JPH0719533B2 - Method of manufacturing rotating target for X-ray tube - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a rotary anode target for an X-ray tube, and more particularly to a method for producing a large-capacity rotary target for a large-diameter X-ray tube using a ceramic substrate.

[Background of the Invention]

The rotary target for the X-ray tube has a disk shape attached to the upper end of the rotary shaft, and the X-ray is generated by irradiating this surface with an electron beam. Conventionally, such rotary targets for X-ray tubes have been manufactured from molybdenum and tungsten by a method such as sintering forging, but in recent years due to the rapid progress of medical equipment, large-capacity targets have been required. In order to obtain a large-capacity target, it is necessary to increase the amount of heat per unit area and to increase the number of rotations in order to reduce the amount of accumulated heat (enlarge the heat sink). A target for meeting such requirements has been proposed in Japanese Examined Patent Publication No. 46-34863. This target is a metal composite target in which only the electron-irradiated surface is made of tungsten or a tungsten alloy, and molybdenum, which has a smaller specific gravity and a larger specific heat than these metals, is used in the other parts, and further improves the heat dissipation of this target. opposite side of the oxide on the surface (mainly _{TiO 2, Al 2 O 3,} ZrrO 2, alone or combined in CaO) those that have been blown black by the thermal spraying, or the back surface of the metal composite Tagetsuto the electron irradiation surface for It has a structure in which graphite is bonded using a high melting point metal solder. However, increasing the rotational speed of the target by increasing the diameter of these targets is limited due to the weight of the target itself being heavy and the strength of other parts of the X-ray tube. Therefore, conventionally, it has been difficult to obtain a large-capacity target by increasing the number of rotations with a large diameter. A graphite base target can be considered in terms of density, but it is inferior to ceramics in terms of rotational strength. It was found that the graphite disk with a diameter of 150 mm broke at 10000 to 13000 rpm, whereas the rotation speed could be increased up to 40,000 rpm for SiC, which is extremely excellent as a high-speed rotating body.

[Object of the Invention]

An object of the present invention is to provide a high-power rotary target for a large-diameter X-ray tube.

[Outline of Invention]

The present inventors have paid attention to a target in which the substrate material is ceramics and the tungsten layer serving as the electron irradiation surface is manufactured by the chemical vapor deposition (CVD) method. In this target, 19.3g / cm ^{3 of} tungsten and 10.2g of molybdenum
Very low density for density of / cm ³ (eg 3.2g / SiC /
Since the base is a ceramic of cm ³ ), the target is lighter in weight and larger in diameter than the conventional metal composite target, and can withstand high-speed rotation. However, the problem with this target is that delamination occurs between the tungsten layer and the ceramic in the electron beam irradiation area.

According to the present invention, in order to reduce the weight of the target itself and improve the adhesion of the layers constituting the target, a heat treatment is performed in a non-oxidizing atmosphere after providing a first layer made of an X-ray source material on a ceramic plate. Therefore, a compound layer of ceramics and the first layer is formed between the substrate and the first layer.

In the present invention, in order to manufacture a target, a layer (first layer) made of an X-ray generation source material is first provided on the ceramic plate. As the X-ray generation source material, a material containing 0 to 26% by weight of Re in W is desirable. Although W alone may be used as the X-ray generation source material, the addition of Re to W improves the X-ray generation characteristics. However, when the Re amount is more than 26% by weight, the X-ray generation source material layer becomes brittle and the X-ray characteristics deteriorate. The thickness of the first layer is preferably 0.05 mm to 2 mm, particularly 0.1 to 1.0 mm. If the thickness of the first layer is less than 0.05 mm, the electron beam will pass through the X-ray generation source material layer and the X-ray generation efficiency will decrease. On the other hand, even if the thickness is more than 2 mm, the workability of layer formation is inefficient, the target window weight becomes large, and the X-ray generation effect is not improved. First
A CVD (Chemical Vapor Deposition) method is used as a method for forming the layer on the ceramic plate. The CVD method is preferable in comparison with the sputtering method, the plating method, the vapor deposition method, the PVD method, and the thermal spraying method because a dense and fine crystal can be obtained in a short time.

After forming the first layer, heat treatment is performed in a non-oxidizing atmosphere. The non-oxidizing atmosphere is a vacuum or reducing atmosphere, and the heat treatment temperature is preferably 1000 to 1400 ° C. This temperature range is for improving the adhesion between the first layer formed on the ceramic plate and the ceramics, and when the heat treatment temperature is lower than 1000 ° C, the X-ray generation source material of the first layer is the ceramic plate. There is no reaction, and no alloy layer is formed during this time, and the effect of improving adhesion is lost. On the other hand, if the heat treatment temperature exceeds 1400 ℃, X
The carbide reaction of the material for the source of the wire tube is promoted, and the thickness becomes too thick, so that the material easily becomes brittle and peels.

In the present invention, when the insulating ceramics is used for the substrate, a conductive film is provided on the ceramics plate by a sputtering method or the like to establish conduction between the rotating shaft and the X-ray generation source material (first layer).

Example of Invention

Example 1 FIG. 1 shows the basic structure of a SiC-based target.
In this embodiment, a SiC plate 1 is coated with tungsten 2 by a CVD method in which tungsten hexafluoride and hydrogen are chemically reacted.
With this structure, a thermal history was given to improve the adhesion. The conditions are heat treatment in vacuum at 1400 ° C. for 1 hour. As shown in FIG. 2, the cross-sectional structure after the heat treatment shows the silicide layer 3 and the carbide layer 4 due to the reaction between the SiC substrate 1 and the tungsten 2 in addition to the SiC substrate 1 and the tungsten 2.

FIG. 3 shows a cross-sectional structure of a SiC substrate 1 coated with tungsten 2 by a CVD method and then heated in a vacuum at 950 ° C., and FIG. 4 shows a cross-sectional structure of the same heated at 1400 ° C. In FIG. 3, there is no diffusion of the SiC substrate 1 and the tungsten 2. On the other hand, in FIG. 4, the silicide layer 3 and the carbide layer 4 in which the SiC substrate 1 and the tungsten 2 have reacted are clearly shown, and it can be seen that the diffusion of each layer is performed. As a result, the adhesion after heat treatment at 950 ° C is 1.0 kg / mm ²
However, the adhesion after heat treatment at 1400 ° C is 4.0 Kgf / m
It was found that it could be a new lightweight high-strength target because it showed extremely excellent adhesion with m ² .

〔The invention's effect〕

As described above, according to the present invention, a thermal history is given before use as a target to improve the adhesion between the ceramics substrate and the X-ray generation source material layer, so that it can withstand the heat cycle of rapid thermal quenching by electron beam irradiation. It enables a lightweight, large-diameter and high-strength rotating anode target.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a ceramics base target before heat treatment, FIG. 2 is a cross-sectional view of an essential part showing an example of the structure of the target of the present invention, and FIG. 3 is a metal of the target cross-section under heat treatment conditions of 950 ° C. Micrograph showing the structure, No. 4
The figure is an electron micrograph showing the metal structure of the cross section of the target under the heat treatment condition of 1400 ° C. 1 ... SiC plate, 2 ... target material, 3 ... silicide layer, 4 ... carbide layer.

Front page continued (72) Inventor Yusaku Nakagawa 3-1-1 Sachimachi, Hitachi, Ibaraki, Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-56-141153 (JP, A) JP-A-SHO 51-117593 (JP, A)

Claims (2)

[Claims] 1. A rotation for an X-ray tube, characterized in that a first layer made of an X-ray generation source material is formed on a ceramic plate by a CVD method and then heat-treated in a non-oxidizing atmosphere at a temperature of 1000 to 1400 ° C. Target manufacturing method. 2. The method of manufacturing a rotary target for an X-ray tube according to claim 1, wherein the ceramic is SiC.