Study Of Several Technologies And Material Properties In The Production Of CuW Contact

In this paper, on the basis of analysis of foreign CuW contact material for middle voltage SF6switch, CuW integrated contact was developed by sintering and infiltrating techniques. The failure mechanism of the materials was analyzed, and a new structure of tensile test specimen was proposed for evaluating the bonding strength of CuW integrated contact materials. Moreover, the effects of the W content and W powder particle size on the bonding" strength were studied. The results show that:1. CuW contact materials used in foreign middle voltage SF6 switch are considered to be CuW70 alloy, in which there exists fine and dispersive distribution of W particles, while the W particles in self-developed CuW alloy are comparative concentration and coarseness. The failure way of CuW contact materials are mainly of forming the chappy, crack and Cu jet voids.2. With the decrease in W powder size, the bonding strength of CuW integrated contact increases. When the micro cracks extend in Cu matrix, it can be inhabited by the fine W particles. Once extending to the interface of W particle/Cu matrix, the micro crack would change its direction and branch off. This process consumes lots of energy and would consume much more energy with the increasing of the amount of W particles, which results in the increase of the bonding strength. CuW contact materials have good properties when it is prepared from 4-6 urn W powders.3. The structure of tensile test specimen has obvious effects on the bonding strength of CuW integrated contact. The specimen with general structure can not prevent the Cu conductorbar from the plastic deformation in the tensile test and the fracture often takes place in Cu part. It can not reflect the connection strength of CuW/Cu(Cr) interface. Whereas the specimen with improved structure can eliminate the effect of non-interfacial factors, prevent Cu conductor bar from plastic deformation, thus the fracture takes place at the connection interface. Therefore, the bonding strength of CuW integrated contact can be factually evaluated by using the improved specimens.