Silver-Tungsten Carbide-Carbon Electric Contact

In recent years, with the development of low-voltage electrical industry, various series of new circuit breakers have been introduced. These new circuit breakers require contact materials with smaller volume and higher breaking capacity. At present, the matching of AgWC₁₂C₃ and AgW50 is often used as asymmetrical and reasonable matching contacts of circuit breakers in AgWC-C electrical contact materials, so as to improve the arc resistance and material transfer resistance of AgWC-graphite electrical contact materials, which is the necessary condition for expanding the application range of AgWC-graphite contact materials and meeting the increasingly stringent performance requirements of circuit breakers for contact materials.

In order to improve the performance, some scholars have designed a voltage-resistant Ag-WC-C electrical contact material. The preparation process includes the following steps:

(1)Tungsten carbide-reinforced phase solid solution is mixed with graphite, additive elements and silver powder in proportion. The mixing method is one of dry mixing or wet mixing.

(2)Mixed powder is granulated in a protective atmosphere, in which the granulation temperature is 650-850 ℃ and the time is 0.5-5 hours in a high temperature sintering furnace.

(3)The initial pressing pressure of the granulated powder is 50 MPa to 200 Mpa.

(4)The compact is sintered in a protective atmosphere. The sintering temperature of the compact is 850-920 ℃, and the sintering time is 3-5 hours. The compact is protected by hydrogen atmosphere.

(5)The sintered green body is repressed once, and the first repression pressure of the sintered green body is 100-300 MPa.

(6)The re-compacted green body is annealed, the annealing temperature is 550-650 ℃, and the annealing time is 2-4 hours.

(7)The final product is obtained by secondary repression of the annealed green body.

The solid solution of tungsten carbide, tantalum carbide and chromium carbide was used in the preparation of silver-tungsten carbide-carbon series electrical contact materials. Tantalum carbide and chromium carbide can obviously reduce the grain size and adjacency of tungsten carbide, and improve the bonding strength of matrix. At the same time, TaC phase can improve the wettability of carbide phase by adding elements Ni, Co, Cr and B, and enhance the bonding strength of matrix. This new type of silver tungsten carbide graphite contact material has higher voltage strength, welding resistance and arc burning resistance. The low-voltage electrical apparatus using this contact material has high electrical life and high reliability. Therefore, this kind of electrical contact material is more suitable for various plastic case circuit breakers, small high breakers and AC contactors.

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