JPS6348028Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an electrical contact with excellent wear resistance and welding resistance. Conventionally, the current value is medium (about several 10s to several 100A)
Electrical contacts used in electrical equipment such as electromagnetic switches and wiring circuit breakers include cadmium oxide-silver contacts consisting of 5 to 15% by weight of cadmium oxide and 95 to 85% by weight of silver, or nickel 10.
Nickel-silver contacts made of ~20% by weight and 90-80% by weight of silver are used in combination with similar types. In particular, the former type of cadmium oxide-silver contacts has been widely used because of its excellent welding resistance, but since cadmium oxide thermally decomposes at around 700°C, silver is also scattered at the same time. It was subject to severe wear and tear, and was therefore prone to insulation deterioration. Also,
Cadmium compounds are harmful cadmium compounds, so from the viewpoint of manufacturing and pollution prevention,
It is desired to develop electrical contacts that do not use this. In addition, the latter type of nickel-silver contact has good workability due to the nickel itself, so even if the proportion of nickel is increased, the workability is not impaired, and in terms of contact performance, the contact resistance is relatively low and stable. It also has excellent wear resistance, so it is often used in practical applications. However, this electrical contact has a disadvantage in that it is inferior in welding resistance compared to the former electrical contact, and is particularly susceptible to initial welding. In this way, in conventional electrical contacts, both the fixed contact and the movable contact are made of the same contact material, so if the welding resistance is good, the abrasion resistance is poor; Problems such as poor welding resistance were observed when the properties were good. Therefore, after various studies in search of an electrical contact that satisfies both wear resistance and welding resistance, the inventor of the present invention decided to use the nickel-silver contact as one of the switching contacts, and make the other contact with copper. - We have previously discovered that this problem can be effectively solved by using a silver-based contact (see Japanese Utility Model Application Publication No. 155118/1983). As a result of further study on electrical contacts with such a configuration, the inventor of the present invention found that a part of the nickel component of one nickel-silver contact was further replaced with tungsten carbide or tungsten-titanium double carbide (tungsten carbide and titanium carbide in solid solution). By replacing carbides (industrially they are used in solid solutions in the ratios of 50:50 and 70:30), the added resistance to wear and welding required for electrical contacts can be achieved. We have found that it is possible to achieve improvements in Therefore, the present invention relates to an electrical contact, which comprises a modified nickel-silver contact consisting of 10 to 60% by weight of nickel, 1 to 10% by weight of tungsten carbide or tungsten-titanium double carbide, and the balance silver, and copper. It serves as an opening/closing contact with a copper-silver type contact consisting of 3 to 20% by weight and 97 to 80% by weight of silver. The modified nickel-silver contact, which serves as one of the opening/closing contacts, is manufactured by powder metallurgy, as has been conventionally done, since nickel and silver hardly form a solid solution. Nickel is carbonyl nickel powder,
It is used in the form of silver-plated carbonyl nickel powder, silver-nickel co-precipitated powder, etc. in a proportion of 10 to 60% by weight, preferably 27 to 48% by weight of the total, but if the mixing proportion is less than this, it has sufficient wear resistance. On the contrary, if it is used at a ratio higher than this, the contact resistance becomes extremely unstable. In addition, when coprecipitated powder or the like is used as nickel, the actual nickel content in the coprecipitated powder becomes the calculation standard. Tungsten carbide or tungsten/titanium double carbide is used in a proportion of 1 to 10% by weight, preferably 2 to 3% by weight, but if the mixing proportion is less than this, the effect of preventing migration to the mating material will be small; If used in such a high proportion, the contact resistance becomes unstable and the sinterability during production is inhibited. In addition, the remaining silver is preferably 50 to 70
It is used in proportions of % by weight. The copper-silver contact, which is the other contact of the opening/closing contact, is
Manufactured using a general melting method. Copper is used in a proportion of 3 to 20% by weight, preferably 7.5 to 10% by weight of the total weight, but if the proportion is less than this, it will increase the welding resistance with the modified nickel-silver type contact that will be the mating contact. On the other hand, if it is used in a proportion higher than this, the contact resistance will increase and the effects of copper oxidation will be seen. One embodiment of a switch provided with such electrical contacts is shown in a plan view in FIG. 1 and in a front view in FIG. 2 of the drawings. That is, screws 1, 1',
Brass fixed contact 2 fixed at 1″,1,
2' is preferably equipped with modified nickel-silver contacts 3, 3' as fixed contacts, and the brass movable contact 4 is preferably equipped with copper-silver contacts 5, 5' as movable contacts. is installed. In the electrical contact according to the present invention, a modified nickel-silver type contact and a copper-silver type contact are used as opening/closing contacts, for example, as described above, and the reason is as follows. In other words, in a modified nickel-silver contact, when the mixing ratio of nickel is increased, the contact surface is very stable and has few irregularities, has good arc blocking properties, and has good wear resistance. Due to the high concentration of nickel, the electric resistance increases, the temperature rises rapidly on the surface, and the welding resistance worsens. By preventing transfer to the material, and by using a copper-silver contact for the mating contact, the electrical resistance is lowered, and by forming the contact with a different material, the ease of welding with the mating material is improved, and these synergistic effects are achieved. As a result, it was possible to form electrical contacts with much better wear resistance and welding resistance than conventional electrical contacts. The electrical contact according to the present invention is mainly used in electrical equipment with a medium current value. This is due to the relationship with the heat generated during opening and closing.At low current values, the copper oxide film formed due to heat generation tends to increase the contact resistance, while at high current values, the contact resistance tends to increase. Sufficient heat resistance cannot be obtained unless tungsten or the like is further added as necessary. Next, the effects of the present invention will be explained with reference to Examples. Example 1 Nickel powder, tungsten carbide powder, and silver powder with an average particle size of several microns were mixed in various proportions (wt%), powder-molded into a predetermined shape, and then sintered in vacuum or in a hydrogen atmosphere. In order to further improve the density, it was recompression molded and then processed into 7.5 mm square or straight 7 mm circular plates (1.5 mm thick) as samples for electrical contact performance tests. Silver soldered on top. On the other hand, copper and silver are used in various proportions (wt%) and alloyed by a melting method, and this is processed into electrical contact performance test samples having the same shape and dimensions as above by processing means such as pressing. It was processed and silver brazed onto a brass base metal. Using these samples, a wear characteristic test and a welding characteristic test were carried out as follows, using a modified nickel-silver contact as a fixed contact and a copper-silver contact as a movable contact. Wear characteristic test: Use the above square contacts for each contact,
Regarding 135A type electromagnetic switch, JIS C-8325 AC
According to Class 3 No. 1 (AC voltage 200V, closed circuit current
480A, breaking current 80A, switching frequency 1200 times/hour),
A 100,000-time opening/closing test was conducted, and the total amount of wear and tear on each of the six contacts was measured. Welding characteristic test: Use the circular contacts mentioned above for each contact, apply electricity to it for two cycles at an AC voltage of 120V and a current of 1200A, measure the welding force with a spring balance, and calculate the 10 measurements for each sample. The average value was determined. The measurement results in each of the above tests are shown in Table 1 below. Note that Nos. 14 and 15 are comparative examples in which the same type of contact material was used. (No.14) Ag87%-CdO13% (No.15) Ag80%-Ni 20%

【table】

[Table] Example 2 In Example 1, nickel-tungsten-titanium double carbide (WC50:
A TiC50 solid solution carbide)-silver sintered plate was used, and wear characteristic tests and welding characteristic tests were similarly conducted. The results obtained are shown in Table 2 below.

[Table] Comparative Example In Example 1, a nickel-silver sintered plate was used as the fixed side contact sample, and a wear characteristic test and a welding characteristic test were similarly conducted. The results obtained are shown in Table 3 below.

[Table] From the above results, the following can be said. (1) The wear resistance of the electrical contact according to the present invention is equivalent to or better than that of electrical contacts made of conventionally used contacts of the same type;
For example, in the case of nickel-tungsten carbide-silver based contacts, in particular modified nickel-silver based contacts with 27-48% by weight of nickel, 2-3% by weight of tungsten carbide and 50-70% by weight of silver and 7.5-10% by weight of copper.
It can be seen that the abrasion resistance of the copper-silver based contacts is significantly superior. (2) Cadmium oxide has traditionally been said to have good welding resistance. Even compared to silver-based contacts, the electrical contacts of this invention are comparable.
Modified nickel-silver contacts with the same mixing proportions as for wear resistance and copper-silver contacts with 7.5 to 10% copper by weight show particularly good properties. (3) Compared to the electrical contacts previously proposed by the present inventor, for example, using a nickel-silver based contact for the fixed side contact and a copper-silver based contact for the movable side contact, the fixed side contact material is By replacing a portion of the nickel with tungsten carbide or tungsten-titanium double carbide, a clear improvement in wear resistance and welding resistance can be seen. Considering the cause of this, it is thought that the addition of tungsten carbide or tungsten/titanium double carbide prevents the transfer to the mating material. Generally, when transfer to the mating material occurs, in this example, the nickel-silver contact part wears out and the unevenness of its surface increases, reducing the lifespan of the contact. Such a contact material effectively prevents this transfer and also improves welding resistance. This is because tungsten carbide or tungsten-titanium double carbide has high hardness and high thermal stability, and has poor wettability with mating metal materials such as copper and silver, making it difficult to transfer. In other words, when these components are dispersed in the nickel-silver system, they improve the heat resistance, improve dispersibility while preventing nickel agglomeration, and serve to strengthen the nickel-silver base. In this way,
Transfer of the three-component contact material to the mating material is prevented, and as a result, formation of irregularities on the contact surface is also prevented.

[Brief explanation of the drawing]

FIG. 1 is a plan view of one embodiment of a switch provided with electrical contacts according to the present invention, and FIG. 2 is a front view thereof. Explanation of symbols: 2... Fixed contact, 3... Fixed side contact, 4... Movable contact, 5... Movable side contact.

Claims (1)

[Scope of utility model registration request] Modified nickel consisting of 10 to 60% by weight of nickel, 1 to 10% by weight of tungsten carbide or tungsten-titanium double carbide, and the remainder silver - Silver-based contacts and copper consisting of 3 to 20% by weight of copper and 97 to 80% by weight of silver. An electrical contact that functions as an opening/closing contact with a silver-based contact.