JPS608575B2 - Manufacturing method of rotating anode for X-ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating anode for an X-ray tube, and more particularly to a rotating anode that has a high bonding strength between each component and that suppresses carbide formation on target plate constituent metals during manufacturing of the rotating anode. Relating to a manufacturing method.

2. Description of the Related Art Rotating anodes for X-ray tubes, which have a large heat capacity and provide a large X-ray output, are widely used in the medical field.

Conventionally, rotating anodes have been made of metals such as tungsten or tungsten alloys, which can withstand thermal shock from irradiated electron beams, have high density, high melting point, and high atomic number, and are efficient in generating X-rays.

Alternatively, a composite plate is also known in which a relatively thick molybdenum plate is integrally bonded to the back surface of a tungsten plate as a heat absorber. However, ``Recently, with advances in X-ray technology, there is a strong demand for rotating anodes with even higher heat capacity that can withstand continuous loads or instantaneous high load inputs. A rotating anode has been developed in which a graphite material with excellent heat radiation ability is used as a base material, and a tungsten or tungsten alloy layer is integrally bonded thereon as an X-ray irradiation surface.

Accordingly, such a rotating anode is formed by forming a rhenium vapor-deposited layer on a graphite substrate of a predetermined shape by, for example, the CVD method, or by applying a slurry of rhinium powder and an organic solvent. A tungsten plate or its alloy is placed on top, and the whole is heated to a temperature of 1400 to 16
It is formed into an integral structure by hot pressing at a pressure of 150 to 300 k9/base.

The rhenium layer used here is heated to a high temperature (1200 ~
This intermediate layer serves to prevent the inconvenience of the tungsten plate becoming carbide at the bonding surface with the graphite substrate due to carbon diffused from the graphite substrate, which has become 1,500 qo), reducing the bonding strength at that portion.

However, with the conventional intermediate layer, it is difficult to sufficiently prevent tungsten from becoming carbide, and the bonding strength of the rotating anode is sometimes insufficient.

The present invention solves the above-mentioned disadvantages of the conventional method for manufacturing a rotating anode, and provides a method for manufacturing a rotating anode that reduces the formation of a carbide layer during manufacturing of the rotating anode and increases the overall bonding strength. The purpose is to provide a manufacturing method.

In the method of the present invention, in order to obtain a rotating anode for an X-ray tube, which is formed by laminating a surface layer made of tungsten or a tungsten plate and a molybdenum plate laminated in this order, an intermediate layer made of a rhenium plate, and a graphite substrate, first the surface layer is laminated. The method is characterized in that the layer and the intermediate layer are bonded by hot pressing in a reducing atmosphere, and then the resulting bonded body and the graphite substrate are bonded by hot pressing in an inert atmosphere.

That is, the method of the present invention achieves the object of the present invention by forming the intermediate layer into a rhenium plate that has been pre-bonded and processed, and by carrying out the bonding step in stages.

The rhenium plate forming the intermediate layer in the method of the present invention is made by, for example, granulating rhenium powder using an organic binder, forming it into a sheet shape with a roll, drying it to remove the binder, and then firing it again. Roll processing
It is manufactured by a method that further adds heat treatment.

Further, the rhenium plate may be made by a so-called powder metallurgy method.

For example, rhenium powder (mixed with a binder if necessary) is molded using an isostatic press, sintered in a vacuum, and then hot forged, hot rolled, and then cold rolled. As described above, the rhenium plate in the present invention is densely sintered and preformed as an intermediate layer.Plates of various thicknesses can be manufactured by these methods, but
It is desirable to use a material with a thickness of 15 to 200 mm, and the charcoal phenomenon of ~W is more likely to occur in a target with such a hollow nium plate as an intermediate layer than in a target with a rhenium intermediate layer formed by a CVD method or the like. Completely prevented.
The method of the present invention includes a first stage hot pressing in which only the metal plates (layers) of a tungsten plate or its alloy plate, or a tungsten plate or its alloy plate, a molybdenum plate, and a rhenium plate are first hot pressed in a reducing atmosphere; The obtained metal plate (
It is constructed by step-by-step hot pressing in which a bonded body (target plate) of layers) is attached to a graphite substrate and then hot pressed in an inert atmosphere.

The first stage hot pressing is carried out in a reducing atmosphere such as hydrogen at a temperature of 1,400 to 17,000° and a pressure of 100 to 300 kg.

When the temperature is less than 140,000 and the pressure is less than 100k9, the bonding strength at each bonding surface of the tungsten plate or its alloy plate, or the tungsten plate and its alloy plate, the molybdenum plate, and the rhenium layer is sufficiently large. Also, the temperature is 1700oo, the pressure is 300k
Although the bonding strength increases sufficiently when the temperature exceeds 100%, the effect of preventing carbon diffusion due to the alloying of the rhenium layer decreases, and due to the limits of the heat resistance and pressure resistance of the bonding device (heating furnace body),
This is not preferable as a practical manufacturing condition. The second stage hot pressing in the method of the present invention involves fixing the bonded metal plates (layers) obtained by the first stage hot pressing on a graphite substrate, and placing them in an inert atmosphere such as nitrogen at a temperature 1
200 to 160,000 and a pressure of 50 to 500 k9/m.

By performing the second stage hot pressing in an inert atmosphere, the bonding strength with graphite becomes sufficient.

Note that if the temperature is less than 1200°C and the pressure is less than 50k9°, the bonding strength between the rhenium foil and the graphite substrate will not be sufficiently large.
If the temperature exceeds 9 mm, the tungsten plate or molybdenum plate above the rhenium layer will partially become carbide due to the diffusion of carbon from the graphite base during the hot-pressing process, and the graphite base will frequently crack and crack.

The present invention will be explained below based on examples.

Note that tungsten in the present invention includes tungsten alloys such as tungsten-rhenium alloys, and also includes doped tungsten containing a dopant.
Example (1) 1st stage hot press press Tungsten plate with diameter 130 mm and rib thickness 2.5 mm Molybdenum plate with diameter 13 mm and rib thickness 2 mm;
A rhenium plate with a diameter of 0 French m was prepared.

A rhenium plate, a molybdenum plate, and a tungsten plate were stacked one on top of the other in a regular press, and these were hot-pressed in a hydrogen atmosphere at a temperature of 160,000 ℃ and a pressure of 250 k9/cm.A bonding aid was placed between these plates. As the agent, a paste made by mixing rhenium powder or rhenium and molybdenum mixed powder with 0.5 to 10% by weight of an organic binder is used.An integral bonded body was obtained. After two-step hot-pressing, the above-mentioned bonded body was placed on a circular columnar graphite substrate with an outer diameter of 130 mm, an inner diameter of 1 mm, and a thickness of 3 ribs, and heated in a nitrogen atmosphere at a temperature of 1,400 m and a pressure of 200 k9. Hot pressed.

Note that the above-mentioned tying aid was used in the joint portion.

No cracks or cracks were generated on the graphite substrate, and all of them were obtained as rotating anodes with an integral structure. The obtained rotating anode is shown in FIG. In the figure, 1 is a graphite substrate, 2 is a nium plate, 3 is a molybdenum plate, and 4 is a tungsten plate. In this way,
Nineteen rotating anodes were manufactured.

For comparison, a tungsten plate, a molybdenum plate, and a graphite substrate having the same specifications were used as an intermediate layer and were sequentially laminated as a nium vapor deposition layer, and this was heated at a temperature of 1400 oo in a nitrogen atmosphere.
, hot pressing was carried out at a pressure of 200 k9/m to produce one randomly solidified rotating anode for each comparative example. A portion of each of these rotating anodes was cut in the thickness direction, and the presence or absence of a carbide layer within the molybdenum layer on the cut surface and the formed thickness were observed. In addition, a bonding strength test specimen having the same size and configuration as the rotating anode was manufactured under the same conditions as the rotating anode, and the bonding strength between the graphite base and the Nimu foil and the bonding strength between the tungsten plate and the molybdenum plate were measured. .

The above results are summarized in a table including average values.

As is clear from the above table, the method of the present invention produces very little carbide layer at the joint with graphite.
Therefore, the bonding strength in the middle layer is high;
Moreover, the overall joint strength is also high.

On the other hand, the bonding strength of the comparative example is particularly low in the intermediate layer. In this embodiment, a tungsten plate is used as an example, but the same effect can be achieved even if a tungsten-rhenium alloy plate is used.

Also, doped tungsten plate (needle 203, Si02, K20
, tungsten doped with Fe, etc.).

[Brief explanation of the drawing]

The figure is a partial sectional view of a rotating anode obtained by the method of the present invention. 1...graphite base, 2...rhenium plate, 3.
...Molybdenum plate, 4...Tungsten plate.

Claims (1)

[Claims] 1. In order to obtain a rotating anode for an X-ray tube which is formed by laminating a surface layer made of tungsten or tungsten and molybdenum, an intermediate layer made of a rhenium plate, and a graphite substrate, first the surface layer and the intermediate layer are laminated. 1. A method for producing a rotating anode for an X-ray tube, which comprises bonding by hot pressing in a reducing atmosphere, and then bonding the obtained bonded body and a graphite substrate by hot pressing in an inert atmosphere. 2. The method for manufacturing a rotating anode for an X-ray tube according to claim 1, wherein the reducing atmosphere is a hydrogen atmosphere and the inert atmosphere is a nitrogen atmosphere.