Grain-oriented electrical steel sheet, method for producing same, and iron core for transformer

Abstract

Provided is a grain-oriented electrical steel sheet capable of effectively suppressing the generation of magnetizing inrush current when used as a core material for a transformer. In a grain-oriented electrical steel sheet having a refined magnetic domain, magnetization that changes with a sine wave of 50 Hz occurs in the rolling direction of the grain-oriented electrical steel sheet, when the magnetization reaches 1.50 T, the power supply is cut off, and the cut residual magnetic flux density (Br), which is the magnetic flux density after 0.1 s from the cut-off, is 1.00 T or less.

Description

Technical Field

[0001] The present invention relates to a grain-oriented electromagnetic steel sheet capable of obtaining a transformer having a small excitation inrush current of the transformer generated when power is turned on, a method for producing the same, and a transformer core using the grain-oriented electromagnetic steel sheet. Background Art

[0002] When designing a transformer, one of the control factors that must be paid attention to is the magnetizing inrush current.

[0003] The excitation inrush current is a transient excitation current generated when voltage is applied to a transformer in a non-excited state at the moment of connecting the transformer, instantaneous voltage drop, instantaneous power outage, etc., but the amount of the excitation current may reach several to dozens of times the rated current. In addition, although it is a transient current generated instantly, if such a large current flows, the equipment may malfunction, resulting in large-scale failures such as emergency stop.

[0004] Therefore, as a countermeasure for the excitation inrush current, it is necessary to install various AC filter devices such as I) transformer protection relay, II) overcurrent relay for receiving power, III) high-voltage current limiting fuse, IV) phase-advancing capacitor, etc., which increases the cost. Therefore, there is a great need to reduce the excitation inrush current.

[0005] In addition, it is known that the excitation inrush current is largely caused by the "residual magnetic flux" and "phase angle of voltage" when the transformer power is turned on. That is, if the phase angle of voltage is controlled, the excitation inrush current can be reduced. (Refer to Patent Document 1)

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2010 / 035778 Summary of the invention

[0009] However, although controlling the phase angle of the voltage can reduce the magnetizing inrush current, such control requires complex control and new auxiliary equipment. Therefore, this method still has disadvantages such as increased costs and larger equipment.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a grain-oriented electromagnetic steel sheet capable of reducing the residual magnetic flux of a transformer core, a method for producing the same, and a transformer core using the grain-oriented electromagnetic steel sheet.

[0011] The inventors have conducted intensive studies repeatedly to solve the above problems.

[0012] Here, since the main cause of the excitation inrush current is the residual magnetic flux in the iron core, it is believed that if the residual magnetic flux characteristics of the grain-oriented electromagnetic steel sheet itself constituting the iron core are controlled, the excitation inrush current can be controlled, and the relationship between the residual magnetic flux density of the grain-oriented electromagnetic steel sheet itself and the excitation inrush current was studied in detail.

[0013] In addition, transformers also require low losses. Therefore, in this study, a 0.23 mm thick low iron loss material that was subjected to a laser domain refinement process was used. In addition, coils with 10 different laser irradiation conditions were prepared. Laser irradiation was performed by various combinations of I) output, II) deflection speed, and III) beam diameter to conduct confirmation tests.

[0014] Then, the 10 types of oriented electromagnetic steel sheets for the coils were bent at two 45° angles at one corner using a UNICORE manufacturing machine manufactured by AEM. Furthermore, 10 types of single-phase wound cores with a total weight of about 20 kg and a length of 250 mm × a width of 250 mm × a width of 100 mm were manufactured using the oriented electromagnetic steel sheets with the bent portions.

[0015] First, in this single-phase wound core, a constant operation with a frequency of 50 Hz and a magnetic flux density of 1.70 T was performed to measure a constant primary-side current value, which will be referred to as a constant current hereinafter.

[0016] Next, the excitation power supply is turned off when the magnetic flux density inside the core reaches 1.70 T, and the power supply is turned off. The power supply is turned on again in a state where the phase at which the excitation inrush current reaches its maximum is 180° different from when the power supply was turned off, and the primary current value generated at this time, i.e., the excitation inrush current, is evaluated. It should be noted that the steady current and the excitation inrush current are measured by a current sensor installed in the primary winding.

[0017] Table 1 shows the evaluation results of each single-phase wound core.

[0018] [Table 1]

[0019]

[0020] As shown in Table 1, the ratio of the excitation inrush current to the constant current varies depending on the laser irradiation conditions, suggesting that the strain introduction state affects the excitation inrush current.

[0021] Next, the residual magnetic flux density of each oriented electromagnetic steel sheet used to make the above 10 types of cores was measured to investigate its relationship with the above current ratio. The measurement conditions were to cut 36 samples of 30 mm × 280 mm from the oriented electromagnetic steel sheet coils used in the production of each core and use an Epstein test frame. The excitation conditions were set to frequency: 50 Hz, magnetic flux density: 1.70 T and 1.50 T. (Hereinafter, when abbreviated as 50 Hz / 1.50 T, it means that the excitation conditions are frequency: 50 Hz, magnetic flux density: 1.50 T.)

[0022] It should be noted that the properties of grain-oriented electrical steel sheets are usually evaluated at a magnetic flux density of 1.70 T. However, under high magnetic fields, the influence of crystal orientation on the flow of magnetization becomes greater, so it is difficult to reflect the influence of strain suggested by previous results. Therefore, evaluation was also conducted at a magnetic flux density of 1.50 T, which is believed to have a small influence on crystal orientation and is more likely to reflect the influence of strain.

[0023] Furthermore, the residual magnetic flux density of the grain-oriented electromagnetic steel sheet used in each core was set to the following two conditions.

[0024] That is, the first residual magnetic flux density is the magnetic flux density when the magnetizing force is zero in the AC hysteresis loss curve during AC excitation (refer to Figure 1 ). Hereinafter, the magnetic flux density when the magnetizing force is zero is recorded as the constant residual magnetic flux density.

[0025] The second residual magnetic flux density is the magnetic flux density after the power is turned off when the magnetic flux reaches the maximum value and 0.1s after the power is turned off and the magnetic flux density changes to saturation (reference Figure 2 ). Hereinafter, the magnetic flux density 0.1s after the cutting is particularly recorded as the cutting residual magnetic flux density Br.

[0026] The relationship between the ratio of the excitation inrush current to the steady current (hereinafter referred to as the current ratio) for each residual magnetic flux density is shown in Figure 3 .like Figure 3 As shown in (a) and (b), no significant correlation was found between the constant residual magnetic flux density and the current ratio. Figure 3 As shown in (c) and (d), in the cut-off magnetic flux density, the cut-off magnetic flux density is cut off when it reaches 1.50T, and there is a particularly good correlation between the cut-off magnetic flux density, that is, the cut-off residual magnetic flux density Br, and the current ratio measured 0.1s after the cut-off. It should be noted that Figure 3 In the figure, the cut-off magnetic flux density is 1.50 T in (a) and (c), and 1.70 T in (b) and (d).

[0027] The reason why no correlation is observed for the constant residual magnetic flux density is not clear, but it is considered that the reason is that the magnetic flux behavior during cutoff is significantly different from the magnetic flux behavior during constant state.

[0028] As described above, in order to evaluate a material capable of suppressing a magnetizing inrush current, it is extremely important to understand the residual magnetic flux at the time of disconnection, which is the actual cause of the magnetizing inrush current, in a low magnetic field (1.50 T) with high strain sensitivity.

[0029] according to Figure 3 (c) The data recorded show that by changing the control factors of general laser irradiation, i) output, ii) deflection speed, and iii) beam diameter, the cut-off residual magnetic flux density Br changes. Therefore, if the cut-off residual magnetic flux density Br is used as an evaluation index to explore the optimal laser irradiation conditions, the excitation inrush current can be suppressed to a certain extent.

[0030] However, the above studies also revealed that the suppression effect of the excitation inrush current was insufficient when only the normal laser irradiation conditions were combined. Therefore, the inventors studied a method for further reducing the cutoff residual magnetic flux density Br.

[0031] Here, try to consider the qualities within the laser.

[0032] It is believed that the intensity of the laser emitted from the oscillator at a certain output is not uniform within the laser, and the intensity in the center is high, and the laser quality is good. Therefore, the effect of laser quality on the cut-off residual magnetic flux density Br and the excitation surge current was investigated. As a means of changing the laser quality, an orifice was set in the laser path, and after removing the laser from the peripheral part (the position where the quality is considered to be poor), the laser was converged and irradiated onto the steel plate (reference Figure 4 ). That is, when removing the laser light, the quality of the focused laser light is changed by changing the aperture diameter.

[0033] In the above-mentioned study, the smaller the aperture diameter is, the more laser light is removed from the outer periphery, and thus irradiation with laser light is considered to be of higher quality.

[0034] It should be noted that in this study, first, laser alignment paper (carving paper) was irradiated with laser under the same conditions before and after the orifice was set, and the beam diameter and the range cut by the orifice were confirmed. The carving paper is thermal paper that changes color only in the portion irradiated with laser.

[0035] Figure 5 The beam cutting ratio of the peripheral portion defined in the present invention is shown. First, the beam shape before the aperture is set is measured ( Figure 5 After the shape is copied onto new recording paper, a hole is set, and the recording paper on which the beam diameter before the hole is set is recorded is irradiated with laser light ( Figure 5 Next, determine the portion of the outermost part that is not cut, and derive the proportion of this portion that is cut ( Figure 5(c)). The minimum beam cutting rate is used as the peripheral removal ratio.

[0036] As an example, based on the irradiation conditions for making the coil of transformer No. 6, only the orifice diameter is changed to introduce strain into the steel plate. At this time, in order to make the laser intensity introduced into the steel plate the same, the laser output is changed according to the transmittance. Specifically, when the laser transmittance is 50%, the laser output is set to 2 times to introduce strain.

[0037] The transmittance is measured by using a camera-type beam analyzer to measure the light intensity received by each pixel of the digital camera, and the ratio of the sum of the beam intensity before the orifice is set to the sum of the beam intensity after the orifice is set is calculated (= the sum of the beam intensity after the orifice is set / the sum of the beam intensity before the orifice is set). The beam intensity measured here is not the beam reaching the surface of the steel plate, but the diameter just after passing through the orifice.

[0038] Figure 6 The relationship between the peripheral removal ratio and the cut-off residual magnetic flux density Br (50Hz / 1.50T) is shown. It is found that if the peripheral removal ratio increases, the cut-off residual magnetic flux density Br is greatly reduced. In particular, it is known that if the peripheral removal ratio is 20% or more, the effect of reducing the cut-off residual magnetic flux density Br caused by the improvement of laser quality can be stably obtained.

[0039] It should be noted that although the reason for the reduction in the off residual magnetic flux density Br is not clear, it is considered that this is the result of a significant change in the introduced strain distribution due to the improvement of laser quality, which improves the laser convergence and steel sheet penetration.

[0040] Next, the cut-off residual magnetic flux density Br was changed by changing the ratio of the peripheral removal using the orifice diameter, and the relationship between the cut-off residual magnetic flux density Br and the excitation inrush current was investigated. In this investigation, based on the irradiation conditions of the coil of transformer No. 4 as an example, the laser output was changed according to the transmittance so that the laser intensity introduced into the steel plate was the same as described above. The evaluation transformer was implemented using the same type of transformer as in Table 1.

[0041] Figure 7 The relationship between the cut-off residual magnetic flux density (50 Hz / 1.50 T) and the excitation inrush current / constant current (current ratio) is shown. The excitation magnetic flux density varies between 1.30 and 1.90 T. As described above, in a transformer using a steel plate whose cut-off residual magnetic flux density Br obtained at 1.50 T is 1.00 T or less, the generation of the excitation inrush current can be suppressed under all conditions.

[0042] The key point of the present invention is to remove the peripheral part by setting the aperture, but even with the same aperture, the quality of the transmitted light beam varies due to deviation of the setting position, etc. For example, if the center of the light beam coincides with the center of the aperture, the light beam near the center is transmitted, but if the center is deviated, the light beam deviating from the center is transmitted.

[0043] The inventors considered that the difference in the quality of the transmitted light beam would also have a significant effect, and investigated the relationship between the intensity distribution in the transmitted light beam and the cutoff residual magnetic flux density Br.

[0044] The intensity distribution of the transmitted beam is changed by changing the position of the aperture and the center of the beam. The maximum intensity in the beam is used as the reference for normalization, and the difference between the maximum intensity ratio and the minimum intensity ratio is used as the deviation evaluation factor of the beam quality. The peripheral removal ratio under each condition is all above 20%.

[0045] Figure 8 The relationship between the deviation of the beam intensity in the transmitted light beam and the cut-off residual magnetic flux density Br (50Hz / 1.50T) is shown. It is found that if the deviation of the beam intensity in the transmitted light beam is reduced, the cut-off residual magnetic flux density Br is greatly reduced. In particular, it is known that when the deviation of the beam intensity is controlled to be below 0.80, the effect of reducing the cut-off residual magnetic flux density Br can be further obtained. In order to stably obtain this effect, the deviation of the beam intensity is more preferably below 0.50.

[0046] It should be noted that the intensity deviation in the light beam can be measured by using a commercially available beam profiler to measure the intensity distribution in the light beam, and the intensity ratio of each measurement point to the maximum intensity of all measurement points (standardization of the light beam intensity) is obtained, and the difference between the maximum intensity ratio and the minimum intensity ratio is obtained. The intensity measurement method is not particularly limited, and the method includes irradiating a laser beam to a fluorescent plate, separating the fluorescence with a wavelength separation mirror, and forming a fluorescent image on the light receiving surface inside a camera. In the present invention, the intensity distribution in the laser is measured using a high-output laser beam profiler BPF series manufactured by CANARE.

[0047] It should be noted that although the above research was conducted using lasers, it is known that the same effect can be obtained using electron beams by selecting conditions. Hereinafter, when referred to as a light beam, it refers to a high-energy beam in the present invention, specifically, laser, plasma or electron beam.

[0048] The present invention is based on the above findings, and the gist of the present invention is as follows.

[0049] 1. A grain-oriented electrical steel sheet obtained by refining magnetic domains by linearly introducing strain from at least one surface of the steel sheet into the interior of the steel sheet in a manner intersecting with a rolling direction of the steel sheet, wherein the cut-off residual magnetic flux density Br is 1.00 T or less.

[0050] remember

[0051] Cut-off residual magnetic flux density Br: The magnetization that changes in a sine wave at 50 Hz is generated in the rolling direction of the grain-oriented electrical steel sheet. When the magnetization reaches 1.50 T, the power is cut off. The magnetic flux density 0.1 s after the cut-off

[0052] 2. A method for manufacturing a grain-oriented electrical steel sheet, which is a method for manufacturing the grain-oriented electrical steel sheet described in 1 above, wherein when a high-energy beam is irradiated on the surface of a steel sheet that has undergone final annealing to perform a magnetic domain refinement treatment, an orifice is provided on an irradiation path of the high-energy beam, the outer periphery of the high-energy beam is removed, and then the high-energy beam is converged to introduce strain into the steel sheet, and the following cut-off residual magnetic flux density Br is 1.00 T or less.

[0053] remember

[0054] Cut-off residual magnetic flux density Br: The magnetization that changes in a sine wave at 50 Hz is generated in the rolling direction of the grain-oriented electrical steel sheet. When the magnetization reaches 1.50 T, the power is cut off. The magnetic flux density 0.1 s after the cut-off

[0055] 3. The method for producing a grain-oriented electrical steel sheet according to 2 above, wherein a variation in beam intensity of the light beam after removing the outer peripheral portion is 0.80 or less.

[0056] 4. A transformer core, comprising the grain-oriented electromagnetic steel sheet according to 1 above.

[0057] According to the present invention, it is possible to provide a grain-oriented electromagnetic steel sheet that can suppress the generation of a magnetizing inrush current when used as a core material of a transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a graph showing an AC hysteresis loss curve during AC excitation.

[0059] Figure 2 1 is a graph showing the temporal change of magnetic flux density, and is a graph showing the magnetic flux density 0.1 s after the power supply is turned off when the magnetic flux reaches the maximum and the magnetic flux density change is saturated.

[0060] Figure 3 (a) and (b) are graphs showing the relationship between the constant residual magnetic flux density and the excitation inrush current / constant current (current ratio). (c) and (d) are graphs showing the relationship between the cut-off residual magnetic flux density and the excitation inrush current / constant current (current ratio).

[0061] Figure 4 This is a schematic diagram showing a state in which the laser light is converged and irradiated onto a steel plate after the laser light at the outer periphery is removed through the orifice.

[0062] Figure 5 (a) to (c) are diagrams for explaining the steps of determining the peripheral portion removal ratio.

[0063] Figure 6 This is a graph showing the relationship between the peripheral portion removal ratio and the cut-off residual magnetic flux density at 50 Hz / 1.50 T.

[0064] Figure 7 This is a diagram showing the relationship between the cut-off residual magnetic flux density and the excitation inrush current / steady current (current ratio).

[0065] Figure 8 This is a diagram showing the relationship between the intensity deviation within the beam after the outer peripheral portion is removed and the cut-off residual magnetic flux density.

[0066] Fig. 9 It is a diagram showing the rolling direction and the direction perpendicular to the rolling direction of a non-heat-resistant magnetic domain refined material. DETAILED DESCRIPTION

[0067] Hereinafter, constituent elements of the present invention will be described.

[0068] In the grain-oriented electrical steel sheet of the present invention, when AC excitation is performed under the condition of 50 Hz / 1.50 T, when the power supply is cut off at the time when the magnetic flux density reaches the maximum, the residual magnetic flux density inside the steel sheet 0.1 s after the cut-off, that is, the cut-off residual magnetic flux density Br must be 1.00 T or less. That is, if the cut-off residual magnetic flux density Br exceeds 1.00 T, the excitation surge current becomes large, and although it is a transient current generated instantly, if such a large current flows, the equipment may malfunction, resulting in large-scale failures such as emergency stop. The cut-off residual magnetic flux density Br is preferably 0.60 T or less. On the other hand, its lower limit is not particularly limited, and it can also be 0.00 T, and it is preferably about 0.10 T in industry.

[0069] The method for producing the grain-oriented electrical steel sheet before magnetic domain refinement used in the present invention is not particularly limited, and a known method may be used. However, a method for producing a grain-oriented electrical steel sheet capable of more preferably controlling the cutoff residual magnetic flux density Br is described below.

[0070] First, preferred basic components and optional added components of a steel material (steel billet) used for production of a grain-oriented electrical steel sheet of the present invention will be described.

[0071] When a component system that does not use inhibitors that limit the contents of Al, N, S, and Se is used, the amounts of Al, N, S, and Se in the steel material are preferably controlled to Al: 100 mass ppm or less, N: 50 mass ppm or less, S: 50 mass ppm or less, and Se: 50 mass ppm or less, respectively.

[0072] On the other hand, when using an inhibitor, for example, when using an AlN-based inhibitor, appropriate amounts of Al and N may be contained in the steel billet, and when using a MnS or MnSe-based inhibitor, appropriate amounts of Mn and Se and / or S may be contained in the steel billet. Of course, both inhibitors may be used in combination.

[0073] When these inhibitors are used, the preferred contents of Al, N, S and Se in the steel material are respectively 0.01 to 0.065 mass % for Al, 0.005 to 0.012 mass % for N, 0.005 to 0.03 mass % for S and 0.005 to 0.03 mass % for Se.

[0074] C: 0.08 mass % or less

[0075] C is added to improve the hot rolled sheet structure, but if the content exceeds 0.08 mass %, it is difficult to reduce C to less than 50 mass ppm that does not cause magnetic aging in the manufacturing process. Therefore, the C content is preferably 0.08 mass % or less. It should be noted that since secondary recrystallization can also be performed in a material without C, the lower limit of the C content does not need to be particularly set, and from the viewpoint of improving the hot rolled sheet structure, it is preferably 0.01 mass % or more.

[0076] Si: 2.0-8.0 mass%

[0077] Si is an element effective in increasing the resistance of steel and improving iron loss, but if the content is less than 2.0 mass%, sufficient iron loss reduction effect may not be achieved. On the other hand, if the Si content is greater than 8.0 mass%, the processability is significantly reduced, and the magnetic flux density is also reduced. Therefore, the Si content is preferably in the range of 2.0 to 8.0 mass%. The Si content is more preferably greater than 2.0 mass%. In addition, the Si content is more preferably less than 4.0 mass%.

[0078] Mn: 0.005-1.0 mass%

[0079] Mn is an element required to improve hot workability, but if the content is less than 0.005 mass%, the effect of its addition is insufficient. On the other hand, if the content of Mn is more than 1.0 mass%, the magnetic flux density of the product sheet decreases. Therefore, the content of Mn is preferably in the range of 0.005 to 1.0 mass%. The content of Mn is more preferably 0.01 mass% or more. In addition, the content of Mn is more preferably 0.1 mass% or less.

[0080] In addition to the above-mentioned basic components, one or more selected from the following elements may be appropriately contained as a magnetic property improving component (optional added component).

[0081] Ni: 0.03-1.50 mass%, Sn: 0.01-1.50 mass%, Sb: 0.005-1.50 mass%, Cu: 0.03-3.0 mass%, P: 0.03-0.50 mass%, Mo: 0.005-0.10 mass%, and Cr: 0.03-1.50 mass%

[0082] Ni: 0.03-1.50 mass%

[0083] Ni is an element useful for improving the hot-rolled sheet structure and improving the magnetic properties. However, when the Ni content is less than 0.03 mass%, the effect of improving the magnetic properties is small. On the other hand, if the Ni content is greater than 1.50 mass%, the secondary recrystallization becomes unstable and the magnetic properties may deteriorate. Therefore, when Ni is contained, its content is preferably in the range of 0.03 to 1.50 mass%.

[0084] In addition, Sn, Sb, Cu, P, Mo and Cr are respectively useful elements for improving magnetic properties, but if the lower limits of the above-mentioned components are not met, the effect of improving magnetic properties is small. On the other hand, if the upper limit of the above-mentioned components is exceeded, the development of secondary recrystallized grains is hindered. Therefore, when at least any one of Sn, Sb, Cu, P, Mo and Cr is contained, the content thereof is preferably in the above-mentioned range.

[0085] It should be noted that the remainder other than the above components is Fe and inevitable impurities mixed in during the manufacturing process. That is, in the steel billet of the present invention, the remainder other than the above components is Fe and inevitable impurities.

[0086] On the other hand, in the grain-oriented electrical steel sheet, C is decarburized in the primary recrystallization annealing, and Al, N, S, and Se are purified in the final annealing. Therefore, in the steel sheet (product sheet) after the final annealing, Al is less than 0.01 mass%, and C, N, S, and Se are all reduced to less than 0.005 mass%.

[0087] Next, the steel billet having the above-mentioned composition can be heated according to a conventional method and then subjected to hot rolling. Alternatively, for example, it can be subjected to hot rolling immediately after being cast into a slab without being heated. In the case of a thin cast piece, it can be subjected to hot rolling, or hot rolling can be omitted and the steel billet can be directly subjected to the following process.

[0088] Furthermore, in order to improve the magnetic properties of the steel sheet, hot-rolled sheet annealing is performed as needed. At this time, in order to make the Gossian structure highly developed in the product sheet, the hot-rolled sheet annealing temperature is preferably in the range of 800 to 1100°C. If the hot-rolled sheet annealing temperature is less than 800°C, the banded structure in the hot rolling remains, it becomes difficult to achieve a whole-grained primary recrystallization structure, and the development of secondary recrystallization may be hindered. On the other hand, if the hot-rolled sheet annealing temperature is greater than 1100°C, the grain size after hot-rolled sheet annealing becomes too coarse, and it may be extremely difficult to achieve a whole-grained primary recrystallization structure.

[0089] For thin cast pieces or steel sheets after hot rolling or hot-rolled sheet annealing, cold rolling is performed once or twice or more with intermediate annealing, and then decarburization annealing is performed, and then an annealing separator is applied, and final annealing is performed to form secondary recrystallization and forsterite film. It is effective to perform flattening annealing after the final annealing to correct the shape. It should be noted that in the present invention, it is preferred to apply an insulating coating to the surface of the steel sheet before or after the flattening annealing.

[0090] In the present invention, the insulating coating refers to a coating that can apply tension to the steel sheet to reduce iron loss (hereinafter, also referred to as a tension coating). It should be noted that examples of the tension coating include inorganic coatings containing silicon dioxide, ceramic coatings formed by physical vapor deposition, chemical vapor deposition, and the like.

[0091] In order to further reduce the iron loss in this manner, at least one surface of the obtained steel sheet is irradiated with a light beam or the like to introduce strain into the steel sheet.

[0092] As described above, in the present invention, since it is found that the cut-off residual magnetic flux density Br is greatly affected by the quality of the light beam, etc., it is important to provide an orifice for removing the portion of the light beam, etc. with low intensity (considered to be of poor quality) during the period from the light beam, etc. being emitted from a light source of the light beam, etc. to the time when the light beam, etc. is converged.

[0093] In the present invention, the aperture refers to a component that effectively extracts the center of a light beam, etc. The configuration of the aperture is not particularly limited as long as the above-mentioned purpose can be achieved, but if a plate having a hole smaller than the diameter of the light beam, etc. is provided as described above, the purpose of the present invention can be achieved.

[0094] By implementing this treatment, the cut-off residual magnetic flux density Br can be controlled more simply and stably within the scope of the present invention. Furthermore, in order to stably control the cut-off residual magnetic flux density Br within the scope of the present invention, it is preferred to control the orifice setting conditions so that the peripheral removal ratio is 10% or more. The peripheral removal ratio is more preferably 20% or more, and further preferably 25% or more. On the other hand, the peripheral removal ratio is preferably 50% or less.

[0095] In addition, reducing the intensity deviation of the beam after passing through the orifice and improving the beam quality are also effective in further reducing the cut-off residual magnetic flux density Br. The deviation of the beam intensity is preferably 0.80 or less, more preferably 0.70 or less, and further preferably 0.50 or less. On the other hand, the lower limit of the deviation of the beam intensity is not particularly limited and can be 0.00. If production management is considered, it is preferably around 0.10.

[0096] It should be noted that by removing the beams at the periphery, the amount of beams reaching the steel sheet is reduced, so the iron loss, which is a basic characteristic of the grain-oriented electrical steel sheet, may be deteriorated. However, if the output of the initial beam is adjusted to refine the magnetic domain of the steel sheet, such concerns can be eliminated.

[0097] The conditions for the magnetic domain refinement not described above are not particularly limited, and the treatment may be performed under, for example, known conditions.

[0098] For example, the irradiation direction of the light beam or the like (the extension direction of the closed magnetic domains formed by the irradiation) is transverse to the rolling direction (long side direction, Fig. 9 The direction of the rolling direction is preferably 60 to 90 degrees relative to the rolling direction. It should be noted that the above-mentioned 90 degree direction is equivalent to the direction perpendicular to the rolling direction ( Fig. 9 TD direction). In addition, for example, the output of laser beam irradiation is preferably 100W to 8kW. In addition, from the viewpoint of productivity, the deflection speed of the laser beam is preferably 10m / s or more. Similarly, the output of electron beam irradiation is preferably 50W to 5kW. In addition, from the viewpoint of productivity, the deflection speed of the electron beam is preferably 10m / s or more. In laser beams and electron beams, due to the different energy absorption efficiency of the steel plate, the preferred range of output is different as described above.

[0099] It should be noted that, according to the combination of the above-mentioned processing conditions (known magnetic domain refinement processing conditions and aperture conditions), there are conditions where the cutoff residual magnetic flux density Br is not less than 1.00 T, so it is necessary to use the optimal combination conditions explored in advance.

[0100] Regarding the line spacing, in order to reduce the cut-off residual magnetic flux density Br, there is no special limitation, but in order to reduce the iron loss, which is the basic characteristic of the oriented electromagnetic steel sheet, as much as possible, the line spacing in the long side direction is preferably greater than 3.0 mm and less than 8.0 mm. In addition, the light beams other than the outer periphery are converged at the orifice and reach the steel sheet. From the perspective of low iron loss, the beam diameter when reaching the steel sheet is preferably 0.20 mm or less. On the other hand, the lower limit of the beam diameter is not particularly limited, and is preferably about 0.010 mm in industry.

[0101] Example

[0102] Next, the present invention will be specifically described based on the examples. The following examples show a preferred example of the present invention, and the present invention is not limited to the examples. The embodiments of the present invention can be appropriately changed within the scope suitable for the gist of the present invention, and all of them are included in the technical scope of the present invention.

[0103] (Example 1)

[0104] A 0.23 mm thick grain-oriented electromagnetic steel sheet (final annealing completed) having the same magnetic flux density (B8 = 1.92T) was prepared, and a non-heat-resistant magnetic domain refinement treatment was performed by irradiation with a laser or electron beam using an appropriate aperture. The irradiation conditions (method, output, deflection speed, beam diameter, irradiation line interval, peripheral portion removal ratio, and beam intensity deviation after peripheral portion removal) are shown in Table 2. Then, the iron loss W of the grain-oriented electromagnetic steel sheet subjected to the non-heat-resistant magnetic domain refinement treatment was derived. 17 / 50 , cut-off residual magnetic flux density Br (50 Hz / 1.50 T). These are also shown in Table 2.

[0105] Next, the grain-oriented electromagnetic steel sheet subjected to the above-mentioned non-heat-resistant magnetic domain refining treatment was used as a core material to produce a three-phase wound core (core including grain-oriented electromagnetic steel sheet). The wound core had a mass of about 40 kg and a capacity of 30 kVA.

[0106] The wound core is a single core having a lap portion on one plane (one lap portion in one cycle) and a bent portion at a corner, or a double core having lap portions on two planes (two lap portions in one cycle) and a bent portion at a corner. It should be noted that the amount of lap in one wound core is fixed. In addition, the single core and the double core are made by processing the grain-oriented electromagnetic steel sheets with the angle of the bent portion set to 45°, and then stacking them to form the wound core.

[0107] Measure the iron loss W of the core 17 / 50 The power is cut off when the magnetic flux of the center leg (V leg) reaches the maximum (1.7 T), and the power is turned on again when the phase is deviated by 180 degrees from the cut-off time.

[0108] The iron loss W of the above-mentioned wound core 17 / 50 The ratio of the magnetizing inrush current to the normal current (current ratio) is also shown in Table 2. It should be noted that the current ratio here means (magnetizing inrush current / steady current).

[0109]

[0110] As shown in Table 2, for the core using the grain-oriented electromagnetic steel sheet within the scope of the present invention, the cut-off residual magnetic flux density Br of the grain-oriented electromagnetic steel sheet is 1.00 T or less, the ratio of the excitation inrush current to the steady current, i.e., the current ratio, becomes lower, and the excitation inrush current becomes lower. It should be noted that, with respect to the iron loss, which is a basic characteristic, the iron loss characteristics of the grain-oriented electromagnetic steel sheet and the iron core to which the present invention is applied are at the same level as those to which the present invention is not applied, and it can be seen that the present invention has no adverse effects on other important characteristics.

[0111] (Example 2)

[0112] A 0.23 mm thick grain-oriented electrical steel sheet (final annealing completed) having the same magnetic flux density (B8 = 1.92 T) was prepared, and a non-heat-resistant magnetic domain refinement treatment was performed by irradiation with a laser or electron beam using an appropriate aperture. The irradiation conditions (method, output, deflection speed, beam diameter, irradiation line interval, peripheral portion removal ratio, and beam intensity deviation after peripheral portion removal) are shown in Table 3. Then, the iron loss W of the grain-oriented electrical steel sheet subjected to the non-heat-resistant magnetic domain refinement treatment was derived. 17 / 50 , cut-off residual magnetic flux density Br (50 Hz / 1.50 T). These are also shown in Table 3.

[0113] Next, a three-phase laminated core (laminated core) (core with oriented electromagnetic steel sheet) was made using the oriented electromagnetic steel sheet that had been subjected to the above-mentioned non-heat-resistant magnetic domain refinement treatment as the core material. The core had an overall width of 890 mm, a depth of 800 mm, a laminate thickness of 250 mm, a core mass of approximately 1.0 t, and a capacity of 2000 kVA. The joining method was a step-lap method.

[0114] The iron loss W of the laminated core is measured. 17 / 50 The power is cut off when the magnetic flux of the center leg (V leg) reaches the maximum (1.70 T), and the power is turned on again when the phase is 180° away from the cut-off phase.

[0115] The iron loss W of the laminated core is 17 / 50 The ratio of the magnetizing inrush current to the normal current (current ratio) is shown in Table 3. The current ratio here means (magnetizing inrush current / steady current).

[0116]

[0117] As shown in Table 3, for the core using the grain-oriented electromagnetic steel sheet within the scope of the present invention, the cut-off residual magnetic flux density Br of the grain-oriented electromagnetic steel sheet is 1.00 T or less, the ratio of the excitation inrush current to the steady current, i.e., the current ratio, becomes lower, and the excitation inrush current becomes lower. It should be noted that, with respect to the iron loss, which is a basic characteristic, the iron loss characteristics of the grain-oriented electromagnetic steel sheet and the iron core thereof to which the present invention is applied are at the same level as those to which the present invention is not applied, and it can be seen that the present invention has no adverse effects on other important characteristics.

Claims

1. A grain-oriented electrical steel sheet obtained by refining magnetic domains by linearly introducing strain from at least one surface of the steel sheet into the interior of the steel sheet in a manner intersecting with a rolling direction of the steel sheet, The following cut-off residual flux density Br is less than 1.00T, The cut-off residual magnetic flux density Br is the magnetic flux density 0.1 s after the power supply is cut off when the magnetization reaches 1.50 T and the magnetization changes in a sine wave of 50 Hz in the rolling direction of the grain-oriented electrical steel sheet.

2. A method for manufacturing a grain-oriented electrical steel sheet, the method comprising: when a surface of a steel sheet that has undergone final annealing is irradiated with a high-energy beam to perform a magnetic domain refinement treatment, an orifice is provided on an irradiation path of the high-energy beam, the peripheral portion of the high-energy beam is removed, and then the high-energy beam is converged to introduce strain into the steel sheet, the cut-off residual magnetic flux density Br is 1.00 T or less, The cut-off residual magnetic flux density Br is the magnetic flux density 0.1 s after the power supply is cut off when the magnetization reaches 1.50 T and the magnetization changes in a sine wave of 50 Hz in the rolling direction of the grain-oriented electrical steel sheet.

3. The method for producing a grain-oriented electrical steel sheet according to claim 2, wherein: The deviation of the beam intensity of the light beam after removing the outer peripheral portion is 0.80 or less.

4. A transformer core, comprising the grain-oriented electromagnetic steel sheet according to claim 1.

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