JP2015052144A - Oriented electromagnetic steel sheet for transformer iron core and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oriented electromagnetic steel sheet applied to a magnetic domain subdivision treatment by an electron beam, excellent in iron loss and capable of reducing noise when made to a transformer because magnetostriction is small and variation of magnetostriction in a coil is also small.SOLUTION: A reflux magnetic domain area is formed to a direction across a rolling direction of the steel sheet and in a position which does not overlap an irradiated position without deflecting an electron beam to a steel sheet rolling direction, while making the reflux magnetic domain area continuous with length: 200 mm or more, and a width of the reflux magnetic domain area: d(μm) satisfy 0.8d≤d≤1.2dwhere d(μm): an average value of the width of the reflux magnetic domain area in the direction across the rolling direction is set.

Description

  The present invention is a grain-oriented electrical steel sheet that is used for applications such as transformer cores, and is subjected to magnetic domain subdivision processing and is excellent in iron loss, and also has a small variation in magnetism, particularly permeability, in a coil. The present invention relates to a grain-oriented electrical steel sheet that is advantageous for reducing iron loss after being assembled in a transformer, and a method for manufacturing the grain-oriented electrical steel sheet.

  The main issues in using transformers are: 1. Improvement of energy usage efficiency Noise reduction. Here, the energy loss that occurs in the transformer mainly includes copper loss that occurs in the conductor and iron loss that occurs in the iron core. Among these, the iron loss has been greatly improved by sharpening the crystal orientation of the grain-oriented electrical steel sheet or increasing the film tension. For example, Patent Document 1 discloses a method of manufacturing a grain-oriented electrical steel sheet having excellent magnetic flux density and iron loss by optimizing the annealing conditions before final cold rolling.

Furthermore, in recent years, a technique has been established that dramatically improves iron loss by irradiating a plasma flame or laser after the final annealing.
For example, in Patent Document 2, the iron loss W _17/50 that was _0.80 W / kg or more before irradiation is 0.65 W / kg or less by irradiating a plasma arc to the steel sheet after secondary recrystallization. The technique to reduce is shown. In Patent Document 3, a transformer material with low iron loss and low noise is obtained by optimizing the average width and film thickness of magnetic domain discontinuities formed on the steel plate surface by electron beam irradiation. Technology is shown.

  Here, it is assumed that the magnetostriction of the iron core, the electromagnetic vibration of the joint, and the resonance of the housing affect the noise of the transformer (see Non-Patent Document 1 and Patent Document 4). Among these, magnetostriction is derived from the domain structure of grain-oriented electrical steel sheets, and the domain (or type of auxiliary domain) that faces in a direction other than the excitation direction called a lancet magnetic domain is the cause of magnetostriction in the excitation direction. Therefore, it is said that a method of reducing the auxiliary magnetic domain as much as possible by increasing the film tension is effective.

  In addition, it is known that auxiliary magnetic domains such as lancet magnetic domains also exist in portions where thermal strain is introduced by a laser or the like (hereinafter referred to as reflux magnetic domains). Interestingly, the magnetization behavior of the two is different, and the lancet domain increases with excitation, while the reflux domain tends to disappear. Therefore, it is said that the magnetostriction can be reduced to the limit by balancing the two (see Non-Patent Document 2).

  In addition, the low magnetostrictive material of the grain-oriented electrical steel sheet irradiated with laser and the manufacturing method thereof are disclosed in, for example, Patent Document 5 and Patent Document 6.

JP 2012-1741 A JP 2011-246782 A JP 2012-52230 A Japanese Patent No. 4840535 Japanese Patent No. 4216488 JP 2002-69594 A JP-A-4-264345 Japanese Patent Laid-Open No. 2-118022 Japanese Patent Laid-Open No. 5-43944 Japanese Patent Publication No. 6-21358

Kawasaki Steel Technical Report Vol.29, No.3, p.164 Journal of Japan Society of Applied Magnetics Vol.25, No.12, p.1618

  Local distortion caused by a laser or an electron beam (hereinafter also simply referred to as a beam) increases the magnetostriction by periodically and repeatedly applying it in the rolling direction with respect to the direction crossing the rolling direction (hereinafter also referred to as the width direction). Although it can be changed, there is a problem that it is difficult to obtain the same quality in the width direction. In particular, from the viewpoint of improving productivity that has been demanded in recent years, when trying to process a steel plate with a width exceeding 1000 mm with as few oscillators or electron guns as possible, the irradiation width of the laser or electron beam increases, and the steel plate It becomes more difficult to maintain the same quality in the width direction.

  Here, in the case of electron beam irradiation, as the electron beam is deflected, the diameter of the electron beam increases, resulting in a beam property different from that of the central portion of the deflection irradiation. Further, in the case of laser irradiation, a uniform distortion introducing portion can be obtained by installing a lens whose focal length is adjusted according to the deflection width position. However, as with electron beam irradiation, as shown in FIG. In addition, since the beam is obliquely incident on the steel plate at the deflection end, a phenomenon that the beam shape is somewhat distorted occurs. Moreover, in the case of laser irradiation, the fluctuation | variation by the reflectance of a steel plate changing cannot be disregarded.

Such a beam property that varies depending on the position of the coil causes variation in magnetic permeability. The inventors have found that the iron loss of the transformer tends to deteriorate particularly when the variation in magnetic permeability is large.
FIG. 2 shows the effect of variation in permeability: σ of the grain-oriented electrical steel sheet assembled on the transformer on the building factor. Here, the building factor indicates the ratio of the iron loss of the transformer after being assembled to the iron core to the iron loss when the grain-oriented electrical steel sheet is single-sheeted before being assembled to the iron core, and is hereinafter referred to as BF.
In addition, the magnetic variation of a single sheet of _grain- oriented electrical steel sheet is _{represented by} the standard deviation σ (H / H) of the permeability μ _17/50 measured by SST measurement at the central part of 20 samples subjected to oblique shearing just before being assembled to the iron core. m).
Furthermore, transformer iron loss was evaluated using a model transformer simulating a three-phase tripod stacking iron core type transformer for laboratory experiments. The external shape of the model transformer is 500mm square, and it is composed of 20 steel plates (4 sheets laminated) with a width of 100mm. The three phases were excited by shifting the phase by 120 °, and the iron loss was measured at a magnetic flux density of 1.7T.
In Fig. 2, each of the two circles is an iron core made of a single plate with an average iron loss of 0.87 W / kg and an average permeability of 0.040 H / m. An iron core was manufactured using a plate average iron loss: 0.74 W / kg and an average permeability: 0.022 H / m.

  From the above measurement results, it has been clarified that it is effective to reduce the magnetic permeability variation in order to reduce BF. As for this mechanism, if the magnetic permeability is not uniform at present, the magnetic flux flows while selecting a portion having a high magnetic permeability, and as a result, the magnetic path length increases and the loss increases. thinking.

  In electron beam irradiation, as a method of suppressing the beam shape change at the deflection end, for example, introduction of Sting Mator (see Patent Document 7), coil current adjustment according to the focusing distance (Patent Document 8, hereinafter dynamic focusing technique) ), A method of defocusing irradiation (see Patent Document 9), a method of correcting the curvature of a steel sheet (see Patent Document 10), and the like are known to be effective.

  However, although the Sting-Mart technique (Patent Document 7) can correct the beam shape in a certain deflection state, it cannot be corrected in all the states in which deflection scanning is performed linearly. Limited to use.

  Further, when the deflection irradiation width is increased, it is difficult to produce a beam having a uniform width even when the dynamic focusing technique (Patent Document 8) is applied. This is because when the deflection irradiation width is large, the difference in beam diameter between the deflection center and the end becomes large. Therefore, particularly when the deflection scanning speed is large, the focusing coil current is greatly changed in a short time during the deflection irradiation. Although it is necessary, a sudden current change is physically difficult due to the influence of the intrinsic impedance of the coil.

  Furthermore, since the method disclosed in Patent Document 9 defocuses the beam, the magnetic characteristics may vary. Further, there is a conventional knowledge that a smaller beam diameter is advantageous for reducing iron loss.

  Further, the method disclosed in Patent Document 10 for correcting the curvature of a steel sheet is not a realistic method because it not only increases the risk of distortion and cracking in the steel sheet, but also requires the introduction of complex equipment. .

  The present invention has been developed in view of the above-described situation, and is a grain-oriented electrical steel sheet that has been subjected to magnetic domain subdivision treatment with an electron beam, and has excellent iron loss, small magnetostriction, and magnetostriction variation within a coil. Therefore, it is an object of the present invention to propose a grain-oriented electrical steel sheet that can reduce noise when used as a transformer, together with its manufacturing method.

The above-mentioned Patent Documents 7 to 10 are based on the idea that since the path length: Δ (mm) of the electron beam is different between the deflection center portion and the end portion, the way of focusing is different. Here, Δ (mm) is expressed as follows.
Δ = WD × [{1+ (L / (2WD)) ² } ^0.5 −1]
WD (mm): Distance from deflection coil center to steel plate

On the other hand, the inventors diligently studied the influence of beam deflection on the magnetic domain fragmentation effect by the electron beam. As a result, it was surprisingly found that the increase in beam diameter occurring at the deflection end is not governed only by the path length: Δ (mm), but by the deflection operation itself.
The experimental results to prove this are shown below.

  As shown in Fig. 3, six directional magnetic steel sheets with RD: 320mm and TD: 60mm are placed side by side in the TD direction so that the beam path length from the center of the focusing coil to the steel sheet is constant. I examined the loss. FIG. 4 shows the result of the investigation. According to the result of FIG. 4, the iron loss is the lowest value near the deflection center (width direction position: 180 mm), and the path length: Δ (= 550 mm) is Even if they were the same, they deteriorated as the deflection amount increased.

  Here, it is difficult to quantitatively describe the detailed mechanism by which the beam becomes non-uniform due to deflection, but it is considered that there is an influence of deflection aberration such as astigmatism.

Based on the above results, the inventors have come to the idea that it is important to suppress the amount of deflection in order to obtain a uniform beam in the width direction.
FIG. 5 shows an electron beam deflection scan. In the conventional method, electrons emitted from the electron gun are deflected only in the width direction by the deflection coil, and irradiation such as S1 → P → E1 is performed on the steel plate. On the other hand, the inventors deflected the electron beam also in the rolling direction, so that the beam position (P in the figure) where the electron beam reaches the steel plate without being deflected in either the rolling direction or the width direction, It has been considered that the point Q is the center of deflection scanning in the figure outside the scanning region.
Here, the amount of change in deflection angle during beam deflection scanning: η (deg.) (Maximum deflection angle−minimum deflection angle), the distance between OPs is w (mm), the distance between PQs is R (mm), and the deflection amount ( When the distance between S1-E1 and the distance between S2-E2 is L (mm), the deflection angle P-O-S2 (PO-E2) at point S2 (or E2), that is, the maximum deflection angle is as follows. Is required.
^{∠PO-S2 = Cos -1 (w} / (w 2 + R 2 + L 2/4) 0.5)
Further, the deflection angle P-O-Q at the point Q, that is, the minimum deflection angle is obtained as follows.
∠POQ = Cos ⁻¹ (w / (w ² + R ² ) ^0.5 )
Therefore,
^{η = Cos -1 (w / (} w 2 + R 2 + L 2/4) 0.5) - Cos -1 (w / (w 2 + R 2) 0.5)
It becomes.

FIG. 6 shows the influence of the PO distance (shift amount) R (mm) on the deflection angle variation calculated with w = 600 mm and L = 200 mm. It was confirmed that the amount of change in the deflection angle is smaller as R is increased.
From this, the inventors changed the deflection angle by shifting the deflection scanning center position from the beam position (P in the figure) where the electron beam reaches the steel plate in a state where the deflection scanning center position is not deflected in either the rolling direction or the width direction. It was thought that the magnetic variation in the deflection scanning region could be suppressed.

Therefore, the inventors considered that variation in the magnetic field in the deflection scanning region can be effectively suppressed by suppressing fluctuations in the deflection angle and providing various conditions in the return magnetic domain region, and conducted more detailed experiments. The present invention has been completed.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
1. In the grain-oriented electrical steel sheet having a reflux domain region formed with respect to the direction crossing the rolling direction and periodically formed with respect to the rolling direction,
The return magnetic domain region is continuous at a length of 200 mm or more, and the width of the return magnetic domain region: d (μm)
0.8d ₀ ≦ d ≦ 1.2d _0,
d ₀ (μm): A grain-oriented electrical steel sheet for a transformer core, which is an average value in the direction across the rolling direction of the width of the reflux magnetic domain region.

2. The width of the reflux magnetic domain region: d (μm) is the average value of the width of the reflux magnetic domain region in the direction crossing the rolling direction: d ₀ (μm),
0.9d ₀ ≦ d ≦ 1.1d ₀ ,
2. The grain-oriented electrical steel sheet for transformer cores according to 1 above, which satisfies the above relationship.

3. In a grain-oriented electrical steel sheet in which n (≧ 1) number of reflux magnetic domain groups formed of a plurality of reflux magnetic domain regions periodically formed with respect to the rolling direction are present in the i-th reflux magnetic domain group, The length of one reflux magnetic domain region is Yi (i = 1 to n) (mm), the entire coil width is Z (mm), and the tilt angle between the direction in which the reflux magnetic domain crosses the rolling direction and the direction perpendicular to the rolling is θ (deg. )
1.05Z ≧ Σ (i = 1 to n) Yi × cos θ ≧ Z
3. The grain-oriented electrical steel sheet for transformer cores according to 1 or 2, which satisfies the above relationship.

4). The directional electrical steel sheet for transformer cores according to any one of 1 to 3, wherein a periodic interval in the rolling direction of the reflux magnetic domain region is equal to or less than an average crystal grain size of the steel sheet.

5. 5. A method for producing a directional electrical steel sheet for a transformer core according to any one of 1 to 4 above, wherein the introduction of the reflux magnetic domain is in a state where the electron beam is always deflected in the rolling direction, in the steel sheet width direction. A method for producing a directional electrical steel sheet for a transformer core, which is deflected and scanned.

6). 6. In the deflection scanning of the electron beam, the directional electromagnetic wave for a transformer core as described in 5 above, wherein a deflection angle fluctuation amount represented by the following formula (1): η (deg.) Is 8 (deg.) Or less. A method of manufacturing a steel sheet.
^{η = Cos -1 (w / (} w 2 + R 2 + L 2/4) 0.5) -Cos -1 (w / (w 2 + R 2) 0.5) ··· (1)
Where w (mm) is the distance between the center of the deflection coil and the steel plate, R (mm) is the shift amount, and L (mm) is the deflection amount.

7). 7. The method for producing a directional electrical steel sheet for a transformer core according to 5 or 6, wherein an acceleration voltage of the electron gun of the electron beam is 40 kV or more and 300 kV or less.

8). 8. The method for producing a directional electrical steel sheet for a transformer core according to any one of 5 to 7, wherein a scanning interval in the rolling direction of the electron beam is equal to or less than an average crystal grain size of the steel sheet.

  According to the present invention, the grain-oriented electrical steel sheet can be processed using a uniform beam in the width direction, so that not only can the magnetic properties be uniform throughout the coil, but also when used as a transformer core. Since iron loss can be suppressed, the energy use efficiency of the transformer is improved, which is industrially useful.

It is the figure which showed the mode of the edge part of the deflection | deviation of the electron beam which passed through the convergence lens. It is the figure which showed the influence which the magnetic permeability dispersion | variation: (sigma) of the grain-oriented electrical steel sheet assembled in a transformer has on a building factor. It is a figure explaining having arranged the directional electromagnetic steel plate so that the beam path length from a convergence coil to a steel plate may become fixed. It is a figure which shows the result of having investigated the iron loss of the steel plate after the beam irradiation in the arrangement | sequence shown in FIG. It is the figure which showed the mode of deflection scanning of an electron beam. It is the figure which showed the relationship between shift amount: R and deflection angle variation | change_quantity: (eta). It is the figure which showed the point which irradiates an electron beam to a sample. It is the figure which showed the relationship between a return magnetic domain width change rate and a magnetic permeability change rate. It is the figure which showed the relationship between deflection angle variation | change_quantity: (eta) and magnetic variation: (sigma). It is the figure which showed the relationship between magnetic variation: (sigma) and building factor: BF.

Hereinafter, the present invention will be specifically described.
The present invention is intended to reduce iron loss and iron loss variation, and magnetostriction and magnetostriction variation in the entire width of the coil for the grain-oriented electrical steel sheet that performs electron beam irradiation.
Hereinafter, reasons for limiting various conditions according to the present invention will be described.

The width of closure domains d (mm): 0.8d in Samples entire width _{0 ≦ d ≦ 1.2d 0, 0.9d} 0 ≦ d ≦ 1.1d 0,
d ₀ (mm): Average value of the width of the reflux magnetic domain in the direction transverse to the rolling direction of the steel sheet When a directional electromagnetic steel sheet is irradiated with a laser or an electron beam, a magnetic domain different from the main magnetic domain (hereinafter referred to as the reflux magnetic domain) is formed. Is done. The reflux magnetic domain occurs along the scanning line of the laser / electron beam, and the width spreading in the direction perpendicular to this is d (mm). When the beam properties subjected to deflection scanning are not uniform, particularly when the beam diameter changes, the incident energy density to the steel plate changes, and therefore d is not uniform in the width direction.
First, the inventors examined the influence of the reflux domain width on the magnetic permeability. As shown in FIG. 7, the beam position at which the electron beam reaches the steel sheet in the state where the directional electromagnetic steel sheet of RD: 320 mm and TD: 30 mm is not deflected in the width direction center of the deflection scan and in the rolling direction and the width direction. The shortest distance f with respect to (P in the figure) was changed, and an electron beam was irradiated parallel to the width direction with a line interval of 5 mm, and the magnetic characteristics after irradiation were examined. Here, the samples before irradiation were all selected to have the same magnetism (B ₈ , W _17/50 , μ _17/50 ). FIG. 8 shows a reflux effect on the magnetic permeability change rate (the change rate of the magnetic permeability of the sample installed by changing f so that f ≠ 0 with respect to the magnetic permeability of the sample installed so that f = 0). Percentage change in magnetic domain width (return of sample center in the sample width direction of the sample installed by changing f so that f ≠ 0 with respect to the reflux domain width of the sample center in the sample width direction of the sample installed so that f = 0 This shows the influence of the change rate of the magnetic domain width.
From this, it can be seen that if the rate of change of the reflux magnetic domain width is 20% or less, the rate of change of magnetic permeability can be reduced to 10% or less, and if the rate of change is 10% or less, the rate of change of magnetic permeability can be extremely small to 5% or less. It was. Thus, closure domain width: d (mm) is be a 0.8d ₀ ≦ d ≦ 1.2d ₀ at sample full width, a essential, it is preferable to 0.9d ₀ ≦ d ≦ 1.1d ₀ .
The average value of the reflux magnetic domain width in the direction transverse to the rolling direction of the steel sheet: d ₀ is the average value of the reflux magnetic domain width in the E2 to S2 directions in the example of irradiation with the point Q in FIG. It becomes. Then, a reflux magnetic domain width d at the respective position in the E2~S2 direction, it is important to the above range with respect to the d _0. In addition, since the reflux magnetic domain may be difficult to observe depending on the crystal orientation, it is preferable to measure d at a place where the Goss orientation divergence angle β is about 2 or 3 °.

Length of one continuous reflux domain: X ≧ 200mm:
X substantially coincides with the scanning length of the electron beam on the steel plate. When the scanning length is small, the deflection angle is small and the change in the beam property is small, so the effect of the present invention is small, and in the range of 200 mm or more where the effect was recognized in the examples described later, It shall be given continuously.

1.05Z ≧ Σ (i = 1 to n) Yi × cos θ ≧ Z
Yi (i = 1 to n) (mm): length of one reflux domain in the i-th reflux domain group, Z (mm): sample (steel plate coil) width, θ (deg.): The reflux domain The inclination of the direction transverse to the rolling direction and the direction perpendicular to the rolling direction,
The above relational expression is a limitation on the relationship between the total length of the reflux magnetic domains and the sample width. When the total length of the reflux magnetic domain width is smaller than the sample width, it means that there is a region where the magnetic domain subdivision is insufficient in the width direction of the steel sheet, which causes a magnetic variation in the width direction. . On the other hand, if it is excessively large, it means that an overlapping area appears, but since the overlapping area is introduced with excessive distortion and slightly different in magnetism from the other parts, the overlapping area should be smaller. More specifically, it should be within 5%. Therefore, it is preferable that the relational expression 1.05Z ≧ Σ (i = 1 to n) Yi × cos θ ≧ Z is satisfied. Hereinafter, it is assumed that b = Σ (i = 1 to n) Yi × cos θ.

η ≦ 8 (deg.)
The smaller the deflection angle difference, the more uniform the beam in the width direction. Specifically, the uniformity of the beam is remarkably improved when it is 8 deg. Or less based on an example described later.
As described above, η is expressed by the following equation.
^{η = Cos -1 (w / (} w 2 + R 2 + L 2/4) 0.5) - Cos -1 (w / (w 2 + R 2) 0.5)
Further, as shown in FIG. 6, it has been confirmed that the amount of change in the deflection angle is smaller as R is increased.
Accordingly, the inventors shift from the beam position (point indicated by P in FIG. 5) where the electron beam reaches the steel plate in a state where the deflection scanning center position on the steel plate is not deflected in either the rolling direction or the width direction. That is, it was concluded that satisfying R ≠ 0 is important as the beam irradiation position. Therefore, in the present invention, it is important that the reflux magnetic domain region is formed at a position that does not overlap the position irradiated with the electron beam without being deflected.

The electron beam generation conditions are as follows:
Acceleration voltage (Va): 40-300kV
Under the same acceleration voltage, as the beam speed increases, the appropriate output increases, causing an increase in the beam diameter that is undesirable for lowering iron loss. Most effective. Here, if Va is less than 40 kV, it is difficult to reduce the beam diameter and the effect of reducing iron loss is reduced. On the other hand, if Va is more than 300 kV, not only the life of the device such as a filament is shortened, In order to prevent X-ray leakage, the apparatus becomes excessively large, and maintenance and productivity are reduced.
Furthermore, the higher the accelerating voltage is, the more the material can permeate and the local energy concentration in the film can be suppressed. Therefore, in order to effectively suppress the damage to the film, the more preferable range is 60 to 200 kV. .

RD line spacing: 4-30mm
The electron beam is radiated from the width end of the steel plate to the other width end in a straight line or a point sequence, and this is periodically repeated in the rolling direction. The repetition interval (RD line interval, also simply referred to as a line interval in the present invention) is preferably 4 to 30 mm. If the line spacing is narrow, the strain area formed in the steel becomes excessively large, and not only the iron loss (hysteresis loss) but also the magnetostriction deteriorates, and the processing time increases, so the productivity decreases. . On the other hand, if the line spacing is too wide, no matter how much the reflux magnetic domain is expanded in the depth direction, the magnetic domain refinement effect is poor and iron loss is not improved.

  In addition, since the magnetic domains in a single crystal grain are well subdivided when a reflux magnetic domain exists in the crystal grain, the RD line interval is desirably smaller than the average grain size in the rolling direction of the material. I want to see that. The average grain size D (μm) in the rolling direction is defined as D = Σ (i = 1 to N) Si × Di, where Di is the maximum length in the rolling direction of the i-th crystal grain and Si is the area ratio. To do. When the RD line interval is larger than D, not only the iron loss is not sufficiently reduced, but also the absolute amount of the return magnetic domain, which is advantageous for reducing the transformer iron loss, is reduced, so that BF is relatively large.

Line angle: 60 ° to 120 °
In the present invention, the irradiation direction from the start point to the end point has no problem in the irradiation from the width end to the other width end of the steel plate, as long as it crosses the rolling direction. The direction is preferably from 60 ° to 120 °. 90 ° is desirable. This is because when the angle is greatly deviated from 90 °, the volume of the strain introduction portion is excessively increased, so that the hysteresis loss is deteriorated.

Processing chamber pressure: 3 Pa or less When the processing chamber pressure is higher than 3 Pa, electrons generated from the electron gun are scattered and the energy of the electrons for forming the return magnetic domain in the ground iron is reduced. Therefore, the processing chamber pressure is preferably 3 Pa or less. The lower limit value of the processing chamber pressure is not particularly limited, but is about 0.02 Pa considering the excessive burden on the equipment.

Electron beam irradiation pattern:
The electron beam scans the electron beam to give a strain distributed in a straight line or a point sequence to the steel sheet to be passed. At this time, the average scanning speed of the electron beam for introducing strain is preferably 30 m / s or more. If the scanning speed is less than 30 m / s, high productivity cannot be achieved. More preferably, it is 60 m / s or more.

  In addition, in this invention, conventionally well-known electron beam irradiation methods and the manufacturing method of grain-oriented electrical steel sheet can be used suitably except the process and manufacturing conditions mentioned above.

Magnetic domain refinement processing was performed using a coil having a thickness of 0.23 mm, and then SST magnetic measurement was performed.
Samples for SST magnetism measurement were cut in a length of 320 mm × width: 100 mm in each condition, and a total of 70 samples were cut out in the width direction of the steel plate and 10 in the rolling direction.
The linear angle of the magnetic domain refinement treatment was 90 °, and the processing chamber pressure was 0.1 Pa. In addition, Test No. For only 14, the line spacing was larger than the average grain size.
Table 1 shows the electron beam irradiation conditions, SST magnetic measurement results, and BF.

The results shown in Table 1 are also shown in FIGS.
From FIG. 9, it can be seen that when η is 8 (deg.) Or less, variation in magnetic permeability is particularly reduced. FIG. 10 also shows that the BF is improved in the present embodiment as the variation in the magnetic permeability is smaller.

Claims (8)

In the grain-oriented electrical steel sheet having a reflux domain region formed with respect to the direction crossing the rolling direction and periodically formed with respect to the rolling direction,
The return magnetic domain region is continuous at a length of 200 mm or more, and the width of the return magnetic domain region: d (μm)
0.8d ₀ ≦ d ≦ 1.2d _0,
d ₀ (μm): A grain-oriented electrical steel sheet for a transformer core, which is an average value in the direction across the rolling direction of the width of the reflux magnetic domain region. The width of the reflux magnetic domain region: d (μm) is the average value of the width of the reflux magnetic domain region in the direction crossing the rolling direction: d ₀ (μm),
0.9d ₀ ≦ d ≦ 1.1d ₀ ,
The grain-oriented electrical steel sheet for transformer cores of Claim 1 which satisfies the relationship of these. In a grain-oriented electrical steel sheet in which n (≧ 1) number of reflux magnetic domain groups formed of a plurality of reflux magnetic domain regions periodically formed with respect to the rolling direction are present in the i-th reflux magnetic domain group, The length of one reflux magnetic domain region is Yi (i = 1 to n) (mm), the total coil width is Z (mm), and the tilt angle between the direction in which the reflux magnetic domain crosses the rolling direction and the direction perpendicular to the rolling is θ (deg. )
1.05Z ≧ Σ (i = 1 to n) Yi × cos θ ≧ Z
The grain-oriented electrical steel sheet for transformer cores of Claim 1 or 2 which satisfies the relationship of these.   The directional electrical steel sheet for a transformer core according to any one of claims 1 to 3, wherein a periodic interval in the rolling direction of the reflux magnetic domain region is equal to or less than an average crystal grain size of the steel sheet.   A method for producing a directional electrical steel sheet for a transformer core according to any one of claims 1 to 4, wherein the introduction of the reflux magnetic domain is such that the electron beam is always deflected in the rolling direction, and the width direction of the steel sheet. Method for producing a directional electrical steel sheet for transformer cores that is deflected and scanned. 6. The directionality for a transformer core according to claim 5, wherein in the deflection scanning of the electron beam, the deflection angle fluctuation amount η (deg.) Represented by the following formula (1) is 8 (deg.) Or less. A method for producing electrical steel sheets.
^{η = Cos -1 (w / (} w 2 + R 2 + L 2/4) 0.5) -Cos -1 (w / (w 2 + R 2) 0.5) ··· (1)
Where w (mm) is the distance between the center of the deflection coil and the steel plate, R (mm) is the shift amount, and L (mm) is the deflection amount.   The method for producing a grain-oriented electrical steel sheet for a transformer core according to claim 5 or 6, wherein an acceleration voltage of the electron gun of the electron beam is 40 kV or more and 300 kV or less. The method for producing a grain-oriented electrical steel sheet for a transformer core according to any one of claims 5 to 7, wherein a scanning interval in the rolling direction of the electron beam is equal to or less than an average crystal grain size of the steel sheet.

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