JPS5849633B2 - electrical contact materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a silver monoxide-based electrical contact material produced by an internal oxidation method.

The main characteristics required of electrical contact materials are excellent welding resistance, low wear, and stable contact resistance.

Although there is no material that satisfies all of these characteristics, silver-tungsten, silver-tungsten carbide, silver-nickel, silver-cadmium monoxide composite alloys, etc. are generally used as electrical contact materials.

Silver cadmium monoxide composite alloy has more stable contact resistance than other composite alloy contact materials, and has relatively low wear and tear.
Widely used as a material for small to medium capacity electrical contacts.

However, it has poorer adhesion resistance than silver-tungsten and silver-tungsten carbide composite alloys, and therefore cannot be used as a large-capacity electrical contact material.

Furthermore, with the recent miniaturization of equipment, the characteristics required of electrical contact materials have become more severe, and conventional silver cadmium monoxide electrical contact materials have poor welding resistance and are no longer usable.

The conventional improvement of silver-cadmium monoxide-based electrical contact materials involves adding trace amounts of other elements to a silver-cadmium monoxide composite alloy containing 10-odd ★ cadmium oxide by weight to improve the size of precipitated cadmium oxide particles. In other words, efforts have been made to improve the welding resistance mainly by making the precipitated particles finer.

In this case, the oxide dispersed in the silver base is mainly cadmium oxide, and although the dispersion becomes finer and the welding resistance is improved to some extent, there is a limit to this.

The present invention relates to an electrical contact material that eliminates the above-mentioned drawbacks, and its gist is that the weight ratio of metal cadmium is 1 to 1.
Cadmium oxide containing 20%, metallic tin exceeding 5% and 10%
This is an electrical contact material characterized by comprising tin oxide containing up to 5% to 15% of metallic indium, indium oxide containing more than 5% to 15% of metallic indium, and the balance being silver.

Here, the melting point and sublimation point of each of the above oxides are as shown in Table 1 below.

Below, we will show the experiments that led to the development of the inventive material and the results.

First, the materials shown in Table 2 below were melted in a high-frequency melting furnace and cast into a mold to obtain an ingot.

A silver layer is adhered to one side of the ingot, rolled to a predetermined size, cut into a predetermined size, and internally oxidized at 700°C and under an oxygen pressure of 3 atm to form silver cadmium monoxide, tin monoxide, and so on. An indium composite alloy was obtained.

Its physical properties are also shown in Table 2 below.

For these samples C, the welding resistance and the amount of wear were measured under the conditions shown in Table 3 by short-circuiting one terminal of the charged capacitor using a commercially available relay.

The results are shown in Table 4.Next, among the above samples, samples 41, 2, 5, and 76 were tested using a commercially available 30A type no-fuse breaker.
A short circuit test was conducted based on the IS standard (JIS-C-8370).

The test conditions were a voltage of 220 V AC and a short circuit current of 2500 A, and three test machines were used for each sample.

The results are shown in Table 5.

As is clear from the above results, the amount of cadmium oxide is 1% to 20% as metal cadmium by weight.
If it is less than 20%, there will be no dispersion effect, and if it exceeds 20%, the internal oxidation rate will slow, productivity will deteriorate, the precipitated particles will become coarse, and the contact performance will deteriorate.

The reason why the amount of tin oxide is set to more than 5% and up to 10% as metallic tin by weight is that if it is less than 5%, there is no dispersion effect and it becomes 10%.
This is because if it exceeds the limit of solid solubility in silver, processability deteriorates and internal oxidation becomes difficult.

The reason why the amount of indium oxide is set at more than 5% and up to 15% by weight as metallic indium is because if it is less than 5%, the welding resistance is not very good, and if it exceeds 15%, internal oxidation becomes difficult.

As described above, according to the material of the present invention, tin oxide, which has better fire resistance and arc resistance than cadmium oxide,
Since both samples contain indium oxide, they are superior to samples A6 and A7, which are conventional electrical contact materials of the same type, in terms of welding resistance and wear resistance.

Claims (1)

[Claims] 1. It is characterized by consisting of cadmium oxide containing 1 to 20% of metallic cadmium by weight ratio, tin oxide containing more than 5% and up to 10% of metallic tin, indium oxide containing more than 5% and up to 15% of metallic indium, and the balance being silver. electrical contact materials.