There are many kinds of low-voltage electrical products, which play an irreplaceable and important role in the national economy. There are about 800 series of low-voltage electrical products in our country, which basically meet the needs of the development of our national economy. Low-voltage electrical products mainly include contactors, relays, circuit breakers, fuses, push button switches, transfer switches, signal lights, etc. Electrical contacts are key components in these low-voltage electrical appliances, and their performance directly affects the stability and reliability of the electrical appliance's operation. Different types of low-voltage electrical appliances have different uses and have different requirements for contact materials. The performance of electrical contact materials directly determines the performance of electrical contacts. For designers of low-voltage electrical appliances, understanding the characteristics of various electrical contact materials is of great significance in their electrical appliance design, and can often get twice the result with half the effort.

    Electrical contacts are the "heart" of low-voltage electrical appliances. According to the use of low-voltage electrical appliances, designers of low-voltage electrical appliances require that electrical contact materials must have the following characteristics:

    ① Good electrical and thermal conductivity

    ② Resistance to welding

    ③ Electrical wear resistance

    ④ Arc re-ignition is less likely to occur when breaking large currents

    ⑤ Low interception level

    ⑥ Low gas content

    These six characteristics are guiding requirements for electrical contact material designers. These characteristics must be fully taken into account in the material composition design and processing technology design.

    According to the different working methods of electrical contacts, the requirements for contact materials on switch devices can be divided into basic categories of contact performance: electrophysical properties, thermodynamic properties, mechanical properties and chemical properties. The interrelationship between various influencing factors, reaction processes and physical and chemical properties of materials during the use of contacts illustrates the basic requirements for contact materials.

    It can be seen from the above comprehensive requirements on material properties that these requirements are diverse and contradictory. Achieving these requirements in one material is almost impossible. Some high melting point metals and graphite can partially meet these requirements. They have high thermophysical properties, high electron work function and ionization energy. Although their corrosion resistance is not high, their oxides are volatile or conductive. However, these materials have many shortcomings: their electrical and thermal conductivity is insufficient, and their plasticity and heat resistance are not high. Therefore, contacts prepared from these materials will undergo fatigue fracture under mechanical and thermal effects. Silver and gold have good electrical and thermal conductivity, good plasticity and high corrosion resistance, but their thermophysical properties are not high and they do not have good electrical corrosion resistance.

    While mutually exclusive properties cannot coexist in one material, they can be combined in composite materials.

    The diverse requirements for the properties of electrical contact materials reflect the complexity and diversity of factors affecting the use of contacts and the physical and chemical processes on the contact surface, and these factors and processes interact with each other. This leads to hypotheses about multiple meanings of experimental facts and brings a considerable amount of empiricism into the design process of new materials. Slight differences in process in material preparation may have increased this empirical component.

——The content of the article comes from the Internet