JPH0760636B2 - Method for manufacturing impregnated cathode - Google Patents

Description

The present invention relates to a method for manufacturing an impregnated cathode.

[Conventional technology]

In the conventional impregnated cathode, for example, as described in JP-A-59-108233, a porous tungsten body is used as a pellet that serves as a cathode substrate, which is impregnated with an emitter agent to form a pellet and a cup. Welding was performed by interposing a joining material between and.

However, the above welding and fixing work has not taken into consideration the difference between the melting point of the emitter material and that of the cup and sleeve made of a high melting point metal.

[Problems to be solved by the invention]

The prior art does not consider the difference in melting point between the emitter agent, the cup and the sleeve when welding and fixing the W pellet impregnated with the emitter agent, the cup and the sleeve,
Since the melting point of the emitter material is as low as 1750 ° C for the cups and sleeves made of high melting point metal, the emitter agent impregnated in the W pellet causes a melting explosion during the welding and fixing work, and the emitter agent evaporates and the welded part There was a problem that there were holes and welding was extremely difficult.

It is an object of the present invention to facilitate the welding and fixing work of pellets, cups and sleeves and the subsequent work of impregnating the pellets with the emitter material.

[Means for solving problems]

In the present invention in order to achieve the above object, the pellet is a porous sintered body, deeper than the thickness of the pellet,
Desirably, it is achieved by using a cup made of a refractory metal having a depth of two times or more and leaving a space for inserting the emitter material in the upper portion.

[Action]

The pellets, which are not impregnated with the emitter agent, and the cup and the sleeve are welded and fixed to each other because the difference in the melting points is small because the emitter agent is not contained and welding can be performed easily.

Next, in the process of impregnating the emitter agent, it is preferable to use a cup having a depth of at least twice the thickness of the pellet and leaving a space for inserting the emitter agent in the upper part. Can be prevented from wrapping around the outer periphery of the cup and the sleeve, and the excess emitter agent can be easily removed after impregnating the emitter agent and the electron emission surface above the pellet can be easily shaped.

〔Example〕

FIG. 1 is a sectional view before welding schematically showing one embodiment of the present invention, and FIG. 2 is a sectional view before welding the emitter agent impregnated, which is also schematically shown. In both figures, 1 is a W pellet showing a porous sintered body of tungsten, 2 is a cup made of a refractory metal molybdenum into which this W pellet 1 is placed, 3 is a high support for supporting the W pellet 1 at an end portion via a cup 2. A melting point metal molybdenum sleeve, 4 is a laser beam for welding, and 5 is an emitter material. W pellet 1 has a porosity of 20
It is a porous sintered body of ˜25% tungsten. Cup two
In order to leave a space into which the emitter agent 5 can be inserted during the impregnation, a molybdenum-made material having a depth tm twice the thickness tw of the W pellet 1 was used. When the W pellet 1 is inserted into the cup 2, the W pellet 1 is housed so that all the surfaces other than the upper surface are in close contact. The cup 2 is further attached to the upper end of the molybdenum sleeve 3 so that the surfaces of the W pellets 1 are aligned.

In this way, the W pellet 1 before impregnation with the emitter agent 5, the cup 2 and the sleeve 3 are assembled, and the laser beam 4 is used for welding and fixing work. Therefore, the melting and explosion phenomenon of the emitter agent 5 can be prevented, and the welding and fixing work can be easily performed.

After the welding and fixing work, pellets of barium, calcium, aluminate or a mixed powder is inserted into the cup 2 as the emitter agent 5 for impregnation. The amount of the emitter agent 5 may be inserted in a specified amount or more so that the W pellet 1 can be sufficiently impregnated.

After the impregnation of the emitter material 5 is completed, the surplus cup portion and the surplus emitter material are polished to the surface AA in FIG.

〔The invention's effect〕

According to the present invention, the welding and fixing work is performed before the impregnation of the emitter agent, and a cup having a thickness equal to or larger than the thickness of the W pellet, preferably about 2 times or more, is used during the impregnation, so that the reliability of the welding and fixing is increased and the impregnation of the impregnation is performed. At this time, the emitter agent can be prevented from wrapping around the outer circumference of the cup and the sleeve, and the excess emitter agent can be easily removed and shaped after the impregnation.

[Brief description of drawings]

FIG. 1 is a sectional view before welding schematically showing one embodiment of the present invention, and FIG. 2 is a sectional view before impregnation of an emitter agent after welding schematically showing one embodiment of the present invention. 1 ... Pellet, 2 ... Cup, 3 ... Sleeve, 4 ...
… Laser beam, 5… Emitter material.

Claims (1)

[Claims] 1. A porous sintered body pellet of tungsten impregnated with an emitter material, a refractory metal cup into which the pellet is inserted, and a refractory metal sleeve for supporting the pellet through the cup. In the method for producing an impregnated cathode having, the pellet is inserted into a cup having a depth deeper than the pellet thickness, both are assembled and fixed, and then the cup is attached to the upper end of the sleeve so that the upper surface of the pellet is almost The sleeve is fixed in the sleeve so as to match, and the amount of the emitter agent that does not exceed the upper end surface of the cup is inserted onto the pellet in the cup and the pellet is impregnated with the emitter agent. An impregnated type cover characterized in that the portion of the cup located above the upper end and the excess of the emitter agent are removed by polishing. Method of manufacturing over de.