JPS5918820B2 - Method for manufacturing targets for X-ray tubes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for manufacturing graphite-based targets for X-ray tubes.

Conventionally, targets for X-ray tubes have been known in which a tungsten-based (metallic) surface layer is provided as a focal plane layer on a graphite base, but between the graphite base and the tungsten-based surface layer,
Since a fragile tungsten carbide layer is formed, there is a drawback that bonding strength deteriorates.

In order to eliminate such drawbacks, rhenium 1. Intermediate layers such as molybdenum or zirconium are interposed, and these targets are conventionally often obtained by vapor phase growth (method by precipitation from gaseous compounds) or thermal spraying. However, these methods have the disadvantage that it is difficult to efficiently obtain a desired amount of intermediate layer, and therefore the bonding strength is not sufficient.

Furthermore, these methods tend to make the focal plane layer non-uniform and require special equipment, so they cannot be said to be practically preferable methods.

Also known is a method previously disclosed by the applicant in which a molybdenum alloy paste is applied onto a graphite substrate to form an intermediate layer.

Although this method is simple and practically preferable, there is still room for improvement in terms of bonding strength.

This invention was made in view of the above circumstances, and aims to reduce manufacturing costs when manufacturing an X-ray tube target consisting of a graphite base, a tungsten surface layer, and an intermediate layer that joins the two. The present invention provides a method for manufacturing an X-ray tube target that provides stable characteristics by increasing the bonding force between the layer and the substrate and by making the characteristics of the tungsten-based surface layer uniform.

That is, in the manufacturing method of the present invention, a paste layer mainly composed of rhenium is formed on the surface of the graphite substrate, and a paste layer mainly composed of molybdenum is formed on the back surface of the target plate, and the graphite substrate is coated through both paste layers. The method is characterized in that hot press molding is performed in a vacuum or an inert gas atmosphere after overlapping the target plate and the target plate.

The drawing shows the schematic structure of the target for an X-ray tube obtained through the above process, and shows 1 graphite base, 2 main rhenium layers, 3 main molybdenum layers, and 4 target plates, and each layer is generally in units of U, and in some cases, in units of μ. It has a thickness of

Since the graphite substrate 1 has a large heat capacity, it can increase the amount of heat load on the target, and it has been used mainly from this point of view.

The target cup 4 can generally be manufactured from tungsten or tungsten alloy powder by methods such as powder metallurgy, forging, and rolling, and has a dense and uniform crystal structure.

The rhenium-based layer 2 refers to a layer of rhenium alone or an alloy layer of rhenium and molybdenum, ruthenium, tungsten, etc., and it is desirable that this alloy contains 70% or more of rhenium.

Further, the molybdenum-based layer 3 refers to a layer of molybdenum alone or an alloy layer of molybdenum and rhenium, ruthenium, tungsten, zirconium, titanium, etc., and it is preferable that this alloy also contains 70% or more of molybdenum.

In this invention, these pastes are used to form the rhenium-based layer 2 and the molybdenum-based layer 3,
A paste layer mainly composed of rhenium is applied to the surface of the graphite substrate 1, and a paste layer mainly composed of molybdenum is applied to the target plate 4.
It is necessary to apply each to the back side of each.

To prepare the paste, for example, an organic solvent such as acetate or tetralin, a binder such as ethyl cellulose or polystyrene, and a specified metal powder may be mixed to form a slurry. , the binder need not be limited to those listed here.

After forming a paste layer mainly consisting of rhenium on the graphite substrate 1 and a paste layer mainly consisting of molybdenum on the target plate 4 with a brush, etc., the paste layers are then overlapped and placed in a vacuum or in a vacuum. Hot press molding is performed in an active gas atmosphere.

Hot press conditions are generally 16000C or higher, Q
, 3tOIL/(7.30 minutes is sufficient.

By this hot pressing, the graphite substrate 1 and the target plate 4 are tightly pressed together with the intermediate layers 2 and 3 interposed therebetween, and a target for an X-ray tube can be obtained here.

Examination of the cross-sectional structure of this target reveals that the graphite base 1 and the rhenium-based layer 2 are in a favorable bonding state in which carbon and rhenium are diffused in solid solution, and the molybdenum-based layer 3 and the target plate 4 are also in a favorable bonding state. Molybdenum and tungsten are in a desirable bonded state in which they are diffused in solid solution.

The middle class 2 and 3 comrades are strongly connected due to their excellent affinity.

As a result, the bonding forces between the graphite base, the intermediate layer, and the target plate are significantly enhanced, and since the target plate itself has a dense structure, the X-ray tube target of the present invention has extremely stable performance as a whole. able to demonstrate.

Furthermore, according to research by the inventors, if slit-like grooves, mesh-like grooves, and fine irregularities are provided on the surface of the graphite substrate in advance before forming the paste layer, bonding between the graphite substrate and the intermediate layer can be improved. It has been revealed that his power has increased further.

Example 1 Rhenium powder with an average particle size of 2 to 4μ and an average particle size of 0.5 to 4
Molybdenum powder of μ was blended into a binder (ethylcellulose:tetralin-1:5) and mixed thoroughly in a mortar to prepare two types of pastes.

On the other hand, a tungsten sintered slag obtained by powder metallurgy is previously forged (or rolled or cut) to produce a disk with a thickness of approximately 1.5 mm.

A paste layer of the molybdenum powder with a thickness of about 0.1 to 11n11L is formed on the back surface of this disk by brush coating, and a paste layer of the rhenium powder with a thickness of 0.1 to 11ftm is formed on the surface of the graphite substrate. Formed in a similar manner.

After that, the target plate and graphite substrate were laminated so that each paste layer overlapped, and the temperature was heated to 1600°C in a vacuum.
Photopress molding was performed at a pressure of 0.3 ttrrb/cyyf for 30 minutes.

The obtained target had the structure shown in the figure, and the formation of a tungsten carbide layer was hardly observed.

Moreover, the bonding strength of the intermediate layers 2 and 3, the graphite substrate 1 and the intermediate layer 2
The bonding strength between the target plate 4 and the intermediate layer 3 is both very excellent, and the target plate 4 itself has a dense and fine crystal structure, making it preferable as a target for an X-ray tube.

Example 2 In Example 1, a plurality of slit-like grooves were carved on the surface of the graphite substrate 1 prior to forming the paste layer.

Thereafter, when an X-ray tube target was manufactured in the same manner as in Example 1, the bonding strength between the graphite substrate 1 and the ruthenium-based layer 2 was increased by about 1.5 to 2 times compared to Example 1. It turned out that there was.

As described above, the method for producing an X-ray tube target of the present invention includes selecting a target plate having a dense structure as the surface layer to be irradiated with electrons, and applying vacuum through the paste layer when bonding the graphite substrate and the target plate. Alternatively, hot pressing may be carried out in an inert gas atmosphere, or the paste layer may be divided into two layers, each containing a high melting point metal powder suitable for promoting bonding with the graphite substrate and the target plate. Due to the structural features, an X-ray target plate with better performance than conventional methods can be manufactured at a lower cost.

Therefore, the present invention provides an economically advantageous target for an X-ray tube with superior performance and is an important contribution to this field.

[Brief explanation of the drawing]

The drawing is a partial cross-sectional view of an X-ray tube target obtained according to an embodiment of the present invention. 1...Graphite base, 2...Ruthenium main layer, 3...Molybdenum main layer, 4...
・Target board.

Claims (1)

[Claims] 1. When manufacturing an X-ray tube target consisting of a graphite base, a tungsten-based surface layer, and an intermediate layer that joins the two, a paste layer mainly composed of rhenium is formed on the surface of the graphite base, and a paste layer is formed on the back surface of the target plate. For X-ray tubes characterized by forming a paste layer mainly composed of molybdenum, laminating a graphite substrate and a target plate through both paste layers, and then hot press molding in a vacuum or inert gas atmosphere. Target manufacturing method.