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→Copper–Tungsten Materials
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W/Cu materials exhibit a very high arc erosion resistance (<xr id="tab:Contact and Switching Properties of Copper–Tungsten (CUWODUR) Contact Materials"/><!--(Table 2.40)-->). Compared to silver–tungsten materials, they are however less suitable to carry permanent current.
With a solid tungsten skeleton, as it is the case for W/C infiltrated materials with 70-85 wt% tungsten, the lower melting component copper melts and vaporizes in the intense electrical arc. At the boiling point of copper (2567°C), the still solid tungsten is efficiently “cooled” and remains pretty much unchanged.
For high voltage load switches, the most advantageous contact system consists of a contact tulip and a contact rod. Both contact assemblies are usually made from the mechanically strong and high conductive CuCrZr material and W/Cu as the arcing tips. The thermally and mechanically highly stressed attachment between the two components is often achieved by utilizing electron beam welding or capacitor discharge percussion welding. Other attachment methods include brazing and cast-on of copper, followed by cold forming steps to increase hardness and strength.
The main application areas for W/Cu materials are as arcing contacts in load and high power switching, in medium and high voltage switchgear as well as electrodes for spark gaps and over voltage arresters (<xr id="tab:Application Examples and Forms of Supply for Tungsten– Copper (CUWODUR) Contact Materials"/><!--(Table 2.41)-->).
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==References==
