Oriented electrical steel sheet and method for micronizing magnetic domain thereof

Abstract

An oriented electrical steel sheet according to one embodiment of the present invention comprises: a steel sheet base material; and an insulating coating layer that is positioned on the electrical steel sheet base material, in which a linear deformed part is present on the surface of the insulating coating layer, a repeated irradiation boundary part is present in the deformed part, and a melt-solidified layer is present below the repeated irradiation boundary part, the melt-solidified layer containing 5 wt% or less of P.

Description

Technical Field

[0001] One embodiment of the present invention relates to an oriented electrical steel sheet and a method for micro-refining magnetic domains thereof. More specifically, one embodiment of the present invention relates to an oriented electrical steel sheet having excellent iron loss characteristics while preventing surface damage by irradiating overlapping lasers on the surface of an electrical steel sheet having secondary recrystallization, and a method for micro-refining magnetic domains thereof. Background Art

[0002] Oriented electrical steel sheets have excellent magnetic properties and are therefore generally used as core materials for transformers. The manufacture of such oriented electrical steel sheets forms a Goss texture recrystallized in the {110}<001> orientation over the entire steel sheet through the inherent rolling and annealing processes only available in the electrical steel sheet manufacturing process.

[0003] In order to address climate change, the global calculation levels of greenhouse gas emissions have been continuously strengthened. In the case of transformer cores, the factors affecting the greenhouse gas emission calculation levels are associated with the improvement of efficiency when using electrical steel sheets. In addition, for the efficiency of transformer cores, the iron loss and magnetic flux density, i.e., magnetic properties, of electrical steel sheets play important roles as elements.

[0004] Regarding the magnetic flux density of electrical steel sheets, in the crystal structure, the higher the degree of accumulation of crystal axes that are easily magnetized, i.e., the higher the crystal orientation, the higher the magnetic flux density, so it may have an important impact on the manufacturing process of electrical steel sheets.

[0005] In addition, regarding the iron loss of electrical steel sheets, the value of W17 / 50 [W / kg] measured when a magnetic field of 50 Hz frequency is applied under the condition of a maximum magnetic flux density of 1.7 T is called the guaranteed iron loss value of the core material, and this value is usually used as a measure of the iron loss of electrical steel sheets. However, when designing a transformer, the value of W15 / 50 [W / kg] measured when a magnetic field of 50 Hz frequency is applied under the condition of a maximum magnetic flux density lower than that, i.e., 1.5 T, is sometimes also used. For the efficiency of a transformer, the lower such an iron loss value, the more excellent its efficiency is evaluated.

[0006] Therefore, in the case of electrical steel sheets, the higher the magnetic flux density and the lower the iron loss of the steel sheet, the more excellent the efficiency of the transformer core can be used. Among them, regarding the magnetic flux density, due to the upward leveling of the manufacturing process of electrical steel sheets, the process technology for ensuring a high magnetic flux density has developed to the extent that it can support the efficiency of transformers. Therefore, iron loss is evaluated as a more important index.

[0007] Such iron losses are divided into eddy current losses and hysteresis losses. Hysteresis losses tend to be lower when the magnetic flux density is higher. Therefore, in grain-oriented electrical steel sheets, eddy current losses play an important role in controlling the overall iron losses. Among iron losses, eddy current losses are divided into conventional eddy current losses and abnormal eddy current losses. Since conventional eddy current losses are proportional to the thickness of the steel sheet, when the steel sheet becomes thinner, the conventional eddy current losses decrease. Therefore, controlling abnormal eddy current losses is regarded as an important technology for reducing iron losses.

[0008] Among such iron losses, as the magnetic wall spacing of 180° magnetic domains, which are magnetic domains in the rolling direction, becomes narrower, the eddy current losses decrease. Therefore, iron losses can be reduced by refining the magnetic domains of the electrical steel sheet.

[0009] In an electrical steel sheet, refining the magnetic domains means the process of separating a crystal particle with a single magnetic domain characteristic into multiple magnetic domains by applying physical stimulation to it. As methods for refining the magnetic domains, methods such as laser irradiation, electron beam irradiation, plasma treatment, etching, or rolling press-in can be used. In addition, after performing such magnetic domain refinement treatment, even after performing stress relief annealing (SRA), it is divided into permanent magnetic domain refinement and temporary magnetic domain refinement depending on whether the magnetic domain refinement effect is maintained.

[0010] In a series of manufacturing processes of electrical steel sheets, the magnetic domain refinement process can be performed before the decarburization process, or there are cases where it is performed after insulation coating.

[0011] In addition, when the produced electrical steel sheet is shipped in a coil state and processed into a final iron core, it takes a relatively long time due to reasons such as product transportation. During such a transportation period or during the period of processing into an iron core, there is a possibility that the part of the electrical steel sheet that has received physical stimulation for magnetic domain refinement will be corroded.

[0012] Corrosion occurs in the part of the surface of the electrical steel sheet that has received physical stimulation, which means that the insulation coating on the surface is peeled off and the base material of the electrical steel sheet is exposed. When it is directly used as an iron core for lamination and used, the insulation coating formed on the surface of the electrical steel sheet is damaged, resulting in electrical conduction between the upper and lower laminated iron cores. In this case, there is a possibility that the transformer will even explode.

[0013] Therefore, even when physical stimulation is applied to the surface of the electrical steel sheet for magnetic domain refinement, it is necessary to apply the stimulation within the range that does not damage the insulation coating. Summary of the Invention

[0014] (I) Technical Problems to be Solved

[0015] An embodiment of the present invention provides an oriented electrical steel sheet and a method for micro-refining magnetic domains thereof. More specifically, an embodiment of the present invention provides an oriented electrical steel sheet and a method for micro-refining magnetic domains thereof, which prevent surface damage and have excellent iron loss characteristics by irradiating overlapping lasers with different wavelengths on the surface of the electrical steel sheet constituting secondary recrystallization.

[0016] (II) Technical Solution

[0017] The oriented electrical steel sheet according to an embodiment of the present invention includes: an electrical steel sheet substrate; and an insulating coating layer located on the electrical steel sheet substrate. There are linear deformation portions on the surface of the insulating coating layer, and there are repeated irradiation boundary portions within the deformation portions. There is a molten and solidified layer below the repeated irradiation boundary portions, and the molten and solidified layer contains 10% by weight or less of P.

[0018] The width M in the vertical direction of the deformation portion length of the molten and solidified layer W can be 0.05 μm to 10 μm.

[0019] The thickness M of the molten and solidified layer D can be 20% or less of the thickness of the insulating coating layer.

[0020] In the insulating coating layer below the deformation portion except for the repeated irradiation boundary portion, the P content within a range of 100 nm from the surface in the steel sheet thickness direction can be 10% by weight to 30% by weight.

[0021] The thickness of the insulating coating layer below the deformation portion can be 60% to 90% of the thickness of the insulating coating layer where no deformation portion is formed.

[0022] A metal oxide layer can be provided between the substrate and the insulating coating layer.

[0023] The method for micro-refining magnetic domains of the oriented electrical steel sheet according to an embodiment of the present invention may include: a first irradiation step of irradiating a first laser beam having a first wavelength; and a second irradiation step of irradiating a second laser beam having a second wavelength, and the first beam point of the first laser beam and the second beam point of the second laser beam overlap by 10% or more.

[0024] The first laser and the second laser can be selected from CO2 laser, fiber laser, YAG laser, ruby laser, sapphire laser, disk laser, diode laser or UV laser.

[0025] The output of each of the first laser and the second laser can be 10 W to 2000 W.

[0026] The wavelengths of the first laser and the second laser can be different from each other.

[0027] At the overlapping position, the interval between the irradiation time of the first laser beam and the irradiation time of the second laser beam can be 18 milliseconds (ms) or less.

[0028] (III) Advantageous Effects

[0029] According to an embodiment of the present invention, by performing optimal magnetic domain refinement using overlapping lasers, it is possible to further enhance magnetism while sufficiently suppressing damage to the steel plate surface.

[0030] According to an embodiment of the present invention, by using a long-wavelength laser, it is possible to easily achieve high output of the average output and ensure the reliability of the processing pipeline. At the same time, by irradiating a short-wavelength laser together, it is possible to minimize the formation of magnetic domains, thereby efficiently improving magnetism.

[0031] According to an embodiment of the present invention, by using lasers in an overlapping manner, it is possible to suppress magnetic deviation caused by the coating while maintaining the iron loss improvement effect.

[0032] According to an embodiment of the present invention, it is possible to stably preheat the steel plate without damaging the insulating coating layer, and without considering the thickness of the insulating coating layer, it is possible to accurately induce residual stress corresponding to the thermoelastic deformation of the steel plate in a width size required for forming closed magnetic domains, thereby enabling accurate magnetic domain refinement.

[0033] According to an embodiment of the present invention, even under low laser output conditions, the thermal shock in the thickness direction is maximized, thereby providing an oriented magnetic domain refined product having excellent iron loss in low magnetic fields and high magnetic fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a graph showing the light absorption rate of a steel plate corresponding to the laser wavelength.

[0035] Figure 2 is a schematic diagram showing the concept of magnetic domain refinement of forming a deformed portion using overlapping lasers according to an embodiment of the present invention.

[0036] Figure 3 is a schematic diagram showing the beam points of overlapping lasers according to an embodiment of the present invention.

[0037] Figure 4 is a schematic diagram showing the beam points of overlapping lasers according to another embodiment of the present invention.

[0038] Figure 5 is a schematic diagram showing the surface of a steel plate having a deformed portion and a repeated irradiation boundary portion in an embodiment of the present invention.

[0039] Figure 6It is a schematic diagram showing a cross-section in the thickness direction (Z direction) of a steel plate with a deformed portion and a repeated irradiation boundary portion in an embodiment of the present invention.

[0040] Figure 7 It is a photograph of the molten solidified layer analyzed by FIB (Focused Ion Beam)-TEM (Transmission Electron Microscopy) in Example 1.

[0041] Figure 8 It is for Figure 7 a graph of elemental analysis of the molten solidified layer in the thickness direction. Detailed implementation manners

[0042] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or elements, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer, or element from another part, component, region, layer, or element. Therefore, without departing from the scope of the present invention, the first part, component, region, layer, or element described below can be referred to as the second part, component, region, layer, or element.

[0043] The technical terms used herein are only used to refer to specific embodiments and are not intended to limit the present invention. Unless explicitly shown to have the opposite meaning, the singular form used herein also includes the plural form. The meaning of "including" used in the specification embodies specific characteristics, regions, integers, steps, actions, elements, and / or components, and does not exclude the existence or addition of other characteristics, regions, integers, steps, actions, elements, and / or components.

[0044] When referring to a certain part being "above" or "on" another part, this can mean that it is directly above or on the other part, or there can be other parts between them. In contrast, when referring to a certain part being "directly above" another part, there are no other parts between them.

[0045] Although not defined otherwise, all terms including technical terms and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in a generally used dictionary are additionally interpreted to have a meaning consistent with the relevant technical literature and the currently disclosed content, and should not be interpreted as ideal or overly formal meanings unless they are defined.

[0046] 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 it. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0047] An object of an embodiment of the present invention is to prevent surface damage and impart excellent iron loss characteristics by irradiating overlapping lasers on the surface of an electrical steel sheet.

[0048] An embodiment of the present invention includes: a first irradiation step of irradiating a first laser beam having a first wavelength; and a second irradiation step of irradiating a second laser beam having a second wavelength, wherein the first beam spot of the first laser beam and the second beam spot of the second laser beam overlap by 10% or more.

[0049] As one of the methods for improving iron loss in grain-oriented electrical steel sheets, the method of micro-refining magnetic domains using lasers is favored.

[0050] As Figure 2 illustrated in, in the magnetic domain micro-refining process of the grain-oriented electrical steel sheet, the laser travels along a direction crossing the rolling direction (RD direction) and is irradiated to form a linear (linear) deformation portion 10. The linear deformation portion can form a dot-shaped or continuous linear deformation portion. Herein, the linear or linear deformation portion means that it includes not only solid lines but also intermittently connected lines such as dotted lines or wavy lines, and at the same time, it includes a sawtooth shape when observed microscopically but a straight line shape when observed macroscopically, and it includes all deformation portions that substantially form a line.

[0051] Forming a deformation portion in the steel sheet using a laser indicates a deformation of the crystal lattice generated due to thermal shock by laser irradiation, and such a deformation of the crystal lattice is formed during the process of the steel sheet being rapidly heated locally by the laser and then immediately cooled. At this time, the heating rate of the steel sheet is proportional to the energy density (power density) of the laser per unit time.

[0052] However, when irradiating the laser, the greater the total laser irradiation energy, the greater the deformation of the crystal lattice caused by thermal shock. Therefore, when the energy above the size required for magnetic domain micro-refinement is irradiated to the steel sheet, the heat source above the size required for forming closed magnetic domains diffuses to the periphery, resulting in a larger magnetic deformation. Therefore, when irradiating the laser, only the lattice deformation energy required for forming closed magnetic domains is accurately needed in the deformation of the crystal lattice caused by thermal shock, and in order to suppress heat diffusion, it is preferable to irradiate the laser incident energy only to a narrow area for as short a time as possible.

[0053] In addition, the interaction conditions between the laser beam and the steel sheet are affected by the characteristics of the laser and the absorption rate of the laser beam with respect to the steel sheet. The absorption rate of the laser beam is affected by the surface roughness of the steel sheet, the temperature of the steel sheet, the absorption characteristics of the coating film on the steel sheet surface, and the laser wavelength. However, when the manufacturing conditions of the grain-oriented electrical steel sheet with a coating film are kept constant, the surface roughness of the steel sheet, the temperature of the steel sheet, and the absorption characteristics of the coating film on the steel sheet surface will be constant. In this case, the absorption rate of the laser beam with respect to the steel sheet will follow the laser wavelength.

[0054] That is, when the manufacturing conditions of the steel sheet are constant, the laser absorption rate is affected by the laser wavelength. As Figure 1 shown, when the wavelength is a short wavelength (for example: YAG or Fiber laser with a wavelength of 1.06 μm), the laser absorption rate of the steel sheet is about 35% to 40% or so, while when the wavelength is a long wavelength (for example: CO2 laser with a wavelength of 10.6 μm), it is about 5% to 10% or so and shows relatively low.

[0055] In the process of micro-refining magnetic domains based on laser in the above-mentioned grain-oriented electrical steel sheet, in order to ensure stable iron loss characteristics, it is more efficient to use a short-wavelength laser than to use a long-wavelength laser.

[0056] In addition, an insulating coating film with a thickness of several μm to several tens of μm and mainly composed of phosphate and silica is formed on the surface of the electrical steel sheet that is the object of magnetic domain micro-refining treatment. These coating films absorb the laser beam relatively less for short-wavelength lasers (for example: YAG or Fiber laser with a wavelength of 1.06 μm), while showing relatively large absorption for long-wavelength lasers (for example: CO2 laser with a wavelength of 10.6 μm). As a result, in the case of long-wavelength lasers, it is necessary to consider the thickness of the insulating coating film, while in the case of short-wavelength lasers, the thickness of the insulating coating film can be considered less than that in the case of long-wavelength lasers.

[0057] As described above, the characteristics of short-wavelength lasers and long-wavelength lasers are different from each other. Therefore, when short-wavelength lasers and long-wavelength lasers are used overlapped simultaneously, only the advantages of each laser applicable to magnetic domain micro-refining can be preferably exerted without side effects, thereby causing a mutual enhancement (synergistic effect) effect.

[0058] Among them, the use of lasers in an overlapping manner means that two or more lasers are used as laser beams irradiated onto the surface of the steel plate, and a part or all of the beam points of one laser beam formed on the surface of the steel plate are located within the beam points of another laser beam. Therefore, in an embodiment of the present invention, the overlapping lasers with different wavelengths refer to not only the case where the beam points of another laser beam completely fall within the beam points of one laser beam and are superimposed, but also the case where a part of them is locally superimposed. And for the irradiation time at the overlapping position, it is not necessary to irradiate simultaneously, but it is also okay to irradiate in an overlapping manner at an interval of a predetermined time. That is, as Figure 4 shown, even if the laser beams do not overlap at a specific time point, when the first laser beam horizontally moves in the traveling direction (X direction) over time and thus overlaps with the position of the second laser beam irradiated previously, it is regarded as overlapping. However, during the process of the first laser beam traveling in the irradiation traveling direction (X direction), the overlapping situation between the first laser beams is not regarded as overlapping.

[0059] In an embodiment of the present invention, the beam point refers to the beam point on the surface 40 of the steel plate. Figure 3 schematically shows the first beam point of the first laser beam 21 and the second beam point of the second laser beam 22.

[0060] The first beam point of the first laser beam and the second beam point of the second laser beam overlap by more than 10%. More than 10% means that with respect to the width B 1W of the first laser beam and the width B 2W of the second laser beam, the width O W of the overlapping region of the smaller laser beam width Figure 3 in is the width B 1W of the first laser beam. In this case, the overlapping ratio can be calculated using O W / B 1W for calculation.

[0061] The width of the laser beam refers to the length of the laser beam in the direction (Y direction) perpendicular to the length direction of the deformed part (or the laser irradiation traveling direction, X direction). The length of the laser beam refers to the length of the laser beam in the length direction of the deformed part (or the laser irradiation traveling direction, X direction). Figure 3 shows the length B 1L of the first laser beam and the length B 2L of the second laser beam.

[0062] Figure 4 As shown, in the case where the laser beams do not overlap at a specific time point, the laser beams are horizontally moved in the traveling direction (X direction), and the width O WWhen it becomes the longest, it is regarded as the overlapping ratio.

[0063] In addition, in one embodiment of the present invention, due to the existence of an overlapping region, there are repeated irradiation boundary portions 23 at both ends in a direction (Y direction) perpendicular to the length direction of the deformed portion of the overlapping region (or the laser irradiation traveling direction, X direction). There is a molten and solidified layer 11 below the repeated irradiation boundary portion 23. The molten and solidified layer 11 will be described later in association with the grain-oriented electrical steel sheet.

[0064] The first laser and the second laser can be selected from CO2 laser, fiber laser, YAG laser, ruby laser, sapphire laser, disk laser, diode laser or UV laser.

[0065] More specifically, as the first laser A of short-wavelength laser, a laser with a relatively short wavelength can be used. For example, fiber (Er-Fiber, Yb-Fiber, Tm-Fiber) laser, YAG (Nd:YAG, Yb:YAG) laser, ruby laser, sapphire laser, etc. can be used. Moreover, as such a first laser, disk laser (1.03μm), diode laser (0.808μm to 0.980μm) or UV laser (0.150μm to 0.355μm) can also be used.

[0066] In addition, as the second laser of long-wavelength laser, a laser with a wavelength relatively longer than that of the short-wavelength laser can be used. For example, the CO2 laser is preferably used as the second laser. However, if the first laser of short-wavelength laser uses UV laser (0.150μm~0.355μm), as long as its wavelength is longer than that of the first laser, any laser can be used as the second laser. For example, in the case where the UV laser (0.150μm~0.355μm) is used as the first laser, the YAG laser can also be used as the second laser.

[0067] Hereinafter, taking the case where the fiber laser is used as the first laser of short wavelength and the CO2 laser is used as the second laser of long wavelength as an example, the method for refining magnetic domains using the overlapping laser 30 will be described in more detail.

[0068] The fiber laser used as the first laser uses a short-wavelength laser wavelength with a relatively high laser absorption rate for the steel plate. Therefore, the laser incident energy can be accurately irradiated to a relatively narrow area only in the shortest possible time, and the incident energy is the degree of lattice deformation and residual stress caused by thermoelastic deformation required to induce the formation of closed magnetic domains. And, because the incident energy range of the fiber laser used as the first laser is narrow, the heat diffusion to the periphery can be suppressed, so that unnecessary thermal deformation can be minimized.

[0069] In addition, the CO2 laser, which serves as the second laser, can be used with high output so that its average output reaches several hundred W to several kW or more according to the steel plate speed, enabling thermoelastic deformation to be easily induced in the irradiated portion of the steel plate. Moreover, the CO2 laser, which serves as the second laser, has a relatively high absorption rate for the insulating coating composed of phosphate and silica, so it can stably penetrate the coating layer. Therefore, the CO2 laser, which serves as the second laser, can also stably induce thermoelastic deformation of the steel plate without damaging the insulating coating layer, and thus is suitable for playing a preheating role. However, since the CO2 laser, which serves as the second laser B, has a relatively low laser absorption rate for the steel plate, although it induces thermoelastic deformation of the steel plate, it is preferably irradiated with laser to such an extent that permanent deformation is not caused.

[0070] That is, when a long-wavelength laser such as a CO2 laser is used as the second laser, the portion that imparts a thermal shock to the steel plate is formed too wide, so that magnetic domain subdivision cannot be well generated. Therefore, a fiber laser with a relatively short wavelength is used as the first laser and serves as the main laser for magnetic domain refinement, while a CO2 laser with a relatively long wavelength is used as an auxiliary laser that plays a preheating role to the extent of inducing thermoelastic deformation of the steel plate.

[0071] As described above, the reason for selecting a short-wavelength fiber laser as the first laser and using it as the main laser for magnetic domain refinement is that a strong compressive stress portion is formed in the laser irradiation portion due to the relatively high laser absorption rate on the steel plate surface. In order to reduce the magnetoelastic energy in such a compressive stress portion, it is possible to easily form lancet magnetic domains (closed magnetic domains).

[0072] In this case, 180° magnetic domains (opposite stimuli of lancet magnetic domains) are formed in the surface direction by magnetoelastic energy due to magnetic domain refinement, and 90° magnetic domains are formed in the plate thickness direction to reduce the magnetoelastic energy, thereby narrowing the interval between magnetic domains, and as a result, reducing abnormal eddy current loss.

[0073] As described above, according to the magnetic domain refinement method of an embodiment of the present invention, since a short-wavelength fiber laser is used as the first laser, it is possible to accurately cause residual stress corresponding to the thermoelastic deformation of the steel plate with a width of the size required for forming closed magnetic domains, and thus accurate magnetic domain refinement can be achieved. Moreover, a long-wavelength CO2 laser is used as the second laser, so that the steel plate can be stably preheated without damaging the coating layer.

[0074] Furthermore, the fiber laser with a short wavelength as the first laser has the advantages of being able to form a relatively small final beam width and improving the laser absorption rate in the steel plate, but its depth of field is relatively short. On the other hand, the CO2 laser as the second laser with a longer wavelength has a wider width of the final beam, a relatively low laser absorption rate in the steel plate, but has the advantage of a deeper depth of field. Therefore, when these two laser beams are irradiated simultaneously in an overlapping manner, the laser absorption rate in the steel plate can be further improved.

[0075] At this time, the beam spot of the fiber laser as the short-wavelength first laser irradiated on the surface of the steel plate is preferably approximately circular, and its diameter B W1 、B L1 can be 10 μm to 200 μm. And the width B W1 of the beam spot of the fiber laser is 10 μm to 200 μm, and its length B L1 can also be less than or equal to the length of the beam spot of the CO2 laser as the second laser and used.

[0076] When the beam width B W1 of the fiber as the first laser is reduced to less than 10 μm, as the energy density accumulates in a narrower area, magnetic flux density and iron loss degradation may occur, and there is a problem that the optical meter structure becomes complicated. In addition, when the beam width B W1 of the fiber as the first laser is increased to more than 200 μm, the magnetic flux density may decrease due to the increased thermal influence in the length direction of the steel plate, so it is not preferred.

[0077] In addition, the beam spot of the CO2 laser as the second laser with a long wavelength irradiated on the surface of the steel plate is preferably an elliptical beam spot, and its beam width B 2W is 100 μm to 400 μm, and its beam length B 2L is 0.4 mm to 20 mm. And the beam spot of the long-wavelength CO2 laser can also be used as a circle with a radius of 100 μm or more.

[0078] In order to form the CO2 beam width B 2W of the second laser within 100 μm, like the fiber laser, the mirror optical meter will become complicated, so it is not preferred. When it is increased to more than 400 μm, due to the increased thermal influence in the length direction of the steel plate, the magnetic flux density decreases, so it is not preferred.

[0079] The reason for limiting the size of the beam spot of the CO2 laser as the long-wavelength second laser as described above is that it takes into account the range in which the thermal deformation effect of the laser beam acting on the steel plate is maintained when the laser is scanned at high speed on the surface of the high-speed moving steel plate.

[0080] A more detailed description will be given of the case where lasers are used in an overlapping manner according to an embodiment of the present invention.

[0081] As Figure 3 and Figure 4 shown, using the first laser beam 21 and the second laser beam 22 in an overlapping manner means controlling so that the beam spot of the first laser beam 21 and the beam spot of the second laser beam 22 overlap. That is, for the laser beam spot 20 irradiated on the steel plate surface, when viewed from a plane as Figure 3 shown, the case where the first laser beam 21 is completely located anywhere within the range of the second laser beam 22 with a larger beam spot is regarded as the beams "overlapping". Further, it also includes the case where the first laser beam 21 is partially located within the range of the second laser beam 22 and is regarded as the beams "overlapping". Further, as Figure 4 shown, even if the laser beams do not overlap at a specific time point, when the first laser beam 21 horizontally moves in the traveling direction (X direction) over time and thus overlaps with the position of the previously irradiated second laser beam 22, it is also regarded as overlapping.

[0082] Regarding the oscillation mode of the laser beams used in an embodiment of the present invention, both the first laser and the second laser preferably use continuous wave lasers (Continuous Wave Laser) that continuously generate lasers, but pulsed lasers (Pulse Laser) can also be used.

[0083] And, regarding the quality of the laser beams used, both the first laser and the second laser are preferably in the TEM 00 Gaussian mode (Gaussian mode), but multi transverse modes (multi transverse mode) of TEM0i can also be used.

[0084] However, since the overlapping laser beams 20 of different wavelengths irradiated on the steel plate surface according to an embodiment of the present invention can minimize the thermal influence in the length direction of the steel plate while maximizing the thermal shock in the thickness direction, the beam shape or beam quality of each laser is not specifically limited.

[0085] The output of each of the first laser and the second laser can be 10 W to 2000 W. More specifically, the output of the first laser can be 1000 W to 2000 W, and the output of the second laser can be 100 W to 700 W. The output ranges of such lasers indicate the laser output conditions when the steel plate is traveling at a speed of 15 mpm, and the output value of the laser can be optimally controlled according to the traveling speed of the steel plate.

[0086] When the laser beam 30 in which the first laser and the second laser are overlapped as described above is irradiated onto the surface of the steel sheet, the interval (i.e., the interval in the steel sheet rolling direction between the deformed portions) can be 2 mm to 10 mm, and the angle between the rolling direction and the laser traveling direction (the length direction of the deformed portion, the X direction) can be 75° to 105°, and the scanning speed can be 0.1 m / sec to 300 m / sec.

[0087] At this time, the electrical steel sheet used is preferably an electrical steel sheet having secondary recrystallization.

[0088] In addition, if the irradiation interval of the overlapping laser beam 20 irradiated onto the steel sheet surface becomes too narrow and is less than 2 mm, the influence of the heat-affected zone becomes large, resulting in deterioration of the magnetic flux density and iron loss. If the irradiation interval is 10 mm or more, it is difficult to exert the effect because the thermal shock effect for ensuring the magnetic domain refinement effect becomes poor.

[0089] Moreover, when irradiating the overlapping laser beam 20 onto the steel sheet surface, it can be irradiated in a direction perpendicular or inclined to the steel sheet rolling direction, and the angle between the rolling direction and the laser traveling direction (the length direction of the deformed portion, the X direction) can be 75° to 105°. If it deviates from this angle range, the desired magnetic domain refinement effect may not occur.

[0090] In addition, when the scanning speed of the overlapping laser increases its traveling speed in the same manner as the steel sheet running speed, the corresponding scanning speed needs to be increased even more. Therefore, it is preferably 0.1 m / sec to 300 m / sec, and this speed represents the value illustrated under the condition of 15 mpm.

[0091] In addition, as Figure 3 shown, although the first laser beam and the second laser beam can be overlapped and irradiated simultaneously, as Figure 4 shown, they can also be irradiated in an overlapping manner with a time interval between them. However, at the overlapping position, the interval between the irradiation time of the first laser beam and the irradiation time of the second laser beam can be 16 milliseconds or less. When it exceeds this time range, it is difficult to sufficiently obtain the effect of irradiating the lasers in an overlapping manner. The time interval means the time until the time point when, after irradiating the second laser (or the first laser), the first laser (or the second laser) travels and the width O W of their overlapping region reaches the maximum.

[0092] In an embodiment of the present invention, the grain-oriented electrical steel sheet 100 includes: an electrical steel sheet base material 50; and an insulating coating layer 60 located on the electrical steel sheet base material 50. Linear deformed portions 10 exist on the surface of the insulating coating layer 60, and repeated irradiation boundary portions 23 exist within the deformed portions 10.

[0093] AsFigure 3 As shown, the overlapping irradiation boundary portion 23 refers to both end portions in the Y direction of the overlapping region when the first laser beam 21 and the second laser beam 22 are irradiated in an overlapping manner. This overlapping irradiation boundary portion 23 is difficult to judge with the naked eye, but can be judged by whether a molten solidified layer 11 is formed in the lower insulating coating layer 10. That is, starting from the overlapping irradiation boundary portion 23, the molten solidified layer 11 is generated below the overlapping irradiation boundary portion 23 in the Y direction. Since this molten solidified layer 11 is generated by the volatilization of phosphorus (P) in the insulating coating layer 10, there is less phosphorus (P) in the molten solidified layer 11. That is, when the P content is 10% by weight or less, it is judged that the molten solidified layer 11 is formed. More specifically, when the P content is 8% by weight or less, it is judged that the molten solidified layer 11 is formed.

[0094] As described above, the reason for generating the molten solidified layer 11 in the case of irradiating overlapping laser beams is that since the vaporization point of the phosphate constituting the insulating coating layer 60 is low, when overlapping lasers are irradiated, phosphorus is first vaporized, and the silicon oxide composed of Si and O is re-solidified in an amorphous state. In the case of forming a re-solidified layer in an amorphous state on the surface of the insulating coating layer as described above, the corrosion resistance is improved by virtue of the inherent characteristics of the amorphous.

[0095] The width M of the deformed portion of the molten solidified layer in the vertical direction (Y direction) W can be from 0.05 μm to 10 μm. When it is in the aforementioned range, the effects of improving iron loss and enhancing corrosion resistance based on overlapping irradiation can be appropriately exerted. More specifically, the width M of the deformed portion of the molten solidified layer in the vertical direction (Y direction) W can be from 0.1 μm to 5 μm.

[0096] The thickness M of the molten solidified layer D can be 20% or less of the thickness of the insulating coating layer. When the thickness M of the molten solidified layer D is too thick, since the absolute thickness of the insulating coating layer becomes thinner, it may act unfavorably on the corrosion resistance, and the iron loss deteriorates due to the reduction of the tension effect based on the insulating coating layer. Therefore, it is preferably limited to the range as described above. More specifically, the thickness M of the molten solidified layer D can be from 1% to 15% of the thickness of the insulating coating layer. The thickness M of the molten solidified layer D refers to the depth from the surface of the insulating coating to the boundary where P reaches 10%. In the case where the molten solidified layer is formed within a thickness of 20% of the thickness of the insulating coating layer 60, it means that, without damaging the insulating coating layer, a sufficient amount of laser is given to the steel plate with respect to the incident energy of the laser in the steel plate. More specifically, the thickness M of the molten solidified layer DIt can be from 50 nm to 500 nm.

[0097] In the insulating coating layer 60 below the deformed portion 10 except for the repeated irradiation boundary portion 23, the P content in the range of 100 nm in the steel plate thickness direction from the surface can be from 10 wt% to 30 wt%. As described above, in the deformed portion 10 and the repeated irradiation region, since the energy of the laser is large enough, rather than melting, the insulating coating layer 60 itself vaporizes, and only phosphorus (P) selectively does not volatilize. More specifically, the P content can be from 12 wt% to 25 wt%.

[0098] The deformed portion 10 cannot be visually distinguished from the surface of the insulating coating layer outside the deformed portion either, but can be distinguished by the thickness of the insulating coating layer 60 below the deformed portion 10. That is, when the first laser or the second laser is irradiated, the thickness of the insulating coating layer at the lower part of the irradiated surface will be reduced compared to the non-irradiated part. In the case where the deformed portion 10 is formed on the electrical steel sheet by overlapping laser irradiation and the molten solidified layer 11 is formed in the insulating coating layer 60, due to the formation of the molten solidified layer 11, shrinkage occurs in the insulating coating layer 60, and thus the thickness of the insulating coating layer 60 of the deformed portion of the steel plate may change.

[0099] More specifically, the thickness of the insulating coating layer 60 below the deformed portion 10 can be from 60% to 90% of the thickness of the insulating coating layer where the deformed portion is not formed. When the thickness of the coating layer formed on the deformed portion of the steel plate is too thin, the corrosion resistance may deteriorate due to the reduction of the coating thickness, and the iron loss may deteriorate due to the reduction of the tension effect. When it is too thick, it means that the molten solidified layer 11 is not properly formed, and it is difficult to expect proper improvement of the iron loss. The thickness of the insulating coating layer 60 refers to the depth from the surface of the insulating coating layer 60 to the boundary portion where the P content is 5 wt% after the P content increases by more than 10 wt% and then decreases to less than 5 wt%.

[0100] In the grain-oriented electrical steel sheet, a metal oxide layer (glass coating layer, not shown) can also be formed between the electrical steel sheet substrate and the insulating coating layer.

[0101] Among them, the metal oxide layer has forsterite as the main component, and the insulating coating layer has phosphate and colloidal silica as the main components. In addition, the main component referred to in the present invention means that in the case of forsterite, it contains 0.7 g / m based on the single-sided coating amount of oxygen on the steel plate surface 2 Above, in the case of phosphate in the insulating coating, it contains 0.1 g / m based on the single-sided coating amount on the steel plate surface 2 Above, and in the case of colloidal silica in the insulating coating, it contains 0.1 g / m based on the single-sided coating amount on the steel plate surface2 Above.

[0102] In one embodiment of the present invention, after performing the heat deformation-based magnetic domain refinement process using overlapping laser beams, in order to ensure the insulation between steel plates, it means not only preventing the peeling of the insulation coating film but also preventing the peeling of the glass coating film.

[0103] In addition, in the case of forming a deformed portion by irradiating overlapping laser light onto the surface of an electrical steel sheet according to one embodiment of the present invention, the W15 / 50 iron loss improvement rate of such a steel sheet is preferably 6% or more. When the W15 / 50 improvement rate is lower than this, since the laser absorption rate of the steel sheet is low, it is difficult to expect the desired iron loss reduction effect.

[0104] Furthermore, in the case of forming a deformed portion by irradiating overlapping laser light onto the surface of an electrical steel sheet according to one embodiment of the present invention, the W17 / 50 iron loss improvement rate of such a steel sheet is preferably 9% or more. When the W17 / 50 iron loss improvement rate is lower than this, similarly, since the laser absorption rate of the steel sheet is low, it is difficult to expect the desired iron loss reduction effect.

[0105] Hereinafter, a method for manufacturing an oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0106] [Manufacture of cold-rolled steel sheet]

[0107] In order to manufacture an oriented electrical steel sheet, first, a slab for the electrical steel sheet base material is manufactured.

[0108] Regarding the chemical composition and metal structure of the slab, as long as the easy magnetization axis is aligned in a predetermined direction and used as an electrical steel sheet, its composition and structure are not otherwise limited. However, when giving an example, the chemical composition of the slab is as follows.

[0109] Containing C: 0.08% or less (excluding 0%), Si: 1.0% - 6.5%, Mn: 0.005% - 3.0%, (total of any one or more of NB, V, Ti): 0.070% or less, (total of any one or more of Cr, Sn, Sb): 2.5% or less, Al: 2.0% or less (excluding 0%), (total of any one or more of P, S): 0.100% or less (excluding 0%), (total of Cu and Sn): 1.0% or less, and the total of rare earth elements and other impurities: 0.2% or less, with the balance being composed of Fe, by mass%.

[0110] (C: 0.08% or less (excluding 0%))

[0111] Carbon (C) is an element inevitably mixed into steel, but it causes deterioration of magnetic properties based on magnetic aging, so it is preferably controlled to an appropriate content. When the content of C in the steel sheet is too low, phase transformation cannot be sufficiently induced in the manufacturing process, resulting in non-uniform fine structure of the steel sheet. As a result, the secondary recrystallization structure may become unstable. When C is contained in excess, carbides become coarse and the precipitation amount is excessive in the manufacturing process. As a result, the accumulation degree of Goss texture decreases due to insufficient decarburization, and the secondary recrystallization texture may be damaged. Therefore, the C content of the steel sheet is 0.08% or less, more preferably 0.001% - 0.040%.

[0112] (Si: 1.0 - 6.5%)

[0113] Silicon (Si) is a basic component of grain-oriented electrical steel sheets, which plays a role in increasing the specific resistance of the steel sheet to reduce iron loss. When it is less than 1.0%, eddy current loss increases due to the decrease in specific resistance, resulting in deterioration of iron loss characteristics and inability to expect the Si addition effect. When it is 6.5% or more, the brittleness of the steel sheet increases and the toughness decreases, so plate breakage may occur during the rolling process, and sufficient grain inhibition force required for secondary recrystallization cannot be ensured during the final high-temperature annealing process because nitrides cannot be sufficiently formed in the manufacturing process. Therefore, Si is preferably 1.0% - 6.5%.

[0114] (Mn: 0.005 - 3.0%)

[0115] Manganese (Mn) reduces eddy current loss by increasing the specific resistance, thus having the effect of reducing the overall iron loss. It not only reacts with S in the small steel state to form Mn-based sulfides, but also reacts with Si and nitrogen (N) introduced by nitriding treatment to form precipitates of (Al, Si, Mn)N, thereby inhibiting the growth of primary recrystallized grains to induce secondary recrystallization. Moreover, it is an important element that affects the surface quality of the final product. However, when Mn is contained in too small an amount, the surface quality of the final product may deteriorate. And when Mn is contained in too large an amount, the austenite phase fraction increases significantly, resulting in damage to the Goss texture and reduction of magnetic flux density, and may hinder decarburization due to excessive formation of an oxide layer during decarburization annealing. Therefore, Mn is preferably 0.005% - 3.0%.

[0116] (Any one or more of Nb, V, Ti in total: 0.05% or less)

[0117] Niobium (Nb), vanadium (V), and titanium (Ti) are elements that react with C and N during the manufacturing process to form precipitates. However, when added in excess, they remain in the steel sheet even after secondary recrystallization annealing and reduce the magnetic properties of the steel sheet. Therefore, it is preferably controlled such that the total of one or more elements selected from Nb, V, and Ti is 0.05% or less.

[0118] (Total of any one or more of (Cr, Sn, Sb): 2.5% or less)

[0119] Chromium (Cr) is added for the purpose of promoting the formation of a Goss texture to reduce iron loss, and Sn is added for the purpose of suppressing grain growth to ultimately increase the magnetic flux density. In addition, antimony (Sb) has the effect of segregating at the grain boundaries to suppress grain growth and stabilize secondary recrystallization. Since all three of these elements are related to the formation of the secondary recrystallization structure, it is preferably controlled such that the total of Sn, Sb, and Cr is 2.5% or less.

[0120] (Al: 2.0% or less (except 0%))

[0121] Aluminum (Al) serves as a strong grain growth inhibitor by forming nitrides in the form of (Al, Si, Mn)N and AlN by combining N introduced by nitriding treatment in the primary recrystallization process with Al, Si, and Mn existing in solid solution in the steel, in addition to Al-based nitrides precipitated during the manufacturing process. However, when the amount of Al is excessive, the formation of secondary recrystallization becomes unstable due to non-uniform precipitates, resulting in a reduction in the magnetic properties of the steel sheet. Therefore, it is preferably added in an amount of 2.0% or less.

[0122] (Total of any one or more of P, S: 0.1% or less (except 0%))

[0123] Phosphorus (P) serves an auxiliary role of segregating at the grain boundaries to impede grain boundary movement and simultaneously suppressing grain growth. If S is added in excess, the formation of secondary recrystallization becomes unstable. Also, P and S are elements that are inevitably added during the process of manufacturing electrical steel sheets, and it is preferably controlled such that the total of P and S is 0.1% or less.

[0124] (Total of Cu + Sn: 0.1% or less)

[0125] Copper (Cu) serves to improve the texture by having a part of it dissolved in the grains. If the content of Cu + Sn is excessive, it may segregate at the grain boundaries and form a liquid phase at high temperatures. Therefore, the total amount of Cu and Sn is preferably controlled to 0.1% or less.

[0126] (Total of rare earths and other impurities: 0.2% or less)

[0127] The grain-oriented electrical steel sheet according to an embodiment of the present invention may contain rare earths such as cerium (Ce) or praseodymium (Pr) and other impurities. Regardless of the rare earths and impurities contained, the total is preferably 0.2% or less. The rare earths and inevitable impurities refer to impurities intentionally added or inevitably mixed during the steelmaking and the manufacturing process of the grain-oriented electrical steel sheet. Since the inevitable impurities are well-known techniques, specific descriptions thereof are omitted. In an embodiment of the present invention, in addition to the aforementioned alloy components, the addition of elements is not excluded, and other elements may be variously included within the scope not departing from the technical idea of the present invention. In the case of further including additional elements, the additional elements are included instead of the balance of Fe.

[0128] Next, after manufacturing a slab from the steel sheet having the above-described components by continuous casting, it is hot-rolled by a usual method and, if necessary, selectively subjected to hot-rolled sheet annealing, and then cold-rolled to a thickness in the range of 0.1 to 0.5 mm. Among them, in the cold rolling, two or more cold rollings with a primary cold rolling or an intermediate annealing provided therebetween may be carried out.

[0129] [Primary recrystallization annealing]

[0130] The cold-rolled steel sheet described above is subjected to simultaneous decarburization nitriding or primary recrystallization annealing is carried out through a nitriding process after decarburization. In the case of primary recrystallization annealing based on simultaneous decarburization nitriding, the structure of the cold-rolled deformed in the annealing process will include primary recrystallization and decarburization annealing. For this purpose, it may be carried out in a mixed gas atmosphere of nitrogen, hydrogen, and moisture. In addition, in the case of nitriding after decarburization, a nitriding treatment of introducing nitrogen ions into the steel sheet by using ammonia gas may also be carried out after decarburization.

[0131] In the case of carrying out simultaneous decarburization nitriding, for the cold-rolled steel sheet charged into the furnace, the dew point temperature of the atmosphere gas is set in the range of 40°C to 70°C in the interval of 700°C to 900°C, and the Fe2SiO4 / SiO2 ratio on the surface is controlled to 0.5 to 3.0, thereby forming an oxide layer on the surface of the electrical steel sheet.

[0132] [Secondary recrystallization annealing]

[0133] Next, after coating an annealing separating agent mainly composed of MgO on the surface of such an electrical steel sheet, it is heated to 1000°C or higher and subjected to long-time soaking annealing to cause secondary recrystallization, thereby forming a texture of a Goss orientation in which the {110} plane of the steel sheet is parallel to the rolling plane and the <001> direction is parallel to the rolling direction. Through the final high-temperature annealing process described above, a glass coating layer containing meerschaum is formed on the surface of the steel sheet, and secondary recrystallization is formed inside the steel sheet.

[0134] [Forming an insulating coating film]

[0135] For a steel sheet having secondary recrystallization, it is coated with a colloidal silica and metal phosphate single or composite insulating coating solution and then annealed, so as to form an insulating coating layer on the surface of an electrical steel sheet having a glass coating layer formed thereon.

[0136] The method for forming such an insulating coating layer can be used without particular limitation. As an example, the insulating coating layer can be formed by coating an insulating coating solution containing phosphate. Preferably used as such an insulating coating solution is a coating solution containing colloidal silica and metal phosphate. At this time, the metal phosphate can be Al phosphate, Mg phosphate, or a combination thereof, and the content of Al, Mg, or a combination thereof can be 15% by weight or more based on the weight of the insulating coating solution.

[0137] [Magnetic domain refinement treatment]

[0138] For the magnetic domain refinement method, it is the same as that described above, so the detailed description thereof will be omitted.

[0139] The present invention will be described in more detail below through specific examples. However, such examples are only for illustrating the present invention, and the present invention is not limited thereto.

[0140] Experimental Example 1

[0141] Cold-rolled steel sheets with thicknesses of 0.20 mm and 0.23 mm were manufactured by using a slab having the components shown in Table 1 below and performing hot rolling and cold rolling. In Table 1, % by element represents % by weight.

[0142] Table 1

[0143]

[0144] For such cold-rolled steel sheets, they were held at 840 °C for 150 seconds in a wet hydrogen, nitrogen, and ammonia mixed gas atmosphere (dew point temperature of 69 °C, Fe2SiO4 / SiO2 ratio controlled to 1.2), and decarburization annealing and nitriding treatment including primary recrystallization annealing were performed.

[0145] An annealing release agent containing MgO was coated on the surface of the steel sheet after primary recrystallization treatment, and final high-temperature annealing was performed. At this time, the final high-temperature annealing was carried out to 1150 °C in a mixed atmosphere of 25% by volume of nitrogen and 75% by volume of hydrogen. After reaching 1150 °C, it was held in a 100% by volume hydrogen atmosphere for about 8 hours and then furnace-cooled.

[0146] On the surface of the steel sheet that has completed secondary recrystallization annealing through the above final high-temperature annealing process, a coating solution in which colloidal silica nanoparticles and metal phosphates are mixed is coated, and heat treatment is performed at a temperature of 870 °C for 55 seconds, thereby forming an insulating coating layer for an oriented electrical steel sheet.

[0147] Next, the lasers tabulated in Table 2 below were irradiated. At this time, both the first laser and the second laser had an elliptical beam shape with a beam width / length ratio (beam width / beam length) of 0.55. The wavelength of the diode laser was 1.03 μm, the wavelength of the fiber laser was 1.08 μm, and the wavelength of the CO2 laser was 10.6 μm. The beam width of each laser was unified to 200 μm. The instantaneous moving speed of the steel sheet in the laser irradiation part was set to 2.3 m / s, the length of the deformed part was set to 160 mm, the scanning speed was set to 60 m / s, the irradiation interval was set to 5.0 mm, and the lasers were irradiated.

[0148] In Comparative Example 3, a 4-second interval was given after irradiating the first laser, and then the second laser was irradiated.

[0149] Regarding the coercive force, the applied magnetic field value required to change the magnetic flux density value to 0 under an alternating magnetic field measured by an SST (single sheet tester) was measured.

[0150] Regarding the corrosion resistance, sodium chloride was dissolved in deionized water according to KS D 9502 and adjusted to a salt concentration of 5 ± 0.5%. After spraying the 35 °C salt solution onto the test piece for a predetermined time, after performing salt spray for the corresponding time, it was taken out, washed with water and dried at room temperature, and it was confirmed whether rust occurred on the surface. In the corresponding salt spray test, when no rust of the laser appeared under the 8-hour salt spray condition, it was classified as good ( ), when no rust of the laser appeared under the 7-hour salt spray condition, it was classified as fair (○), and when rust of the laser appeared under the 4-hour salt spray condition, it was classified as poor (△).

[0151] Table 2

[0152]

[0153] As shown in Table 2, in the case of overlapping irradiation of the first laser and the second laser, it was confirmed that a molten and solidified layer was generated, and improvement in iron loss and enhancement of corrosion resistance could be achieved. On the other hand, in the case of using a single laser or irradiating the laser after a relatively long time, appropriate improvement in iron loss and enhancement of corrosion resistance could not be obtained.

[0154] Figure 7 is a photograph for analyzing the molten and solidified layer of the steel sheet manufactured in Example 1. AsFigure 7 As shown, it can be confirmed that a molten and solidified layer with a width of about 300 nm is formed. As Figure 8 shown, it can be confirmed that the thickness of the molten and solidified layer is about 200 nm. Figure 7 This is a photograph of the solidified layer analyzed by FIB (Focused Ion Beam)-TEM (Transmission Electron Microscopy). In this process, ions are generated by applying an acceleration voltage to the FIB source, and the area where ions are to be selectively observed is scanned using an electric field. The required part of the sample is processed and observed using TEM.

[0155] Experimental Example 2

[0156] The same procedure as in Experimental Example 1 was carried out, and the laser irradiation interval and scanning speed were changed as shown in Table 3 below and the experiment was carried out. In Examples 5 to 7, the overlap ratio was set to 100%. In Comparative Example 6, a 4-second interval was given after the first laser was irradiated, and then the second laser was irradiated.

[0157] Table 3

[0158]

[0159] As shown in Table 3, when the first laser and the second laser are overlapped and irradiated, it can be confirmed that a molten and solidified layer is generated, and improvement in iron loss and enhancement of corrosion resistance can be achieved. On the other hand, when using a single laser or irradiating the laser after a relatively long time, appropriate improvement in iron loss and enhancement of corrosion resistance cannot be obtained.

[0160] The present invention is not limited to the above-described embodiments, but can be manufactured in various different forms. Those of ordinary skill in the technical field to which the present invention pertains should understand that it can also be implemented in other specific forms without changing the technical idea or essential features of the present invention. Therefore, the above-described embodiments are to be understood as illustrative in all respects and not restrictive.

[0161] Explanation of Reference Numerals

[0162] 100: Grain-oriented electrical steel sheet 10: Deformed portion

[0163] 11: Molten and solidified layer 20: Laser beam spot

[0164] 21: First laser beam 22: Second laser beam

[0165] 23: Repeated irradiation boundary portion 30: Overlapped laser

[0166] 40: Steel plate surface 50: Steel plate substrate

[0167] 60: Insulating coating layer

Claims

1. An oriented electrical steel sheet, Among them, including: an electric steel sheet substrate; and an insulating coating layer located on the electric steel sheet substrate, wherein linear deformation parts exist on the surface of the insulating coating layer, repeated irradiation boundary parts exist within the deformation parts, a molten and solidified layer exists below the repeated irradiation boundary parts, and the molten and solidified layer contains 10% by weight or less of P.

2. The grain-oriented electric steel sheet according to claim 1, wherein, The width (M W ) in the vertical direction of the length of the deformed portion of the molten solidified layer is 0.05 μm to 10 μm.

3. The grain-oriented electric steel sheet according to claim 1, wherein, The thickness (M D ) of the melting and solidifying layer is 20% or less of the thickness of the insulating coating film layer.

4. The grain-oriented electric steel sheet according to claim 1, wherein, in the insulating coating layer below the deformation parts except for the repeated irradiation boundary parts, the P content within a range of 100 nm in the steel sheet thickness direction from the surface is 10% by weight to 20% by weight.

5. The grain-oriented electric steel sheet according to claim 1, wherein, the thickness of the insulating coating layer below the deformation parts is 60% to 90% of the thickness of the insulating coating layer where no deformation parts are formed.

6. The grain-oriented electric steel sheet according to claim 1, wherein, a metal oxide layer is provided between the electric steel sheet substrate and the insulating coating layer.

7. A method for micro-refining magnetic domains of an oriented electrical steel sheet, Among them, including: a first irradiation step of irradiating a first laser beam having a first wavelength; and a second irradiation step of irradiating a second laser beam having a second wavelength, wherein the first beam point of the first laser beam and the second beam point of the second laser beam overlap by 10% or more.

8. The method for refining magnetic domains of the grain-oriented electric steel sheet according to claim 7, wherein, the first laser and the second laser are selected from CO2 laser, fiber laser, YAG laser, ruby laser, sapphire laser, disk laser, diode laser or UV laser.

9. The method for refining magnetic domains of the grain-oriented electric steel sheet according to claim 7, wherein, the output of each of the first laser and the second laser is 10 W to 2000 W.

10. The method for refining magnetic domains of the grain-oriented electric steel sheet according to claim 7, wherein, the wavelengths of the first laser and the second laser are different from each other.

11. The method for refining magnetic domains of the grain-oriented electric steel sheet according to claim 7, wherein, at the overlapping position, the time interval between the irradiation time of the first laser beam and the irradiation time of the second laser beam is 16 milliseconds or less.

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