JPH0790385A - Grain-oriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet remarkably improved in magnetic properties, as for a grain-oriented silicon steel sheet excellent in iron core properties and magnetostriction properties, by making the traces of a uniform continuous pattern in the width direction of the steel sheet by pulse CO2 laser beam irradiation in particular. CONSTITUTION:The surface of a grain-oriented silicon steel sheet 10 is irradiated with a pulse laser beam 1 in which the frequency of a Q switch CO2 laser is regulated to >=30kHz in such a manner that the traces of perfect continuous pattern irradiation are made over >=150mm at an interval of 3 to 10mm in the rolling direction and at an interval of 0.3 to 1.0mm in the width direction of the steel sheet. Thus, the grain-oriented silicon steel sheet in which the total width of the steel sheet is divided into plural regions and the traces by the laser irradiation in the region 1 are made under the conditions as mentioned above and excellent in magnetic properties can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet having excellent iron loss characteristics and magnetostriction characteristics, and in particular, a trace of a uniform continuous pattern is formed in the steel sheet width direction of pulsed CO ₂ laser beam irradiation, and its magnetic characteristics. Is related to grain-oriented electrical steel sheets that have been significantly improved.

[0002]

2. Description of the Related Art Conventionally, many means have been proposed as a grain-oriented electrical steel sheet having excellent magnetic properties by a laser beam and a method for producing the same, and among them, JP-A-55-1856.
The method of improving the iron loss value by laser beam irradiation disclosed in Japanese Patent Laid-Open No. 6 (hereinafter referred to as [1]) has a high degree of improvement effect and high reliability due to non-contact processing. Due to its good controllability, grain-oriented electrical steel sheets having excellent magnetic properties by this method are widely put into practical use. This method is intended to reduce the eddy current loss while suppressing the increase of the hysteresis loss by subdividing the magnetic domain of the grain-oriented electrical steel sheet by the reaction force of the thermal shock wave generated by irradiating the laser beam.

As shown in FIG. 5, the surface of a magnetic steel sheet is instantaneously irradiated with a pulsed laser beam substantially at right angles to the rolling direction to form a local laser irradiation mark on the steel sheet, whereby a grain-oriented magnetic steel sheet is produced. It is intended to improve the iron loss of. The irradiation conditions of the laser beam are the irradiation interval d (mm) of the laser beam in the steel plate width direction and the irradiation interval l of the rolling direction.
(Mm) and energy density P (J / cm ² ) are given by the following equation (1)
Irradiate to satisfy the relationship. 0.005 ≦ (d / l) P ² ≦ 1.0 ……………… (1) (d / l) P ² = Ua ……………… (2) This formula (1 ), The irradiation energy density Ua per unit area, which is the heat input range of laser irradiation, is conditioned. This irradiation energy density is defined as Ua by the equation (2).

Further, in this publication [1], as shown in FIG. 6, there is shown the relationship between the irradiation condition of the laser beam and the iron loss reduction value as the iron loss improvement rate. The horizontal axis of FIG. 6 represents the energy density P of the pulsed laser beam, the irradiation interval d, and the parameter (d / l) P ² corresponding to the irradiation energy density Ua per unit area from the irradiation width 1, and the vertical axis represents the iron loss. The decrease value ΔW is shown. It is clear from FIG. 6 that the iron loss decrease value changes greatly when the irradiation energy density Ua changes, and even in the publication [1], when the irradiation energy density Ua changes from 0.005 to 0.01, the iron loss decrease value is changed. There is a large change from 0.01 to 0.03. As described above, making the irradiation energy density uniform under the irradiation conditions of the laser beam is extremely important in the production of an electromagnetic steel sheet having excellent electromagnetic characteristics. In this publication [1], the irradiation energy density Ua of the laser beam is applied to the entire surface of the steel sheet. There is no disclosure of a method for uniform irradiation of light.

Further, Japanese Patent Laid-Open No. 58-19440 (hereinafter referred to as [2]) discloses a method of improving iron loss characteristics of an electromagnetic steel sheet, which discloses a scanning method as a laser beam irradiation method. In this method, since the size of the laser oscillator cannot be increased (higher frequency and higher output), it is necessary to perform multiple irradiation with multiple laser beams due to the limited scan width in order to ensure uniform irradiation. Says.
That is, as shown in FIG. 7, the publication [2] uses a plurality of laser beams and a plurality of irradiation optical systems to divide the entire width of the steel plate into a plurality of regions, and the whole width of the steel plate is corresponding to the traveling speed of the steel plate and the laser output. This is a method for obtaining an irradiation mark having a uniform size at a desired interval over the entire length and appropriately improving the iron loss characteristics.

FIG. 8 shows a typical pattern of irradiation marks irradiated by the optical system of FIG. Here, in the irradiation in such a plurality of regions, in order to prevent the non-irradiation region from being generated in the steel plate width direction, it is necessary to configure such that the end portions of the respective regions partially overlap each other. I don't get it. Considering the long-term stability of the scanning optical system, it is necessary to secure the overlap region Lp of about 5 to 10 mm. Therefore, when the scanning width is 100 mm, double irradiation is performed on 5 to 10% of the entire width direction of the steel sheet. Here, referring to FIG. 6, (d / l) P ²
A value of about 0.4 gives the optimum value of iron loss improvement, but it is shown that the iron loss improvement width deteriorates rapidly in a region higher than this. It greatly deteriorates the loss improvement range.

The above deterioration not only deteriorates the iron loss improvement width of the steel sheet as a whole, but when the steel sheet is cut out for use in the transformer iron core, the ratio of the double irradiation area may increase. Further, it is necessary to assemble a transformer in a situation where the iron loss value is bad, or it is necessary to cut out a steel plate to avoid the double irradiation area, and in that case, there is a large practical problem that the yield is greatly reduced.

The condition as the embodiment of the publication [2] is that when the finish annealed grain-oriented electrical steel sheet having a total width W = 1000 mm is traveling at a traveling speed V = 500 mm / sec, 10 units (N)
The laser irradiating unit is installed in the width direction, and the irradiating width w = 100 mm, the irradiating interval in the rolling direction is 1 = 5 mm, and the irradiating interval in the steel sheet width direction is d = 0.5 mm. the f _m by reciprocated at 71Hz, and by scanning a laser beam with a pulse oscillation of f _Q = 20 kHz. The irradiation energy per pulse at that time is E = 4 mJ.

However, under this condition, the peak power density which is P of the irradiation energy density (d / l) P ² is unknown,
Further, similar to the publication [1], there is a problem in uniform irradiation of the irradiation energy density per unit area on the steel plate surface. That is, the publication [2] discloses the traces on the surface of the steel sheet due to the irradiation of the laser beam. However, as shown in FIG. 8, the traces on the surface of the steel sheet become wavy or linear, and the trace pattern is formed at each irradiation boundary. A discontinuous portion, that is, an uneven portion of the irradiation energy density is generated. The technical limit to the need for multiple beams is that there is a limit to the oscillation frequency of the pulsed laser beam with respect to the processing speed of the steel sheet.

In order to correspond to the speed of the actual line, it is necessary to increase the scanning speed and the pulse repetition frequency, but in the publication [2], the steel sheet full width W = 1000 mm is 10
A single laser irradiation unit is installed in the width direction, and each has a width of w = 100 mm as an irradiation area. This is because the pulse oscillation with the oscillation frequency f _Q = 20 kHz of the laser oscillator is the limit in the current laser oscillator. For this reason, there is a continuous pumped Q-switched Nd-YAG laser as a high-frequency pulsed laser, but the limit of the oscillation frequency is specified in the publication of laser technology.

9 and 10 are published by Asakura Shoten, Masayuki Ikeda et al., "Laser Process Technology Handbook" (1992) P6.
10 is a graph showing the relationship between the repetition frequency of the Q-switched Nd-YAG laser of continuous pumping shown in FIG. 9, the peak output as the Q-switch oscillation characteristic, the average output, and the pulse width. The peak output of the Q-switched pulse of the continuous laser is 10 ³ to 10 ⁴ times the CW oscillation output level, and the pulse repetition frequency is possible up to around 50 kHz, but in the actual device it is continuous as shown in FIGS. 9 and 10. Excitation Q-switch Nd-Y
The pulse oscillation of the AG laser is limited by the required pulse energy and the peak output, and its oscillation frequency is 10-20kH.
z. When the repetition frequency is 2kHz or more, the pulse width increases and the peak value sharply decreases. For example, the oscillation frequency is 1
At 0 kHz, the pulse width is 170 ns and the peak value is 4 kW. Under this condition, the energy of each pulse is 0.6 mJ
Becomes

Here, in order to obtain the stable effect of improving the magnetic characteristics shown in the patent [1], l = 5 m
Irradiation energy density (d / l) P ² at m, d = 0.5 mm
When p is 0.4, the peak power p is ² J / cm ² .
If the focused diameter of the pulse laser is 0.4 mm, the required energy per pulse is 2.5 mJ, and the above value of 0.6 mJ is approximately one fourth of the required pulse energy. Also, when the condensing diameter is set to 0.6 mm, the required energy per pulse is 5.7 mJ, and the above value of 0.6 mJ is about one-ninth of the required energy, which is smaller than that of the laser irradiation. The effect of improving the characteristics cannot be obtained.

The capability of a general continuous pumped Q-switched Nd-YAG laser that can be put to practical use can be improved to that of FIG. 9 by about one digit, but the energy of a pulsed laser is still 10 kHz. It is 6.0 mJ / P. Thus, when a continuous wave pumped Q-switched Nd-YAG laser is used, even if the beam is focused to 400 μm, the upper limit of the pulse frequency is 20 kHz due to the limit of its oscillation capability, and it is practical considering the stability of continuous operation. The upper limit is 10kHz which is half of that.

As described above, in the conventional method, the pulse oscillation frequency is limited, and the value is as low as 10 kHz or less. Therefore, in order to secure a processing speed of about 500 mm / sec in practice, the pulse laser is uniform. The maximum irradiation width is 50 mm. Therefore, it was difficult to manufacture an electrical steel sheet having excellent magnetic properties by uniformly irradiating a wider width.

[0015]

Since the conventional electromagnetic steel sheet has a limited pulse oscillation frequency of the laser oscillator and its value is as low as 10 kHz or less, the maximum width capable of uniformly irradiating the laser beam is 50 mm, which is wide. There was a problem in the uniformity of magnetic properties in the electrical steel sheet. The object of the present invention is to solve the problems caused by the limit frequency of the conventional laser oscillator, to realize a laser irradiation method having a wide range of high reliability and high iron loss improvement characteristics, extremely excellent electrical steel sheet To provide.

[0016]

The present invention provides a product of an electromagnetic steel sheet having excellent magnetic properties, in which the frequency of a Q switch pulse oscillation laser is 30 on the surface of the grain-oriented electrical steel sheet.
Irradiation with a pulsed laser at a frequency of kHz or more makes a trace in the rolling direction l so that the irradiation energy density Ua becomes 0.3 to 0.4.
= 3 to 10 mm, and d = 0.3 to 1.
By irradiating a complete continuous pattern of 150 mm or more at intervals of 0 mm, the magnetic characteristics can be made uniform and improved.
Q-switched pulsed laser has a pulse half-width of 10 nsec
It has an initial spike of 1 μsec or less, and 10 more
It is a pulse Q-switched CO ₂ laser having a pulse tail of 0 nsec or more and 10 μsec or less. And the formula (3)
As described above, the peak power density E of the pulse peak portion determined by the peak value PP (W) of the pulse and the focused diameter DO at the irradiation point
Set d in the region of 1 × 10 ⁵ to 1 × 10 ⁸ w / cm ² . Ed = PP / DO ………………………………………… (3)

In this way, the conventional electromagnetic steel sheet has a maximum width of 50 mm at which uniform irradiation of the laser beam is possible due to the limit of the pulse oscillation frequency of the conventional laser oscillator.
Although there was a problem in the uniformity of magnetic properties in a wide electromagnetic steel sheet, this problem was solved by the present invention, and laser irradiation having a high reliability that is at least three times wider than the conventional one and a high iron loss improving property is provided. The method was realized, and an extremely excellent electrical steel sheet could be provided.

The present invention will be described in detail below. Figure 1
In the iron loss improving method for a grain-oriented electrical steel sheet using a pulsed CO ₂ laser that achieves the present invention, the configuration of a Q-switched pulse CO ₂ laser resonator, which is the main component of the present invention, and the output pulse of the electrical steel sheet The irradiation optical system of FIG. The laser discharge part 2 is a part that supplies energy to the laser gas, which is a CO ₂ laser medium, by continuous discharge excitation, and is cut off from the atmosphere by a total reflection mirror 3 and a telescope lens 4 that form a laser resonator. .

A Q-switching device composed of a rotary chopper 6 is installed between the output mirror 7 and the telescope lens 4 installed in the atmosphere. Rotating chopper 6
Has a slit for transmitting the laser beam at a constant interval, and the Q value, which is the figure of merit of the resonator, increases only when the slit comes on the laser optical axis, and thus Q switching is realized. Here, in the case of Q switching by the rotation chopper of the CO ₂ laser, since there is no theoretical upper limit of the average output due to the acousto-optic device, which is a problem in the YAG laser, it is possible to achieve a high average output and an average output of 1 kW or more. The output is obtained. This is a typical Q switch YA
The output value is 10 or more G lasers. Therefore, even if the pulse repetition frequency f _Q is increased, it is possible to secure the pulse energy value necessary for improving the magnetic characteristics.

The pulsed laser beam 1 extracted from the Q-switch CO ₂ laser resonator is reflected by the plane total reflection mirror 11 and scanned by the rotary scanner by the polygon mirror 8 in the plate width direction of the electromagnetic steel plate 10 to produce fθ condensing optics. After being collected by the parabolic mirror 9 that constitutes the system, the electromagnetic steel sheet 10 is irradiated.

FIGS. 3 and 4 show the difference in the pattern of traces on the surface of the steel sheet by the pulse laser irradiation of the present invention and the conventional method (Japanese Patent Laid-Open No. 55-18566). FIG. 3 (a) shows a pattern of traces on the surface of the steel sheet by irradiation with a pulse laser having an oscillation frequency of 30 kHz according to the present invention, and FIG. 3 (b) shows a surface of the steel sheet by irradiation with three-divided pulse laser by three conventional oscillators. It shows the pattern of traces in.
FIG. 4A shows a pattern of traces on the surface of the steel sheet when the pulse laser of the present invention having an oscillation frequency of 60 kHz is divided into two, and FIG. The pattern of traces on the steel plate surface is shown.

FIG. 2 shows a Q at a pulse repetition frequency of 30 kHz.
7 shows a pulse waveform of a Q-switch CO ₂ laser in the case of switch oscillation. The initial spike portion is a giant pulse oscillating portion peculiar to the Q-switch laser, and its half-width changes sequentially depending on the discharge excitation intensity, the laser resonator, and the pulse repetition frequency, but the range is 10 nsec or more and 1 μsec or less. Furthermore, this Q switch CO ₂
It is accompanied by a long tail after the initial spike of the laser pulsed beam. This is a part of the laser pulse that is oscillated by energy transfer mainly from the N ₂ excited molecule contained in the laser medium due to collision of the CO ₂ molecule with the laser upper level.

The maximum length of this tail portion is determined by the time constant of collision energy transfer and is about 10 μsec. This is a pulse tail specific to Q-switched CO ₂ lasers that YAG lasers do not. In Q switching using the rotary chopper, the pulse tail length can be controlled by appropriately changing the width of the transmission slit of the laser beam.

The maximum value of the pulse repetition frequency during Q-switch oscillation is the delay time until the Q-switch pulse oscillation occurs after the resonator Q value rises and the energy to the upper level of the laser while the resonator Q value is low. Is determined by the balance of the storage time, but when a general continuous wave CO ₂ laser is used for Q-switch oscillation, a frequency up to about 100 kHz can be realized. The method for irradiating the grain-oriented electrical steel sheet with the Q switch pulse CO ₂ laser beam as described above to produce an electrical steel sheet having excellent iron loss characteristics will be described in detail below.

According to the present invention, the Q-switched pulsed CO ₂ laser beam 1 having a high repetition frequency of 30 kHz or more is reflected by the plane total reflection mirror 11, and is scanned in the plate width direction of the electromagnetic steel plate 10 by the rotary scanner by the polygon mirror 8. After being focused by the parabolic mirror 9, the electromagnetic steel plate 10 is irradiated. The electromagnetic steel plate 10 having a width of W (mm) changes the traveling speed to V (mm / se).
The laser beam is emitted from the scanning device 8 while traveling in the arrow direction of the sheet passing direction RD in c). Time t (s
If the moving distance of the steel sheet between ec) is l (mm), the following equation (4) is obtained. t = 1 / V ………………………………………… (4)

During this time, the pulse oscillation frequency is changed to f _Q
Oscillate the laser at (Hz) and set the width W (mm) to the spot interval d
Scanning irradiation in (mm) gives the following formula (5). t = (W / d) / f _Q ……………………………… (5) And, if the number of revolutions M (rps) and the number of faces N of the polygon mirror 8 per second are: The following expression (6) is obtained. t = 1 / (M · N) ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
(Mm / sec), irradiation point interval d (mm), pulse oscillation frequency f
_Q (Hz), polygon mirror 8 revolutions per second M (rps)
And the number of faces N, and the moving distance of the steel plate 1 (mm), the following equation (7)
The relationship is established. l / V = W / (f _Q · d) = 1 / (M · N) ……………… (7)

Therefore, the parameters must be selected so as to satisfy the relation of this expression (7). In particular, when it is applied to an actual production line, it is necessary to increase the traveling speed V of the steel sheet. However, when the traveling speed V is increased, the traveling speed V is maintained while maintaining the laser irradiation effect such as the moving distance 1 and the spot distance d. Therefore, in order to process the full width W of the steel plate, it is necessary to increase the oscillation frequency f _Q of the pulse laser. The irradiation energy density Ua = (d / l) P ² is 0.3 to 0.4.
So that the spot spacing l in the steel plate moving direction is 5 to 7 m
m, spot spacing d in the laser scanning direction is 0.3 to 1.0 m
Set to m.

[0028]

【Example】

(Example 1) The traveling speed V of the steel sheet was 650 mm / sec, and the width was 1
A 50 mm electromagnetic steel sheet with a pulse repetition frequency of 30 kHz and a laser with a wavelength of 10.6 μm has a pulse half-width of 250 nsec at the initial spike portion and a pulse tail of 2 μsec, and the energy of a single pulse is 7.5 mJ of Q-switched CO ₂ laser pulse. It is focused to 0.4 mm, the peak power density Ed of the initial spike portion is set to 2 × 107 w / cm ² , and the irradiation energy density Ua = (d / l) P ^{2 is set} to 0.3 to 0.4. The steel plate was irradiated. The irradiation position conditions at this time were such that the spot distance d in the laser scanning direction was set to 0.5 mm and the spot distance 1 in the moving direction of the steel sheet was set to 6.5 mm.

For comparison, a pulse repetition frequency of 10
Laser irradiation was performed with a Q-switched Nd-YAG laser with a frequency of 1.06 μm at a frequency of 1.06 μm and dividing the range of the electromagnetic steel sheet in the irradiation width direction into three parts under the same other laser irradiation conditions. As a result, the material irradiated by the Q-switched CO ₂ laser, which uniformly radiated the entire steel plate width, suppressed an increase in magnetostriction to an extremely small value, and improved the total iron loss value (W _17/50 ) by 11%, and the three-divided irradiation Y
It was found that the iron loss improving effect of the material irradiated with the AG laser greatly exceeds the total iron loss value improving width of 8%. Here, the improvement of the iron loss improvement rate of 1% leads to a significant improvement in the efficiency of the transformer when used for a large-capacity transformer core, which is a very large practical effect.

(Embodiment 2) The traveling speed V of the steel sheet is 650 mm.
/ sec, the irradiation area of a magnetic steel sheet with a width of 300 mm is divided into two, and each irradiation area has a scanning width of about 150 mm, a laser with a pulse repetition frequency of 60 kHz and a wavelength of 10.6 μm,
The initial spike of the pulse half width 250 nsec, a pulse tail 2μsec energy of a single pulse of Q-switched CO ₂ laser pulses 7.5 mJ, and Atsumariko径0.4mm and condensed,
The peak power density Ed of the initial spike part is 2 × 10 ⁷ w /
Irradiation energy density Ua = (d / l) P ² is 0.3 at cm ^2.
The electromagnetic steel sheet was irradiated so as to be 0.4. The irradiation position conditions were set such that the spot interval d in the laser scanning direction was 0.5 mm and the spot interval l in the steel plate rolling direction was 6.5 mm.

As a result, it was found that the material irradiated by the Q-switched CO ₂ laser with which the entire steel plate width was uniformly irradiated can improve the total iron loss value (W _17/50 ) by 10% in a situation where the increase in magnetostriction is extremely small. did. Conventional pulse repetition frequency 10
With a Q-switched YAG laser with a frequency of 1.06 μm and a wavelength of 1.06 μm, it is necessary to irradiate at least 6 divisions to irradiate this electromagnetic steel sheet with a width of 300 mm. The iron loss improving effect and the economic effect of are also great, which is an extremely large effect in practical use.

The following are the results of trial calculation of specific effects relating to iron loss improvement. Since the total iron loss of the grain-oriented electrical steel sheet used in the examples of the present invention is about 0.84 w / kg, using the results of Example 1, the total iron loss value ΔW improved by the present invention is It becomes 0.025w / kg at 3%. The most common use of grain-oriented electrical steel sheets is in columnar transformers for power transmission, in which case 2.0 kg of electrical steel sheet is required per 1 kVA of electric energy. Therefore, in the columnar transformer according to the present invention, 1 kV
Energy saving of about 0.05W can be realized for A power.

At present, the electric power cost is about 20 yen / kWhr, and if the power factor is 0.8, it is 0.05 W / kW according to the present invention.
It is possible to reduce the power cost by 0.8kW × 20 yen / kWhr = 1.26 × 10 ⁻³ yen / kWhr. Since the total power consumption in Japan is 6000 to 700 billion kWh per year, the power cost reduced by applying the present invention is 1.
26 × 10 ⁻³ Yen / kWhr × 6000 to 700 billion kWhr / year = 7.6 to 880 million Yen / year.

[0034]

EFFECTS OF THE INVENTION By the laser irradiation effect using the Q-switch CO ₂ laser of the present invention, a pattern of uniform laser traces of 150 mm or more is made possible, resulting in an electromagnetic steel sheet having excellent magnetic properties. This magnetic steel sheet suppresses magnetic distortion, has a large effect of reducing iron loss and improving stable magnetic characteristics.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a pulse Q-switched CO ₂ laser oscillator and an irradiation optical system thereof that enables the present invention.

FIG. 2 is a chart of typical measurement results of an oscillation waveform of a pulse Q-switch CO ₂ laser.

3 (a) and 3 (b) show the present invention and a conventional method (JP-A-55).
Typical patterns of laser irradiation traces (Japanese Patent Publication No. -18566).

4A and 4B are typical patterns of laser irradiation traces of an example of irradiation of a plurality of regions of the present invention and a conventional method (Japanese Patent Laid-Open No. 55-18566).

FIG. 5 is a schematic diagram of a laser irradiation method according to a conventional method.

FIG. 6 is a table showing an example of reduction of iron loss value and its change by a conventional laser irradiation method.

FIG. 7 is a schematic view of a laser irradiation method using a plurality of laser beams and a plurality of irradiation optical systems according to a conventional method.

8 (a) and 8 (b) are typical patterns of laser irradiation traces on a magnetic steel sheet by the method of FIG.

FIG. 9 is a chart showing the relationship between the repetition frequency of a continuously pumped Q-switch Nd-YAG laser and the peak output and average output of the Q-switch oscillation characteristic.

FIG. 10 is a chart showing the relationship between the repetition frequency and pulse width of a continuously pumped Q-switched Nd-YAG laser.

[Explanation of symbols]

 1 Pulsed laser beam 2 Laser discharge part 3 Total reflection mirror 4 Telescope lens 5 Motor for rotary chopper 6 Rotation chopper 7 Output mirror 8 Polygon mirror 9 Parabolic mirror 10 Electromagnetic steel plate 11 Planar total reflection mirror

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takamichi Kobayashi 5-10-1 Fuchinobe, Sagamihara City Inside the Electronics Research Laboratory, Nippon Steel Co., Ltd. (72) Keisuke Yamochi No. 1 Tobata-cho, Tobata-ku, Kitakyushu Nippon Steel Co., Ltd., Yawata Works (72) Inventor Hirohiko Sato 1-1, Tobatacho, Tobata-ku, Kitakyushu City (72) Inventor, Toshitaka Ota Tobata Ota, Tobata-ku, Kitakyushu City No. 1 No. 1 Nippon Steel Yawata Works Co., Ltd.

Claims (3)

[Claims] 1. A Q switch CO on the surface of a grain-oriented electrical steel sheet.
₂ Magnetic characteristics characterized by having continuous pattern traces without overlapping for 150 mm or more at intervals of 3 to 10 mm in the rolling direction by irradiation with a laser beam and at intervals of 0.3 to 1.0 mm in the steel plate width direction Excellent grain-oriented electrical steel sheet. 2. The entire width of the steel sheet is divided into a plurality of regions,
A grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that traces of a region irradiated by laser irradiation satisfy the condition of claim 1. 3. The grain-oriented electrical steel sheet with excellent magnetic properties according to claim 1, wherein the Q-switched CO ₂ laser has a trace of laser irradiation applied by a pulse having a repetition frequency of 30 kHz or more.