Why use copper-based electrical contact materials

In order to meet high performance and reduce costs, copper-based contact materials replacing silver-based contact materials is a major development direction.

What materials are there?

Mainly pure copper; copper tungsten; copper chromium; copper oxide, etc.

The properties of these materials

Cu is currently the most widely used electrical contact material due to its excellent electrical conductivity, thermal conductivity and low processing difficulty. Some of copper contacts are tin-plated or silver-plated.

Cu has good electrical conductivity, but low melting point and low strength, while Cr has high melting point and high strength, which can greatly improve the hardness, wear resistance and fusing property of the alloy. At the same time, Cr has a low cutoff value, and as an added element, it has little effect on the resistance of the alloy. Homogeneous Cu-Cr alloy can retain the good properties of Cu and Cr. Therefore, Cu-Cr alloy is widely used as a contact material in 10~40.5 KV medium voltage vacuum interrupter due to its high strength and good electrical conductivity. At present, the Cu content in Cu-Cr contact materials is generally above 50%.

Cu-W contact material inherits the high hardness of W, and has good arc erosion resistance and welding resistance. Pure W is also used as a contact material in switches. Therefore, Cu-W contact material uses W as the matrix, and the addition of Cu improves the electrical and thermal conductivity and thermal shock resistance of pure W. In the Cu-W series of contact materials, the W content is usually between 50% and 90%.

Cu-oxide contacts mainly include Cu-Al2O3, Cu-SnO2, etc. Cu-Al2O3 is also called alumina dispersed copper. It is made by adding tiny Al2O3 particles to the copper-based alloy to increase strength and hardness.

It has good electrical and thermal conductivity, high hardness, and is not easy to soften at high temperatures.

The key research directions of copper-based electrical contact materials in the future are:

(1) Improving the key properties of contact materials such as breaking performance, burning resistance, and welding resistance;

(2) Improving its oxidation resistance, conductivity, and other properties.

(3) Reducing process complexity, improving material utilization, and reducing raw material costs.

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