WO2015129253A1

WO2015129253A1 - Oriented electromagnetic steel sheet for low-noise transformer, and method for manufacturing said sheet

Info

Publication number: WO2015129253A1
Application number: PCT/JP2015/000931
Authority: WO
Inventors: 広朗戸田; 重宏 ▲高▼城; 龍一末廣; 小松原　道郎
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2014-02-28
Filing date: 2015-02-24
Publication date: 2015-09-03
Also published as: JP2015161017A

Abstract

　An oriented electromagnetic steel sheet processed using magnetic domain segmentation by the steel sheet surface being irradiated with an electron beam in a linear area having a direction intersecting with the rolling direction, wherein: the irradiation line area is made into repeating units made up of two types of areas comprising a retention area and a travel area; modulated-irradiation line areas are obtained by connecting the repeating units in the line-area direction; the period of the repeating units in the modulated-irradiation line area is 0.20-1.0 mm; the repeating interval of the modulated-irradiation line area in the rolling direction is 4.0-12.5 mm; and the intensity of the electron beam is brought to a level equal to or greater than that at which split magnetic domains are formed extending in the direction of the modulated-irradiation line area at least on the irradiation-surface side, and up to a level at which the coating is not damaged and no plastic strain areas are formed on the irradiation-surface side. It is thereby possible to carry out a hitherto challenging magnetic-domain segmentation process in a transformer in which iron loss and noise are both low, and obtain an oriented electromagnetic steel sheet that has unprecedentedly low iron loss and magnetic distortion.

Description

Directional electrical steel sheet for low noise transformer and method of manufacturing the same

The present invention relates to a grain-oriented electrical steel sheet for a low noise transformer and a method for manufacturing the same.
As a technique for subdividing the magnetic domains of grain-oriented electrical steel sheets, there is a technique in which the effect does not disappear even when strain relief annealing is performed, such as forming grooves on the steel sheet surface. On the other hand, the present invention is an electron known as one of techniques for subdividing magnetic domains and reducing iron loss by introducing strain into the steel sheet surface layer such as laser irradiation, plasma jet flame irradiation, and marking. It is a technique that uses a beam irradiation method, and is particularly intended to simultaneously achieve low iron loss and low magnetostriction.

In recent years, against the background of efficient use of energy, transformer manufacturers and the like have desired low-loss and low-noise transformers. For this reason, a grain-oriented electrical steel sheet with high magnetic flux density, low iron loss, and low magnetostriction is required. A grain-oriented electrical steel sheet has a tension coating that also serves to provide electrical insulation on its outermost surface, and the magnetic flux density can be improved by accumulating the crystal orientation of the steel sheet in the Goss orientation.
For example, Patent Document 1 discloses a method for manufacturing a grain-oriented electrical steel sheet having a magnetic flux density B ₈ exceeding 1.97T.

On the other hand, the iron loss can be improved by increasing the purity of the material, high orientation, reducing the plate thickness, adding Si, Al, and subdividing the magnetic domain (for example, Non-Patent Document 1).
However, generally, as the magnetic flux density B ₈ increases, the iron loss tends to deteriorate. For example, when the crystal orientation is highly integrated in the Goss orientation for the purpose of improving B ₈ , the magnetostatic energy decreases, the domain width increases, and the eddy current loss increases. Therefore, as a method of reducing such eddy current loss, a technique is used in which the above-described tension coating is applied, or a magnetic domain is subdivided by introducing thermal strain into the steel sheet surface layer to reduce iron loss. .

However, for example, in the method of improving the tension of the coating as shown in Patent Document 2, the strain to be applied is small and limited within the vicinity of the elastic region, and the tension effect only acts on the surface layer portion of the ground iron. The iron loss cannot be reduced sufficiently.

On the other hand, magnetic domain fragmentation by introduction of thermal strain is performed by plasma flame or laser irradiation.
For example, Patent Document 3 discloses that laser scanning irradiation is performed under certain conditions to impart thermal strain to the steel sheet, and Patent Document 4 discloses a pulse Q-switched laser having a half width of 10 nsec or more and 1 μsec or less. A technology to reduce iron loss by subdividing magnetic domains by concentrating the light intensity of 1 × 10 ⁵ to 1 × 10 ⁸ W / cm ² and intermittently applying thermal strain to the steel sheet is disclosed. Has been.

These techniques introduce thermal strain on the surface of the steel sheet, so that the magnetic domains are subdivided to reduce eddy current loss, while hysteresis loss increases. In particular, in the case of pulse irradiation, for example, Patent Document 5 describes that a hardened region generated in a steel sheet surface layer by laser irradiation or the like, that is, a plastic strain region obstructs domain wall movement and increases hysteresis loss. In this case, the strain concentrates locally on a part of the surface layer of the steel sheet, and the effect of reducing iron loss is not sufficient, and the effect of reducing iron loss is insufficient due to the increase in hysteresis loss due to strain. There was also a disadvantage that magnetostriction due to strain increased.

With respect to such a problem, in Patent Document 5, the laser output and the spot diameter ratio are adjusted, the plastic strain region cured by laser irradiation in the direction perpendicular to the laser scanning direction is reduced to 0.6 mm or less, and the hysteresis loss is reduced. By reducing this, iron loss is reduced. However, even in these techniques, the plastic strain on the surface of the steel sheet causes an increase in magnetostriction, and as a result, the noise of the transformer increases.

Further, in the case of the technique of irradiating the electron beam shown in Patent Document 6 and Patent Document 7, since the irradiation is continuously performed in the plate width direction, the strain distribution in the steel plate width direction is relatively uniform. However, unlike the laser, the irradiated electrons penetrate deeply into the thickness direction of the steel sheet, so energy efficiency is good, but thermal distortion occurs due to heat generation inside the steel sheet, resulting in a problem that noise characteristics deteriorate. It was.

In order to solve this, in Patent Document 8, the current value of the electron beam to be irradiated, the traveling speed of the electron beam in the width direction of the steel plate, the irradiation pitch in the rolling direction, and the beam diameter of the electron beam are controlled within a certain range. Discloses a technology for obtaining a grain-oriented electrical steel sheet that is excellent in noise and iron loss by suppressing the occurrence of thermal distortion.

However, even with this technique, it cannot be said that it is sufficient to reduce the magnetostriction causing the noise of the transformer, and there is a demand for a grain-oriented electrical steel sheet having a smaller magnetostriction and a lower iron loss.

Japanese Patent No. 4123679 Japanese Patent Publication No. 2-8027 Japanese Patent Publication No.3-13293 JP-A-6-57333 Japanese Patent No. 4344264 U.S. Pat.No. 4,195,750 US Patent No. 4199733 JP-A-5-335128

Generally, when the magnetic domain of a grain-oriented electrical steel sheet is subdivided by laser light irradiation, the interaction between the laser light and the surface film is strong, which is accompanied by rapid thermal deformation of the steel sheet near the irradiated surface or rapid evaporation of the film. Due to the reaction force on the steel plate, a region with a higher dislocation density is formed on the steel plate near the irradiated portion. As a result, it has been shown that the hardness of the steel sheet increases, and at the same time, the steel sheet is deformed to increase the hysteresis loss (for example, Non-Patent Document 2).
In other words, forming a 90 ° magnetic domain in the steel sheet by forming a region with a higher dislocation density in the vicinity of the irradiated part of the steel sheet surface layer is the basic principle of magnetic domain subdivision by this technology. Accompanying the reduction is necessarily accompanied by an increase in hysteresis loss and an increase in magnetostriction. That is, as long as it is a technology for irradiating laser light utilizing thermal distortion as in the prior art, it is not possible to establish all of magnetic domain subdivision, low hysteresis loss, and low magnetostriction.

On the other hand, in the technique of irradiating an electron beam, since electrons penetrate into the steel sheet rather than the steel sheet surface, it is considered that the magnetic domain can be subdivided without using the plastic strain of the steel sheet surface layer. However, as described in Patent Document 8, thermal strain is generated in the steel sheet depending on the intensity of the electron beam, resulting in an increase in hysteresis loss and an increase in magnetostriction. Therefore, as shown in Patent Document 8, it is necessary to control the surface energy density α of the electron beam and the energy density β (energy density on the beam scanning line) of the irradiation part of the electron beam to a certain range. In the technology, the optimum condition of iron loss shown in FIG. 2 of Patent Document 8 and the optimum condition of low noise shown in FIG. 3 are greatly different, and neither of them can find an optimum condition. It was insufficient as a technique to improve.

The inventors considered that, in general, when an electron beam is irradiated onto a steel sheet, it is possible to find an optimum condition common to both iron loss and magnetostriction by adjusting the energy density of the irradiated portion.
That is, the beam irradiation linear density β disclosed in Patent Document 8 corresponds to this, and a magnetic domain subdividing effect can be obtained by increasing the value of β from a predetermined minimum value, and by reducing the value from the maximum value, a steel plate It was thought that the plastic strain of the surface layer could be reduced, and as a result, the increase in hysteresis loss and noise could be suppressed.
That is, an excellent iron loss is obtained in the region of β ≧ 10−α / 0.06 (J / cm ² ) in FIG. 2 of Patent Document 8, and β ≦ 11.25−α / 0.08 in FIG. This corresponds to low noise at J / cm ² ).

However, the interaction between the domain wall and strain, such as magnetostriction degradation due to suppression of domain subdivision and domain wall movement, is a local physical action in the vicinity of the domain wall, and this is the energy density of the entire steel plate surface as shown in Patent Document 8. It is inherently impossible to depend on α.
Therefore, as a result of diligent research seeking the essential physical action of the value of β, the occurrence of film damage due to thermal strain on the steel sheet surface is involved in magnetostriction degradation when the value of β is large. On the other hand, when the value of β is small, it has been found that the disappearance of the divided magnetic domains elongated in the irradiation line direction in the irradiation line region is the essence of the presence or absence of magnetic domain subdivision. In other words, the required electron beam irradiation energy intensity is such that the irradiation is performed at an intensity higher than the level at which the magnetic domains elongated and divided in the direction of the irradiation line exist in the electron beam irradiation line region, and the occurrence of thermal distortion on the steel sheet surface is suppressed. It has been clarified that it is an essential technique to suppress the occurrence of film damage on the irradiation side surface of the steel sheet and to perform irradiation at a strength level that does not form a plastic strain region.

Table 1 shows that the acceleration voltage Vk is 40 kV to 120 kV and the beam is radiated to the directional electrical steel sheet with a plate thickness of 0.23 mm, B ₈ of 1.943 T, and iron loss W _17/50 of 0.85 W / kg. Assuming that the current I is 0.5 to 8 mA, the beam diameter d is 0.015 to 0.040 cm, the scanning speed V is 900 to 5000 cm / s, and the irradiation interval L in the rolling direction is 0.5 cm, β = (Vk · I) / (V · d ) Is varied from 0.43 to 24.7 (J / cm ² ), and the coating damage on the steel sheet surface at this time, the presence or absence of the formation of split magnetic domains extending in the direction of the irradiation line, and the iron loss of the steel sheet The results of examining the hysteresis loss and magnetostriction λp-p are shown.

As shown in Table 1, as a good range of iron loss, hysteresis loss, and magnetostriction, the lower limit value of the energy density of the irradiated portion includes a divided magnetic domain elongated in the irradiation direction (Non-Patent Document 3). On the other hand, it is indicated that the upper limit value of the energy density is an upper limit value at which damage to the coating does not occur. Further, it can be seen from Table 1 that the conditions that minimize the iron loss (condition numbers 8 and 9) do not necessarily match the conditions that minimize the magnetostriction (condition numbers 5 and 6).

Therefore, intensive research was then conducted on an electron beam irradiation method capable of realizing the minimum value of iron loss and the minimum value of magnetostriction under the same irradiation conditions. As a result, when irradiating an electron beam to a line region in a direction intersecting with the rolling direction, the irradiation region is not continuous and uniform as in the conventional case, but two types of irradiation conditions, a stagnant region and a traveling region, are used. It is a new combination that the minimum value of iron loss and the minimum value of magnetostriction can be realized under the same irradiation conditions by combining and repeating this combination unit and connecting them to form an irradiation region (referred to as a modulated irradiation region). I found it.

The experiment that led to this is described below.
In plate thickness 0.23 mm, B ₈ is 1.943T, iron loss W _17/50 is oriented electrical steel sheet is 0.85 W / kg, the acceleration voltage Vk: 50 kV, beam current I: 8 mA, beam diameter d: 0.30 mm The scanning speed V was 25 m / sec, the irradiation line interval L in the rolling direction was changed to 2.5 to 30 mm, and the electron beam was irradiated. At that time, one of them was continuously irradiated under a constant irradiation condition (condition 1) to obtain a comparative example. On the other hand, as shown in FIG. 1, modulated irradiation is performed by repeatedly irradiating a total area of 0.50 mm of a beam residence area: 1 and a traveling area: 2 as a repeating unit: 3 (which is also a period of the repeating unit) in the width direction of the steel sheet. Irradiation was performed under irradiation conditions (condition 2) for forming a line region. At this time, the dwell time at the dwell point was 0.020 msec, and the running speed in the running region: 2 was adjusted so that the average scanning speed was 25 m / sec.
FIG. 2 shows the results of examining the relationship between the distance L in the rolling direction of the irradiated region and the iron loss and magnetostriction when the electron beam irradiation is performed under the above conditions 1 and 2.

As is clear from FIG. 2, when irradiated according to the method of the present invention (Condition 2), not only the ultimate values of iron loss and magnetostriction are excellent compared to the conventional continuous irradiation (Condition 1), It can be seen that the best values of both are obtained under irradiation conditions (interval in the rolling direction of the irradiation region: 4.0 to 12.5 mm).
This result means that using a grain-oriented electrical steel sheet that has been subjected to magnetic domain refinement treatment, a transformer with low iron loss and low noise can be obtained with the same material. It can be seen that this is an excellent technology with a large meaning.
The present invention has been completed after further research based on the above findings.

That is, the gist configuration of the present invention is as follows.
1. The surface of the steel sheet is irradiated with an electron beam in a line area in a direction intersecting the rolling direction, the irradiation line area is set as a modulated irradiation line area having two types of areas consisting of a stay area and a running area as repeating units, and In the grain-oriented electrical steel sheet subjected to magnetic domain subdivision by repeating the modulation irradiation region in the rolling direction with an interval,
A modulated irradiation region in which the repeating units are connected in the direction of the line region,
The period in the modulated irradiation region of the repeating unit is 0.20 to 1.0 mm,
The repetition interval in the rolling direction of the modulated irradiation region is set to 4.0 to 12.5 mm, and the intensity of the electron beam is at least equal to or more than the strength at which the elongated magnetic domains extending in the direction of the modulated irradiation region are formed on the irradiation surface side. A grain-oriented electrical steel sheet for a low-noise transformer that has a strength that prevents the occurrence of film damage and the formation of a plastic strain region on the irradiated surface side.

2. 2. The grain-oriented electrical steel sheet for a low noise transformer according to 1 above, wherein a period of the repeating unit in the modulated irradiation region is 0.25 to 0.80 mm, and a repetition interval in the rolling direction of the modulated irradiation region is 5.0 to 10 mm. .

3. The surface of the steel sheet is irradiated with an electron beam in a line area in a direction intersecting the rolling direction, the irradiation line area is set as a modulated irradiation line area having two types of areas consisting of a stay area and a running area as repeating units, and When producing a grain-oriented electrical steel sheet by applying a magnetic domain refinement process consisting of repeating the modulation irradiation region in the rolling direction with an interval,
A modulated irradiation region in which the repeating units are connected in the direction of the line region,
The period in the modulated irradiation region of the repeating unit is 0.20 to 1.0 mm,
The repetition interval in the rolling direction of the modulated irradiation region is set to 4.0 to 12.5 mm, and the intensity of the electron beam is at least equal to or more than the strength at which the elongated magnetic domains extending in the direction of the modulated irradiation region are formed on the irradiation surface side. And the manufacturing method of the grain-oriented electrical steel sheet for low noise transformers made into the intensity | strength which does not produce generation | occurrence | production of a film damage and the formation of a plastic strain area | region on the irradiation surface side.

4). 4. The grain-oriented electrical steel sheet for low noise transformers according to 3 above, wherein a period of the repeating unit in the modulated irradiation region is 0.25 to 0.80 mm, and a repetition interval in the rolling direction of the modulated irradiation region is 5.0 to 10 mm. Manufacturing method.

According to the present invention, it is possible to carry out magnetic domain subdivision processing under conditions that satisfy both the low iron loss and low noise of the transformer, which has been difficult in the past, and the direction of low magnetostriction with low iron loss that has not been achieved conventionally. Since the electromagnetic steel sheet can be obtained, the energy use efficiency in the transformer can be improved and the noise can be suppressed, which is extremely useful industrially.

It is a figure which shows the staying area | region and traveling area | region which make the modulated irradiation area | region which is the characteristics of this invention, and the repeating unit when irradiating an electron beam to a steel plate width direction. In the conventional magnetic domain subdivision technique (condition 1) for continuously irradiating an electron beam, and in the magnetic domain subdivision technique (condition 2) of the present invention for irradiating an electron beam by repeating a modulated irradiation region, rolling of the irradiation region is performed. It is a figure which shows the relationship between the _{space |} interval L of a direction, the magnetostriction ( _lambda) p-p of the _grain -oriented electrical steel sheet after a magnetic domain refinement process, and the iron loss _{W17 / 50} . It is a figure which shows the irradiation line area | region by the prior art which irradiates an electron beam continuously, when irradiating an electron beam to a steel plate width direction. It is a figure which shows the size and shape of the iron core of the transformer manufactured in the Example. It is a figure which shows the size and shape of the steel piece after the bevel cutting of the iron core of the transformer manufactured in the Example.

Hereinafter, the present invention will be specifically described.
[Irradiated material]
The irradiation object in the present invention is a grain-oriented electrical steel sheet. Usually, the grain-oriented electrical steel sheet is provided with an insulation coating such as a tension coating on the forsterite film on the ground iron. In the present invention, the forsterite film is provided between the ground iron and the insulation coating. There is no problem even if is not present.

[Types of radiation]
In the present invention, the magnetic domain refinement process is performed by scanning the surface of the grain-oriented electrical steel sheet with an electron beam in a direction intersecting with the rolling direction and at intervals in the rolling direction. The introduction means is limited to electron beam irradiation. Other than the electron beam, the interaction with the insulation coating existing on the surface of the steel plate is large, and the damage of the insulation coating and the plastic strain consisting of high dislocation density are introduced into the surface layer of the underlying iron, so the deterioration of hysteresis loss, That is, the iron loss is deteriorated and the best iron loss characteristic cannot be obtained.
On the other hand, when an electron beam is used, the interaction with the insulating coating is limited to a small size due to the dynamic action of the electron beam, and the interaction with the ground iron inside the steel plate is increased. Therefore, it is possible to impart the magnetic domain refinement effect without damage of the insulating coating, the forsterite film, or the introduction of plastic strain having a high dislocation density in the surface layer of the base iron immediately below the coating.

Further, the steel plate surface irradiated with the electron beam may be one side of the steel plate or both sides. Further, the direction intersecting the rolling direction is a direction perpendicular to the rolling direction, that is, a range of 75 ° to 105 ° when the sheet width direction of the steel sheet is 90 °. It is suitably exhibited.

[Modulated irradiation area]
An electron beam is scanned in a direction crossing the rolling direction to form an irradiation region of the electron beam, but this irradiation region is not continuous irradiation as shown in FIG. The two types of regions consisting of the stay region 1 and the travel region 2 as shown in FIG. 1 are used as repeating units, and the repeating units are connected in the direction of the irradiation region and repeated to form a modulated irradiation region. However, this is the most important technique of the present invention.
In the case of so-called continuous irradiation in which the irradiation of the electron beam irradiated in the intersecting direction is performed under a constant irradiation condition, as shown as condition 1 in FIG. The best magnetostriction characteristics could not be obtained, and as a result, the same transformer with low iron loss and low noise could not be obtained.

In order to satisfy the low iron loss and low noise at the same time with the same transformer by obtaining the best iron loss value and the best magnetostriction characteristics under the same irradiation conditions, it is not from continuous irradiation but from the staying area and the running area. It is important to use the two types of regions as repeating units, and to connect the repeating units in the direction of the irradiation line region as shown in FIG. In the figure, reference numeral 1 is a staying region, 2 is a traveling region, 3 is a repeating unit (spacing point interval), and d indicates a beam diameter.
Here, the period of the repeating unit in the modulated irradiation region needs to be 0.20 to 1.0 mm. If the period of this repeating unit is less than 0.20 mm, the magnetic domain width becomes too narrow and the iron loss and magnetostriction increase, and conversely if it is larger than 1.0 mm, the magnetic domain width becomes too wide, so that sufficient magnetic domain refinement effect is achieved. Cannot be obtained. Therefore, the period of the repeating unit is 0.20 to 1.0 mm. The range is preferably 0.25 to 0.80 mm. In addition, when the units of the repeating unit are not connected and are discrete, a sufficient magnetic domain subdivision effect cannot be obtained in the non-irradiated region. Therefore, it is also an essential requirement that the repeating units are connected. is there.

Further, the repetition interval in the rolling direction of the above-described modulated irradiation region needs to be 4.0 to 12.5 mm.
When the repetition interval in the rolling direction of the modulated irradiation region is less than 4.0 mm, the iron loss increases as shown in FIG. 2, and the magnetostriction also deteriorates. On the other hand, if it exceeds 12.5 mm, the iron loss increases and the magnetostriction also deteriorates, so the repeat interval in the rolling direction must be 4.0 to 12.5 mm. The range is preferably 5.0 to 10 mm.

In the present invention, the beam diameter d of the electron beam is not particularly limited. However, if the beam diameter d is too small, it is disadvantageous for the generation of the divided magnetic domain, while if too large, the divided magnetic domain is excessively generated. The diameter d is preferably about 0.05 to 0.5 mm.
In the present invention, the acceleration voltage of the electron beam is not particularly limited, but if the acceleration voltage is too small, the penetration of electrons into the steel plate is insufficient, while if too large, the electron gun or the power source Since the manufacturing cost of equipment and the like becomes large, the acceleration voltage is preferably about 30 to 300 kV.

[Energy density of radiation]
Next, with respect to the intensity of the electron beam, a divided magnetic domain extending elongated in the direction of the modulated irradiation line region is formed at least on the irradiation surface side rather than being determined by the value of the beam irradiation line density β disclosed in Patent Document 8. It is simpler and more practical to use a technique in which the intensity is set to the lower limit value and the intensity is set to the upper limit value so that no film damage occurs on the irradiated surface side.
Therefore, this technique is adopted in the present invention.

[Evaluation of transformer iron loss and noise]
The iron loss and noise of the transformer were evaluated using a three-phase tripod stacked iron core type transformer as shown in FIG. As shown in FIG. 4, the outer shape of the transformer is composed of a steel plate having a 500 mm square and a width of 100 mm. Cut the steel plate into the shape shown in Fig. 5 and stack it with a stacking thickness of 100mm, tighten it with a band, and then wind the secondary coil and primary coil around the legs of the steel plate and put it in a tank filled with insulating oil The measurement was carried out by connecting the measuring instrument.
The three phases are excited by using a primary coil with a 120 ° phase shift, and the cross-sectional area is obtained from the weight of the iron core generated from the induced voltage generated in the secondary coil. It was measured. The noise was expressed in dBA units where vibrations generated around the transformer were recorded with a microphone and A scale correction was performed. The iron loss was expressed as a loss per weight of the transformer by subtracting the copper loss from the voltage and current value on the primary coil side in the unloaded state with the secondary coil open.

Example 1
Has a forsterite film on the steel sheet surface, the sheet thickness was baked tension coating thereon: 0.23 mm, the magnetic flux density B _8: 1.942T, iron loss W _17/50: oriented electrical steel sheet 0.870W / kg 6 Each was divided and subjected to magnetic domain refinement treatment under the following conditions.
As magnetic domain subdivision means, electron beam irradiation with acceleration voltage: 60kV, beam current: 12mA, beam diameter: 0.30mm is used, and irradiation is performed continuously at a scanning speed of 40m / sec under constant irradiation conditions in the plate width direction. And one was irradiated with an interval in the rolling direction of 5.0 mm (Comparative Example A1) and the other was 7.5 mm (Comparative Example A2). In these comparative examples, a part where the coating partly peeled off was confirmed.

Next, the other two were irradiated with an electron beam under the same conditions as above, but the residence time was 0.010 msec, the residence point interval was 0.40 mm, and the residence unit and the running region were repeated units. And a modulated irradiation region was formed at an average scanning speed of 40 m / sec. At this time, one was irradiated with a repetition interval in the rolling direction of 5.0 mm (Invention Example A3), and the other was 7.5 mm (Invention Example A4). In these inventive examples, no damage to the coating was observed, and magnetic domains that were elongated and divided in the plate width direction were observed on the irradiated region by magnetic domain observation by the bitter method.

The remaining two were subjected to discontinuous pulse irradiation in the plate width direction of the steel sheet using an Nd: YAG laser device equipped with a Q switch. The irradiation conditions at this time are conventionally known conditions, that is, the laser pulse energy is 3.3 mJ / pulse, the laser spot size is a circle with a diameter of 0.18 mm, the irradiation interval in the plate width direction is 0.3 mm, and the laser wavelength is 1064 nm. It was. One irradiation interval in the rolling direction was 5.0 mm (Comparative Example A5), and the other was 7.5 mm (Comparative Example A6). In these comparative examples, a clear circular coating defect and bare iron bareness were observed in the place where the laser beam was received, so the insulating coating was thinly reapplied and baked at a low temperature to improve insulation. .

These six types of grain-oriented grain-oriented electrical steel sheets are partly used for measuring iron loss and magnetostriction, and the remaining steel sheets are used to manufacture transformers by the method described above. Noise was measured. The results are shown in Table 2.

As shown in Table 2, the grain-oriented electrical steel sheet subjected to magnetic domain subdivision according to the present invention is superior in iron loss characteristics and magnetostriction characteristics and also in transformer iron loss and noise characteristics as compared with the comparative example. ing. Furthermore, it should be noted that when the irradiation interval in the rolling direction is set to 7.5 mm, unlike the comparative example, both the iron loss and the noise show the best values, and it is excellent as a grain-oriented electrical steel sheet for a transformer. It turns out that it has an effect.

(Example 2)
Has a forsterite film on the steel sheet surface, the sheet thickness was baked tension coating thereon: 0.27 mm, the magnetic flux density B _8: 1.949T, iron loss W _17/50: oriented electrical steel sheet 0.903W / kg 6 Each was divided and subjected to magnetic domain refinement treatment under the following conditions.
As magnetic domain subdivision means, electron beam irradiation with acceleration voltage: 50kV, beam current: 12mA, beam diameter: 0.20mm is used, and irradiation is continuously performed at a scanning speed of 30m / sec under constant irradiation conditions in the plate width direction. And one was irradiated with an interval in the rolling direction of 5.0 mm (Comparative Example B1) and the other was 7.5 mm (Comparative Example B2). In these comparative examples, a part where the coating partly peeled off was confirmed.

Next, the other two were irradiated with an electron beam under the same conditions as above, but the residence time: 0.010 msec and the residence point interval: 0.30 mm was used as the repeat unit for the residence region and travel region, and the repeat unit in the plate width direction. And a modulated irradiation region was formed at an average scanning speed of 30 m / sec. At this time, one was irradiated with a repetition interval in the rolling direction of 5.0 mm (Invention Example B3), and the other was 7.5 mm (Invention Example B4). In these inventive examples, no damage to the coating was observed, and magnetic domains that were elongated and divided in the plate width direction were observed on the irradiated region by magnetic domain observation by the bitter method.

The remaining two were subjected to discontinuous pulse irradiation in the plate width direction of the steel sheet using an Nd: YAG laser device equipped with a Q switch. The irradiation conditions at this time are conventionally known conditions, that is, the laser pulse energy is 4.5 mJ / pulse, the laser spot size is a circle with a diameter of 0.22 mm, the irradiation interval in the plate width direction is 0.3 mm, and the laser wavelength is 1064 nm. It was. One irradiation interval in the rolling direction was 5.0 mm (Comparative Example B5), and the other was 7.5 mm (Comparative Example B6). In these comparative examples, a clear circular coating defect and bare iron bareness were observed in the place where the laser beam was received, so the insulation coating was thinly reapplied and baked at a low temperature to improve insulation. It was.

These six types of grain-oriented grain-oriented electrical steel sheets are partly used for measuring iron loss and magnetostriction, and the remaining steel sheets are used to manufacture transformers by the method described above. Noise was measured. The results are shown in Table 3.

As shown in Table 3, the grain-oriented electrical steel sheet subjected to magnetic domain subdivision according to the present invention is superior in iron loss characteristics and magnetostriction characteristics as compared with the comparative example, and also excellent in iron loss and noise characteristics of the transformer. ing. Furthermore, it should be noted that when the irradiation interval in the rolling direction is 7.5 mm, unlike the comparative example, both the iron loss and the noise show the best values, which is excellent as a grain-oriented electrical steel sheet for a transformer. It turns out that it has an effect.

1 Residence area 2 Traveling area 3 Repeating unit (interval between residence points)

Claims

The surface of the steel sheet is irradiated with an electron beam in a line area in a direction intersecting the rolling direction, the irradiation line area is set as a modulated irradiation line area having two types of areas consisting of a stay area and a running area as repeating units, and In the grain-oriented electrical steel sheet subjected to magnetic domain subdivision by repeating the modulation irradiation region in the rolling direction with an interval,
A modulated irradiation region in which the repeating units are connected in the direction of the line region,
The period in the modulated irradiation region of the repeating unit is 0.20 to 1.0 mm,
The repetition interval in the rolling direction of the modulated irradiation region is set to 4.0 to 12.5 mm, and the intensity of the electron beam is at least equal to or more than the strength at which the elongated magnetic domains extending in the direction of the modulated irradiation region are formed on the irradiation surface side. A grain-oriented electrical steel sheet for a low-noise transformer that has a strength that prevents the occurrence of film damage and the formation of a plastic strain region on the irradiated surface side.
The directional electromagnetic wave for a low noise transformer according to claim 1, wherein a period in the modulated irradiation region of the repeating unit is 0.25 to 0.80 mm, and a repetition interval in the rolling direction of the modulated irradiation region is 5.0 to 10 mm. steel sheet.
The surface of the steel sheet is irradiated with an electron beam in a line area in a direction intersecting the rolling direction, the irradiation line area is set as a modulated irradiation line area having two types of areas consisting of a stay area and a running area as repeating units, and When producing a grain-oriented electrical steel sheet by applying a magnetic domain refinement process consisting of repeating the modulation irradiation region in the rolling direction with an interval,
A modulated irradiation region in which the repeating units are connected in the direction of the line region,
The period in the modulated irradiation region of the repeating unit is 0.20 to 1.0 mm,
The repetition interval in the rolling direction of the modulated irradiation region is set to 4.0 to 12.5 mm, and the intensity of the electron beam is at least equal to or more than the strength at which the elongated magnetic domains extending in the direction of the modulated irradiation region are formed on the irradiation surface side. And the manufacturing method of the grain-oriented electrical steel sheet for low noise transformers made into the intensity | strength which does not produce generation | occurrence | production of a film damage and the formation of a plastic strain area | region on the irradiation surface side.
4. A directional electromagnetic wave for a low noise transformer according to claim 3, wherein a period of the repeating unit in the modulated irradiation region is 0.25 to 0.80 mm, and a repetition interval in the rolling direction of the modulated irradiation region is 5.0 to 10 mm. A method of manufacturing a steel sheet.