A Study On Cu-Cr Contact Composites Fabricated By Combustion Synthesis-Casting Technology

Cu-Cr is an ideal contact composite material due to its favorable properties, such as opening and breaking, enduring voltage, resisting cauterization and lower chopping current for high to medium voltage vacuum circuit. However, it's very diffcult for traditional casting technology to gain ideal Cu-Cr alloy structures because Cu-Cr is a sort of"false alloy", which is hard to blend and melt. Therefore, the fabrication technology of Cu-Cr contact composities is a main research direction.Taking Cu and Cr oxids as raw materials, a new technology-SHS-casting was propsed to fabricate Cu-Cr contact composites. The SHS reaction thermodynamics of CuO-Cr2O3-Al system and the formation of Cu-Cr alloy melt and its solidification process were analyzed. The effects of the proportion of raw materials, additive, solidification rate and further process of cold extrusionon on the structures and properties of the Cu-Cr composites were also investgated. The results show that the SHS reaction of CuO-Cr2O3-Al system can be carried through favorably. The synthesized Cu, Cr and Al2O3 products can be melt because of high adiabatic combustion temperature (848K), and Cu-Cr alloy melt can be form by separating from Al2O3. Then, Cu-Cr alloy melt solidifies under the rapid cool of cupper mould and form Cu-Cr composite structure, in which fine Cr particles disperse uniformly in Cu matrix. Moreover, increasing cooling rate of Cu-Cr melt can decrease the size of Cr particles and improve their distribution in the solidified microstruction. Appending the additive-CaF2 in reaction system can decrease the melting point and improve the fluidity of slag in order to separate slag and metal liquid fully. As a result, the electric conductivity of the prepared composites is improved because of little slag inclusion.With the increase of the Cr content, the size of the grain was angmented and the hardness was boosted. The further cold extrusion process on the synthesized Cu-Cr alloy can improve its density, hanrdness and electric conductivity.Cu-Cr composites can be sitmultaneously synthesized and formed by the SHS-casting technology, which has characteristics such as the economy of energy sources, handy technics and low-cost. So, SHS-casting technology is an alternatively promising method to fabricate Cu-Cr contact composites.