JPS6180726A - Manufacture of sintering electrode for discharge lamp - Google Patents

Abstract

PURPOSE:To obtain a sintered electrode having good characteristics and being suitable for mass-production by introducing a reduction gas of a particular pressure into a changer and sintering a compressed molding body of metal powder while keeping such pressure. CONSTITUTION:A compressed molding body 1 of powder including electron radiation substance is put into a container 3 with molybdenum used as a based metal and the interior is exhausted until the pressure reaches 1X10<-5>Torr or less. While, the container 3 is exhausted, a variable leak valve 4 is opened in order to supply the hydrogen gas into the container 3, and while pressure is maintained, a compressed molding material 1 is heated by a heater for sintering. When the pressure is in the range of 1X10<-4>-300Torr, the oxidation gass generated during sintering is reduced by the hydrogen gas. Accordingly, the sintered electrode, which prevents the oxidation not only at the surface but also interior of sintered material, assures good discharge characteristic and least amount of degassing from sintered body, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a sintered electrode for a discharge rung.

Structure of conventional example and its problems Conventionally, in the manufacturing method of sintered electrodes for discharge lamps, when sintering a compressed body of a mixed powder of metal powder and electron radioactive material suitable as electrode material, a pressure of 1 atm is applied. In a reducing gas atmosphere,
Alternatively, a method has been adopted in which the compression molded body is heated and sintered in a vacuum.

However, in the former case, the reducing gas does not reach the inside of the porous compression molded body sufficiently, and the inside of the compression molded body is oxidized by residual gas and impurity gas generated during sintering. There was a problem. In particular, when sintering a compacted compact using a carbonate such as an alkaline earth metal as an electron radioactive substance, K is removed from the compact when the electron radioactive substance reacts with a reducing gas in the presence of the base metal. There was a problem with being exposed.

On the other hand, in the latter case, the problems in the former case do not occur, but especially when carbonates of alkaline earth metals are used as the electron radioactive substance, oxidizing gas is generated due to the decomposition of the carbonates, resulting in the compression molding. is oxidized, and discharge lamps that use it for electrochromics do not have good characteristics.To prevent this, the amount of compression molded material in one batch during sintering may be limited, or the amount of compression molded material during sintering may be There was the problem of slowing down the temperature increase rate, which hindered productivity.

OBJECTS OF THE INVENTION The present invention provides a method for manufacturing a sintered electrode for discharge lamps that has good characteristics and is suitable for mass production.

Structure of the Invention The present invention involves placing a compression molded body of metal powder in a container, and after evacuating the inside of the container to a vacuum at a pressure of 1 x 10' Torr or less, while continuing the evacuation, 1.
× A method for manufacturing a sintered electrode for a discharge lamp is characterized in that reducing gas at a pressure of 10-4 to 300 Torr is introduced, the exhaust is continued while maintaining this pressure, and the compression molded body is sintered. It is something.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

As shown in the figure, as a sample, a compression molded body 1 of a powder containing molybdenum (MO) as a base metal and an electron radioactive substance made of 10% by weight of an alkaline earth metal carbonate is placed inside, and a heater 2 is placed inside. 100 pieces were placed in a container 3 of a vacuum evacuation device having a vacuum evacuation system, and evacuation was performed using a vacuum pump until the pressure reached 1×1 o -5 Torr or less. The weight of 10 compression molded bodies is 500 mg/piece.

Molybdenum and electron radioactive material are almost uniformly mixed. In such a case, if the exhaust pressure exceeds 1 x 10' Torr, the gas remaining inside the compression molded body will oxidize the interior of the compression molded body during sintering, so the pressure should be reduced to 1 x 10' Torr or less. It is necessary to Next, while continuing to exhaust the inside of the container 3, open the barrier pull/leak pulp 4 and introduce the hydrogen gas in the hydrogen cylinder 5 into the container 3 until the pressure shown in the table below is reached, and continue to exhaust while maintaining this pressure. Then, the compression molded body 1 is heated with the heater 2 to perform sintering. A diffusion pump and an oil rotary pump 7 were used as the vacuum pump. The pumping speed was 300 l/s in both cases. Pressure is 1×1Q-2 Torr
Both the diffusion pump 6 and the oil rotary pump 7 were operated in the following cases, and only the oil rotary pump 7 was operated when the temperature exceeded 1 Xl 0-2 Torr. Note that when operating the diffusion pump 6 and the oil rotary pump 7, both the main pulp 8 and the rough intake valve 90 are opened, and when only the oil rotary pump 7 is operated, only the rough intake valve 9 is opened. The heating rate of heater 2 was 10'C/min. The temperature was raised from room temperature to a sintering temperature (maximum temperature) of 1000°C.

The above experimental results are shown in the table below.

(Left below) As is clear from the table above, the pressure of hydrogen gas is 5X10-
In the case of 5 Torr, oxidizing gas was generated during sintering and the surface of the sintered body was oxidized, as in the case of conventional vacuum sintering in which no hydrogen gas was introduced. However, the pressure is 1×
In the range of 10-4 to 300 TOrr, oxidizing gas generated during sintering was reduced by hydrogen gas, so oxidation was prevented not only on the surface of the sintered body but also inside it. Furthermore, as is clear from the percent weight loss after sintering, there is a sufficient amount of electron radioactive material remaining.Therefore, when a strobe xenon discharge lamp was fabricated and tested using this sintered body as an electrode, it was found that The discharge characteristics were good, and the amount of gas released from the sintered body was extremely small.

On the other hand, the pressure of hydrogen gas is 3s o Torr and 76
In the case of 0 Torr, the reaction between the electron radioactive material and hydrogen gas is intense during sintering, so the weight loss percentage is 8.5% or more, and these sintered bodies are used as electrodes to manufacture xenon discharge lamps for strobes. When the lamp was tested, defects such as an increase in lighting voltage due to depletion of electron radioactive substances and darkening of the lamp occurred in the early stages of its life.

In addition, in order to prevent oxidation of the sintered body and to improve the characteristics of the discharge lamp, the compression molded body used in the above experiment was subjected to normal vacuum sintering using the above vacuum evacuation device. , reduce the number of compression molded bodies in the container to 10 or less, or
Alternatively, it was recognized that the heating rate of the heater needs to be 1° C./min or less.

As described in detail, the method for producing a sintered electrode for a discharge lamp of the present invention is different from the conventional sintering method in a reducing gas atmosphere of 1 atm, in which oxidation of the sintered body and electron It can solve the problem of scattering of radioactive materials, and it can greatly improve production efficiency compared to normal vacuum sintering methods, and its effects are significant.

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[Brief explanation of drawings]

The figure is a schematic diagram showing an example of an apparatus for carrying out the method of manufacturing a sintered electric lamp for discharge lamps according to the present invention. 1... Compression molded body, 2... Heater, 3...
... Container, 4... Barrier pull leak valve, 5...
...Hydrogen cylinder, 6...Diffusion pump, 7.
...Oil rotary pump.

Claims (1)

[Claims] A compression molded body of metal powder is placed in a container, and the inside of the container is
×10^-^ After evacuating to a vacuum at a pressure of 3 Torr or less, while continuing the evacuation, 1 × 10^-^ was placed in the container.
A method for manufacturing a sintered electrode for a discharge lamp, comprising introducing a reducing gas at a pressure of 4 to 300 Torr, and continuing the evacuation while maintaining this pressure to sinter the compression molded body.