JPH01319227A - Manufacture of electron tube cathode - Google Patents

Abstract

PURPOSE:To uniformly spread a wax material over the whole area by inserting a wax material layer obtained by press-molding the high-melting point wax material powder on the surface of a support sleeve, sintering it in the vacuum atmosphere or the like, then machining it in the preset size between the inner face of an electron emitting body structure and the whole area of the soldering section on the surface of the support sleeve. CONSTITUTION:For example, the mixed powder of molybdenum powder and ruthenium powder with the average grain size of about 5mum respectively at the weight ratio of 1:1 is press-molded at the soldering section on the surface of a support sleeve 2 made of molybdenum with the outer diameter of 6.8mm, the inner diameter of 5.2mm, and the length of 50mm. A press-molded layer is sintered in a hydrogen furnace for about 15 min at the temperature of about 1200 deg.C, then the press-molded layer is machined to the preset outer diameter size and again sintered in the hydrogen furnace for about 30 min at the temperature of about 1700 deg.C, a fixed wax material layer 3 is formed on the surface of the support sleeve 2. The excess wax material layer stuck on the surface of the support sleeve 2 except the wax soldering section is removed at the time of machining. The whole inner face of an electron emitting body structure is uniformly soldered to the surface of the support sleeve.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a cathode mainly used in microwave electron tubes, in which a cylindrical electron emitting structure having a high melting point metal as a base is brazed to the structure. The present invention relates to a method of manufacturing an electron tube cathode having a structure in which it is supported by a support sleeve made of a melting point metal.

[Conventional technology]

Cylindrical cathodes are usually used in magnetrons, cross-field amplification tubes (CFA), etc. due to their design structure.These cathodes have a high degree of dimensional accuracy and heat resistance that does not cause minute deformation even under high temperature conditions. In particular, gender is desired.

Therefore, the cylindrical electron emitting structure is manufactured using a high melting point metal as a base, and the support sleeve is made of a high melting point metal.

The electron emitting structure based on these high melting point metals and the support sleeve made of the high melting point metal must be bonded together by brazing.

Conventionally, the above-mentioned brazing was performed by inserting a support sleeve into which the brazing part on the surface was coated with high melting point brazing powder to a predetermined thickness into the hollow part of the electron emission structure, and then melting the applied brazing powder. Alternatively, a method is adopted in which the support sleeve is fitted into the hollow part of the electron emitting structure, high-melting point brazing filler metal powder is poured onto both ends of the structure and melted, and the molten brazing filler metal permeates into the gap between the inner surface of the structure and the surface of the support sleeve. I've been exposed to it.

[Problem to be solved by the invention]

In the former method described above, when the support sleeve is fitted into the hollow part of the electron emission structure, the brazing filler metal powder applied to the support sleeve peels off and falls off, making it difficult to ensure a sufficient amount of brazing filler metal. Since the volume of the brazing material is greatly reduced by melting compared to the powder state, the brazing material does not spread over the entire surface, resulting in unbrazed portions, as shown in FIG. 4, for example. In Fig. 4, 1 is an electron emission structure;
2 is a support sleeve, and 3a is a brazing material.

In the latter method, the penetration of the brazing material is insufficient, resulting in an unbrazed portion in the middle, as shown in FIG. In FIG. 5, the symbols are the same as or correspond to the same symbols in FIG. 4.

In particular, when the electron emission structure 1 is long in the axial direction or when the gap between the electron emission structure 1 and the support sleeve 2 is narrow, the above-mentioned drawback becomes noticeable. Furthermore, the thermal expansion of tungsten, which is the base material of the electron emission structure 1, is larger than that of molybdenum, which is the material of the support sleeve 2, and because the gap between the brazed parts is reduced during brazing, it is almost impossible to sufficiently infiltrate the brazing material into the intermediate part. It's impossible.

In the conventional method, as mentioned above, there are parts that are not brazed, the electron radiation temperature during operation becomes uneven on the surface, the emitted emission becomes uneven on the surface, and abnormal evaporation of the electron radioactive material occurs. There was a problem in that arcing occurred, leading to a short life.

Further, serious defects such as cracks occurring at the boundary between the brazed portion and the unbrazed portion due to fatigue over time may occur.

Furthermore, in the conventional method, skill and attention are required for the work, and due to the lack of these skills, there is a problem in that the brazing filler metal adheres to the electron emitting surface during the work.

High melting point brazing filler metals have poor ductility and malleability, and have excellent hardness, making machining difficult and making it impossible to process them into plate or wire shapes.

The present invention has been made in view of the above circumstances, and includes an electron emission structure and a support sleeve. It is an object of the present invention to provide a method of brazing in which the brazing material is uniformly distributed over the entire area.

[Means to solve the problem]

The method of the present invention involves press-molding high melting point brazing filler metal powder on the surface of the support sleeve between the entire brazed portion between the inner surface of the electron emitting structure and the surface of the support sleeve, and sintering the powder in a vacuum atmosphere or a reducing atmosphere. After that, the support sleeve is brazed to the electron emitter with a brazing material layer machined to a predetermined size interposed therebetween.

〔Example〕

Fig. 1 is a sectional view showing the brazing method in the present invention, Fig. 2 is a sectional view showing the brazing method in the present invention;
The figure is a flowchart showing an example of the flow of the brazing method in the present invention, and FIG. 3 is a flowchart showing another example of the flow of the brazing method in the present invention. 3 indicates the same or equivalent, and 3 indicates the brazing material layer.

Specific examples will be described below.

A mixed powder of molybdenum powder and ruthenium powder each having an average particle size of about 5 μm and a weight specific gravity of 1 was mixed into a powder with an outer diameter of 6.8 m.
x, inner diameter 5.2 mm + length 50 wings made of molybdenum support sleeve 2 is press-molded onto the surface to be brazed. The pressing is carried out by a hydraulic press method at a pressure of about 5 watts i2. Next, the press forming layer was heated to about 1200°C in a full hydrogen furnace.
After sintering for about 15 minutes at a temperature of A brazing filler metal layer 3 is formed. If the outer diameter of the brazing material layer 3 is larger than the inner diameter of the electron emission structure 1, polish the part with an alumina bake and attach the support sleeve 2 with the brazing material layer 3 fixed to the hollow part of the electron emission structure 1. Inset, approx. 200
Brazing is carried out at a temperature of 0°C.

The electron emission structure 1 is made of tungsten as a base material, mixed with electron radioactive substance doria, and has an outer diameter of 10 am +
It has an inner diameter of 6.9 m and a length of 14.5 m.

The excess brazing material layer adhering to the surface of the support sleeve 2 other than the brazed portion is removed during machining.

In addition, when using a brazing material having a rather low melting temperature, such as a mixed powder of molybdenum powder and nickel powder, a method that does not involve sintering again is used.

As the brazing filler metal powder, a mixed powder of molybdenum and iridium is sometimes used, and as the electron emission structure, a porous tungsten base impregnated with electron radioactive material and barium, calcium, aluminate is sometimes used. ．． The effect will not change〇Also, the sintering time and sintering temperature depend on the composition ratio of the brazing metal.

Of course, it varies depending on the particle size, etc.

〔Effect of the invention〕

As explained above, according to the present invention, the entire inner surface of the electron emitting structure is uniformly brazed to the surface of the support sleeve, and radioactivity is reduced due to temperature asymmetry on the electron emitting surface, which occurs in conventional structures. Abnormal evaporation of substances and arcing will no longer occur, and cracks due to fatigue over time will also no longer occur, greatly contributing to improving the reliability of electron tubes using B@ electrodes.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the brazing method in the present invention, Fig. 2 is a sectional view showing the brazing method in the present invention;
3 are flowcharts showing an example of the flow of the brazing method according to the present invention, and FIGS. 4 and 5 are sectional views showing examples of malfunctions that occur in the conventional brazing method. 1... Electron emission structure, 2... Support sleeve, 3...
・Brazing metal layer. Note that the same reference numerals in the figures indicate the same or equivalent parts. Patent applicant: New Japan Radio Co., Ltd. Figure 1 ↓ Primary sintering machining ↓ Tertiary sintering polishing ↓ Brazing Figure 2 Figure 4 Figure 5 Sintering machining ↓ Brazing Figure 3

Claims (1)

[Claims] In a method for manufacturing an electron tube cathode in which a cylindrical electron emission structure having a high melting point metal as a base is supported by a support sleeve made of a high melting point metal and brazed to the structure, the inner surface of the electron emission structure and the surface of the support sleeve are brazed. An electron emitting structure is formed by interposing a brazing material layer which is press-molded with high melting point brazing material powder on the surface of the support sleeve between the parts, sintered in a vacuum atmosphere or a reducing atmosphere, and then machined to a predetermined size. A method for manufacturing an electron tube cathode, comprising brazing a support sleeve to the electrode.