JP2012035288A - Electron beam irradiation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method that enables electron beam irradiation to be surely detected in real time.SOLUTION: When an electron beam is applied to a traveling metal strip, an electron beam irradiation state is grasped by detecting an X-ray generated on a surface of the metal strip along with the electron beam irradiation.

Description

  The present invention relates to an electron beam irradiation method for continuously irradiating a metal strip such as a grain-oriented electrical steel sheet with an electron beam to improve the properties of the metal strip.

  The grain-oriented electrical steel sheet is mainly used as an iron core of a transformer and is required to have excellent magnetization characteristics, particularly low iron loss. For this purpose, it is important to highly align the secondary recrystallized grains in the steel sheet in the (110) [001] orientation (so-called Goth orientation) and to reduce impurities in the product steel sheet. However, controlling the crystal orientation and reducing impurities are limited in view of the manufacturing cost. Therefore, a technique for reducing the iron loss by introducing non-uniformity (strain) to the surface of the steel sheet by a physical method and subdividing the width of the magnetic domain has been developed, that is, a magnetic domain subdivision technique.

  For example, Patent Document 1 proposes a technique for narrowing the magnetic domain width and reducing iron loss by irradiating the final product plate with laser and introducing a high dislocation density region into the steel sheet surface layer. Patent Document 2 proposes a technique for controlling the magnetic domain width by electron beam irradiation. In this iron loss reducing method by electron beam irradiation, since the damage of the insulating coating on the surface of the magnetic steel sheet is extremely small, it is not necessary to form the insulating coating again after irradiation, which is advantageous for industrial production.

  However, since the electron beam is irradiated under vacuum, there is a problem that it is difficult to inspect whether the metal strip is normally irradiated in the vacuum chamber. Here, there is a method to detect that the steel plate surface is locally heated with a TV camera or an optical sensor, but the light emission generated on the steel plate surface depends on the thickness and properties of the coating on the steel plate surface. Have difficulty. In this respect, the method disclosed in Patent Document 3 is advantageous in that the surface of the steel sheet is covered with a film to check the irradiation trace.

Japanese Patent Publication No.57-2252 Japanese Examined Patent Publication No. 6-72266 JP-A-5-84583

  However, in the method disclosed in Patent Document 3, since it is difficult to detect the irradiation of the electron beam in real time, it has been desired to cope with the case where the irradiation position and intensity fluctuate during a long continuous operation.

  Therefore, an object of the present invention is to propose a method capable of reliably detecting electron beam irradiation in real time.

Inventors can inspect the irradiation state in real time by detecting X-rays generated by the electron beam hitting the metal strip rather than detecting the trace or light irradiated by the electron beam. And gained new knowledge.
That is, the gist configuration of the present invention is as follows.

(1) When irradiating an electron beam toward a traveling metal strip, the irradiation state of the electron beam is grasped by detecting X-rays generated on the surface of the metal strip as the electron beam is irradiated. An electron beam irradiation method characterized by the above.

(2) The method according to (1), wherein at least one of the generation position and intensity of X-rays generated on the surface of the metal strip is detected to determine whether the electron beam irradiation is normal. The electron beam irradiation method described.

  According to the present invention, even when the electron beam is irradiated in the vacuum chamber, the irradiation state of the electron beam can be grasped in real time. Therefore, it is possible to easily determine whether the electron beam is normally irradiated.

It is a figure which shows an electron beam irradiation apparatus. It is a figure which shows the detection point of the electron beam irradiation according to this invention. It is a figure which shows the example of detection of an electron beam. It is a figure which shows the detection point of another electron beam irradiation according to this invention. It is a figure which shows the scanning locus | trajectory of the X-ray detection apparatus according to this invention.

The method of the invention is advantageously adapted in an apparatus for continuously irradiating an electron beam onto a metal strip. For example, it is suitable when using the apparatus shown in FIG. That is, the apparatus shown in FIG.
A vacuum chamber 1 for introducing a metal strip S in atmospheric pressure is provided, and differential pressure chambers 2a and 2b are provided on the inlet side and the outlet side of the metal strip S of the vacuum chamber 1, respectively. The inside of the vacuum chamber 1 is held at a low pressure by interposing 2b. In the vacuum chamber 1, a plurality of, in the illustrated example, four electron guns 3a to 3d and a metal strip S are installed toward the transport path, and an electron beam can be irradiated from each electron gun 3a to 3d toward the metal strip S. I have to.

  Here, it is effective for preventing the scattering of the electron beam that the pressure in the vacuum chamber 1 for irradiating the electron beam is 10 Pa or less. On the other hand, the lower limit of the pressure is not particularly required, but is generally set to 0.01 Pa or more because of the capability of the vacuum pump and the differential pressure chamber. Although a method can be used in which the entire equipment including the coil is evacuated without using the differential pressure chamber, the differential pressure method shown in FIG. 1 is advantageous in that the size of the vacuum equipment can be reduced.

  For example, in order to perform magnetic domain subdivision processing on a directional electromagnetic steel sheet using this electron beam irradiation apparatus, a plurality of electron guns are used on the directional electromagnetic steel sheet (metal strip) as shown in FIG. Irradiate an electron beam. That is, in order to reduce the iron loss of the grain-oriented electrical steel sheet, an electron beam whose beam diameter at the irradiation position is converged to 0.05 to 1 mm is scanned in the width direction of the steel sheet (direction intersecting the rolling direction). Introduce thermal strain linearly. The output of the electron beam is 10 to 2000 W, the scanning speed is 1 to 100 m / s, and the output per unit length is adjusted to 1 to 50 J / m, and irradiation is performed linearly at intervals of 1 to 20 mm. Is preferred.

  It is important for safety to suppress leakage of X-rays to the outside of the vacuum chamber 1 during electron beam irradiation. For this purpose, a lead plate having X-ray absorption capability is provided on the inner side (or outer side) of the vacuum chamber 1 as a shield layer. It is usual to provide as 4.

  In such an electron beam irradiation apparatus, as shown in FIG. 2, an X-ray detection device, in the illustrated example, three X-ray detection devices 6 </ b> A to 6 </ b> C are arranged at a position that does not block the passage position of the electron beam 5. By performing the X-ray measurement, it is possible to monitor whether the metal strip S is normally irradiated with the electron beam. In this X-ray detection, for example, the inspection can be performed earlier and more simply than when the irradiation trace of the grain-oriented electrical steel sheet after the magnetic domain subdivision processing is confirmed.

  Specifically, by measuring the intensity of the X-ray, it can be confirmed whether or not the electron beam irradiation is performed at an output suitable for improving the characteristics of the metal strip. For example, as shown in FIG. 2, when the electron beam 5 is irradiated from the front side to the back side in the direction orthogonal to the rolling direction (feeding direction) of the strip S, the electrons are synchronized with the feeding speed of the strip S. Since it is necessary to scan the beam, the trajectory of the electron beam is a straight line having an angle with respect to the direction orthogonal to the strip passing direction (arrows indicated by bold broken lines in FIG. 2; hereinafter referred to as irradiation lines). . Accordingly, three X-ray detection devices 6A to 6C are arranged so that X-rays can be detected at the start point, the intermediate point, and the end point of the irradiation beam, respectively, and each detection device shows, for example, FIG. If such sequential outputs are obtained, irradiation is normally performed.

  Further, as shown in FIG. 4, as indicated by a two-dot chain line, the scanning of the X-ray detection device 6 is performed two-dimensionally with respect to the electron beam 5 irradiation region of the strip S (a scanning locus along the two-dot chain line in FIG. 4). (A scanning line 60 is shown) is added, a mechanism for adjusting the angle of the X-ray detector 6 is added, and the X-ray is sufficiently slow with respect to the scanning speed of the electron beam scanned at a high speed. If the detection position of the detection device is moved, the position irradiated with the electron beam 5 (electron beam trajectory 50) can be detected via the scanning line 60 of the X-ray detection device 6, as shown in FIG.

  Here, a scintillation detector, a gas detector, a semiconductor detector, and the like are used for the X-ray detection device, and the semiconductor detector is particularly preferable in terms of maintenance. By providing a pinhole or slit at the tip of the X-ray detection device so that only X-rays that reach the detection device linearly from the irradiation point can be detected, disturbance can be prevented and the detection position can be obtained accurately. .

  As described above, a plurality of detection devices can be arranged to monitor different irradiation points shown in FIG. 2, or the monitoring points can be changed one-dimensionally or two-dimensionally as shown in FIG. It is possible to confirm whether or not the electron beam is irradiated in a desired pattern.

  In addition, the position on which the electron beam is irradiated is detected two-dimensionally with a TV camera or CCD camera, and the light emission on the strip caused by the electron beam irradiation is measured, and only the irradiation intensity of the electron beam is measured with an X-ray detector. It is also possible to confirm the irradiation pattern and the beam intensity by a combination of the above.

Furthermore, it is also possible to use an X-ray CCD as an X-ray detection device to simultaneously check the irradiation pattern and beam intensity without mechanical scanning.
Each of the above aspects may be appropriately selected depending on the purpose and required detection accuracy.

  Using the apparatus shown in FIG. 1, the electromagnetic steel sheet (strip S) was irradiated with an electron beam continuously. The width of the electromagnetic steel sheet is 1 m, and four electron guns are installed in the strip transport direction, and one electron gun irradiates the range of 1/4 width in the width direction of the steel sheet, and after passing four electron guns Scanning was performed so that the entire width of the electromagnetic steel sheet was irradiated with an electron beam.

The electrical steel sheet is a grain oriented electrical steel sheet having a thickness of 0.23 mm containing 3.4 mass% Si.
The electron gun has an accelerating voltage of 150 kV, a beam diameter at the irradiation point of 0.2 mm, a beam current of 5 mA and a scanning speed of 20 m / s, linearly scanned in the width direction of the steel sheet, and this is the rolling direction. Were repeatedly irradiated at intervals of 6 mm.

  Further, as shown in FIG. 2, three X-ray detectors per electron gun can detect the positions corresponding to the start point, the intermediate point, and the end point of the electron beam scanning through the pinhole. A detector was provided that could measure the intensity of the line with a scintillation detector. The pinhole has a diameter of 1 mm so that only X-rays from an X-ray generation source coaxial with the detector can be detected.

  Here, in the past, whether or not the electron beam was normally irradiated was inspected by investigating the steel plate after irradiation, but when the film was not irradiated with an electron beam, the magnetic domain pattern of the steel plate was observed. Because it was necessary to investigate by doing so, it took a lot of time, and many were limited to partial inspection.

  On the other hand, according to the method of the present invention, as shown in FIG. 3, it is possible to monitor in real time whether the irradiation position and intensity of the electron beam on the steel sheet are set as set. In addition, the relationship between the irradiation conditions such as the beam current and the acceleration voltage measured in advance and the X-rays generated thereby is obtained, and by comparing with the relationship, the output of the electron beam is in the normal range. It has become possible to manage these with high accuracy.

  The electron beam irradiation method of the present invention, in addition to magnetic domain subdivision treatment for the above-mentioned grain-oriented electrical steel sheet, surface processing such as removal of irregularities, matte processing, muscle processing, welding, surface quenching, alloying, amorphization, It is suitable for processing such as marking.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2a, 2b Differential pressure chamber 3a-3d Electron gun 4 Shield layer 5 Electron beam 6, 6A-6C X-ray detection apparatus S Metal strip

Claims (2)

  When irradiating an electron beam toward a traveling metal strip, the irradiation state of the electron beam is grasped by detecting X-rays generated on the surface of the metal strip as the electron beam is irradiated. An electron beam irradiation method. 2. The electron beam according to claim 1, wherein at least one of the generation position and intensity of X-rays generated on the surface of the metal strip is detected to determine whether the irradiation of the electron beam is normal. Irradiation method.

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