A Study On Preparation Process Of CuCr25 High-Voltage Contact Material

Vacuum switches have been extensively used in high-voltage electric power systems. CuCr alloys have been identified as the best contact materials in vacuum switches. Due to the high melting point of Cr, CuCr alloys are very difficult to make. Optimization of processing technology and refinement of the microstructures has thus drawn great attention in the recent decade. In the present work, we investigated into powder metallurgy processes of CuCr25 alloy, including use of pre-alloyed CuCr10 powders for obtaining in-situ grown finer Cr particles, press-shaping powders, solid-phase and liquid-phase sintering in hydrogen and vacuum respectively, a new sintering method involving fast melting / solidification under electric arc, and heat treatment of the sintered CuCr25 alloys.The research results show that using pre-alloyed CuCr10 powder can obtained in-situ grown finer Cr particles in the sintered CuCr25 alloys, and can refine the microstructure and improve the mechanical property and electric property of the sintered CuCr25 alloys; The pressing property of CuCr10 alloying powder is not so good however, it can be improved by adding pure Cr powder; The research result about three different conventional sintering processes shows that the regularity of the effect of press shape's pressure force on property is resemble. When the pressure force is 763MPa, the hardness and conductivity of CuCr25 reach maximum.The research results of sintering in hydrogen show that the density, conductivity and hardness of CuCr25 prepared by liquid-phase sintering in hydrogen apparently higher than solid-phase sintering, and vacuum liquid-phase sintering apparently higher than liquid-phase sintering in hydrogen; A new sintering method involving fast melting / solidification under electric arc has been used to prepare CuCr25 contact material. We obtained CuCr25 contact material with good structural homogeneity and finer Cr particle (about 10μm), and its' properties are better than the sample prepared by vacuum liquid-phase sintering.