Title of Invention: Grain-oriented electrical steel sheet and manufacturing method thereof
technical field
[One]
It relates to a grain-oriented electrical steel sheet and a method for manufacturing the same. More specifically, after primary recrystallization annealing, by controlling the weight ratio of SiO 2 /Fe x SiO y to properly form an island, it relates to a grain-oriented electrical steel sheet having improved magnetism and a method for manufacturing the same.
background
[2]
Since grain-oriented electrical steel sheet is used as an iron core material for electronic products such as transformers, in order to improve energy conversion efficiency by reducing power loss in electrical equipment, a steel sheet with excellent iron loss and a high space factor during lamination and winding is required. .
[3]
Grain-oriented electrical steel sheet refers to a functional steel sheet having a texture (also called "Goss Texture") in which crystal grains secondary recrystallized through hot rolling, cold rolling and annealing processes are oriented in the {110}<001> direction in the rolling direction.
[4]
As a method of lowering the iron loss of a grain-oriented electrical steel sheet, a magnetic domain refining method is known. That is, the size of the large magnetic domain of the grain-oriented electrical steel sheet is miniaturized by scratching the magnetic domain or applying an energy impact. In this case, when the magnetic domain is magnetized and its direction is changed, energy consumption can be reduced compared to when the size of the magnetic domain is large. As the magnetic domain refining method, there are permanent domain refining, which maintains the effect by improving magnetic properties even after heat treatment, and temporary domain refining, which is not.
[5]
The permanent magnetic domain refining method that shows the effect of improving iron loss even after stress relaxation heat treatment above the heat treatment temperature at which recovery occurs can be divided into etching method, roll method and laser method. Since the etching method forms a groove (groove) on the surface of the steel sheet through a selective electrochemical reaction in the solution, it is difficult to control the shape of the groove, and it is difficult to uniformly secure the iron loss characteristics of the final product in the width direction. In addition, it has a disadvantage that may cause environmental pollution due to an acid solution used as a solvent.
[6]
The permanent magnetic domain refining method using a roll forms a groove having a certain width and depth on the plate surface by processing the protrusion on the roll and pressing the roll or plate, and then annealing to improve the iron loss by partially causing recrystallization at the bottom of the groove. It is a magnetic domain refinement technique that represents. The roll method has disadvantages in that it is difficult to obtain stability against machining and stable iron loss according to thickness, and the process is complicated, and the iron loss and magnetic flux density characteristics deteriorate immediately after groove formation (before stress relief annealing).
[7]
The permanent magnetic domain refining method by laser uses a method of irradiating a high-power laser to the surface of an electrical steel sheet moving at high speed, and forming a groove accompanied by melting of the base portion by laser irradiation. However, it is difficult to refine the magnetic domain to the minimum size even in this permanent magnetic domain refining method.
[8]
In the case of temporary domain refining, we do not try to irradiate the laser with an intensity higher than a certain level because we are researching in the direction of not applying the coating once more after applying the laser in the coated state. This is because it is difficult to properly exert the tension effect due to damage to the coating if applied over a certain level.
[9]
In the case of permanent magnetic domain refinement, a groove is dug to widen the free charge area that can receive static magnetic energy, so a groove depth as deep as possible is required. Of course, side effects such as a decrease in magnetic flux density also occur due to the deep groove depth. Therefore, in order to reduce the deterioration of the magnetic flux density, an appropriate groove depth is maintained.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[10]
One embodiment of the present invention provides a grain-oriented electrical steel sheet and a method for manufacturing the same. More specifically, an embodiment of the present invention provides a method of manufacturing a grain-oriented electrical steel sheet with improved magnetism by appropriately forming an island by controlling the weight ratio of SiO 2 /Fe x SiO y after the primary recrystallization annealing .
means of solving the problem
[11]
A grain-oriented electrical steel sheet according to an embodiment of the present invention includes a groove located on the surface of the electrical steel sheet, a metal oxide layer located on the groove, and a metal oxide-based island that is discontinuously distributed and located below the groove.
[12]
The number of islands positioned below the groove may be 15 or less per groove.
[13]
The density of the islands positioned under the groove may be 0.5 pieces/μm 2 or less.
[14]
Among the islands positioned under the groove, the number of islands having a sphericity (short axis/long axis) of 0.6 to 1.0 may be 60% or more.
[15]
With respect to the rolling vertical direction, there may be 2 to 10 intermittent grooves.
[16]
The longitudinal direction of the groove and the rolling direction of the steel sheet may form an angle of 75 to 88 °.
[17]
A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises the steps of manufacturing a cold-rolled sheet; forming a groove in the cold-rolled sheet; primary recrystallization annealing the cold-rolled sheet; and applying an annealing separator to the primary recrystallized cold-rolled sheet, and performing secondary recrystallization annealing.
[18]
After the primary recrystallization annealing of the cold-rolled sheet, the weight ratio of SiO 2 /Fe x SiO y of the surface layer of the cold-rolled sheet is 0.3 to 3.
[19]
(wherein x is an integer of 1 to 2, and y is an integer of 2 to 4.)
[20]
In the step of forming the groove, the cold-rolled sheet is irradiated with a laser to form the groove, the laser output may be 1.5 kW or more, the laser scanning speed may be 8 m/s or more, and the laser scanning distance may be 100 mm or more.
[21]
In the step of forming the groove, a re-solidification layer may be formed under the groove.
[22]
In the step of forming the groove, a re-solidification layer may be formed with a thickness of 3 μm or less under the groove.
[23]
The primary recrystallization annealing of the cold-rolled sheet may be performed at a temperature of 710 to 870°C and a dew point temperature of 40 to 70°C.
Effects of the Invention
[24]
According to one embodiment of the present invention, after the primary recrystallization annealing, by controlling the weight ratio of SiO 2 /Fe x SiO y to properly form the island, the magnetism can be improved.
Brief description of the drawing
[25]
1 is a schematic diagram of a rolled surface (ND surface) of a grain-oriented electrical steel sheet according to an embodiment of the present invention.
[26]
2 is a schematic diagram of a groove according to an embodiment of the present invention.
[27]
3 is a schematic diagram of a cross-section of a groove according to an embodiment of the present invention.
Modes for carrying out the invention
[28]
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.
[29]
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.
[30]
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.
[31]
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.
[32]
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.
[33]
1 shows a schematic diagram of a grain-oriented electrical steel sheet 10 that has been refined into magnetic domains according to an embodiment of the present invention.
[34]
As shown in FIG. 1, the grain-oriented electrical steel sheet 10 according to an embodiment of the present invention has a linear groove 20 formed in a direction crossing the rolling direction (RD direction) on one or both sides of the electrical steel sheet; is formed has been
[35]
Hereinafter, each step will be described in detail.
[36]
First, a cold-rolled sheet is manufactured. In an embodiment of the present invention, as a characteristic of the magnetic domain refining method after manufacturing the cold rolled sheet, the cold rolled sheet to be subjected to domain refining may be a cold rolled sheet used in the grain-oriented electrical steel sheet field without limitation. In particular, the effect of the present invention is expressed regardless of the alloy composition of the grain-oriented electrical steel sheet. Therefore, a detailed description of the alloy composition of the grain-oriented electrical steel sheet will be omitted. As an example, the cold-rolled sheet is, by weight, C: 0.10% or less, Si: 2.0 to 6.5%, Mn: 0.005 to 1.0%, Nb+V+Ti: 0.02% or less, Cr+Sn: 0.8% or less, Al : 3.0% or less, P+S: 0.09% or less, and the total amount of rare earth and other impurities is 0.5% or less and the remainder may contain Fe.
[37]
The cold-rolled sheet manufacturing method used in the grain-oriented electrical steel sheet field may be used without limitation as to the cold-rolled sheet manufacturing method, and a detailed description thereof will be omitted.
[38]
Next, a groove is formed in the cold-rolled sheet.
[39]
In the step of forming the grooves, 2 to 10 grooves may be intermittently formed with respect to the rolling vertical direction. 1 shows an example in which four grooves are intermittently formed with respect to the vertical direction of rolling. However, the present invention is not limited thereto, and it is also possible to continuously form the groove.
[40]
1 and 2 , the longitudinal direction (RD direction in FIG. 1 , X direction in FIG. 2 ) and the rolling direction (RD direction) of the groove 20 may form an angle of 75 to 88°. When the groove 20 is formed at the above-described angle, it can contribute to improving the iron loss of the grain-oriented electrical steel sheet.
[41]
The width (W) of the groove may be 10 to 200㎛. If the width of the groove 20 is short or large, an appropriate magnetic domain refining effect may not be obtained.
[42]
Also, the depth H of the groove may be 30 μm or less. If the depth (H) of the groove is too deep, the structure properties of the steel sheet 10 may be greatly changed due to strong laser irradiation, or the magnetism may be deteriorated by forming a large amount of heel-up and spatter. Therefore, the depth of the groove 20 can be controlled within the above-described range. More specifically, the depth of the groove may be 3 to 30㎛.
[43]
In the step of forming the groove, the cold-rolled sheet may be irradiated with a laser or plasma to form the groove.
[44]
In the case of using a laser, the laser output may be 1.5 kW or more, the laser scanning speed may be 8 m/s or more, and the laser scanning distance may be 100 mm or more. By using an appropriate power, scanning speed and scanning distance, it is possible to properly form a re-solidification layer under the groove. This leads to the component content of the surface layer after the primary recrystallization annealing, and ultimately helps to improve iron loss. More specifically, the laser output may be 1.5 to 10 kW, the laser scanning speed may be 8 to 15 m/s, and the laser scanning distance may be 100 to 200 mm.
[45]
The laser oscillation method can be used without limitation. That is, continuous oscillation or pulsed mode can be used. In this way, the laser is irradiated so that the surface beam absorption rate is greater than or equal to the heat of fusion of the steel sheet, thereby forming the groove 20 shown in FIGS. 1 and 2 . In FIG. 2 , the X direction represents the longitudinal direction of the groove 20 .
[46]
In this way, when a laser or plasma is used, a re-solidification layer may be formed under the groove by heat emitted from the laser or plasma. The re-solidification layer is distinguished because the overall structure and grain size of the electrical steel sheet being manufactured are different. The thickness of the re-solidification layer may be formed to be less than 3㎛. If the thickness of the re-solidification layer is too thick, the weight ratio of SiO 2 /Fe x SiO y of the surface layer portion of the cold-rolled sheet to be described later is affected, and the magnetism may be reduced. More specifically, the thickness of the re-solidification layer may be 0.1 to 3㎛.
[47]
After the step of forming the groove, the method may further include removing spatters or heal-ups formed on the surface of the cold-rolled sheet.
[48]
Next, the cold-rolled sheet is subjected to primary recrystallization annealing.
[49]
Since the step of primary recrystallization annealing is widely known in the field of grain-oriented electrical steel sheet, a detailed description thereof will be omitted. It may include decarburization or decarburization and nitridation in the primary recrystallization annealing process, and may be annealed in a wet atmosphere for decarburization or decarburization and nitridation. The cracking temperature in the primary recrystallization annealing step may be 710 to 870 ℃. In addition, the dew point temperature may be 40 to 70 ℃.
[50]
In an embodiment of the present invention , due to the control of the weight ratio of SiO 2 /Fe x SiO y of the surface layer portion of the cold-rolled sheet , iron loss can be improved. Specifically, the weight ratio of SiO 2 /Fe x SiO y of the surface layer portion of the cold-rolled sheet may be 0.3 to 3. If out of the above range, after the secondary recrystallization annealing, a large amount of islands are generated in the lower portion of the groove, which may adversely affect the magnetism.
[51]
The surface layer means a thickness of 1 to 2 μm from the surface of the steel sheet.
[52]
The weight ratio of SiO 2 /Fe x SiO y can be measured by the FT-IR method.
[53]
Next, an annealing separator is applied, followed by secondary recrystallization annealing. Since the annealing separator is widely known, a detailed description thereof will be omitted. As an example, an annealing separator containing MgO as a main component may be used.
[54]
The purpose of the secondary recrystallization annealing is broadly to form a {110}<001> texture by secondary recrystallization, and to form a metal oxide (vitreous) film by the reaction of the oxide layer formed during the primary recrystallization annealing and MgO to provide insulation and magnetic properties It is the removal of impurities that harm the As a method of secondary recrystallization annealing, in the temperature increase section before secondary recrystallization occurs, a mixed gas of nitrogen and hydrogen is maintained to protect nitride, which is a grain growth inhibitor, so that secondary recrystallization can develop well, and secondary recrystallization is completed. In the post-cracking stage, impurities are removed by maintaining it in a 100% hydrogen atmosphere for a long time.
[55]
The secondary recrystallization annealing may be performed at a cracking temperature of 900 to 1210 °C.
[56]
In the secondary recrystallization annealing process, the MgO component in the annealing separator may react with the oxide layer formed on the surface of the steel sheet to form a metal oxide layer (forsterite layer) on the surface of the steel sheet and the groove. 3 schematically shows the metal oxide layer 30 . In an embodiment of the present invention, since the groove is formed before the secondary recrystallization annealing, the metal oxide layer 30 may be formed on the surface of the groove as well as the steel sheet.
[57]
In an embodiment of the present invention, after the primary recrystallization, since the weight ratio of SiO 2 /Fe x SiO y of the surface layer portion is appropriately controlled, MgO in the annealing separator penetrates or passes into the steel sheet to form an island in the metal oxide layer 30 lower (40) can be formed. This island 40 comprises a metal oxide. more specifically forsterite.
[58]
3 schematically shows the island 40 . As shown in FIG. 3 , the island 40 may be formed by being separated from the metal oxide layer 30 .
[59]
By appropriately forming the island 40 discontinuously, it can contribute to improving the magnetism.
[60]
More specifically, the island 40 may have a density of 15 or less per groove. 3 shows an example in which three islands 40 are formed under the groove. That is, the density per groove is three. More specifically, the island 40 may have a density of 3 to 15 per groove. More specifically, it may be 10 to 15 pieces.
[61]
The density of the islands positioned under the groove may be 0.5 pieces/μm 2 or less.
[62]
In this case, the reference means the density of islands per groove for an area within 5 μm below the groove in the cross section (TD surface) including the steel sheet rolling direction (RD direction) and the thickness direction (ND direction).
[63]
Among the islands 40 positioned under the groove 20 , the number of islands having a sphericity (short axis/long axis) of 0.6 to 1.0 is 60% or more. At this time, the reference is a cross section (TD surface) including the steel sheet rolling direction (RD direction) and the thickness direction (ND direction). In addition, the island 40 located below the surface on which the groove 20 is not formed is excluded from the above-described distribution calculation. In other words, less than 30% of the islands having a sphericity (short axis/long axis) 0.6 or less among the islands 40 positioned under the groove 20 . More specifically, 60 to 90% of the islands having a sphericity (short axis/long axis) of 0.6 to 1.0 among the islands 40 positioned under the groove 20 . More specifically, 70 to 80% of the islands having a sphericity (short axis/long axis) of 0.6 to 1.0 among the islands 40 positioned below.
[64]
After the secondary recrystallization annealing, the method may further include forming an insulating coating layer on the metal oxide layer.
[65]
A method of forming the insulating coating layer may be used without particular limitation, and, for example, the insulating coating layer may be formed by applying an insulating coating solution containing a phosphate. It is preferable to use a coating solution containing colloidal silica and metal phosphate as the insulating coating solution. In this case, the metal phosphate may be Al phosphate, Mg phosphate, or a combination thereof, and the content of Al, Mg, or a combination thereof relative to the weight of the insulating coating solution may be 15% by weight or more.
[66]
The grain-oriented electrical steel sheet according to an embodiment of the present invention has a groove 20 located on the surface of the electrical steel sheet 10, a metal oxide layer 30 located on the groove 20, and an island 40 located under the groove. ) is included.
[67]
The island 40 may have a density of 15 or less per groove. More specifically, the island 40 may have a density of 3 to 15 per groove. More specifically, it may be 10 to 15 pieces. If the density per groove is more than 15, the magnetism becomes inferior.
[68]
Among the islands 40 positioned under the groove 20, the number of islands having a sphericity (short axis/long axis) of 0.6 to 1.0 among the islands 40 positioned under the groove 20 is 60% or more. By appropriately forming the island 40, the magnetism can be improved. More specifically, 60 to 90% of the islands having a sphericity (short axis/long axis) of 0.6 to 1.0 among the islands 40 positioned under the groove 20 . More specifically, 70 to 80% of the islands having a sphericity (short axis/long axis) of 0.6 to 1.0 among the islands 40 positioned below.
[69]
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.
[70]
Example
[71]
A cold-rolled sheet having a thickness of 0.23 mm was prepared. The cold-rolled sheet was irradiated with a 2.0 kW Gaussian mode continuous wave laser at a scanning speed of 10 m/s and a scanning distance of 150 mm to form a groove at an angle of 85° to the RD direction. After that, primary recrystallization annealing was performed, and secondary recrystallization was performed after applying an MgO annealing separator. Then, an insulating coating layer was formed.
[72]
After the primary recrystallization annealing, the weight ratio of SiO 2 /Fe x SiO y on the surface was measured and shown in Table 1, and the island density under the groove was measured and shown in Table 1. In addition, the iron loss (W17/50) was measured and shown in Table 1 below.
[73]
[Table 1]
[74]
As shown in Table 1, when the weight ratio of SiO 2 /Fe x SiO y is appropriately controlled, an appropriate number of islands is formed, and it can be confirmed that the iron loss is excellent. On the other hand, in the comparative example in which the weight ratio of SiO 2 /Fe x SiO y was not properly controlled, a large amount of islands were generated, confirming that the magnetism was relatively poor.
[75]
Also, in Examples 1 to 10, it was confirmed that the number of islands having a sphericity of 0.6 to 1.0 among the islands positioned under the groove was 50% or more, and the density of the islands positioned under the groove was 15 or less.
[76]
On the other hand, in the comparative example, it was confirmed that the number of islands having a sphericity of 0.6 to 1.0 among the islands positioned under the groove was less than 50%, and it was also confirmed that the density of islands positioned under the groove exceeded 15.
[77]
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.
[78]
[Explanation of code]
[79]
10: grain-oriented electrical steel sheet,
[80]
20: Groove,
[81]
30: metal oxide layer;
[82]
40: Ireland
Claims
[Claim 1]
a groove positioned on the surface of the electrical steel sheet, a metal oxide layer positioned on the groove, and discontinuously distributed and distributed metal oxide-based islands positioned under the groove, wherein the density of the islands positioned under the groove is 15 per groove Grain-oriented electrical steel sheet with no more than one.
[Claim 2]
The grain-oriented electrical steel sheet according to claim 1, wherein a density of islands positioned under the groove is 0.5 pieces/㎛ 2 or less.
[Claim 3]
The grain-oriented electrical steel sheet according to claim 1, wherein the number of islands having a sphericity of 0.6 to 1.0 among the islands positioned under the groove is 60% or more.
[Claim 4]
The grain-oriented electrical steel sheet according to claim 1, wherein 2 to 10 grooves are intermittently present with respect to the vertical direction of rolling.
[Claim 5]
The grain-oriented electrical steel sheet according to claim 1, wherein the longitudinal direction of the groove and the rolling direction of the steel sheet form an angle of 75 to 88°.
[Claim 6]
manufacturing a cold-rolled sheet; forming a groove in the cold-rolled sheet; primary recrystallization annealing the cold-rolled sheet; And applying an annealing separator to the primary recrystallized cold-rolled sheet first, the second comprising the step of recrystallization annealing and, after the step of annealing the cold-rolled sheet the primary recrystallization, the surface layer portion of the cold-rolled sheet SiO 2 / Fe x SiO y of A method of manufacturing a grain-oriented electrical steel sheet having a weight ratio of 0.3 to 3. (wherein x is an integer of 1 to 2, and y is an integer of 2 to 4.)
[Claim 7]
7. The method of claim 6, wherein in the forming of the groove, the cold-rolled sheet is irradiated with a laser to form the groove, the laser output is 1.5 kW or more, the laser scanning speed is 8 m/s or more, and the laser scanning distance is 100 mm A method of manufacturing a grain-oriented electrical steel sheet.
[Claim 8]
The method of claim 6 , wherein in the forming of the groove, a re-solidification layer is formed under the groove.
[Claim 9]
The method of claim 6 , wherein in the forming of the groove, a re-solidification layer is formed to a thickness of 3 μm or less under the groove.
[Claim 10]
The method of claim 6, wherein the primary recrystallization annealing of the cold-rolled sheet is performed at a temperature of 710 to 870°C and a dew point temperature of 40 to 70°C.