abstract
As we all know, various failure situations may occur in the use of contacts. Similarly, the factors that affect the normal operation of Electrical Tungsten Contact Rivets are also extremely complex, but they can be summarized into two types.
1. External factors. That is, they are determined by the working environment and working characteristics of the Tungsten Contacts, including current characteristics, surrounding media, Tungsten Contact closing and breaking speed, and initial pressure.
2. Internal factors. That is, they are determined by the structural dimensions, particle size composition, manufacturing process, and application occasions of the contacts themselves.
Internal influencing factors
1) Structural dimensions.
Theoretically, due to the relatively dispersed energy, the larger the structural dimensions of the contacts, the stronger their ability to resist arc burning during use. However, in practical applications, due to the limitations of the entire electrical switch structure, the size of the Tungsten Metal Small Polished Discs with 99.95% purity cannot be very large. Recently, some people have developed hollow contacts, plug-in contacts, or contacts with arc-starting angles or arc-starting rings. The purpose is to dissipate heat faster after the arc is generated and to keep the contacts in good contact after burning.
2) Manufacturing process.
At present, domestic manufacturers of copper-tungsten electrical contact materials generally use mixing, pressing, sintering, and infiltration methods (or impregnation methods). The difference is that some use a pre-burned tungsten skeleton melt impregnation process for extraction, while others do not. In recent years, to improve the service life of electrical contact materials, foreign countries have adopted more advanced manufacturing processes, such as fiber reinforcement, isostatic pressing-impregnation method, sintering and rolling process, ion implantation, arc melting method, etc.
3) Tungsten powder particle size.
Regarding the powder particle size composition, that is, the effect of the size of tungsten powder on the performance of tungsten-copper electrical contact materials, studies have shown that contacts made of finer or coarser tungsten powder have poor arc burn resistance. The idea is to mix coarse and fine tungsten powder in a certain proportion to manufacture, but it should be noted that contact materials of different components should be mixed in different proportions.
4) Application occasions.
Experiments have found that contact materials of different components have their best application occasions. For example, in sulfur hexafluoride circuit breakers, Cu20~30/W80~70; in air or vacuum switches, Cu10/W90; in oil circuit breakers, Cu15~20/W85~80 are the most resistant to burning.
External influencing factors
Research shows that different current characteristics produce different characteristics during the on-off process, and there are also differences in the burning intensity of the contact. Once the contact is selected, its current characteristic is a fixed value, and the surrounding medium has a greater impact on the arc-extinguishing ability of the electrical contact. If the arc extinguishing ability of the medium is strong, the arc burning of the contact material can be reduced to a large extent (it is one of the main reasons for the failure of the electrical contact). In addition, factors such as the breaking and closing speed of the contact and the initial closing pressure have a greater impact on the contact. Because the breaking speed determines the arc burning time, especially the initial opening speed, increasing the initial opening speed will shorten the arc burning time and reduce contact burning. Increasing the initial pressure can reduce the mechanical vibration caused by the impact of the contact, thereby reducing mechanical wear and arc burns.
conclusion
In the 1930s, tungsten-copper high-density alloys began to be developed. Due to its excellent comprehensive performance, it has been widely used in power high-voltage switches. And tungsten-copper alloys have always been highly valued by countries around the world and have become one of the more active research fields in the materials science community. In recent years, due to the good performance and low cost of tungsten-copper composite materials, tungsten-copper composite materials are considered to be new functional materials with great development potential and application prospects.