JPS6218613B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Technical Field The present invention relates to electrical contact materials used in air circuit breakers and switches such as no-fuse breakers. (b) Technical background As is well known, the requirements for electrical contact materials are high welding resistance. It has excellent corrosion resistance, excellent insulation properties, long switching life, and low contact resistance. Among these requirements, the welding resistance and insulation resistance of the contacts are the most important for no-fuse breakers, disconnectors, and switches that serve as protective equipment for electrical circuits. The contact materials used as air contacts to protect these electric circuits include relatively many silver-oxide contacts made by internal oxidation, and in higher current ranges, silver-tungsten carbide, silver-tungsten contacts, etc. is used. The reason why silver-oxide contacts are relatively often used as air contacts is that they have high resistance to welding and arc wear against current application and tearing, and they have low contact resistance even when the contacts are opened and closed many times. This is because it maintains a good balance of excellent properties as a contact, such as a small increase in the amount of electricity and high conductivity. However, along with the miniaturization and performance improvement of switching equipment, there is a growing desire for improved contact performance, and in particular, contacts that have both anti-welding performance and dielectric strength characteristics are considered important. If the contacts do not open when they should, but instead become firmly welded and cannot be disconnected, or if the dielectric strength deteriorates after the welding breaks, it may cause damage to electrical equipment, electric shock, etc., and cause secondary damage. It will cause a disaster. There are two main ways to obtain silver-oxide contacts: powder metallurgy and internal oxidation.
Each method is used depending on the purpose, but the internal oxidation method is most commonly used because it is advantageous in terms of performance and cost. The internal oxidation method, needless to say, applies the phenomenon that when an alloy is heated to high temperature in an atmosphere that is sufficiently supplied with oxygen, the constituent metals of the alloy are selectively oxidized before the base of the alloy is oxidized. It is something. As mentioned above, welding resistance and insulation resistance are the most important characteristics for silver-oxide contacts in no-fuse breakers used in air.
Furthermore, high-performance materials are required. Conventionally, silver-tin-indium alloys have been used for such purposes, but this has a drawback of temperature rise characteristics, but this has been improved by internally oxidizing the alloy with cadmium. It is known that However, the conventional silver-tin-indium
Although cadmium alloys improve temperature rise, they do not have sufficient insulation resistance or welding resistance, and there is a problem in that cadmium scatters and deteriorates due to arc heat when the contacts open and close under load. (C) Disclosure of the Invention The present invention relates to high current switching of contacts, particularly anti-welding,
As a result of various studies regarding insulation resistance properties and temperature rise properties, we found that tin is more than 6% by weight and up to 8% by weight, indium is 2 to 4% by weight, cadmium is 1% by weight.
~3% by weight and 0.10 to 0.30% by weight of Ni and 0.001 to 0.008 to make the alloy fine and uniform.
By adding % by weight of Mn and internally oxidizing these alloys, it is possible to achieve excellent welding resistance, insulation resistance, and temperature rise properties that were previously unattainable. By making the tetraoxide into fine spherules, the amount of arc generated during load switching of electrical contacts is extremely reduced, and as a result, the insulation properties are greatly improved compared to conventional silver-tin-indium-cadmium contacts. Moreover, an electrical contact with excellent welding resistance and temperature rise could be obtained. In the alloy of the present invention, nickel is
The reason why 0.1% by weight is set as the lower limit is because below this, the effect of making the oxide finer is small. In addition, the upper limit for the amount of nickel is 0.3% by weight.
Above that, nickel segregates and uniform dispersion becomes difficult. Note that when the Ni amount is 0.20% by weight, the tin-indium-cadmium oxide is most uniformly dispersed, and the effect of improving welding resistance is most remarkable. The reason why the lower limit of the amount of tin is set to 6% by weight is that if the content is less than this, the oxide content is small and the effect of welding resistance is small. In addition, the upper limit for the amount of tin was set at 8 weight because if the content exceeds 8 weight, workability deteriorates and tin oxide aggregates within the alloy, making internal oxidation unstable. That would be very unlikely. Further, the lower limit of indium is set to 2% by weight because if the indium content is less than this, internal oxidation becomes unstable, oxide agglomeration occurs, and welding resistance cannot be ensured.
In addition, the upper limit of indium was set at 4% by weight because
If it is more than this, the oxide tends to become acicular
This is because sufficient fineness and spheroidization cannot be obtained by adding Mn and Mn, and the welding resistance is, on the contrary, inferior. Moreover, since indium is expensive, it is desirable to minimize the amount of indium necessary. The lower limit of cadmium content was set to 1% by weight because
This is because if the content is less than this, there is little effect on welding resistance and improvement of temperature rise characteristics. Further, the reason why the upper limit of the amount of cadmium is set to 3% by weight is that the insulation properties deteriorate if the content exceeds this value. The reason why the lower limit of the amount of manganese is set to 0.001% by weight is that a content below this value has little effect on spheroidizing the oxide. Furthermore, the upper limit of Mn that exhibits an effect on the spheroidization of the oxides of tin, indium, and cadmium is 0.008% by weight. This is because if the amount is increased more than this, the oxide becomes extremely fine and agglomeration, cracking, etc. are likely to occur due to slight fluctuations in oxidation temperature or oxygen pressure. Preferably,
It is 0.005% by weight. The alloy of the present invention is produced by adding nickel and manganese to the silver-tin-indium-cadmium alloy as described above and causing internal oxidation.
(SnO ₂ / CdO / In ₂ O ₃ ), it contains a large amount of fine metal oxides to ensure welding resistance, and at the same time does not easily evaporate or scatter, such as SnO ₂ / In ₂ O ₃ By using oxide as the main constituent, deterioration of insulation voltage due to evaporation and scattering is prevented, and as a result, it simultaneously exhibits excellent insulation resistance and anti-welding properties that could not have been expected in the past. Next, the present invention will be explained in detail by way of examples. Example Ingots were made by melting each ingot at 6 kg/lot with the composition shown in Table 1. After rolling, the ingots were punched out into a shape of 6φ x 0.5 x 30R as shown in Figure 1, and heated at 720°C. After internal oxidation in an oxidizing atmosphere with an oxygen pressure of 4 atm, the 6φ×1×3φ× shown in FIG.
The brazed Cu screw of No. 4 was incorporated into a 50A rated wiring breaker, and an evaluation test was conducted under the test conditions shown in Table 2.

【table】

[Table] In addition, after overload and durability tests, the
A temperature rise test was conducted by applying AC5V and a current of 50A. Furthermore, insulation deterioration between terminals was measured after the short circuit test. Table 3 shows the results of testing the same sample installed in five 50A rated wiring breakers. As a comparison material, a contact point of the same shape as the present invention material was made with the composition shown in Table 1, and the temperature was
The material used was internally oxidized in an oxidizing atmosphere at 720°C and oxygen pressure of 4 atm.

【table】

[Table] As is clear from Table 3, the material of the present invention has well-balanced and excellent performance in insulation resistance in the large current region, welding resistance, and temperature rise. As detailed above, the contact material of the present invention is
When switching large currents, it has extremely high insulation resistance and welding resistance, and can be used in air circuit breakers and switchgears such as no-fuse breakers and safety breakers.
Make full use of its effects.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a test piece according to an embodiment of the present invention, in which 1 is the electrical contact material of the present invention, and 2 is a base metal copper screw.

Claims (1)

[Claims] 1 In the silver-oxide contact material obtained by the internal oxidation method, tin is 6% by weight as a metal component.
% up to 8%, 2-4% indium, 1-3% cadmium, 0.1-0.3% nickel, and 0.001-0.008% manganese, the balance being silver. Electrical contact material for circuit breakers.