JPS588530B2 - Manufacturing method of electrode material for vacuum switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing electrode materials for vacuum switches such as vacuum breakers and vacuum contactors, and particularly relates to a method of manufacturing electrode materials for vacuum switches such as vacuum breakers and vacuum contactors, and in particular, tungsten carbide-silver-cobalt (WC-) having stable contact resistance and breaking properties.
The present invention relates to a method for manufacturing a Ag-Co) based electrode material.

Electrode material for vacuum switches (hereinafter referred to as electrode material).

), tungsten carbide-silver-(WC-Ag) type materials are often used because of their low cutting current values.

The present inventors have discovered that stable contact resistance and interrupting properties can be obtained by adding a predetermined amount of CO to the WC-Ag system.

Now, as a method for adding Co to WC-Ag-Co based materials, a method using powder is generally known.

That is, this is a method in which a predetermined amount of cobalt powder and a predetermined amount of Ag powder are added and mixed to WC powder, the mixture is molded, and then sintered.

However, according to this method, it is difficult to uniformly disperse the WC powder and the cobalt powder, and the resulting sintered body does not necessarily have stable characteristics as an electrode material.

As a result of repeated research to improve this point, the inventor found that the WC
It has been found that the addition of Co in Ag-Co-based materials mainly works to improve the sinterability of WC, and this affects the stability of contact resistance, blocking performance, and low surge performance as an electrode material.

Based on this knowledge, the present invention aims to improve the characteristics as an electrode material by uniformly dispersing WC and cobalt.

The purpose is to improve the characteristics as an electrode material by strengthening the base skeleton of WC-Co and stabilizing the effect of adding Ag.

That is, in the manufacturing method according to the present invention, when manufacturing a WC-Ag-Co vacuum switch electrode material, carbon is added to the WC powder.
It is characterized in that WC and Co are uniformly dispersed by including a step of coating o.

As a method for coating WCKCo, chemical plating is reliable and practical.

By the method of the present invention and the conventional method, WC-35%
, Ag-3.9% Co were manufactured and their properties were compared.

The results are shown in the table.

The characteristics in the table are expressed by the results of the opening/closing test and the breaking test under the following conditions.

Voltage: 1.5KV, current: 5KA Electrode dimensions: diameter 25.4mm, degree of vacuum: 105torr
As is clear from the table, the material obtained by the method of the present invention has a low breaking current value, a low and stable contact resistance, and a high breaking limit, making it extremely suitable as an electrode material.

In particular, sample number 4 has particularly stable contact resistance and is excellent in other properties as well.

In addition, in addition to the methods shown in the table, we also tried a method of coating WC powder with Co by vapor deposition, and a method of coating WC powder with Co by vapor phase plating, but in the case of the former, C
Due to the high melting point of Co, vapor deposition is difficult and almost no coating is possible, and in the latter case, it takes a long time to coat and it is difficult to coat a predetermined amount of Co.

According to the inventor's research, the chemical plating method for coating WC with Co can reliably and uniformly coat a predetermined amount of Co in a short time.

Among these, a method in which cobalt is added to WC together with nitric acid as a cobalt nitrate aqueous solution and cobalt is precipitated on WC while being neutralized with an alkaline solution improves the properties as an electrode material.

Example 1 A cobalt chloride aqueous solution was added to tungsten carbide powder having an average particle size of about 2 microns, and drying was performed in a low depth.

This was degassed to 101 torr in a quartz container, and while being heated to about 450° C., high purity hydrogen was passed through it to obtain a tungsten carbide-cobalt composite powder.

Add silver nitrate, aqueous ammonia, and sodium hydroxide (1 each
Aqueous solution with a concentration of mol/l) is added to form a tungsten carbide-cobalt silver composite powder by a so-called silver mirror reaction.
This was molded at a molding pressure of 1.5 ton/cm2, 1200
After sintering in hydrogen at 0.degree. C., the material was pressurized again at 3 ton/cm.sup.2 or more, and further vacuum purification was performed at 1200.degree. C. and 104 torr to obtain an electrode.

The electrode thus obtained had excellent electrode properties.

Example 2 An aqueous solution of cobalt nitrate, aqueous ammonia, and an aqueous sodium hydroxide solution were added to tungsten carbide powder with an average particle size of about 2 microns to form a tungsten carbide-cobalt composite powder, which was molded at a molding pressure of 2 ton/cm. ℃
Sintered in hydrogen, infiltrated with silver in hydrogen at 1100°C, 12
A vacuum purification treatment was performed at 00° C. and 104 torr to obtain an electrode.

(Corresponding to sample number 4) The thus obtained electrode had particularly stable contact resistance and was extremely desirable.

The improvement in the properties of the electrode material by the method of the present invention can be considered as follows.

With the electrode material of air switches, an arc is generated using air and other ions as a medium when switching in air, and the movement of the arc is determined by various surrounding conditions, whereas with the electrode of a vacuum switch, the movement of the arc is determined by various surrounding conditions depends mostly on the uniformity of the electrode surface.

Therefore, by forming a uniform skeleton of WC-Co by the method of the present invention, Ag is uniformly dispersed, and as a result, the surface potential of the electrode becomes uniform, allowing the arc to move freely and receive the arc over a wide electrode surface. Therefore, it is thought that the electrode characteristics are improved.

This stabilizes the contact resistance, and with the same dimensions, the breaking capacity can be increased, and the electrode can be easily miniaturized.

Claims (1)

[Scope of Claims] 1. A method for producing an electrode material for a vacuum switch, which comprises the step of coating tungsten carbide powder with cobalt in producing a tungsten carbide-silver-cobalt based electrode material for a vacuum switch. The manufacturing method according to claim 1, characterized in that tungsten dicarbide powder is coated with cobalt by chemical plating. 3. The manufacturing method according to claim 2, wherein cobalt is added as an aqueous solution of cobalt nitrate together with nitric acid, and cobalt is precipitated on the tungsten carbide powder while being neutralized with an alkaline solution.