Copper Refractory Contact Materials
Like silver-tungsten, copper-tungsten is used in applications where extensive arcing is experienced. High voltage circuit breakers, switchgear and transformer tap changers are typical applications. The materials exhibit very low contact erosion rates. The refractory component (W) provides the necessary durability to withstand arcing, while the copper component provides high electrical conductivity. As the tungsten content increases the resistance to erosion
increases, however, the resistivity of the material increases also. Like silver refractory materials, high contact pressures are required. The materials experience increasing contact resistance as the service life progresses. The arc mobility of copper-tungsten materials is poor, much like silver-tungsten.
Copper-tungsten contact materials are dual phase materials and are produced through powder metallurgy processes. Compositions range from a low of 25% copper, to a high of 50% copper. The materials are produced through unit compaction techniques and therefore the fabrication costs are relatively high. Discrete contacts are available, usually supplied with a solder flush applied. Contact assemblies are also supplied. Where high volumes are required, furnace brazing is the most economical method of attachment. Where volumes are lower, resistance brazing or torch brazing techniques are more economical.