JPS60100354A - Processing method for tungsten electrode - Google Patents

Abstract

PURPOSE:To easily process a tungsten electrode used in an arc discharge lamp, and so on without using cutting processing by discharging the electrode under inert atmospheres containing nitrogen and making the discharge tip side of the electrode spherical using the heat. CONSTITUTION:When a tungsten electrode used in an arc discharge lamp, and so on is processed, a tungsten rod 7 cut in a preset length is fixed to a chuck 6 and is airtightly arranged on both ends of a chamber 3. In addition, after the inner part of the chamber 3 is exhausted through an exhaust pipe 1, the inert gas containing nitrogen gas is sealed in 3-1,000Torr or less and direct current or alternate current is applied to the terminal 4 of the enclosure body 2 of the chamber 3 to generate discharge between the tungsten rods and then the tip of the tungsten rod 7 is made spherical by the heat. As a result, spherical processing can be performed and the arc spot of the discharge lamp can be stabilized.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a method for processing tungsten electrodes.

In particular, the present invention relates to improvements in methods for processing tungsten electrodes to make them suitable for discharge electrodes in arc discharge lamps.

[Technical background and problems of the invention]

As is well known, tungsten electrodes are normally used as discharge electrodes in arc discharge lamps and the like. By the way, this tungsten electrode is generally made by cutting a tungsten rod substantially at right angles to the axial direction, and the end surface on the discharge side has a flat shape. However, in the case of arc discharge lamps equipped with lightning and lightning, the initial arc spot during discharge (lighting) is formed as a burr-like spot on the electrode end surface that remains during cutting, which also causes the above-mentioned inconvenient problem. On the other hand, attempts have been made to make the tip (discharge side) of the tungsten electrode into a spherical shape, for example, by cutting, but this is impractical as it requires complicated cutting of hard tungsten.

On the other hand, a method is also known in which, after completion of the arc discharge lamp, a voltage is applied to cause a large current to flow between the two electrodes, thereby making the discharge side end surface of the sealed tungsten electrode into a spherical shape. However, in this case, since a larger current flows than when the lamp is lit steadily, there are problems in terms of practical use, such as operation being dangerous.

[Purpose of the invention]

The present invention has been made in response to these circumstances, and it is an object of the present invention to provide a processing method that can easily and mass-produce tungsten electrodes suitable for arc discharge lamps.

[Key points of the invention]

In the present invention, a tungsten rod for an electrode of an arc discharge lamp is used as an electrode, and a required voltage is applied to the electrode in an inert atmosphere containing at least nitrogen to cause discharge.

This method of processing a tungsten electrode is characterized by comprising the step of sphericalizing the discharge side tip of a tungsten rod forming the electrode using heat generated by the discharge.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings showing an example of the configuration of an apparatus for carrying out the processing method of the present invention. The attached drawing shows a cross-sectional view of the main part of the device. First, a chamber (3) is prepared which is equipped with an exhaust pipe (1) and has removable closing bodies (2) at both ends. The closure bodies (2) each have an electric terminal (4) on the outside, and a chuck (6) equipped with a tightening screw (5) for fixing the electrode rod inside the chamber (3).
) is provided. The chuck (6) of the closing body (4) is fixed with a tungsten rod cut to the required length to form an electrode. 3) They are each airtightly attached to the chamber (3) so as to be sealed therein.

Next, the inside of the chamber (3) is evacuated through the exhaust pipe (1), and then nitrogen gas or an inert gas containing nitrogen is injected into the chamber (3).
It is sealed in a chamber (3) at about 1000 torr.

The inside of the chamber (3) is made into an inert atmosphere containing nitrogen.

However, a direct current or alternating current of several hundred to several thousand volts is applied to the electrical terminal (4) of the closure body (2), and a discharge is caused in the tungsten rod (7) in an inert atmosphere containing nitrogen. . Due to the discharge between the tungsten rods (7), the discharge side tips of both the tungsten rods (7) are easily spherical, and a tungsten electrode suitable for arc discharge lamps is obtained. The time for the tip of the tungsten rod (7) to become spheroidized is almost unaffected by the thickness if the tungsten rod (7) has a diameter of 0.2 to 5 mm as long as the current density to the electrode is constant. is about the same as y.

The tungsten electrode used in the present invention is not limited to pure tungsten, but may also be tungsten doped with a trace amount of thoria, alumina, silica, or the like. In addition, the inert atmosphere containing nitrogen, which is an important requirement in electric discharge machining, may be nitrogen only, but may also be nitrogen-argon system, nitrogen-xenon system, etc. In this case, the nitrogen composition ratio is generally at least 10%. It is preferable to choose

〔Effect of the invention〕

As described above, according to the present invention, the discharge end side of the tungsten electrode can be easily machined into a spherical shape, and even when mounted in an arc discharge lamp, stable discharge can be achieved. For example, choose argon (no nitrogen) for the atmosphere during electrical discharge machining and use a tungsten rod (electrode).
When electrical discharge machining was carried out by applying a current of 15 A per 1 to 2, the tip of the tungsten electrode on the discharge side hardly deformed (it did not become spherical), whereas in the case of 2 according to the present invention (
Example of 10% nitrogen - 90% argon atmosphere) Even if a current of 7.5 A was applied per tungsten electrode 1y+it2 and electrical discharge machining was performed, it was possible to easily obtain an electrode with a spherical tip at the discharge side.

As described above, according to the present invention, a tungsten electrode with a spherical tip suitable for arc discharge lamps can be easily obtained.9 It is believed that the reason is as follows. That is, tungsten used for the electrodes of this type of arc discharge lamp usually has a melting point of 3000C or higher and is difficult to melt and deform. However, in the present invention, electrical discharge machining is carried out in an inert atmosphere containing at least nitrogen, and during this electrical discharge machining process, partially chambered tungsten is produced transiently (temporarily), which contributes to lowering the melting point. Therefore, in the processing method according to the present invention, it is thought that even with discharge with a small input power, the tip of the tungsten rod melts and easily forms a spherical shape due to surface tension. However, even if some of the tungsten nitrides mentioned above are generated, it will be temporary and will not pose a practical problem even when installed in an arc discharge lamp, but if necessary, further vacuum treatment can be performed after electrical discharge machining to remove nitrogen. It is better to plan.

[Brief explanation of drawings]

The accompanying drawings are explanatory diagrams showing embodiments of the method of the present invention. (3)...Chamber, (4)...Electrical terminal, (
7) Tungsten rod agent Patent attorney Kensuke Chika (and 1 other person)

Claims (1)

[Claims] 1. A method for processing a tungsten electrode, comprising the step of subjecting a tungsten rod to an electrode in an inert atmosphere containing at least nitrogen, and spheroidizing the tip of the electrode on the discharge side.