JPH0265021A - Contact material for vacuum valve - Google Patents

Abstract

PURPOSE:To aim at lowering the cut current by selecting a specific tungsten carbide particle in a contact material made of the eutectic crystal of copper silver, cobalt and tungsten carbide. CONSTITUTION:The smaller a tungsten carbide particle, an arc-resistant material in contact material, is, the smaller its cut value is, but from the economical point of view, the easiness in making and the effect are correlative so that it is important to select an effective particle size distribton. The tungsten carbide made of more than 80 percent of the particle with its diameter being below 0.8mum and less than 10 percent of the particle with its diameter being over 1mum is selected. The cut current value can be thus considerably lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a contact material that has excellent cutting current characteristics in order to prevent generation of surge voltage in a vacuum breaker.

(Prior Art and Problems to be Solved by the Invention) In a vacuum breaker, it is necessary to reduce the cutting current in order to prevent the generation of surge voltage.

Conventionally, materials made of silver, cobalt, and tungsten carbide are known as basic materials for low-surge contact materials. And the average grain size of tungsten carbide is usually IP
It was more than that.

Regarding vacuum contacts, there is a strong desire to lower both the maximum value and average value of the cutting current characteristics as much as possible.

[Structure of the invention] (Means and effects for solving the problem) The present inventor was able to significantly reduce the cutting current by selecting fine tungsten carbide particles with a particle size below a certain level. .

That is, the present invention provides a contact material for a vacuum valve made of eutectic copper and silver, cobalt, and tungsten carbide, in which 80% or more of the tungsten carbide particles have a particle size of 0.8 or less, and the material has a particle size of IP or more. is 10% or less.

The contact material of the present invention has a content of silver and copper of 25 to 65% by weight, and a ratio of silver to the total weight of silver and copper of 40 to 9.
A highly conductive material consisting of a eutectic of copper and silver containing 0% by weight; an auxiliary material consisting of O, 1 to 1.0% by weight of cobalt, and an arc-resistant material consisting of 35 to 75% by weight of tungsten carbide. Ru.

The smaller the tungsten carbide particles, the smaller the cutting value, but economically there is a correlation between ease of production and effectiveness, and it is important to select an effective particle size distribution. The tungsten carbide of the present invention requires that 80% or more have a particle size of 0.8 or less, and 10% or less has a particle size of IP or more.

Examples of the present invention are shown below.

Examples 1 to 4 Raw material powders were obtained by adding and mixing half of the predetermined amounts of Ag and Cu powders to WC powder and Co powder. This raw material powder is 1 to 7
The molded body was molded at a pressure of t/cm2, and the molded body was sintered at 1200° C. for 1 hour in a non-oxidizing atmosphere to obtain a pressed compact. The remaining amount of Ag and Cu was added to this sintered body in a hydrogen atmosphere at a temperature of 1100~
A contact material was obtained by impregnation at 1200° C. for 1 hour, from which contacts were manufactured. Table 1 shows the compositions of the contact materials obtained in Examples 1 to 4 and Comparative Examples 1 to 4 depending on the particle size distribution of the WC powder used.

Table 2 shows the results of testing the cutting current characteristics of the contacts manufactured according to the above examples.

The cutting current was measured as follows.

Diameter 10mm, thickness 4mm, one side is flat, the other is 20mm
A pair of test contacts with a spherical surface of 0 mmH was heated to 400°C.
After baking and discharge aging, the voltage drop across a coaxial shunt inserted in series was observed using a synchroscope. A current of 44 A was applied to the contact through the L and C circuits, and the cutting current value after 300 openings and closings at a contact pressure of 10 kg was compared with the average value of the contact material shown in Example 4 as 1.0. It was shown in In addition, the numerical value is the number of contacts 3
This is the average value of

Table [Effects of the Invention] By making the tungsten carbide particles, which are the arc-resistant material in the contact material of the present invention, 80% or more of them have a particle size of 0.8 pm or less, and 10% or less of tungsten carbide particles that have a particle size of IP or more. ,
As is clear from Table 2, the cutting current value can be significantly reduced.

Claims (1)

[Claims] In a vacuum valve contact material made of copper and silver eutectic, cobalt and tungsten carbide, 80% or more of the tungsten carbide particles have a particle size of 0.8 μm or less, and 1
A contact material for a vacuum valve, characterized in that the content of particles larger than μm is 10% or less.