Chemical Coating Method for Silver Tungsten Carbide Contact Material

Silver tungsten carbide contact material has the advantages of high hardness, oxidation resistance and relatively stable contact resistance compared with silver-tungsten contact material under the same manufacturing process, especially high breaking ability, low corrosion and low welding tendency. Silver tungsten carbide 40 contact material is usually used as contact material in modern circuit breakers abroad. Because of its superior performance, there has been a trend to replace silver tungsten 50.

At present, the traditional process of manufacturing Ag-WC 40 contact material in China is mixing Ag powder with WC and pressing it into skeleton blank of contact material, then sintering and infiltration at high temperature, shaping and pressing it into contact material products. Therefore, in order to obtain high-performance silver tungsten carbide powder contact materials, the first key technology is to manufacture high-purity fine particles of silver powder and tungsten carbide powder. The homogeneous silver tungsten carbide skeleton mixed powder was obtained by mixing powder. However, the traditional powder mixing process is mechanical mixing, and its mixing uniformity is limited by the original particles, that is, the finer the particles, the more difficult it is to mix uniformly.

For this reason, some scholars have proposed a preparation method of silver-tungsten carbide contact material skeleton-coated powder with high homogeneity and good bonding strength.

1.The tungsten carbide powder slurry containing hydrazine hydrate was prepared. The tungsten carbide powder slurry containing hydrazine hydrate was prepared by adding hydrazine hydrate solution to the slurry and ultrasonic treatment.

2.Dispose silver ammonia complex ion dilution solution, ammonia water and silver nitrate complex reaction to obtain silver ammonia complex ion solution, and then after filtration and water dilution to obtain silver ammonia complex ion dilution solution, the amount of ammonia required is: in silver nitrate per kg of silver, the amount of ammonia required is 1.2-2 liters;

3. The silver-coated tungsten carbide powder was prepared by chemical coating method. The silver-ammonia complex ion dilution solution was added slowly to the tungsten carbide powder slurry containing hydrazine hydrate, and the precipitated silver was deposited on the surface of the tungsten carbide particles to form the silver-coated tungsten carbide powder slurry.

4.Cleaning, drying, sintering, pelleting, the silver-coated tungsten carbide slurry is cleaned, dried, sintered and pelleted to form the silver-coated tungsten carbide contact material skeleton powder for the melting and infiltration of the silver-coated tungsten carbide contact material.

The silver tungsten carbide powder was prepared by chemical coating technology, which solved the technical problem that the mechanical mixing powder was difficult to achieve uniformity and good bonding strength because of the fine particles of the powder for a long time in China. The new silver tungsten carbide 40 contact material has good arc resistance, wear resistance, contact resistance stability, oxidation resistance, so that the circuit breaker has a very high short-circuit breaking ability.

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