Silver Nickel Tungsten Carbide Contact

With the development of social economy, there are many applications requiring smart frame circuit breakers to have higher electrical life. Therefore, it is necessary to develop a kind of material with strong resistance to arc erosion as static contacts, which can be used in pairs with AgW50 dynamic contacts, so as to greatly improve the electrical life of intelligent frame circuit breakers and meet the requirements of various applications.

In order to replace the out-of-date Ag-Ni carbide contacts, some scholars added tungsten carbide into the Ag-Ni contacts to make a new Ag-Ni carbide contact material. It is known that this kind of Ag-Ni carbide contact material has strong arc erosion resistance and can greatly improve the electrical life of low-voltage intelligent frame circuit breakers when used in pairs with the existing AgW50 contacts.

The preparation process of silver nickel tungsten carbide contact material includes: selecting tungsten carbide powder with average fineness of 1 micron, - 200 mesh silver powder and - 300 mesh nickel powder, weighing 20 kg of silver-nickel carbide powder according to the following weight percentages (tungsten carbide 25%, nickel 1.55%, residual silver). Putting the powder into 30-liter V mixer for 2.5 hours, mixing the mixed silver nickel tungsten carbide powder and 180 kg of 6m. The high purity nickel ball and 4400 ml deionized water were put into a 100 liter drum ball mill for ball milling (45 rpm). The ball milling time was 30 hours. The powder was taken out and dried for 3 hours (the nickel content in the powder material was 2%) at 120 ℃. The powder was annealed at 700 ℃ in hydrogen atmosphere for 2 hours. The powder was annealed in steel mould under 6 T/cm² pressure. The billet is pressed and sintered at 900 C in hydrogen atmosphere for 1.5 hours. The billet is repressed in steel mould under 10.5T/cm² pressure. The billet is annealed at 500 ℃ in hydrogen atmosphere for 50 minutes. The silver nickel tungsten carbide contact can be obtained.

The silver nickel tungsten carbide static contacts and silver-tungsten 50 dynamic contacts are paired and installed on a low-voltage intelligent frame circuit breaker with rated current of 1600 A. The test proves that the silver nickel tungsten carbide static contacts and silver-tungsten 50 dynamic contacts can match the requirements of the test project stipulated by the circuit breaker, and the electric life of the circuit breaker is greatly improved, reaching more than 8000 times.

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