Grain-oriented electrical steel sheet processing state determining method, processing state determining device, manufacturing facility adjustment method, manufacturing method, quality control method, and manufacturing facility

Abstract

A grain-oriented electrical steel sheet processing state determining method according to the present invention includes: a magnetization step for applying a DC or AC magnetic field to a region of a grain-oriented electrical steel sheet that has been subjected to magnetic domain refinement processing; a detection step for detecting leakage magnetic flux generated in the grain-oriented electrical steel sheet concomitant with the application of the magnetic field, for each of a plurality of regions in the width direction of the grain-oriented electromagnetic steel sheet; a calculation step for calculating a frequency distribution in each region from an output signal relating to a position in a longitudinal direction of the grain-oriented electrical steel sheet, for the leakage magnetic flux of each region detected in the detection step; and a determination step for determining the state of the magnetic domain refinement processing for each region on the basis of a determination index calculated from an intensity level within a predetermined range for the frequency distribution in each region.

Description

Method for determining the processing state of grain-oriented electrical steel sheet, processing state determination device, method for adjusting manufacturing equipment, manufacturing method, quality control method, and manufacturing equipment

[0001] The present invention relates to a method for determining the processed state of grain-oriented electrical steel sheet, a processed state determination device, a manufacturing equipment adjustment method, a manufacturing method, a quality control method, and a manufacturing equipment.

[0002] The electromagnetic properties of electrical steel sheets are important factors that determine product performance. Evaluation items include iron loss, maximum magnetic permeability, and magnetostriction. Iron loss refers to the energy loss that occurs when an AC magnetic field is applied to electrical steel sheets, as magnetic energy is converted into heat energy due to magnetic hysteresis and eddy currents. Therefore, electrical steel sheets with low iron loss have an advantage over those with high iron loss because they have higher energy conversion efficiency. Technologies have been developed to reduce iron loss in grain-oriented electrical steel sheets. One such technology is the magnetic domain refinement process, which uses physical techniques to introduce periodic localized inhomogeneities in the rolling direction into the surface layer, thereby refining the width of magnetic domains and reducing iron loss.

[0003] This magnetic domain refinement process is sufficient as long as it introduces nonuniformities into the surface layer. It is not necessarily limited to methods that create shaped variations, such as holes or grooves, in the surface layer, but can be any method that introduces nonuniformities without causing shape variations in the surface layer. This can be achieved, for example, by applying heat or pressure. More specifically, nonuniformities can be introduced into the surface layer by irradiating it with a laser, electron beam, plasma jet, or the like. Grain-oriented electrical steel sheets have magnetic domains magnetized in the rolling direction parallel to the easy axis of magnetization. However, in the nonuniform portions of the surface layer created by the magnetic domain refinement process, even if there are no scratches or shape variations, magnetic domains magnetized in a direction different from the rolling direction are locally formed, and this discontinuity of magnetization causes magnetic domain refinement.

[0004] A method for evaluating a magnetic domain refining process using an electron beam is known, as described in Patent Document 1. Specifically, the method described in Patent Document 1 evaluates the focal position deviation of the electron beam based on the emission brightness distribution of the electron beam. Furthermore, methods described in Patent Documents 2 and 3 are known as methods for evaluating the processing state of a magnetic domain refining process. The method described in Patent Document 2 evaluates the magnetic domain refining processing state using eddy currents, while the method described in Patent Document 3 evaluates the magnetic domain refining processing state using leakage magnetic flux. Both methods perform fast Fourier transform processing and evaluate the magnetic domain refining processing state based on the intensity level of a wavelength corresponding to the magnetic domain refining processing interval.

[0005] Patent No. 6398961 Patent No. 6562055 Patent No. 6607242

[0006] The method described in Patent Document 1 requires the electron beam irradiation position to be imaged using an imaging device, but dirt or deposition due to processing may adhere to the lens of the imaging device or windows along the imaging path. Therefore, frequent maintenance of the imaging device is required to stably evaluate the electron beam focal position shift, which requires a lot of effort. On the other hand, the methods described in Patent Documents 2 and 3 may not always correlate the intensity level of the wavelength corresponding to the magnetic domain refining interval with the quality of the magnetic domain refining processing state due to signals from other equipment on the production line and variations in manufacturing conditions. For this reason, the magnetic domain refining processing state may not be accurately determined. Furthermore, while the methods described in Patent Documents 2 and 3 can determine the quality of the magnetic domain refining processing state of the entire steel sheet, they cannot determine the quality of the magnetic domain refining processing state of a specific area of ​​the steel sheet, such as only a portion of the steel sheet in the width direction.

[0007] The present invention has been made to solve the above-mentioned problems, and its object is to provide a method and device for determining the processed state of grain-oriented electrical steel sheet that can accurately determine the magnetic domain refinement processed state in a specific area of ​​the steel sheet without requiring much labor. Another object of the present invention is to provide a method for adjusting and manufacturing equipment for grain-oriented electrical steel sheet that can produce grain-oriented electrical steel sheet with a high yield. Another object of the present invention is to provide a quality control method for grain-oriented electrical steel sheet that can stably provide high-quality grain-oriented electrical steel sheet. Another object of the present invention is to provide manufacturing equipment for grain-oriented electrical steel sheet that can produce grain-oriented electrical steel sheet with a high yield.

[0008] [1] A method for determining the processing state of an electrical steel sheet according to the present invention includes: a magnetization step of applying a DC or AC magnetic field to a region of a grain-oriented electrical steel sheet that has been subjected to magnetic domain refinement processing; a detection step of detecting leakage magnetic flux generated in the grain-oriented electrical steel sheet as a result of the application of the magnetic field, for each of a plurality of regions in the width direction of the grain-oriented electrical steel sheet; a calculation step of calculating a frequency distribution for each region from an output signal for a position in the longitudinal direction of the grain-oriented electrical steel sheet, for the leakage magnetic flux in each region detected in the detection step; and a determination step of determining the state of the magnetic domain refinement processing for each of the regions, based on a determination index calculated from an intensity level within a predetermined range of the frequency distribution for each of the regions.

[0009] [2] In the method for determining the processed state of an electrical steel sheet according to the present invention, in the invention [1] above, the predetermined range is set based on the interval of the magnetic domain refining process.

[0010] [3] The method for determining the processed state of an electrical steel sheet according to the present invention is the method according to the invention [1] or [2] above, wherein the determination step includes a step of determining the state of the magnetic domain refinement processing based on a two-dimensional distribution of the strength level in the in-plane direction of the grain-oriented electrical steel sheet.

[0011] [4] An apparatus for determining the processing state of an electrical steel sheet according to the present invention comprises a magnetizer that applies a DC or AC magnetic field to a region of a grain-oriented electrical steel sheet that has been subjected to magnetic domain refinement processing; a plurality of magnetic sensors that detect leakage magnetic flux generated in the grain-oriented electrical steel sheet as a result of application of the magnetic field, for each of a plurality of regions in the width direction of the grain-oriented electrical steel sheet; and a signal processing unit that calculates a frequency distribution for each region from output signals of the leakage magnetic flux in each region detected by the plurality of magnetic sensors with respect to a position in the longitudinal direction of the grain-oriented electrical steel sheet, and determines the state of the magnetic domain refinement processing for each of the regions based on a determination index calculated from an intensity level within a predetermined range of the frequency distribution for each of the regions.

[0012] [5] The device for determining the processed state of an electromagnetic steel sheet according to the present invention is the device according to the above [4], wherein the predetermined range is set based on the interval of the magnetic domain refining process.

[0013] [6] The device for determining the processing state of an electrical steel sheet according to the present invention is the device for determining the processing state of an electrical steel sheet according to the invention [4] or [5] above, wherein the signal processing unit determines the state of the magnetic domain refinement processing based on the two-dimensional distribution of the strength level in the in-plane direction of the grain-oriented electrical steel sheet.

[0014] [7] A method for adjusting manufacturing equipment for grain-oriented electrical steel sheets according to the present invention includes a step of adjusting the state of the manufacturing equipment for grain-oriented electrical steel sheets based on the state of magnetic domain refinement processing for each region determined using any one of the above-mentioned methods for determining the processing state of grain-oriented electrical steel sheets [1] to [3].

[0015] [8] A method for manufacturing a grain-oriented electrical steel sheet according to the present invention includes a step of controlling the conditions of the magnetic domain refinement processing based on the state of the magnetic domain refinement processing for each of the regions determined using any one of the processing state determination methods for grain-oriented electrical steel sheet [1] to [3] above.

[0016] [9] A quality control method for grain-oriented electrical steel sheet according to the present invention includes a step of performing quality control for the grain-oriented electrical steel sheet based on the state of magnetic domain refinement processing for each of the regions determined using any one of the processing state determination methods for grain-oriented electrical steel sheet according to the above [1] to [3].

[0017]

[10] A manufacturing facility for grain-oriented electrical steel sheets according to the present invention includes the processing state determination device for grain-oriented electrical steel sheets according to any one of [4] to [6] above.

[0018] The method and device for determining the processed state of grain-oriented electrical steel sheet according to the present invention enable the magnetic domain refinement processed state of a specific portion of a steel sheet to be determined with high accuracy without requiring much labor. Furthermore, the method for adjusting manufacturing equipment for grain-oriented electrical steel sheet and the manufacturing method according to the present invention enable grain-oriented electrical steel sheet to be manufactured with a high yield. Furthermore, the method for quality control of grain-oriented electrical steel sheet according to the present invention enables the stable provision of high-quality grain-oriented electrical steel sheet. Furthermore, the manufacturing equipment for grain-oriented electrical steel sheet according to the present invention enables grain-oriented electrical steel sheet to be manufactured with a high yield.

[0019] FIG. 1 is a schematic diagram showing the configuration of a processing state determination device for grain-oriented electrical steel sheets according to the present invention. FIG. 2 is a diagram showing two-dimensional maps of leakage magnetic flux detected from grain-oriented electrical steel sheets with good and poor magnetic domain refinement processing states. FIG. 3 is a schematic diagram showing the configuration of a processing state determination device for grain-oriented electrical steel sheets according to one embodiment of the present invention. FIG. 4 is a diagram showing the output signal of a magnetic sensor from a certain channel on an actual production line, converted into the longitudinal position of the measured grain-oriented electrical steel sheet. FIG. 5 is a diagram showing the results of FFT calculation of leakage magnetic flux measurement results in the easy axis direction for grain-oriented electrical steel sheets with sufficient and insufficient magnetic domain refinement processing. FIG. 6 is a diagram showing FFT intensity levels within the calculation range of the judgment index for the example shown in FIG. 5. FIG. 7 is a diagram plotting the correlation coefficient between the judgment index and the predicted and actual difference in iron loss. FIG. 8 is a diagram showing an example of the arrangement of a processing machine and magnetic sensors. FIG. 9 is a diagram showing an example of determining the magnetic domain refinement processing state using an FFT judgment index. Fig. 10 is a diagram showing an example of determining the magnetic domain refinement processing state using an FFT determination index. Fig. 11 is a schematic diagram showing an example of a two-dimensional map of FFT intensity levels. Fig. 12 is a flowchart showing the flow of a method for adjusting manufacturing equipment for grain-oriented electrical steel sheets according to one embodiment of the present invention. Fig. 13 is a flowchart showing the flow of a process for creating two-dimensional data of FFT intensity levels.

[0020] The method and device for determining the processed state of grain-oriented electrical steel sheet according to the present invention determine the magnetic domain refinement processed state of grain-oriented electrical steel sheet by non-destructively and non-contactly measuring the leakage magnetic flux of the grain-oriented electrical steel sheet using a magnetic leakage flux method. In the manufacturing process of grain-oriented electrical steel sheet, the magnetic domain refinement process, in principle, locally changes the magnetic properties of the grain-oriented electrical steel sheet. Therefore, if we consider the area subjected to magnetic domain refinement processing (hereinafter referred to as the magnetic domain refinement processed area) as a localized magnetic discontinuity, there will be magnetic flux leaking from the magnetic domain refinement processed area (leakage magnetic flux). In other words, the magnetic domain refinement processed state of the grain-oriented electrical steel sheet can be determined by measuring the leakage magnetic flux using the magnetic leakage flux method.

[0021] Fig. 1 is a schematic diagram showing the configuration of a processing state determination device for grain-oriented electrical steel sheets according to the present invention. As shown in Fig. 1, the processing state determination device 1 for grain-oriented electrical steel sheets according to the present invention mainly comprises a leakage flux detection unit 2 and a signal processing unit 3. The leakage flux detection unit 2 comprises a magnetizer 2a, such as an electromagnet, that magnetizes the grain-oriented electrical steel sheet S in the direction of its easy axis of magnetization, and a magnetic sensor 2b. The leakage flux detection unit 2 is installed on the grain-oriented electrical steel sheet S in a non-contact manner, and applies external magnetization to the grain-oriented electrical steel sheet S passing below the leakage flux detection unit 2 and detects leakage flux from the grain-oriented electrical steel sheet S. The signal processing unit 3 determines the magnetic domain refinement processing state of the grain-oriented electrical steel sheet S based on the leakage flux detected by the leakage flux detection unit 2. In Fig. 1, the symbol SP denotes a magnetic domain refinement processing unit.

[0022] 2(a) and 2(b) are two-dimensional maps of leakage magnetic flux detected from grain-oriented electrical steel sheets with good and poor magnetic domain refinement processing, respectively. As shown in FIG. 2(a), streaky magnetic domain refinement processed areas can be confirmed in the grain-oriented electrical steel sheet with good magnetic domain refinement processing. However, as shown in FIG. 2(b), streaky magnetic domain refinement processed areas cannot be clearly confirmed in the grain-oriented electrical steel sheet with poor magnetic domain refinement processing. The iron loss value of grain-oriented electrical steel sheets with good magnetic domain refinement processing is lower than that of grain-oriented electrical steel sheets with poor magnetic domain refinement processing. Therefore, the iron loss value of grain-oriented electrical steel sheets can also be estimated based on the detection status of streaky magnetic domain refinement processed areas.

[0023] Generally, magnetic domain refinement processing is performed in a direction perpendicular to the easy axis direction of magnetization. When determining the magnetic domain refinement processing state of a grain-oriented electrical steel sheet, a magnetic field is applied that is smaller than the magnetic field at which the width of the magnetic domains whose magnetization direction is parallel to the easy axis direction becomes the width of the magnetic domains in the magnetic domain refinement processing area. In actual operation, the magnitude of the magnetic field to be applied is determined in advance through experiments and simulations depending on the composition and thickness of the grain-oriented electrical steel sheet, and when determining the magnetic domain refinement processing state, a magnetic field corresponding to the composition and thickness of the grain-oriented electrical steel sheet to be evaluated is applied.

[0024] If the result of the judgment is that the magnetic domain refinement processed state of the grain-oriented electrical steel sheet is not in the desired state, the result is fed back to the processing machine so that the magnetic domain refinement processed state can be corrected at an early stage. This early correction makes it possible to avoid producing grain-oriented electrical steel sheets that do not meet specifications and improve the production yield of grain-oriented electrical steel sheets. Specifically, when the magnetic domain refinement processed portions are formed using a laser or electron beam, the magnetic domain refinement processed state of the grain-oriented electrical steel sheet is adjusted to the desired state by adjusting the output, focus, scanning speed, or longitudinal strain repetition interval (line spacing) of the laser or electron beam.

[0025] Hereinafter, the configuration and operation of an apparatus for determining the processed state of grain-oriented electrical steel sheets according to one embodiment of the present invention will be described.

[0026] 3( a ) and 3 ( b ) are schematic diagrams showing the configuration of an apparatus for determining the machining state of grain-oriented electrical steel sheets according to one embodiment of the present invention. As shown in FIGS. 3( a ) and 3 ( b ), an apparatus 10 for determining the machining state of grain-oriented electrical steel sheets according to one embodiment of the present invention includes, as main components, a leakage flux detector 12, a signal processor 13, and an excitation power supply 14. In this embodiment, the signal processor 13 and the excitation power supply 14 are configured as separate units, but the signal processor 13 and the excitation power supply 14 may also be configured as an integrated unit. Furthermore, in FIGS. 3( a ) and 3 ( b ), the longitudinal direction of the grain-oriented electrical steel sheet S is the same as the rolling direction in FIG. 3( b ). Meanwhile, in FIGS. 3( a ) and 3 ( b ), the width direction of the grain-oriented electrical steel sheet S is a direction perpendicular to the rolling direction in FIG. 3( b ).

[0027] The leakage magnetic flux detection unit 12 includes a magnetizer 12a and a plurality of magnetic sensors 12b, and is disposed opposite the upper surface of the grain-oriented electrical steel sheet S.

[0028] The magnetizer 12a applies external magnetization to the grain-oriented electrical steel sheet S using excitation power (or excitation frequency in the case of AC) supplied from the excitation power supply 14. In this embodiment, the external magnetization is set to a value within the range of 0 to 100 AT (100 AT: the magnitude of external magnetization obtained by passing a current of 0.1 A through a 1,000-turn coil). This value is large enough to move the magnetic domain walls in areas not subjected to magnetic domain refinement processing, but prevent the magnetization direction of magnetic domains in areas subjected to magnetic domain refinement processing from being parallel to the easy axis of magnetization. In this case, the magnetic flux density of the grain-oriented electrical steel sheet S was 0 to 1.7 mT. The magnetizer 12a may be an electromagnet or may use a permanent magnet. Considering the thickness of the grain-oriented electrical steel sheet S and fine adjustment of lift-off, an electromagnet is considered easier to adjust. However, even if a permanent magnet is used, it can be applied by separately adjusting the relative position of the magnetic sensor 12b and the permanent magnet.

[0029] The multiple magnetic sensors 12b are arranged in the width direction of the grain-oriented electrical steel sheet S. The magnetic sensors 12b detect leakage magnetic flux from the grain-oriented electrical steel sheet S, which occurs when external magnetization is applied, for each of multiple regions (channels) in the width direction of the grain-oriented electrical steel sheet S. When the external magnetization applied to the grain-oriented electrical steel sheet S is AC, the leakage magnetic flux from the grain-oriented electrical steel sheet S is detected by detecting the excitation frequency. It is also desirable to adjust the phase of the detection signal at this time. In this embodiment, the magnetic sensors 12b are configured as TMR (tunneling magnetoresistive) sensors and detect leakage magnetic flux components parallel to the surface of the grain-oriented electrical steel sheet S. It is desirable to use a highly sensitive magnetic sensor 12b, and examples of the magnetic sensors that can be used include SQUIDs, MI (magnetic impedance sensors), Hall elements, GMR (magnetoresistive sensors), and E-type sensors with a coil wound around an E-type ferromagnetic core.

[0030] The signal processing unit 13 includes an amplifier 13a, multiple band-pass filters (BPFs) 13b, and an information processing unit 13c. The amplifier 13a amplifies the output signals of the multiple magnetic sensors 12b and outputs the amplified signals to the corresponding BPFs 13b. The multiple BPFs 13b extract output signals of set frequency bands from the output signal of the amplifier 13a and output the extracted output signals to the information processing unit 13c. The information processing unit 13c uses the output signals of the multiple BPFs 13b to determine the processing state of the magnetic domain refinement processed portion of the grain-oriented electrical steel sheet S for each of multiple regions (channels).

[0031] When using the skin effect to generate a magnetic flux distribution in the thickness direction of grain-oriented electrical steel sheets, the AC leakage flux method using AC current can also be applied. However, in this case, a separate AC processing circuit is required. If only the amplitude value of the output signal is to be evaluated, an absolute value circuit and a low-pass filter are sufficient as the AC processing circuit. If the amplitude value and phase of the output signal are to be evaluated, detection must be performed at the excitation frequency, so a detection circuit is required.

[0032] When measuring with the magnetic sensor 12b, the grain-oriented electromagnetic steel sheet S is moved relatively a predetermined length in the direction of the easy axis of magnetization. In this case, the grain-oriented electromagnetic steel sheet S may be moved a predetermined length using a conveying device or the like, or the magnetizer 12a and the magnetic sensor 12b may be moved a predetermined length over the grain-oriented electromagnetic steel sheet S using a moving device or the like, or the movements of the grain-oriented electromagnetic steel sheet S and the magnetic sensor 12b may be combined. In the present invention, the easy axis of magnetization of the grain-oriented electromagnetic steel sheet S is the longitudinal direction and the rolling direction of the grain-oriented electromagnetic steel sheet S. In the case of this embodiment, the magnetic sensor 12b and the magnetizer 12a are fixed, and the grain-oriented electromagnetic steel sheet S is transported a predetermined length in the longitudinal direction (the rolling direction in FIG. 3(b)).

[0033] FIG. 4 shows the output signal of the magnetic sensor 12b of a channel in an actual production line, converted into the measured position (unit: mm) in the longitudinal direction of the grain-oriented electrical steel sheet S. In the example shown in FIG. 4, the detection pitch of the magnetic sensor 12b is 0.1268 mm / point, and magnetic domain refinement processing areas spaced 8.0 mm apart are detected as changes in the output signal. In this embodiment, frequency analysis is used as an example of an index for determining such output signals. In this case, it is preferable to adjust the predetermined length in the longitudinal direction so that the number of signals is such that frequency analysis can be performed appropriately. In the case of FIG. 4, the relative movement distance of the magnetic sensor 12b in the longitudinal direction of the grain-oriented electrical steel sheet S is 200 mm under the above detection pitch conditions.

[0034] 5(a) and 5(b) show the results of FFT calculations performed in the easy axis direction on the leakage flux measurement results of grain-oriented electrical steel sheets with and without sufficient magnetic domain refinement processing. The vertical axis shows the complex number of the FFT calculation results expressed as an absolute value (hereinafter referred to as FFT intensity level), and the horizontal axis shows the frequency obtained as a result of the FFT calculation converted to wavelength. As shown in FIG. 5(b), the grain-oriented electrical steel sheet with insufficient magnetic domain refinement processing has a low FFT intensity level near a wavelength of 8.0 mm. In contrast, as shown in FIG. 5(a), the grain-oriented electrical steel sheet with sufficient magnetic domain refinement processing has a high FFT intensity level near a wavelength of 8.0 mm. In addition, in this example, the grain-oriented electrical steel sheets with both sufficient and insufficient magnetic domain refinement processing have a high FFT intensity level near a wavelength of 9.4 mm, due to noise signals thought to be from other equipment on the production line. In this way, the FFT intensity level also changes depending on noise signals and the interval of magnetic domain refining. For this reason, if the intensity level of a specific wavelength is used as an indicator for determining magnetic domain refining, as in the method described in Patent Document 3, it may not be possible to accurately determine the state of magnetic domain refining.

[0035] Therefore, in this embodiment, the information processing unit 13c calculates a more accurate judgment index as follows. First, the calculation range of the judgment index in the wavelength (frequency) direction is set in advance according to the spacing of the magnetic domain refinement processed sections. For example, if the magnetic domain refinement processed sections are spaced 8.0 mm apart and the noise signal is near a wavelength of 9.4 mm as in the example shown in Figures 5(a) and 5(b), the calculation range of the judgment index is set to a wavelength range of 7.0 to 9.0 mm. This calculation range of the judgment index is preferably set so that the spacing of the magnetic domain refinement processed sections is always within that range and so that peak values ​​of the noise signal due to variations in other equipment or manufacturing conditions are not within that range. Figure 6 shows the FFT intensity levels within the calculation range of the judgment index for the example shown in Figures 5(a) and 5(b).

[0036] Next, the information processing unit 13c calculates a signal value (S) and a noise value (N) from the FFT intensity level within the set calculation range. The signal value (S) may be the maximum value of the FFT intensity level within the calculation range, or may be the sum of three FFT intensity levels before and after the wavelength corresponding to the spacing of the magnetic domain refinement processed sections. The noise value (N) may be the average value of the FFT intensity level within the calculation range, or may be a predetermined fixed value. The calculation ranges for the signal value (S) and the noise value (N) may be set to different ranges. Finally, the information processing unit 13c calculates the ratio (S / N) of the signal value (S) to the noise value (N) as a judgment index. This eliminates the influence of peak values ​​of the FFT intensity level due to known noise signals and reduces the influence of changes in the FFT signal level caused by steady changes in the noise signal.

[0037] This judgment index was confirmed to have a high correlation with the difference between the predicted and actual iron loss in an actual production line. Figure 7 is a plot of the correlation coefficient between the judgment index (leakage flux S / N value) and the difference between the predicted and actual iron loss, ΔW. In the example shown in Figure 7, the spacing between the magnetic domain refinement processed sections is 8.0 mm, and the calculation range of the judgment index is a wavelength range of 7.0 to 9.0 mm. The signal value (S) is the maximum value of the FFT intensity level within the calculation range, and the noise value (N) is the average value of the FFT intensity level within the calculation range. As shown in Figure 7, it can be seen that there is a good correlation between the judgment index and the difference between the predicted and actual iron loss, ΔW. Therefore, by using this judgment index, the quality of the magnetic domain refinement processing can be accurately determined.

[0038] It is also desirable to create two-dimensional data on FFT intensity levels in the width and length directions of the steel sheet and determine the magnetic domain refinement processing state based on the two-dimensional FFT intensity level data. Specifically, for example, as shown in FIG. 8 , when two processing machines are arranged in parallel in the width direction and magnetic domain refinement processing is performed across the entire width of the grain-oriented electrical steel sheet, the first processing machine 1 corresponds to magnetic sensors with channels 1 to 5, and the second processing machine 2 corresponds to magnetic sensors with channels 6 to 10. An example of the flow of the two-dimensional data creation process is shown in FIG. 13 . In this example, there are 10 channels of measurement data in the width direction. First, in step S11, leakage magnetic flux output signals (e.g., 32,768 points, which is a power of 2) are collected at regular intervals in the length direction. Next, in step S12, a fast Fourier transform is performed for each channel to calculate the frequency distribution, and the FFT intensity level is calculated for each channel. In this case, the calculation is performed for each channel. In step S11, the output signals of each channel are not added, and in step S12, the results of the FFT calculation process, as in the method described in Patent Document 2, are not added. Next, in step S13, the ratio of signal value (S) to noise value (N) (S / N) is calculated as a judgment index from the calculated FFT intensity level, and each channel is classified based on the calculated judgment index. Then, for channels whose judgment index is in the range of 0 to 8 (step S14), the FFT intensity level in the corresponding two-dimensional data region is set to "low" (step S15). On the other hand, for channels whose judgment index is in the range of 8 to 10 (step S16), the FFT intensity level in the corresponding two-dimensional data region is set to "medium" (step S17). Furthermore, for channels whose judgment index is greater than 10 (step S18), the FFT intensity level in the corresponding two-dimensional data region is set to "high" (step S19). By repeating this process, two-dimensional data of FFT intensity levels, such as 10 channels in the width direction and several tens of points in the length direction, can be created for a coil, which is one manufacturing unit.

[0039] Possible causes of unstable magnetic domain refinement processing states include misadjustments in the laser or electron beam output, focus, scanning speed, and longitudinal distortion repetition interval (line spacing) of the processing machine due to roll wear, etc. Another possible cause is fluttering of the grain-oriented electrical steel sheet when the conveying speed of the grain-oriented electrical steel sheet changes during processing. Furthermore, unstable magnetic domain refinement processing states occur on a machine-by-machine basis and continuously in the longitudinal direction. For example, if the focus of the processing machine is misadjusted, the FFT intensity level decreases continuously in the longitudinal direction in multiple channels corresponding to a specific processing machine. Furthermore, even if the cause is fluttering of the steel sheet when the conveying speed changes, the intensity level decreases continuously in the longitudinal direction in multiple channels corresponding to a specific processing machine or multiple processing machines.

[0040] Therefore, due to noise and variations, it is difficult to accurately determine the quality of the magnetic domain refinement processing state using a measurement range index based on a single frequency distribution. However, by using two-dimensional data such as those described above, the quality of the magnetic domain refinement processing state can be accurately determined. An example of determination using data obtained on an actual production line is shown below. As described above, assume that 10 magnetic sensors are arranged in the width direction, and that the sheet actually passed through nine channels (channels 2 to 10). For example, Figure 9 shows an example of determining the magnetic domain refinement processing state using a determination index obtained by adding the results of FFT calculations of nine channels, as in the method described in Patent Document 2. If an FFT determination index threshold of 10 or more is determined as good and one below 10 is determined as poor, the magnetic domain refinement processing state would be determined to be good in this case. In contrast, Figure 10 shows excerpts of determination indexes for channels 2, 4, 6, and 8 obtained from the same data. By individually determining each channel in the width direction, the magnetic domain refinement processing state can be determined to be poor in the area corresponding to channel 6. In fact, in the steel sheet of this data, the state of magnetic domain refining processing was not good in the relevant width direction, resulting in a state where iron loss was poor.

[0041] In such a judgment using two-dimensional data, a two-dimensional map of FFT intensity levels may be created for each coil, which is a manufacturing unit, by displaying one intensity level calculation value in color, etc. For example, by displaying the FFT intensity level in red, yellow, green, etc., as shown in Figure 11 , it is easy to visually distinguish between a normal state where the FFT intensity level is stably high, or a state where only a single low FFT intensity level occurs, and an abnormal state where the FFT intensity level at a location corresponding to a specific processing machine is continuously low. The threshold value of the FFT intensity level calculation value can be set separately for each channel and manufacturing condition. Furthermore, an automatic judgment may be created, such as determining an abnormality when adjacent channels in the two-dimensional data fall below the threshold value a certain number of times consecutively. In this way, by obtaining the judgment index calculated from the FFT calculation results as two-dimensional data, it is possible to accurately judge the status of magnetic domain refining processing.

[0042] The closer the magnetic sensor is to the grain-oriented electromagnetic steel sheet, the higher the detection accuracy of leakage magnetic flux. However, due to contact caused by flapping of the grain-oriented electromagnetic steel sheet, the distance between the magnetic sensor and the grain-oriented electromagnetic steel sheet (lift-off amount) is actually approximately 0.3 to 3 mm. If the detection signal varies due to fluctuations in the lift-off amount, correction of the lift-off amount is necessary. Installing a distance meter (laser or eddy current type) to measure the distance between the magnetic sensor and the electromagnetic steel sheet is also important for maintaining the detection accuracy of leakage magnetic flux. Furthermore, if the flapping of the grain-oriented electromagnetic steel sheet is significant, it is possible to install a new transport roll, place a magnetizer adjacent to an existing roll, or place a magnetizer inside an existing roll. Furthermore, since the magnetization level applied to the grain-oriented electromagnetic steel sheet is small, an air-core coil can be used as the magnetizer.

[0043] As is clear from the above explanation, the method for determining the processed state of a grain-oriented electrical steel sheet, which is one embodiment of the present invention, applies a DC or AC magnetic field to a region of the grain-oriented electrical steel sheet that has been subjected to magnetic domain refinement processing, detects leakage magnetic flux that occurs in the grain-oriented electrical steel sheet as a result of the application of the magnetic field in each of a plurality of regions in the width direction of the grain-oriented electrical steel sheet, calculates a frequency distribution for each region from an output signal for the detected leakage magnetic flux in each region with respect to a position in the longitudinal direction of the grain-oriented electrical steel sheet, and determines the magnetic domain refinement processing state for each region based on the intensity level within a predetermined range of the frequency distribution for each region, thereby making it possible to accurately determine the magnetic domain refinement processing state of a specific portion of the steel sheet without requiring much effort.

[0044] Furthermore, the manufacturing yield of grain-oriented electrical steel sheets can be improved by adjusting the state of the manufacturing equipment for grain-oriented electrical steel sheets based on the magnetic domain refinement processing state for each region determined using the method for determining the processing state of grain-oriented electrical steel sheets according to one embodiment of the present invention. Specifically, as shown in FIG. 12 , a two-dimensional map of FFT intensity levels is created (step S1), and the magnetic domain refinement processing state is determined based on the two-dimensional map (step S2). Then, locations where the magnetic domain refinement processing state is determined to be poor are confirmed on a sample (step S3), and the state of the manufacturing equipment, such as the electron gun, is adjusted based on the confirmation results (step S4). This improves the manufacturing yield of grain-oriented electrical steel sheets. Furthermore, for the same reasons as above, the manufacturing yield of grain-oriented electrical steel sheets can be improved by using a grain-oriented electrical steel sheet manufacturing equipment equipped with a processing state determination device for grain-oriented electrical steel sheets according to one embodiment of the present invention.

[0045] Furthermore, by controlling the conditions for magnetic domain refinement processing based on the magnetic domain refinement processing state for each region determined using the processing state determination method for grain-oriented electrical steel sheet according to one embodiment of the present invention, it is possible to improve the production yield of grain-oriented electrical steel sheets. Specifically, by feeding back the determination result of the magnetic domain refinement processing state to the processing machine and correcting the magnetic domain refinement processing state at an early stage, it is possible to avoid producing grain-oriented electrical steel sheets that do not meet specifications and improve the production yield of grain-oriented electrical steel sheets.

[0046] Furthermore, by performing quality control of grain-oriented electrical steel sheets based on the state of magnetic domain refinement processing for each region determined using the method for determining the processing state of grain-oriented electrical steel sheets according to one embodiment of the present invention, it is possible to stably provide high-quality grain-oriented electrical steel sheets. Specifically, by classifying grain-oriented electrical steel sheets by quality based on the determination results of the magnetic domain refinement processing state, it is possible to stably provide high-quality grain-oriented electrical steel sheets.

[0047] Although the present invention has been described above as an embodiment, the present invention is not limited to the descriptions and drawings that form part of the disclosure of the present invention. In other words, other embodiments, examples, and operational techniques that can be made by those skilled in the art based on the present invention are all included in the scope of the present invention.

[0048] According to the present invention, it is possible to provide a method and an apparatus for determining the processed state of grain-oriented electrical steel sheet, which are capable of accurately determining the magnetic domain refinement processed state in a specific area of ​​the steel sheet without requiring much labor. Furthermore, according to the present invention, it is possible to provide a method for adjusting manufacturing equipment for grain-oriented electrical steel sheet and a manufacturing method for grain-oriented electrical steel sheet, which are capable of manufacturing grain-oriented electrical steel sheet with a high yield. Furthermore, according to the present invention, it is possible to provide a quality control method for grain-oriented electrical steel sheet, which is capable of stably providing high-quality grain-oriented electrical steel sheet. Furthermore, according to the present invention, it is possible to provide manufacturing equipment for grain-oriented electrical steel sheet, which is capable of manufacturing grain-oriented electrical steel sheet with a high yield.

[0049] REFERENCE SIGNS LIST 1, 10 Processing state determination device for grain-oriented electrical steel sheet 2, 12 Leakage magnetic flux detection unit 2a, 12a Magnetizer 2b, 12b Magnetic sensor 3, 13 Signal processing unit 13a Amplifier 13b Band-pass filter (BPF) 13c Information processing unit 14 Excitation power supply S Grain-oriented electrical steel sheet SP Magnetic domain refining processing unit

Claims

1. a magnetization step of applying a DC or AC magnetic field to the region of the grain-oriented electrical steel sheet that has been subjected to the magnetic domain refinement process; a detection step of detecting leakage magnetic flux generated in the grain-oriented electrical steel sheet due to application of the magnetic field for each of a plurality of regions in a width direction of the grain-oriented electrical steel sheet; a calculation step of calculating a frequency distribution of each region from an output signal with respect to a position in a longitudinal direction of the grain-oriented electrical steel sheet, in the leakage magnetic flux of each region detected in the detection step; a determination step of determining a state of the magnetic domain refining processing for each of the regions based on a determination index calculated from an intensity level within a predetermined range of a frequency distribution of each of the regions; The method for determining the processing state of a grain-oriented electrical steel sheet includes:

2. The method for determining a processed state of a grain-oriented electrical steel sheet according to claim 1 , wherein the predetermined range is set based on an interval of the magnetic domain refinement processing.

3. 2. The method for determining a processed state of a grain-oriented electrical steel sheet according to claim 1, wherein the determining step includes a step of determining a state of the magnetic domain refinement processing based on a two-dimensional distribution of the strength level in an in-plane direction of the grain-oriented electrical steel sheet.

4. A method for determining the processing state of a directional electromagnetic steel sheet as described in claim 2, wherein the judgment step includes a step of determining the state of the magnetic domain refinement processing based on a two-dimensional distribution of the strength level in the in-plane direction of the directional electromagnetic steel sheet.

5. a magnetizer that applies a DC or AC magnetic field to a region of the grain-oriented electrical steel sheet that has been subjected to magnetic domain refinement processing; a plurality of magnetic sensors for detecting leakage magnetic flux generated in the grain-oriented electrical steel sheet due to application of the magnetic field, for each of a plurality of regions in a width direction of the grain-oriented electrical steel sheet; a signal processing unit that calculates a frequency distribution of each region from output signals with respect to a position in the longitudinal direction of the grain-oriented electrical steel sheet in the leakage magnetic flux in each region detected by the multiple magnetic sensors, and judges a state of the magnetic domain refinement processing for each region based on a judgment index calculated from an intensity level within a predetermined range of the frequency distribution of each region; The processing state determination device for grain-oriented electrical steel sheet is provided with:

6. The device for determining a processed state of a grain-oriented electrical steel sheet according to claim 5 , wherein the predetermined range is set based on an interval of the magnetic domain refinement processing.

7. The device for determining a processed state of grain-oriented electrical steel sheet according to claim 5 , wherein the signal processing unit determines a state of the magnetic domain refinement processing based on a two-dimensional distribution of the strength level in an in-plane direction of the grain-oriented electrical steel sheet.

8. The processing state determination device for directional electromagnetic steel sheet described in Claim 6, wherein the signal processing unit determines the state of the magnetic domain refinement processing based on the two-dimensional distribution of the strength level in the in-plane direction of the directional electromagnetic steel sheet.

9. A method for adjusting manufacturing equipment for grain-oriented electrical steel sheet, comprising a step of adjusting a state of the manufacturing equipment for the grain-oriented electrical steel sheet based on the state of magnetic domain refinement processing for each region determined using the method for determining the processing state of grain-oriented electrical steel sheet according to any one of claims 1 to 4.

10. 5. A method for manufacturing a grain-oriented electrical steel sheet, comprising a step of controlling conditions for the magnetic domain refinement processing based on a state of the magnetic domain refinement processing for each of the regions determined using the method for determining the processing state of a grain-oriented electrical steel sheet according to any one of claims 1 to 4.

11. A quality control method for grain-oriented electrical steel sheet, comprising a step of performing quality control of the grain-oriented electrical steel sheet on the basis of a state of magnetic domain refinement processing for each region determined using the processing state determination method for grain-oriented electrical steel sheet according to any one of claims 1 to 4.

12. A manufacturing facility for grain-oriented electrical steel sheet, comprising the processing state determination device for grain-oriented electrical steel sheet according to any one of claims 5 to 8.