0001]The present invention relates to a grain-oriented electrical steel sheet preferably used for an iron core such as a transformer and a method for manufacturing the same. More specifically, the present invention relates to a grain-oriented electrical steel sheet having low iron loss and low noise and a method for manufacturing the same, which contributes not only to low iron loss of the iron core but also to low noise.
　The present application claims priority based on Japanese Patent Application No. 2019-012090 filed in Japan on January 28, 2019, the contents of which are incorporated herein by reference.
Background technology
[0002]
　In recent years, reduction of noise and vibration has been increasingly required for electromagnetic application equipment such as transformers, and grain-oriented electrical steel sheets used for transformer cores are suitable for low noise and low vibration as well as low iron loss. It has come to be required to be a material. It is said that one of the causes of the material for the noise and vibration of the transformer is the magnetostriction of the grain-oriented electrical steel sheet. The magnetostriction here is the rolling direction of the grain-oriented electrical steel sheet due to a slight change in the outer shape of the grain-oriented electrical steel sheet as the magnetization strength changes when the grain-oriented electrical steel sheet is excited by alternating current. The magnitude of this magnetostriction, which is the vibration seen in, is very small on the order of 10-6 , but the magnetostriction causes vibration in the iron core, which is an external structure such as a transformer tank. Propagates to noise.
[0003]
　The magnetostrictive characteristics change depending on various factors such as the structure and state of the grain-oriented electrical steel sheet, specifically, the degree of integration of crystal orientation, the tension applied to the steel sheet by the insulating coating, and the strain inherent in the steel. When the magnetostrictive characteristics change, the noise level changes, and in some cases, the noise can be reduced.
[0004]
　As one of the processes for changing the magnetostrictive characteristics, a technique of locally irradiating the surface of a grain-oriented electrical steel sheet with a laser, an electron beam, or the like to subdivide the magnetic domain is known. In general, irradiation with this laser or the like is performed linearly in a direction substantially orthogonal to the rolling direction of the steel sheet, and as a result, a reflux magnetic domain extending in the irradiation direction is formed and the striped magnetic domain is subdivided. Iron loss is reduced. On the other hand, the magnetostrictive characteristics can be changed and the noise level can be changed by irradiation with this laser or the like. Therefore, irradiation conditions that can reduce iron loss and noise are required.
[0005]
　Patent Document 1 is an object of providing a grain-oriented electrical steel sheet having low iron loss and low noise, which has both low iron loss and low noise of a transformer, and has a magnetostriction 0-p value of a saturation magnetic flux density and a saturation magnetic flux. Focusing on the difference between the density and the magnetostriction 0-p value at 1.7 T, it is suggested that these changes should be kept below a certain value before and after laser irradiation.
　However, in the grain-oriented electrical steel sheet of Patent Document 1, a low-noise grain-oriented electrical steel sheet is manufactured by paying attention only to the difference in the peak intensity of magnetostriction. The noise was not enough.
[0006]
　Patent Document 2 has an object of providing a directional electromagnetic steel plate capable of changing the magnetostrictive characteristics of a steel plate as a material of an iron core and changing or reducing the noise level with respect to the noise generated by a transformer or a reactor. It is presented to specify the amplitude of the magnetostrictive component at the 4f frequency when the directional magnetostrictive steel plate subdivided into magnetic domains by linear strain is excited at the fundamental frequency f, and to specify the amplitude difference before and after the SRA.
　However, in Patent Document 2, although the amplitude of the 4f frequency magnetostriction component is defined based on the finding that the magnetostriction of the 4f component depends on the shape of the reflux magnetic domain generated by the introduction of strain locally, other frequencies are specified. The components were not considered, and the reduction of iron loss was not fully investigated.
[0007]
　Patent Document 3 is an object of providing a unidirectional electromagnetic steel plate for a low noise transformer that effectively reduces noise by reducing harmonics having a large human audibility, such as laser irradiation and magnetostriction. Therefore, the magnetostriction λ 0-B (difference in the shape of the steel plate when the magnetic flux density is BT and 0T) is set in the range of 0 ≤ λ 0-B ≤ 0.5 × 10 -6 , and the change in the magnetostrictive waveform is gentle. It is presented to be.
　However, in the grain-oriented electrical steel sheet of Patent Document 3, although it has been shown that the noise of the transformer is reduced, the iron loss has not been sufficiently examined. Further, attention is paid only to the shape difference between the maximum magnetic flux densities B and 0T, and the time-magnetostriction waveform itself has not been studied.
Prior art literature
Patent documents
[0008]
Patent Document 1: Japanese Patent No. 4216488
Patent Document 2: Japanese Patent Application Laid-Open No. 2017-128765
Patent Document 3: Japanese Patent No. 3500103
Outline of the invention
Problems to be solved by the invention
[0009]
　As described above, various studies have been made on grain-oriented electrical steel sheets that can reduce iron loss and noise, but in recent years, further improvement in performance has been required. The present invention is based on the premise of a "magnetic domain control material" such as a laser irradiation material and an electron beam irradiation material used for a highly efficient core transformer, and has a direction in which core loss and noise in a transformer can be reduced at the same time. It is an object of the present invention to provide an electromagnetic steel plate.
Means to solve problems
[0010]
　The present invention provides means of the following aspects.
　[1] The grain-oriented electrical steel sheet according to one aspect of the present invention has a steel sheet and optionally an insulating film formed on the steel sheet, and is subjected to a heat treatment of retaining at 800 ° C. for 2 hours. For the time-magnetostriction waveform (t-λ waveform) when excited to 1.7 T, the peak value of the difference waveform obtained by subtracting the time-magnetostriction waveform after the heat treatment from the time-magnetostriction waveform before the heat treatment is It is 0.01 × 10-6 or more and 0.20 × 10-6 or less, and the difference obtained by subtracting the iron loss before the heat treatment from the iron loss after the heat treatment is 0.03 W / kg or more and 0.17 W / It is less than kg.
　[2] In the grain-oriented electrical steel sheet according to the above [1], at least the surface of the steel sheet may have linear or intermittent linear strain introduced in a direction intersecting the rolling direction of the steel sheet. ..
　[3] The method for manufacturing a grain-oriented electrical steel sheet according to another aspect of the present invention is the method for manufacturing a grain-oriented electrical steel sheet according to the above [1] or [2], and is applied to the surface of the grain-oriented electrical steel sheet. Irradiate a laser beam or an electron beam linearly.
The invention's effect
[0011]
　In the grain-oriented electrical steel sheet shown in the above aspect of the present invention, the peak value of the difference waveform obtained by subtracting the time before heat treatment-magnetostriction waveform and the time after heat treatment-magnetostriction waveform is 0.01 × 10-6 or more, 0.20 × 10 -6 or less, the difference obtained by subtracting the iron loss before the heat treatment of iron loss 0.03 W / kg or more after the heat treatment, by at most 0.17 W / kg, trans loss low when applied to the transformer (Iron loss) and low transformer noise can be achieved at the same time.
A brief description of the drawing
[0012]
FIG. 1 shows an example of a time-magnetostrictive waveform when a directional electromagnetic steel sheet before strain annealing heat treatment (SRA) is excited with a sine wave having a magnetic flux density amplitude of 1.7 T at a frequency of 50 Hz. Is.
FIG. 2 is a diagram showing an example of a time-magnetostrictive waveform when a directional electromagnetic steel plate after strain annealing heat treatment (SRA) is excited with a sine wave having a magnetic flux density amplitude of 1.7 T at a frequency of 50 Hz. Is.
FIG. 3 is a diagram showing the difference between the time-magnetostrictive waveforms before and after the strain-removing annealing heat treatment (SRA).
Mode for carrying out the invention
[0013]
　The grain-oriented electrical steel sheet according to one aspect of the present invention is magnetic domain controlled.
　This magnetic domain control has the effect of subdividing the striped magnetic domain and reducing iron loss. The magnetic domain control can be confirmed by observing whether the striped magnetic domain is divided.
[0014]
　On the other hand, this magnetic domain control also changes the magnetostrictive characteristics, and the noise level may change as the magnetostrictive characteristics change. This is because various vibration modes are generated in the structure due to magnetostriction, and noise is generated when the structure vibrates. In the vibration mode of the structure, in addition to the vibration of the fundamental frequency, the vibration of a frequency (double frequency) that is an integral multiple of the fundamental frequency overlaps. The fundamental frequency is, for example, 100 Hz when the exciting current frequency is 50 Hz, and the multiple frequency frequencies are 200 Hz, 300 Hz, 400 Hz, and so on.
　The present inventors have studied to reduce the noise level by changing the magnetostrictive characteristics by controlling the magnetic domain.
[0015]
　The present inventors are surprised that the change in magnetostriction characteristics due to magnetic domain control can be evaluated by the difference waveform (same time axis) obtained by subtracting the time-magnetostrictive waveform before magnetic domain control from the time-magnetostrictive waveform after magnetic domain control. It should be found that if the magnetic domain control conditions are constant, the difference waveforms will be almost the same even if the magnetostrictive waveforms of the mother samples are different.
　In addition, as a result of the studies by the present inventors, it is possible to control iron loss and noise characteristics at the same time with higher accuracy and reproducibility by evaluating the shape of the difference waveform itself without limiting to a specific frequency component. Do you get it.
[0016]
　The above new findings will be described with reference to FIGS.
　First, the present inventors prepared nine types of high magnetic flux density directional electromagnetic steel sheets (HGO), performed magnetic domain control on these under the same conditions, and measured the time-magnetostriction waveform. FIG. 1 is a superposition of the waveforms of the measured grain-oriented electrical steel sheets. Under the same magnetic zone control conditions, the laser output power P = 250 (W), parallel to the direction perpendicular to the rolling direction, PL (irradiation line spacing) = 4 mm spacing, irradiation minor axis diameter dL (rolling direction diameter) = 0.08 mm. , Irradiation long axis diameter dC (diameter in the direction perpendicular to rolling) = 1.0 mm, and laser irradiation was performed linearly.
　Then, the grain-controlled grain-controlled electrical steel sheet was subjected to strain annealing (SRA) at 800 ° C. for 2 hours as a heat treatment, and the time-magnetostriction waveform was measured. The measurement results are shown in FIG.
　FIG. 3 shows a difference waveform obtained by subtracting the time-magnetostrictive waveform (FIG. 1) before the strain-removing annealing heat treatment (SRA) from the time-magnetostriction waveform (FIG. 2) after the strain-removing annealing heat treatment (SRA). Although the time-magnetostrictive waveforms before and after SRA were different waveforms, the difference waveforms before and after SRA were almost the same waveforms for all of the steels 1 to 9. It is considered that the reason is that the heat treatment eliminates the effect of magnetic domain control, but does not change the crystal orientation of the grain-oriented electrical steel sheet having a coarse crystal grain size. Although the original magnetostrictive waveform changes due to factors such as crystal orientation, the difference waveform is almost the same, so it is considered that this difference waveform corresponds to the amount of change in the magnetostrictive characteristics caused by magnetic domain control performed under the same conditions. .. In other words, it is possible to quantify and evaluate the magnetostrictive characteristics that change by magnetic domain control based on the difference between the magnetostrictive waveforms before and after the heat treatment. In FIGS. 1 to 3, the horizontal axis is "time for one excitation cycle".
[0017]
　As described above, it is possible to quantify the change in magnetostriction characteristics by magnetic domain control from the difference waveform. Here, the peak value (amplitude) of this difference waveform is considered to be proportional to the volume of the recirculated magnetic domain of the magnetic domain control portion, and the difference waveform is mainly composed of a vibration component having a fundamental frequency. Therefore, when the magnetostrictive change of the differential waveform by magnetic domain control is added to the grain-oriented electrical steel sheet of the material, the vibration component of the fundamental frequency is canceled out, but the harmonic component is relatively emphasized, which may lead to transformer noise. .. Therefore, transformer noise can be reduced by defining the upper limit of the peak value (amplitude) of this difference waveform. Specifically, the peak value of the difference waveform is set to 0.20 × 10-6 or less.
　On the other hand, if the peak value (amplitude) of the difference waveform is too small, the magnetic domain control effect does not appear sufficiently, and the transformer loss cannot be sufficiently reduced. Therefore, the peak value of the difference waveform is set to 0.01 × 10-6 or more.
[0018]
　In the grain-controlled electrical steel sheet according to the present embodiment, when the iron loss before and after the heat treatment is measured and the difference between the measured values ​​is obtained, the difference in the iron loss (iron loss after the heat treatment-iron before the heat treatment) is obtained. Loss) is 0.03 W / kg or more and 0.17 W / kg or less.
　If the difference in iron loss is less than 0.03 W / kg, the improvement of the iron loss characteristic by magnetic domain control is insufficient, and if it exceeds 0.17 W / kg, the noise characteristic deteriorates.
[0019]
　From the viewpoint of quantifying the difference waveform before and after the magnetic domain control, it is necessary that the heat treatment sufficiently eliminates the effect of the magnetic domain control. Therefore, the heat treatment temperature must be set appropriately. As the heat treatment conditions, it is sufficient to set the heat treatment conditions that sufficiently eliminate the effect of magnetic zone control and do not deteriorate the insulating film of the directional electromagnetic steel plate by appropriately combining the heat treatment temperature and the retention time. The conditions may be such that the heat treatment temperature is set to 500 to 900 ° C. and the retention time is set to 30 minutes to 8 hours.
　If the temperature of the heat treatment is too high, not only the effect of magnetic domain control is eliminated, but also the insulating film of the grain-oriented electrical steel sheet may be deteriorated. Therefore, the upper limit of the heat treatment temperature is set to 900 ° C. On the other hand, if the heat treatment temperature is too low, the effect of magnetic domain control may not be eliminated. Therefore, the lower limit of the heat treatment temperature is set to 500 ° C.
　In addition, the retention time of the heat treatment can be appropriately selected. However, if the retention time is too long, not only the effect of magnetic zone control is eliminated, but also the insulating film of the directional electromagnetic steel plate may be deteriorated. Therefore, the upper limit of the retention time may be 8 hours. Further, if the retention time is too short, the effect of magnetic domain control may not be eliminated. Therefore, the lower limit of the retention time may be set to 30 minutes.
　As an example of a combination of an appropriate heat treatment temperature and retention time, it may be 30 minutes or 4 hours at 780 ° C. or 850 ° C., or 2 hours at 800 ° C. It is preferable that the heat treatment temperature is 800 ° C. and the retention time is 2 hours from the viewpoint of stably obtaining the effect of strain removal and annealing.
　For the heat treatment, it is preferable to use a batch tanner or a continuous tanner. Directional to be annealed It is preferable to limit the rate of temperature decrease during cooling so that the temperature deviation in the electromagnetic steel plate does not become excessive. As a specific example, for example, in the case of batch annealing, it is preferable that the temperature is 500 ° C. to 800 ° C. for 30 minutes to 8 hours, and the temperature lowering rate is about 50 ° C./hour or less, 10 ° C./hour or more, for example, about 30 ° C./hour. If the temperature drop rate is too large, a temperature deviation may occur in the sample, residual strain may occur, and the iron loss value or the like may deteriorate. On the other hand, if the temperature decrease rate is too small, the heat treatment time is excessively required, and the residual strain avoidance effect is saturated. Therefore, it is preferable to set an appropriate lapse rate.
[0020]
　The means for controlling the magnetic domain is not particularly limited as long as it can obtain desired properties, in other words, the peak value of the difference waveform and the iron loss difference specified in the present embodiment, and is not particularly limited, and is limited to laser irradiation and electrons. Beam irradiation, mechanical strain introduction, etc. can be appropriately used. The appropriate value of the conditions of each means for magnetic domain control varies slightly depending on the characteristics of the material, but the conditions are grasped in advance for some materials, and the operation is performed so that the difference waveform is in the good range shown in the present embodiment. The conditions etc. may be adjusted. Such adjustments are not so difficult for those skilled in the art who routinely adjust operating conditions to control magnetic strain.
[0021]
　In the grain-oriented electrical steel sheet according to the present embodiment, linear (continuous) introduced into at least the surface of the steel sheet (the surface of the steel sheet portion excluding the film when having an insulating film) in a direction intersecting the rolling direction of the steel sheet. There are linear or intermittent linear strains), and these linear strains may realize magnetic domain control. The surface of the steel sheet may be irradiated with a laser or an electron beam for a long time with a lower irradiation power density than before so that the peak value of the difference waveform and the iron loss difference specified in the present embodiment can be obtained. For example, with respect to the laser output power P (W), the irradiation minor axis diameter dL (diameter in the rolling direction) and the irradiation major axis diameter dC (diameter in the direction perpendicular to the rolling direction) of the elliptical irradiation are set sufficiently large, and Ip = (4). By reducing the irradiation power density expressed by × P) / (π × dL × dC), the “peak value of the difference waveform and the iron loss difference” may be controlled within the specified range. A laser or the like may irradiate the surface of the steel sheet linearly.
[0022]
　The irradiation conditions of the laser or electron beam may be adjusted individually.
　The irradiation energy (Ua) of the laser or electron beam may be 0.1 to 10 mJ / mm 2 . This range is preferable in terms of a sufficient iron loss improving effect.
　The laser diameter or electron beam diameter may be 0.001 to 0.4 mm as long as it is a perfect circle. If it is elliptical, the minor axis diameter dL is the same as the above, but the major axis diameter dC may be 0.001 to 50 mm.
　The number of pulses of the laser or electron beam, the pulse width, the scanning speed, the undulation conditions, and the like may be appropriately adjusted.
　In laser or electron beam irradiation, the focus lens or focus coil may be vibrated up and down, and the vibration may be controlled by synchronizing the scanning speed of the laser or electron beam.
[0023]
　Laser irradiation can be performed using a CO 2 laser, a YAG laser, a fiber laser, or the like. From the viewpoint of reducing iron loss, it is desirable that the magnetic domain control region extends in a strip shape or a linear shape substantially at right angles to the rolling direction of the steel sheet, and the region is periodically introduced in the rolling direction.
[0024]
　The magnetostrictive characteristics also change depending on the tension applied to the steel sheet by the insulating film. Therefore, the magnetostrictive characteristics may be adjusted by forming an insulating film on the grain-oriented electrical steel sheet. That is, the grain-oriented electrical steel sheet according to the present embodiment may be a grain-oriented electrical steel sheet in which an insulating film is formed on the surface of the steel sheet. It is also possible to adjust the tension by adjusting the thickness of the insulating coating. For example, when forming an insulating film, the film tension may be 1 to 20 MPa.
[0025]
　The thickness of the grain-oriented electrical steel sheet according to the present embodiment is not limited, but is preferably 0.10 to 0.35 mm, preferably 0.15 to 0.27 mm in consideration of application to a transformer. More preferred.
[0026]
　As a method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment, it is exemplified to linearly irradiate the surface of the grain-oriented electrical steel sheet with a laser beam or an electron beam under the above-mentioned conditions.
Example
[0027]
　The present invention will be described with reference to the following examples. However, the present invention should not be construed as being limited to this example.
[0028]
　A high magnetic flux density directional electromagnetic steel plate with a thickness of 0.23 mm manufactured by a normal method is subjected to irradiation minor axis diameter dL at intervals of PL = 4 mm parallel to the rolling perpendicular direction with a laser output power P = 250 (W). The magnetic domain was controlled by linearly irradiating the laser with various changes in (diameter in the rolling direction) and irradiation major axis diameter dC (diameter in the direction perpendicular to the rolling direction). The irradiation energy was 2.1 mJ / mm 2 , and the scanning speed of the irradiation beam was 30 m / s. A fiber laser was used as the laser. When the directional electromagnetic steel plate after laser irradiation and before the magnetostrictive annealing heat treatment (SRA) and the directional electromagnetic steel plate after the laser irradiation and after the magnetostrictive annealing heat treatment (SRA) are sine wave excited to 1.7 T at a frequency of 50 Hz. Each time-magnetostriction waveform was measured using a laser Doppler magnetostriction measuring device. Since the response speed of the laser-Doppler measuring device is sufficiently fast, the excitation frequency when measuring magnetostriction is not limited to 50 Hz, and can be measured at higher frequencies such as 100 Hz and 200 Hz, but a commercial excitation frequency. Is 50 Hz to 60 Hz, so the measurement was set to 50 Hz.
　Table 1 shows the sample preparation conditions and the magnetic strain measurement results (peak values ​​of the difference waveform before and after the heat treatment). The table also shows the difference in iron loss before and after SRA.
[0029]
[table 1]

[0030]
　As can be seen from Table 1, the peak value of the magnetostrictive difference waveform produced by the material under the irradiation condition in which Ip = (4 × P) / (π × dL × dC) was 0.66 or less became small.
　On the other hand, in the samples A to C having a large Ip, the peak value of the magnetostrictive difference waveform became large.
　However, in sample G, the magnetic domain control effect became insufficient as dL × dC became larger and Ip became smaller, and the magnetic domain width became wider, so that the difference in iron loss became excessively small.
[0031]
　Using these steel plates A to G (the ones after laser irradiation and before SRA), a three-phase three-legged iron core transformer having a capacity of 400 kVA was manufactured. The maximum width of the steel plate was 180 mm, and the number of stacked sheets was 650. The design magnetic flux density was Bd = 1.7T. Table 2 shows the noise measurement results. The table also shows transformer loss.
[0032]
[Table 2]

[0033]
　As can be seen from Table 2, the peak value of the difference waveform is 0.01 × 10-6 or more and 0.20 × 10-6 or less, and the difference after deducting the iron loss is 0.03 W / kg or more and 0. In the example using the directional electromagnetic steel plates D, E, and F having a value of .17 W / kg or less, the transformer noise and the transformer loss were reduced.
　On the other hand, in the example using the grain-oriented electrical steel sheets A to C and G, either the transformer noise or the transformer loss was inferior.
Industrial applicability
[0034]
　With the grain-oriented electrical steel sheet of the present invention, low transformer loss (iron loss) and low transformer noise can be achieved at the same time. Therefore, it has high industrial applicability.

WE CLAIMS

[Claim 1]And the steel sheet,
　optionally, an insulating film formed on the steel sheet
has,
　when performing heat treatment for 2 hours retention at 800 ° C.,
　　the time when the excitation to 1.7 T - magnetostriction waveform (t- λ waveform), the peak value of the difference waveform obtained by subtracting the time-magnetostriction waveform after the heat treatment from the time-magnetostriction waveform before the heat treatment is 0.01 × 10-6 or more, 0.20 × 10-6. The
　　grain-
　oriented electrical steel sheet according to the following, wherein the difference obtained by subtracting the iron loss before the heat treatment from the iron loss after the heat treatment is 0.03 W / kg or more and 0.17 W / kg or less .
[Claim 2]
　The grain-oriented electrical steel sheet according to claim 1, wherein at least the surface of the steel sheet has linear or intermittent linear strain introduced in a direction intersecting the rolling direction of the steel sheet.
[Claim 3]
　The method for manufacturing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein
the surface of the grain-oriented electrical steel sheet is linearly irradiated with a laser beam or an electron beam. Method.