Progress in the Preparation of Large-Size High-Performance CuCr Alloys

CuCr contact material, whose mass fraction of Cr is generally in the range of 25% to 50%, is one of the most desirable contact materials for medium- and high-voltage vacuum switches. The homogeneity and denseness of CuCr alloy are the keys to its application. The infiltration and powder sintering have defects, such as uneven distribution of Cr phase, and great difficulties in preparing high-performance CuCr alloys with low gas content; the equipment investment in the vacuum consumable arc melting method is large and the production cost is high, while mechanical alloying, vacuum induction melting, and laser-selective melting as new technologies are still in the laboratory stage. From the perspective of surface modification treatment and multicomponent alloying, refinement of Cr phase grains can improve the properties of CuCr alloy. The new process of aluminothermic reduction-electromagnetic coupling refining-water and gas composite rapid cooling takes oxides as raw material and obtains a fully miscible CuCr alloy melt by aluminothermic reduction theoretically at 2848K, followed by secondary refining under electromagnetic field coupling and water-gas composite cooling and casting, which can obtain alloy ingots of 50 mm in diameter and 10 mm in height. The density and hardness of CuCr alloy prepared by this process as vacuum contact material are better than the requirements of GB/T 26867-2011, so this process has the potential to become a new-generation preparation method for large-size homogeneous high-performance CuCr alloy.