JP6471682B2 - Electron beam irradiation device - Google Patents

Description

  The present invention relates to an electron beam irradiation apparatus used for continuously irradiating a metal strip with an electron beam to improve the properties of the metal strip. In particular, the present invention relates to an electron beam irradiation apparatus suitable for improving iron loss by irradiating the surface of a grain-oriented electrical steel sheet with an electron beam to subdivide the magnetic domain.

  A grain-oriented electrical steel sheet, which is a typical example of a metal strip, is mainly used as an iron core of a transformer, and is required to have excellent magnetization characteristics, particularly low iron loss. For that purpose, it is important to highly align the secondary recrystallized grains in the steel plate in the (110) [001] orientation (so-called Goth orientation) and to reduce impurities in the product steel plate. However, controlling the crystal orientation and reducing impurities are limited in view of the manufacturing cost. In view of this, 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.

  For example, Patent Document 1 proposes a technique for reducing the iron loss of a steel sheet by irradiating the final product plate with a laser, introducing a linear high dislocation density region into the steel sheet surface layer, and narrowing the magnetic domain width. ing. Patent Document 2 proposes a technique for reducing the iron loss of a steel sheet by narrowing the magnetic domain width by irradiating an electron beam. In this method of reducing iron loss by electron beam irradiation, scanning of the electron beam can be performed at high speed by magnetic field control. Therefore, since there is no mechanical moving part as found in an optical scanning mechanism of a laser, it is advantageous when a beam is irradiated at a continuous and high speed particularly for a strip having a width of 1 m or more. .

  Here, since X-rays are generated when the metal strip is irradiated with an electron beam, it is necessary to provide a shield layer that absorbs X-rays such as lead along the wall surface of the vacuum chamber into which the metal strip is introduced. 3 is disclosed.

Japanese Patent Publication No.57-2252 Japanese Examined Patent Publication No. 6-72266 JP-A-6-109900

  As described above, when a shield layer is provided, a large amount of X-rays generated in the central part of the vacuum chamber where the electron beam is irradiated can be sufficiently shielded only by the shield layer on the vacuum chamber wall surface. When irradiating an electron beam to a long strip like this, an opening for carrying in and out a steel plate (steel strip) is always required in the vacuum chamber, so leakage of X-rays from the opening is a problem. Become. In addition, the shield layer needs to be thickly spread with heavy metal plates such as lead, but if the vacuum chamber size increases, the shielding range will be widened, and the weight and cost of the equipment will be excessive. there were.

  In view of the above, an object of the present invention is to propose a technique for more reliably performing shielding of X-rays generated with irradiation of an electron beam even in a vacuum chamber having an opening.

  The inventors can not only provide a shield layer on the inner wall surface of the vacuum chamber as in the prior art, but also provide specific irregularities on the surface of the shield layer to reliably block X-ray leakage. I found out. Furthermore, it has also been found that by covering the surface with a material that transmits X-rays, maintenance such as cleaning of the inner surface of the vacuum chamber is not hindered and leakage from the X-ray opening can be prevented.

That is, the gist configuration of the present invention is as follows.
1. A vacuum chamber having at least one opening through which the metal strip passes, and an electron gun installed toward the transport path of the metal strip passing through the vacuum chamber,
Provided on the inner wall surface of the vacuum chamber is a shield layer that blocks leakage of X-rays to the outside of the vacuum chamber due to electron beam irradiation from the electron gun,
An electron beam irradiation apparatus, wherein at least a part of the shield layer has an uneven surface layer portion.

2. 2. The electron beam irradiation apparatus according to 1 above, wherein the uneven surface layer portion is provided at least in an inner region of the opening.

3. 3. The electron beam irradiation apparatus according to 1 or 2, wherein the uneven surface layer portion has a convex portion having a triangular cross section.

4). 4. The electron beam irradiation apparatus according to 1, 2, or 3, wherein the shield layer has a coating layer that covers the uneven surface layer portion and transmits X-rays.

  According to the present invention, X-rays can be sufficiently shielded even if an opening is provided in the vacuum chamber. Therefore, without increasing the weight and cost of the facility, it is possible to improve the productivity by improving the processing capability for the metal strip typically made of grain-oriented electrical steel sheets.

It is a figure which shows the structure of an electron beam irradiation apparatus. It is a figure which shows the structure of the shield layer of the electron beam irradiation apparatus of this invention. It is a figure which compares the structure of the shield layer of this invention and a prior art. It is a figure which shows the other structure of the shield layer of the electron beam irradiation apparatus of this invention. It is a figure which shows the other structure of the shield layer of the electron beam irradiation apparatus of this invention.

  The present invention is applied to an apparatus that continuously irradiates a metal strip with an electron beam. As this type of apparatus, for example, as shown in FIG. 1, a vacuum chamber 1 for introducing a metal strip S in atmospheric pressure is provided, and the metal strip S of the vacuum chamber 1 is respectively provided on the inlet side and the outlet side thereof. Opening portions 2a and 2b for allowing the strip S to pass therethrough, and differential pressure chambers 3a and 3b extending on the entrance side and the exit side of the metal strip S so as to cover the openings 2a and 2b. The vacuum chamber 1 is held at a low pressure by interposing these differential pressure chambers 3a and 3b. Further, in the vacuum chamber 1, an electron gun 4 is installed toward the transport path R of the metal strip S so that an electron beam can be irradiated toward the metal strip S.

  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, an electron gun 4 is directed toward the directional electromagnetic steel sheet (metal strip) S 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 about 0.05 to 1 mm is scanned in the width direction of the steel sheet (direction intersecting the rolling direction). Then, heat distortion is introduced linearly. At that time, 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 further adjusted to 1 to 50 J / m. Irradiation is preferred.

  In such an electron beam irradiation apparatus, X-rays are inevitably generated along with the electron beam irradiation. At that time, it is important for safety to suppress X-ray leakage to the outside of the vacuum chamber 1. For this purpose, for example, a lead plate having X-ray absorption capability, for example, as the shield layer 5 is usually provided inside (or outside) the vacuum chamber 1. For example, if the shielding layer 5 can reduce the amount of X-ray leakage to the outside of the vacuum chamber 1 to 1.3 millisieverts or less per three-month working hours, there is no need to provide a radiation control area outside the apparatus. Administratively advantageous.

  By the way, in order to increase the processing amount per unit time in the electron beam irradiation processing for the metal strip, it is necessary to increase the scanning speed of the electron beam. In order to increase the scanning speed while securing a predetermined irradiation amount, it is necessary to increase the output of the electron beam, so that the intensity of X-rays generated at the electron beam irradiation position also increases. In particular, as described above, openings 2a and 2b are provided in the vacuum chamber because it is necessary to continuously carry in and out the metal strip. Since these openings cannot naturally be provided with a shield layer, there is a high possibility that X-rays generated by electron beam irradiation will leak from the openings. In order to attenuate the amount of X-ray leakage to a safe level, it is necessary to increase the distance from the central portion of the vacuum chamber 1 that is the electron beam irradiation region to the opening. In that case, the size of the vacuum chamber increases, and the area of the inner surface of the vacuum chamber covered with the shield layer also increases, increasing the overall weight of the vacuum chamber, increasing the size of the frame that supports the equipment, and reducing the equipment cost. Will increase.

  Furthermore, the cost of the material of the shield layer itself increases, and the excessively sized vacuum chamber is liable to be distorted in shape, and air leakage into the vacuum chamber is likely to occur. . Therefore, it is unavoidable to shield X-rays as much as possible in terms of equipment cost and equipment structure. Under the above constraints, it is difficult to proceed with the increase in the amount of processing described above, so that the manufacturing capacity is limited in the end.

  Therefore, in the present invention, in the electron beam irradiation apparatus, not only simply providing a shield layer on the inner wall surface of the vacuum chamber, but also by providing an uneven shape on the surface layer of the shield layer, the processing speed by the electron gun is increased. Even when the amount of generated lines increases, the intensity of X-rays reaching the opening of the vacuum chamber is particularly reduced to suppress leakage of X-rays, and as a result, an increase in throughput is realized. .

  Specifically, as shown in FIG. 2, in the electron beam irradiation apparatus shown in FIG. 1, the surface layer 5a on the inner side of the vacuum chamber of the shield layer 5 has an uneven shape, for example, the metal strip conveying direction shown in FIG. A convex portion having an isosceles triangular cross section or a triangular columnar convex portion having an axial direction perpendicular to the metal strip conveyance direction, such as a convex portion having a right-angled triangle cross section in the metal strip conveyance direction shown in FIG. By providing a concavo-convex shape in which the rows are parallel to the metal strip conveying direction, X-rays generated by electron beam irradiation to the metal strip S at the central portion of the vacuum chamber 1 can be scattered by the concavo-convex. X-rays are attenuated by this scattering action, the X-ray intensity at the openings 2a and 2b of the vacuum chamber 1 is reduced, and leakage of X-rays from the openings 2a and 2b is suppressed.

  That is, as in the conventional example shown in FIG. 3B, when the surface of the shield layer 50 is not provided with irregularities, the X-rays are not sufficiently absorbed by the shield layer 50 and are reflected or scattered without being absorbed. When the line reaches the opening, the X-ray intensity at the opening increases, and the amount of X-ray leakage from the opening increases. On the other hand, as shown in FIG. 3A, when the surface of the shield layer 5 is uneven, the number of X-ray reflections / scattering until the X-ray reaches the opening increases. Since the absorption efficiency to the shield layer 5 is also increased, the intensity of X-rays reaching the opening is reduced, and the amount of X-ray leakage from the opening is reduced.

Here, the unevenness imparted to the surface layer 5a of the shield layer 5 is such that the uneven shape in which the laterally oriented triangular prisms shown in FIG. 2 (b) and FIG. Any structure that reduces the X-ray intensity in the opening may be used, but a preferred form of the shield layer 5 is as follows.
First, it is preferable to appropriately set the thickness t of the surface layer 5a giving the uneven shape so as to produce an X-ray reduction effect according to the shape of the vacuum chamber and the size of the internal space. The thickness of the surface layer 5a is the height of the convex portion as it is.
Moreover, when the convex part has a triangular cross section shown in FIG. 2, the angle α of the elevation angle of the surface of the triangular vacuum chamber center is preferably 15 ° or more and 90 ° or less. This is because the reflected X-rays can be returned to the center of the vacuum chamber by setting such an elevation angle.
Further, a plane portion may be formed between the adjacent triangular portions, but strip transfer of adjacent triangular portions is prevented so that X-rays from the central portion of the vacuum chamber are not reflected by this plane portion. It is preferable to adjust the interval in the direction. This is because when X-rays are reflected by this plane portion, the X-rays reach the opening and the X-rays are likely to leak. The spacing may be appropriately adjusted according to the size of the triangular portion (surface thickness t) and the internal structure from the center of the vacuum chamber to the entry side (exit side), but the interval (plane portion) is not provided. It is more preferable to continuously provide triangular portions on the surface.

  The unevenness shown in FIG. 2 has a shape in which horizontal triangular prisms are arranged side by side, but it is not necessarily continuous in a triangular prism shape, and each column may be configured by arranging triangular prisms having a short axial length in the axial direction. Alternatively, the surface layer 5a of the shield layer 5 can be a plate-like body or an aggregate thereof whose end is inclined toward the opening as shown in FIG. Also in these forms, it is preferable that the thickness t, the angle α, and the mutual distance d between the apexes are in the above-described ranges.

  In addition, the area | region which makes the shield layer 5 uneven | corrugated shape may be formed in a part inside a vacuum chamber at least from an opening part. This is because, depending on the shape of the vacuum chamber, it can be formed on a part of the inner side to prevent the X-ray from reaching the vacuum chamber opening. Of course, the entire inner wall of the vacuum chamber may have an uneven shape.

  Furthermore, as shown in FIG. 5, after providing the surface layer of the shield layer 4 with unevenness, the surface layer region is covered with a coating layer 5b made of a material that transmits X-rays, and the surface of the shield layer 4 is flattened. It is also possible to arrange. Providing this coating layer 5b is preferable because maintenance such as cleaning and repair inside the vacuum chamber 1 can be easily performed. Incidentally, as a material that transmits X-rays, for example, a metal such as a resin or a thin steel plate can be used.

  Although FIG. 1 shows an example in which one electron gun is provided, a plurality of electron guns may be provided. In that case, a partition wall for partitioning adjacent electron guns may be provided, and a shield layer is provided on the partition wall. It is good also as a structure which provides unevenness in the surface layer.

  In addition to lead, a sheet containing a heavy metal such as tin, antimony, tantalum, tungsten and bismuth or a compound of a heavy element such as strontium, barium and lanthanoid can be used for the shield layer.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2a, 2b Opening part 3a, 3b Differential pressure chamber 4 Electron gun 5 Shield layer 5a Surface layer 5b Coating layer S Metal strip R Conveyance path

Claims (3)

Comprising a vacuum chamber having at least one opening through which the grain oriented electrical steel sheet, an electron gun placed toward the conveying path of oriented electrical steel sheet through a vacuum chamber, and
Provided on the inner wall surface of the vacuum chamber is a shield layer that blocks leakage of X-rays to the outside of the vacuum chamber due to electron beam irradiation from the electron gun,
At least a portion of the shield layer have a uneven surface portion,
The shield layer, an electron beam irradiation apparatus characterized in that it have a coating layer which transmits flat X-ray surface to cover the uneven surface portion.   The electron beam irradiation apparatus according to claim 1, wherein the uneven surface layer portion is provided at least in an inner region of the opening. The electron beam irradiation apparatus according to claim 1, wherein the uneven surface layer portion has a convex portion having a triangular cross section.

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