluminum (rhombohedral) crystal analysis result for 2 in FIG.
Modes for carrying out the invention
[31]
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.
[32]
The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” specifies a particular characteristic, region, integer, step, operation, element and/or component, and the presence or absence of another characteristic, region, integer, step, operation, element and/or component; It does not exclude additions.
[33]
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.
[34]
In addition, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.
[35]
In an embodiment of the present invention, the meaning of further including the additional element means that the remaining iron (Fe) is included by replacing the additional amount of the additional element.
[36]
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.
[37]
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 various different forms and is not limited to the embodiments described herein.
[38]
The annealing separator composition for grain-oriented electrical steel sheet according to an embodiment of the present invention contains 100 parts by weight of at least one of magnesium oxide (MgO) and magnesium hydroxide (Mg(OH) 2 ) and γ (gamma)-aluminum oxide 5 to 200 including parts by weight. Here, parts by weight means a relative weight of each component.
[39]
The annealing separator composition for grain-oriented electrical steel sheet according to an embodiment of the present invention is aluminum oxide (γ-Al 2 O 3 ) present in a γ-phase crystal form in addition to magnesium oxide (MgO), which is one of the components of the conventional annealing separator composition . By adding, a part reacts with the annealing separator to form a complex of Al-Mg, and part penetrates into the matrix tissue to cause a phase change from γ crystal to α crystal phase to improve the modulus of elasticity of the film created on the surface of the electrical steel sheet Ultimately, it plays a role in reducing the iron loss of the material, making it possible to manufacture a high-efficiency transformer with low power loss.
[40]
In the manufacturing process of grain-oriented electrical steel sheet, when the cold-rolled sheet passes through a heating furnace controlled in a wet atmosphere for primary recrystallization, Si with the highest oxygen affinity in the steel reacts with oxygen supplied from the steam in the furnace to form SiO 2 on the surface. do. Thereafter, as oxygen penetrates into the steel, an Fe-based oxide is produced. SiO 2 thus formed forms a forsterite (Mg 2 SiO 4 ) layer through a chemical reaction as shown in Reaction Formula 1 below with magnesium oxide or magnesium hydroxide in the annealing separator .
[41]
[Scheme 1]
[42]

[43]
That is, the electrical steel sheet that has undergone primary recrystallization annealing is subjected to secondary recrystallization annealing, that is, high temperature annealing, after applying magnesium oxide slurry as an annealing separator. The forsterite layer prevents the material from shrinking. When the coefficient of thermal expansion of the forsterite film is very small compared to that of the material, the residual stress σ RD in the rolling direction can be expressed by the following formula.
[44]

[45]
here
[46]
△T= the temperature difference between the secondary recrystallization annealing temperature and room temperature (℃),
[47]
α Si-Fe = coefficient of thermal expansion of the material,
[48]
α C = coefficient of thermal expansion of the primary coating,
[49]
E c = average value of the primary film elasticity (Young's Modulus)
[50]
δ = thickness ratio of material and coating layer,
[51]
ν RD = Poisson's ratio in the rolling direction
[52]
indicates
[53]
From the above formula, the tensile stress improvement coefficient by the primary film includes the difference in the thickness of the primary film or the coefficient of thermal expansion between the substrate and the film. The tensile stress can be increased by increasing the coefficient difference. However, since the annealing separator is limited to magnesium oxide, there is a limit to improving the film tension by increasing the difference in thermal expansion coefficient or increasing the film elasticity (Young's Modulus).
[54]
In one embodiment of the present invention, in order to overcome the physical limitations of pure forsterite, when magnesium oxide annealing separator is introduced, aluminum oxide (γ-Al 2 O 3 ) is present in γ-phase crystal form. By adding, pure forsterite Forms an Al-Mg complex phase in addition to the light film, and some of it penetrates into the matrix tissue to induce a phase change from the γ crystal phase to the α crystal phase, thereby lowering the coefficient of thermal expansion and improving the elastic modulus compared to the pure forsterite coating. .
[55]
As described above, the conventional coating includes forsterite formed by the reaction of Mg-Si, and the thermal expansion coefficient is about 11×10 -6 /K, and the difference in thermal expansion coefficient with the base material does not exceed about 2.0. On the other hand, as an Al-Mg-based composite phase with a low coefficient of thermal expansion, there is spinel, and the difference in coefficient of thermal expansion with the material is about 5.0. Furthermore, when aluminum oxide does not form a complex phase with Mg in the film and a phase change occurs from a pure γ crystal to an α crystal phase, the film elasticity (Young's Modulus) is 200 GPa, 450 GPa compared to normal forsterite. more values ​​are displayed.
[56]
In one embodiment of the present invention, as described above, the aluminum-based additive introduced with the annealing separator partially reacts with the annealing separator to form an Al-Mg composite to lower the thermal expansion coefficient of the film, and some It penetrates into the matrix tissue and causes a phase change from the γ crystal phase to the α crystal phase to improve the elastic modulus of the coating film, thereby ultimately improving the film tension.
[57]
Hereinafter, the annealing separator composition according to an embodiment of the present invention will be described in detail for each component.
[58]
In an embodiment of the present invention, the annealing separator composition includes 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide. In one embodiment of the present invention, the annealing separator composition may be present in the form of a slurry in order to be easily applied to the surface of the grain-oriented electrical steel sheet substrate. When water is included as a solvent of the slurry, magnesium oxide is easily dissolved in water and may exist in the form of magnesium hydroxide. Therefore, in an embodiment of the present invention, magnesium oxide and magnesium hydroxide are treated as one component. The meaning of including 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide means that when magnesium oxide is included alone, 100 parts by weight of magnesium oxide is included, and when magnesium hydroxide is included alone, magnesium hydroxide is included in 100 parts by weight When including part and magnesium oxide and magnesium hydroxide are included at the same time, it means to include 100 parts by weight in the total amount.
[59]
The activation degree of magnesium oxide may be 400 to 3000 seconds. When the activation degree of magnesium oxide is too large, a problem of leaving a spinel-based oxide (MgO·Al 2 O 3 ) on the surface after the secondary recrystallization annealing may occur. When the activation degree of magnesium oxide is too small, it may not react with the oxide layer and thus a film may not be formed. Therefore, it is possible to control the degree of activation of magnesium oxide within the above-described range. In this case, the degree of activation means the ability of the MgO powder to cause a chemical reaction with other components. The degree of activation is measured as the time it takes for MgO to completely neutralize a certain amount of citric acid solution. If the activation level is high, the time taken for neutralization is short, and if the activation level is low, it can be said to be high on the contrary. Specifically, it is measured as the time it takes for the solution to change from white to pink when 2 g of MgO is added to 100 ml of a 0.4N citric acid solution added with 2 ml of 1% phenolphthalein reagent at 30° C. and stirred.
[60]
In an embodiment of the present invention, the annealing separator composition includes 5 to 200 parts by weight of γ-aluminum oxide (γ-Al 2 O 3 ). γ-aluminum oxide is different from general α-aluminum oxide in crystal structure. That is, while γ-aluminum oxide (Boemite) has a ruby ​​or spinel structure in terms of crystal structure, α-aluminum oxide has a high-temperature stable structure and a corundum structure, so there is a difference in the arrangement and position of Al/O atoms. Due to this crystal structure difference, α-aluminum oxide has higher density and thermal conductivity than γ-aluminum oxide (Boemite). Also, in the case of γ-aluminum oxide (Boemite), when sufficient energy is applied, the crystal structure tends to be phase transformed into α-aluminum oxide, which is more stable.
[61]
After the primary recrystallization annealing process, γ-aluminum oxide reacts with Si in the silica oxide layer formed on the material surface to form a Si-Al composite, and also reacts with magnesium oxide and magnesium hydroxide in the annealing separator to react with Mg-Al form a complex In addition, a portion of γ-aluminum oxide penetrates into the matrix and undergoes a crystal phase change to α-aluminum oxide in a high-temperature environment in the secondary recrystallization annealing process. This is because γ-aluminum oxide mostly undergoes a phase transition from the γ phase to the α phase at about 1100°C.
[62]
On the other hand, when α-aluminum oxide rather than γ-aluminum oxide is added as an annealing separator, α-aluminum oxide has a complex and stable atomic structure, so it has little chemical reactivity with the surrounding oxide layer or magnesium oxide, and the thickness direction of the oxide layer concentration gradient does not occur. For this reason, it is difficult to penetrate into the matrix tissue between α-aluminum oxide, and it remains only in the film, making it difficult to contribute to the improvement of adhesion and tension.
[63]
On the other hand, when aluminum hydroxide, not γ-aluminum oxide, is added as an annealing separator, it is very difficult to uniformly prepare a powder particle size that controls the diffusion of aluminum hydroxide, and thus it is very difficult to improve adhesion and tension.
[64]
γ-Aluminum oxide is included in an amount of 5 to 200 parts by weight based on 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide. If too little γ-aluminum oxide is included, it is difficult to sufficiently obtain the effect of the above-described addition of γ-aluminum oxide. If too much γ-aluminum oxide is included, the applicability of the annealing separator composition may deteriorate. Therefore, γ-aluminum oxide may be included in the above-described range. More specifically, 10 to 100 parts by weight of γ-aluminum oxide may be included. More specifically, it may contain 20 to 50 parts by weight of aluminum hydroxide.
[65]
The average particle size of the γ-aluminum oxide may be 3 to 1000 nm. If the average particle size is too small, it is difficult to manufacture, and when introduced as an additive, a diffusion reaction occurs mainly with the silica oxide layer formed on the material surface. The intended purpose of the invention cannot be achieved. On the other hand, when the average particle size is too large, aluminum oxide does not exist in the forsterite film, but is mostly present only on the surface, so that the film tension improvement effect may be significantly reduced. More specifically, it may be 3 to 50 nm.
[66]
The annealing separator composition for grain-oriented electrical steel sheet may further include 1 to 10 parts by weight of the ceramic powder based on 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide. The ceramic powder may be at least one selected from SiO 2 , TiO 2 and ZrO 2 . When the ceramic powder is further included in an appropriate amount, the insulating properties of the film may be further improved. Specifically, the ceramic powder may further include TiO 2 .
[67]
The annealing separator composition may further include a solvent for uniform dispersion of solids and easy application. As the solvent, water, alcohol, etc. may be used, and 50 to 500 parts by weight may be included based on 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide. As such, the annealing separator composition may be in the form of a slurry.
[68]
The grain-oriented electrical steel sheet 100 according to an embodiment of the present invention has a base tissue 10, an Al permeation layer 11 positioned on the base tissue 10, and a film 20 positioned on the Al permeation layer 11. ) is included. 1 is a schematic side cross-sectional view of a grain-oriented electrical steel sheet according to an embodiment of the present invention.
[69]
As described above, the coating film 20 according to an embodiment of the present invention is annealed separator composition in which appropriate amounts of magnesium oxide/hydroxide and γ-aluminum oxide are added, undergoes a secondary recrystallization annealing process, and a part of γ-aluminum oxide is a matrix structure (10) Penetrates into the inside to cause a crystal phase change to α-aluminum oxide, and some react with Mg, which is the main component of the annealing separator, to form an Al-Mg complex such as spinel in the coating film 20 . The phase change of γ → α aluminum oxide increases the elastic modulus of the Al permeation layer 11, and the additionally generated Al-Mg composite such as spinel lowers the thermal expansion coefficient of the film 20, ultimately improving the film tension. will make it Since this has been described above, a redundant description thereof will be omitted.
[70]
The film may further include a Si-Mg composite, and a Si-Al composite in addition to the Al-Mg composite.
[71]
The film 20 may include 0.1 to 10 wt% of Al, 5 to 30 wt% of Mg, 0.1 to 20 wt% of Si, 10 to 55 wt% of O, and Fe as the balance. In the case of O, it may be infiltrated during the secondary recrystallization annealing process. It may further contain other impurity components, such as carbon (C). The alloy component in the film 20 may have a concentration gradient depending on the thickness, and the above-mentioned content means an average content with respect to the entire thickness in the film 20 .
[72]
The film 20 may have a thickness of 0.1 to 10 μm. If the thickness of the film 20 is too thin, the film tension imparting ability may be lowered, which may cause a problem of poor iron loss. If the thickness of the film 20 is too thick, the adhesiveness of the film 20 is inferior, and peeling may occur. Accordingly, the thickness of the film 20 can be adjusted within the above-described range. More specifically, the thickness of the film 20 may be 0.8 to 6 μm. The film 20 is a portion in which Fe is included in an amount of less than 90 wt%, and is distinguished from the Al permeation layer 11 and the matrix tissue 10 containing Fe in an amount of 90 wt% or more.
[73]
As shown in FIG. 1 , the Al permeation layer 11 may be formed from the interface between the coating film 20 and the matrix tissue 10 into the matrix tissue 10 . The Al permeation layer 11 is a layer containing 0.5 to 5% by weight of Al, and is distinguished from the matrix 10 containing less Al.
[74]
As described above, in one embodiment of the present invention, by adding γ-aluminum oxide to the annealing separator composition, a part penetrates into the matrix tissue 10 and undergoes a secondary recrystallization annealing process, α in the Al penetration layer 11 -Aluminum oxide causes a crystal phase change. Through this phase change of γ→α aluminum oxide, the modulus of elasticity is higher than that of the conventional forsterite film, and thus the film tension is superior to that of the prior art. More specifically, with respect to the cross section in the thickness direction of the steel sheet, the area occupied by α-aluminum oxide with respect to the area of ​​the Al permeation layer 11 may be 0.1 to 50%. The cross section in the thickness direction means a cross section (ND-RD surface, ND-TD surface) including the thickness direction (ND direction).
[75]
In addition, a portion of γ-aluminum oxide introduced into the annealing separator composition forms an Al-Mg complex such as spinel in the film 20 . Al-Mg composites such as spinel have a lower coefficient of thermal expansion compared to the material or the conventional forsterite film, and also improve the adhesion between the matrix tissue 10 and the film 20 to improve the tension by the film 20. do. Since the Al-Mg composite has been described above, the overlapping description will be omitted.
[76]
In an embodiment of the present invention, the effects of the annealing separator composition and the coating film 20 appear irrespective of the components of the grain-oriented electrical steel sheet matrix structure 10 . Supplementally, the components of the grain-oriented electrical steel sheet matrix 10 will be described as follows.
[77]
The grain-oriented electrical steel sheet matrix structure 10 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 wt% or less (excluding 0%), N: 0.005 to 0.05 wt% and antimony (Sb), tin (Sn), or a combination thereof in 0.01 to 0.15 wt%, The parts may contain Fe and other unavoidable impurities. Since the description of each component of the grain-oriented electrical steel sheet matrix structure 10 is the same as the generally known content, a detailed description thereof will be omitted.
[78]
A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises the steps of preparing a steel slab; heating the steel slab; Hot rolling the heated steel slab to manufacture a hot-rolled sheet; cold-rolling the hot-rolled sheet to manufacture a cold-rolled sheet; primary recrystallization annealing the cold-rolled sheet; applying an annealing separator on the surface of the steel sheet subjected to the primary recrystallization annealing; and performing secondary recrystallization annealing of the steel sheet coated with the annealing separator. In addition, the method of manufacturing a grain-oriented electrical steel sheet may further include other steps.
[79]
First prepare a steel slab.
[80]
Next, the steel slab is heated. At this time, the slab heating can be heated by a low-temperature slab method at 1,200 ° C or less.
[81]
Next, the heated steel slab is hot-rolled to manufacture a hot-rolled sheet. Thereafter, the manufactured hot-rolled sheet may be hot-rolled and annealed.
[82]
Next, a hot-rolled sheet is cold-rolled, and a cold-rolled sheet is manufactured. In the step of manufacturing the cold-rolled sheet, cold rolling may be performed once, or cold rolling including intermediate annealing may be performed two or more times.
[83]
Next, the cold-rolled sheet is subjected to primary recrystallization annealing. In the primary recrystallization annealing process, the cold-rolled sheet may be simultaneously subjected to decarburization annealing and nitridation annealing, or may include a step of nitriding annealing after decarburization annealing.
[84]
Next, on the surface of the steel sheet subjected to the primary recrystallization annealing, an annealing separator is applied. Since the annealing separator has been specifically described above, a repeated description will be omitted.
[85]
The application amount of the annealing separator may be 6 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 secondary recrystallization. Therefore, the application amount of the annealing separator can be adjusted within the above-described range.
[86]
After applying the annealing separator, drying may be further included. The drying temperature may be 300 to 700 °C. If the temperature is too low, the annealing separator may not be easily dried. If the temperature is too high, it may affect secondary recrystallization. Therefore, the drying temperature of the annealing separator can be adjusted in the above-described range.
[87]
Next, the steel sheet coated with the annealing separator is subjected to secondary recrystallization annealing. During the secondary recrystallization annealing, a film 20 including an Al-Mg composite such as Mg-Si forsterite, α-aluminum oxide, and spinel is formed on the outermost surface by the reaction of the annealing separator component and silica during the secondary recrystallization annealing. In addition, oxygen and aluminum permeate into the substrate 10 to form the Al permeation layer 11 .
[88]
The secondary recrystallization annealing may be performed at a temperature increase rate of 18 to 75 °C/hr in a temperature range of 700 to 950 °C, and a temperature increase rate of 10 to 15 °C/hr in a temperature range of 950 to 1200 °C. By adjusting the temperature increase rate in the above-described range, the film 20 can be smoothly formed. In addition, the process of increasing the temperature of 700 to 1200 ℃ is carried out in an atmosphere containing 20 to 30% by volume of nitrogen and 70 to 80% by volume of hydrogen, and after reaching 1200 ℃, it can be carried out in an atmosphere containing 100% by volume of hydrogen. there is. By controlling the atmosphere in the above-described range, the film 20 can be smoothly formed.
[89]
Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for illustrating the present invention, and the present invention is not limited thereto.
[90]
Example
[91]
A steel slab containing Si: 0.04%, Sb: 0.03%, P: 0.03% by weight percent and Fe and unavoidable impurities as the balance was prepared.
[92]
The slab was heated at 1150° C. for 220 minutes and then hot-rolled to a thickness of 2.8 mm to prepare a hot-rolled sheet.
[93]
After heating the hot-rolled sheet to 1120° C. and maintaining it at 920° C. for 95 seconds, it was rapidly cooled in water and pickled, and then cold-rolled to a thickness of 0.23 mm to prepare a cold-rolled sheet.
[94]
After the cold-rolled sheet was put into a furnace maintained at 875°C, it was held for 180 seconds in a mixed atmosphere of 74 vol % hydrogen, 25 vol % nitrogen, and 1 vol % dry ammonia gas, followed by simultaneous decarburization and nitridation.
[95]
As an annealing separator composition, an annealing separator prepared by mixing 100 g of magnesium oxide with an activation degree of 500 seconds, γ-aluminum oxide in the amounts listed in Table 1 below, and 2.5 g of titanium oxide and 250 g of water in a solid phase mixture was prepared. 10 g/m 2 of an annealing separator was applied, and secondary recrystallization annealing was performed in a coil shape. During the secondary recrystallization annealing, the primary cracking temperature was 700 ℃, the secondary cracking temperature was 1200 ℃, and the temperature increase condition of the temperature increase section was 45 ℃/hr in the temperature section of 700 to 950℃, and in the temperature section of 950 to 1200℃ It was 15 degreeC/hr. On the other hand, the soaking time at 1200°C was 15 hours. The atmosphere during the secondary recrystallization annealing was a mixed atmosphere of 25 vol% nitrogen and 75 vol% hydrogen until 1200 °C, and after reaching 1200 °C, it was maintained in a 100 vol% hydrogen atmosphere and then furnace cooled.
[96]
Table 1 summarizes the components of the annealing separator applied to the present invention. Table 2 below summarizes the improvement in tension, adhesion, iron loss, magnetic flux density, and iron loss after secondary recrystallization annealing after applying the annealing separator prepared as shown in Table 1 to the specimen.
[97]
In addition, the film tension is obtained by measuring the radius of curvature (H) of the specimen generated after removing the coating on one side of the double-coated specimen and substituting the value into the following equation.
[98]

[99]
E c = average value of the primary film elasticity (Young's Modulus)
[100]
ν RD = Poisson's ratio in the rolling direction
[101]
T: thickness before coating
[102]
t: thickness after coating
[103]
I: Specimen length
[104]
H: radius of curvature
[105]
In addition, adhesion is expressed by the minimum arc diameter without film peeling when the specimen is bent 180° in contact with a 10 to 100 mm arc.
[106]
The iron loss and magnetic flux density were measured using a single sheet measurement method, and the iron loss (W17/50) means the power loss that occurs when a magnetic field with a frequency of 50 Hz is magnetized up to 1.7 Tesla. The magnetic flux density (B8) indicates the value of the magnetic flux density flowing through the electrical steel sheet when an amount of current of 800 A/m is passed through the winding around the electrical steel sheet.
[107]
The iron loss improvement rate was calculated as ((Comparative example iron loss - Example iron loss)/ Comparative example iron loss) × 100 based on the comparative example using the MgO annealing separator.
[108]
[Table 1]
[109]
[Table 2]
[110]

[111]
As shown in Tables 1 and 2, when γ-aluminum oxide is used as the annealing separator, it can be confirmed that the film tension, adhesion and magnetism are improved compared to the case of using α-aluminum oxide. It can be confirmed that this is the effect of the Al content in the Al permeation layer and the Al 2 O 3 occupied area.
[112]
2 and 3 are GDS analysis results for the grain-oriented electrical steel sheets prepared in Example 4 and Comparative Example 2. In Example 4, a large number of Al was detected in the Al permeation layer (range of 1 to 3 μm thickness), but in Comparative Example 2, it can be confirmed that relatively little Al was detected in the lower portion of the film (range of 3 μm or more).
[113]
4 is a focused ion beam-scanning electron microscope (FIB-SEM) analysis results for the grain-oriented electrical steel sheet prepared in Example 4. As shown in FIG. 5 , spinel, which is an Al-Mg composite, was detected in 1 (film) in FIG. 4 . As shown in FIG. 6 , α-aluminum oxide was detected in 2 (Al permeation layer) in FIG. 4 .
[114]
The present invention is not limited to the embodiments, but can be manufactured in various different forms, and those of ordinary skill in the art to which the present invention pertains can use other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that this may be practiced. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.
[115]
[Explanation of code]
[116]
100: grain-oriented electrical steel sheet 10: base structure
[117]
11: Al penetration layer 20: film
Claims
[Claim 1]
A matrix tissue, an Al permeation layer positioned on the matrix tissue, and a film positioned on the Al permeation layer, wherein the Al permeation layer contains 0.5 to 5% by weight of Al, and the film comprises an Al-Mg composite. Grain-oriented electrical steel sheet containing.
[Claim 2]
The grain-oriented electrical steel sheet according to claim 1, wherein the film contains 0.1 to 10% by weight of Al, 5 to 30% by weight of Mg, 0.1 to 20% by weight of Si, 10 to 55% by weight of O, and Fe as the balance. .
[Claim 3]
The grain-oriented electrical steel sheet according to claim 1, wherein the film has a thickness of 0.1 to 10 μm.
[Claim 4]
The grain-oriented electrical steel sheet according to claim 1, wherein the Al penetration layer comprises α-aluminum oxide.
[Claim 5]
The grain-oriented electrical steel sheet according to claim 4, wherein, with respect to the cross section in the thickness direction of the steel sheet, the area occupied by the α-aluminum oxide with respect to the area of ​​the Al permeation layer is 0.1 to 50%.
[Claim 6]
The grain-oriented electrical steel sheet according to claim 1, wherein the Al penetration layer has a thickness of 0.1 to 10 μm.
[Claim 7]
According to claim 1, wherein the matrix 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 wt% or less (excluding 0%), N: 0.005 to 0.05 wt% and antimony (Sb), tin (Sn), or a combination thereof in 0.01 to 0.15 wt%; The balance is grain-oriented electrical steel sheet containing Fe and other unavoidable impurities.
[Claim 8]
An annealing separator composition for grain-oriented electrical steel sheet comprising 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide and 5 to 200 parts by weight of γ-aluminum oxide.
[Claim 9]
The annealing separator composition for a grain-oriented electrical steel sheet according to claim 8, wherein the γ-aluminum oxide has an average particle size of 3 to 1000 nm.
[Claim 10]
The annealing separator composition for grain-oriented electrical steel sheet according to claim 8, further comprising 1 to 10 parts by weight of ceramic powder.
[Claim 11]
The annealing separator composition for grain-oriented electrical steel sheet according to claim 10, wherein the ceramic powder is at least one selected from SiO 2 , TiO 2 and ZrO 2 .
[Claim 12]
The annealing separator composition for grain-oriented electrical steel sheet according to claim 8, further comprising 50 to 500 parts by weight of a solvent.
[Claim 13]
preparing steel slabs; heating the steel slab; manufacturing a hot-rolled sheet by hot rolling the heated steel slab; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; primary recrystallization annealing the cold-rolled sheet; applying an annealing separator on the surface of the steel sheet subjected to the primary recrystallization annealing; and performing secondary recrystallization annealing of the steel sheet coated with the annealing separator, wherein the annealing separator contains 100 parts by weight of at least one of magnesium oxide and magnesium hydroxide and 5 to 200 parts by weight of γ-aluminum oxide A method of manufacturing a grain-oriented electrical steel sheet.