JP2000336430A - Magnetic domain control method for grain-oriented electrical steel sheets - Google Patents

Abstract

(57) [Problem] To provide a grain-oriented electrical steel sheet whose magnetic properties are improved by irradiating a laser beam with a simple irradiator, capable of high-speed processing, and capable of flexibly responding to a change in sheet passing speed. Provided is a magnetic domain control method for an electrical steel sheet. SOLUTION: In a method of manufacturing a grain-oriented electrical steel sheet for improving magnetic properties by irradiating a laser, a plurality of pulse laser devices are arranged over the entire length in the width direction of the sheet, and a laser beam from each pulse laser is emitted in the width direction of the plate. Focusing on long linear beams, the linear directions of these linear beams are almost perpendicular to the passing direction, and each pulsed laser is irradiated at the same frequency in synchronization with the passing speed of the steel sheet. This is a method for controlling the magnetic domain of a grain-oriented electrical steel sheet. The pulse frequency of the pulsed laser is F, the passing speed of the steel sheet is V, and the irradiation interval a of the linear beam in the passing direction is F = V / a. A magnetic domain control method for grain-oriented electrical steel sheets in which the laser pulse frequency is synchronized with the sheet passing speed such that

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet whose magnetic properties are improved by laser beam irradiation.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is an electrical steel sheet in which the direction of easy magnetization is aligned with the rolling direction, and the domain wall is formed parallel to the rolling direction. The smaller the magnetic domain width, which is the domain wall interval, the lower the iron loss. Therefore, various magnetic domain control techniques for subdividing magnetic domains have been proposed and put into practical use. Above all, JP
As disclosed in Japanese Patent Application Laid-Open No. 55-18566, a method in which a pulse laser or a continuous wave laser beam is condensed and irradiated on the surface of a steel sheet to introduce local distortion and subdivide magnetic domains based on the distortion. Is a magnetic domain control method for grain-oriented electrical steel sheets, which has a great effect of improving iron loss and has high reliability and controllability because of non-contact processing.

In the laser domain control process of the directional electromagnetic steel sheet, the rolling direction and the sheet passing direction coincide with each other, and the pattern of laser irradiation is periodically perpendicular to the sheet passing direction of the steel sheet as shown in FIG. It is a linear shape. In such an irradiation pattern that is periodic in the sheet passing direction, if the influence range of the magnetic domain refining effect of each linear distortion is larger than the irradiation line interval a, the magnetic domains are subdivided over the entire steel sheet, and iron loss is reduced. . In the case of pulse laser irradiation, as shown in FIG. 3, an effective linear irradiation pattern is formed by a set of continuous irradiation point sequences, and in the case of continuous wave laser, a continuous irradiation pattern is inevitably obtained. In both cases, a good iron loss reduction effect can be obtained by optimizing the irradiation conditions. Incidentally, an irradiation optical device as shown in FIG. 2 has been conventionally used for performing periodic linear irradiation. In this method, a laser beam output from a laser device 7 is time-divided into an A phase and a B phase by a beam splitting device 8, further scanned at high speed by a polygon mirror or a galvano mirror 10, respectively, and further collected by an fθ lens. The optical device has to be illuminated and applied to the grain-oriented electrical steel sheet 5, and the optical device is complicated. Furthermore, in order to keep the magnetic characteristics constant at a good value, it is necessary to keep the irradiation interval a constant. However, in the actual continuous manufacturing process, the sheet passing speed may fluctuate due to the influence of processes before and after laser irradiation. At that time a
In order to keep the constant, it is necessary to readjust the rotational speed and the scanning speed of each of the beam splitters and the scanning devices while maintaining mechanical synchronization. However, it has been difficult to control these mechanical operations at high speed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a grain-oriented electrical steel sheet whose magnetic properties are improved by irradiation with a laser beam. An object of the present invention is to provide a magnetic domain control method of a grain-oriented electrical steel sheet that can flexibly respond.

[0005]

According to the present invention, there is provided a method for manufacturing a grain-oriented electrical steel sheet for improving magnetic properties by irradiating a laser. The laser beam is focused on a linear beam that is long in the plate width direction and is substantially perpendicular to the plate passing direction, and is irradiated over the entire width in the plate width direction, and all pulse lasers are irradiated at the same frequency. This is a magnetic domain control method for grain-oriented electrical steel sheets.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. FIG. 1 is an explanatory diagram of an embodiment of the present invention. The laser irradiation apparatus 1 includes a pulse oscillation type multi-stage array type semiconductor laser and an integrated combination lens, and is illustrated in FIG. As shown in FIG. 4, the multi-stage array semiconductor laser 12 is obtained by stacking the array semiconductor lasers 13 in multiple stages.
A pulse laser having a peak power of about 100 W per stage is output. Therefore, for example, 800
A peak output of W is obtained. The semiconductor laser device is driven by a pulse modulation current, and has the same frequency as the modulation current,
A pulse laser beam having a pulse time width is obtained. The pulse time width is 5 to 200 when the pulse duty is 20% or less.
It is variable in the range of μs, and can oscillate at a frequency of about 1 kHz, depending on the power supply capacity.

Next, an optical system for converging and irradiating a laser beam will be described. The laser light from each array of the arrayed semiconductor lasers is first collimated by the micro-cylindrical lens array 14 in the light passing direction, and then focused by the light passing direction cylindrical lens 15. Next, the light is condensed or magnified by the cylindrical lens 16 in the plate width direction orthogonal thereto. As a result, a linear beam 6 having a minute width of about 0.1 mm in the sheet passing direction and about 10 mm in the sheet width direction is formed. Here, the lenses 14 to 16 are manufactured as an integrated lens by omitting the adjustment mechanism and the like. The irradiation device 1 composed of these semiconductor lasers 12 and lenses is very compact with a size per device of about 100 mm in depth, about 20 mm in the board width direction, and about 150 mm in the board direction, as shown in FIG.

Since the linear beam width from a single irradiator is 10 mm in the plate width direction, as shown in FIG. 1, 100 irradiators are divided into, for example, two phases and arranged in a 1000 mm width. A linear beam can be applied to the entire surface of the steel sheet. The two phases are divided here because the size of the apparatus is longer than the linear beam width and is about 20 mm, and is based on simple space restrictions. Depending on the case, it may be three-phase or single-phase.

Semiconductor lasers have the advantage that they are very small and do not require maintenance work such as alignment of the laser resonator. Further, the array semiconductor laser has a feature that although the light condensing property is inferior in the plate width direction in the coordinate setting of FIG. Therefore, it is optimal for forming a linear beam as the object of the present invention. Further, as described above, a compact integrated laser irradiating apparatus in which the condensing optical system is combined can be obtained. Therefore, it is an optimal laser device for use in the irradiation method of the present invention.

Next, a method for controlling the oscillation frequency and pulse time width of the pulse laser will be described with reference to FIG. In the present invention, the passing speed V is measured in real time by the passing speed detector 2 and is input to the pulse generator 3 with an arithmetic circuit. Here, the linear irradiation interval a in the passing direction is used as a set value,
A pulse signal having a frequency F that satisfies the following equation is generated.

F = V / a For example, at a running speed of 50 m / min and an irradiation interval of 6.5 mm, which are typical operating conditions, the laser pulse frequency is 128 H
z. This frequency control signal becomes a trigger signal for the laser power supply 4, and a laser driving pulse current having the same frequency as the frequency control signal and having the same time width as the desired laser pulse time width T is output. A laser pulse having substantially the same waveform is obtained. The linear laser beam 6 is emitted by this device at the interval a in the passing direction.
Further, the speed of the steel plate is measured in real time, and the control of the pulse oscillation based on the measured signal is all performed by an electric signal, so that a high-speed response is possible.

Next, the installation of the laser irradiation device will be described. FIG. 1, which is an embodiment of the present invention, illustrates a case where the size of the laser irradiation device in the plate width direction is longer than the length of a linear beam irradiated from a single laser device. Therefore, in order to irradiate a linear beam without interruption over the entire width of the plate, as shown in FIG. 1, the laser irradiation device is divided into two parts and is shifted by d in the passing direction. Here, d is set so as to be an integral multiple of a. As a result, even if the irradiation position is shifted by d, all the lasers are simultaneously pulse-oscillated, and as shown in FIG. Uniform linear irradiation is achieved. If the linear beam is not uniform in the width direction of the plate and has a sufficient magnetic domain refining effect even if it is interrupted, or if the linear beam length from each laser irradiation device is longer than the device size, The laser devices may be arranged on a straight line in the width direction.

In this embodiment, an example in which an array semiconductor laser is used has been described. However, any pulse laser capable of condensing linearly can be applied to the irradiation method of the present invention. For example, a pulsed YAG laser or a pulsed CO2 laser can be used.Particularly, in the case of a YAG laser, the laser light can be guided to the vicinity of the steel plate by using an optical fiber, and it can be focused linearly by a combination of cylindrical lenses. A simple irradiation device is possible.

[0014]

As described above, according to the present invention, a simple laser irradiation optical system can be used for a steel plate passed at a high speed without using a beam splitting device or a high-speed scanning device. There is an effect that uniform linear beam irradiation can be performed in a direction substantially perpendicular to the sheet passing direction and arranged at equal intervals in the sheet passing direction. Since the linear beam irradiation interval is controlled by pulse laser frequency control corresponding to the passing speed,
High speed and flexible response to variations in threading speed
Since a constant irradiation interval can always be maintained, there is an effect that stable and good magnetic characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional technique.

FIG. 3 is a laser irradiation pattern in laser domain control of a grain-oriented electrical steel sheet.

FIG. 4 is a schematic view of a laser irradiation apparatus using a multi-stage array semiconductor laser and an integrated lens.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser irradiation apparatus 2 ... Pulling speed detection apparatus 3 ... Pulse generator with arithmetic circuit 4 ... Semiconductor laser power supply 5 ... Oriented electromagnetic steel sheet 6 ... Linear condensed beam 7 ... Laser apparatus 8 ... Beam splitting apparatus 9 ... All Reflective bending mirror 10 Galvano mirror and driving device 11 fθ lens 12 Multi-stage array semiconductor laser 13 Array semiconductor laser 14 Micro-cylindrical lens 15 Cylindrical lens in passing direction 16 Cylindrical lens in width direction

Claims (2)

[Claims] In a method of manufacturing a grain-oriented electrical steel sheet for improving magnetic properties by irradiating a laser, a plurality of pulsed laser devices are arranged in a plate width direction, and a laser beam from each pulse laser is emitted in a plate width direction. A magnetic domain control of a grain-oriented electrical steel sheet, wherein the beam is focused on a linear beam that is long and substantially perpendicular to the sheet passing direction, and is irradiated over the entire width in the sheet width direction, and all pulse lasers are irradiated at the same frequency. Method. 2. The pulse frequency of a pulse laser is F, the passing speed of a steel plate is V, and the laser pulse frequency is such that F = V / a with respect to the irradiation interval a of the linear beam in the passing direction. 2. The method according to claim 1, wherein the magnetic domain control is synchronized with the passing speed.