Fabrication And Properties Of SiC_p /Cu-SnO₂ Composite Materials For Contactor

In this theses, a new Cu-based electric contactor composite material has been designed, which is silver free and toxin free, to meet the low-voltage electric wirings demands. The Cu-SiC-SnO₂ composite samples were fabricated through high-energy milling, powder-packing, sintering and hot-extrusion process. The technical parameters, including milling time, preform packing pressure,sintering temperature, sintering time, and hot-extrusion pressure, mechanical and electrical properties of the final composite samples are investigated.The relationships between the density of the mixed powders and milling time, as well as between the packing density of the preform and the packing pressure have been studied, the optimized parameter is , milling for 4 hours, packing at 600MPa. The effects of hot-extrusion temperature and extrusion pressure on the density of the received composite sampls have been studied, and the optimized hot-extrusion temperature is 1000℃, and the extrusion pressure is 1400MPa.The microstructure of the Cu-SiC-SnO₂ composite is found to be homogenously dispersed with the second phase particles. After the hot-extrusion process, the second phase particles were found to be fine and like strips along the extrusion direction. The microhardness were tested to be in the range of 55¹10 HV, which meets the need of electric cantactoers. Obviously, the second phase particles have a strong effect on the increasing of the microhardness of the material.The electric conductivity of the extruded material is 25⁴0μ?-1?m-1, and increased to 30⁴5μ?-1?m-1 after annealling. It is indicated by XRD that the conductivity is controlled by lattice distortion under 450℃, while in higher annealling temperature, it is controlled by growing of crystalline grain. Anti-oxidation teast shows that the new composite material has a better anti-oxidation property than that of pure Cu.The effect of additive on anti-arc erosion has been investigated by means of a self-made electric duribility testing device, and microstructure analysing. The results indicate that the spray decreased with the increase of SnO₂ content, and the surface of the contactor tend to be smooth, implys that SnO₂ has a strong role of anti-spraying, thus result in an anti-welding property.The comparing XPS analysis of before and after the swithing test shows that, SnO₂ did not decompose after arc-erosion, indicate that the role of SnO₂ in Cu-based contactor material is similar to that of SnO₂ in silver-based contactor material. Namely, to increase the viscosity of the melt under the arc-erosion, so to decrease the spray, and result in an anti-welding property.