Research On A-TIG Welding And Vacuum Brazing Of Cu-Cr-Zr Alloy

In this paper, A-TIG welding and vacuum brazing experiments were carried out on Cu-Cr-Zr alloy. Optimum technique paramenters of A-TIG butt welding with3mm plates was found and the mechanism of the fluxes how to increase the penetration was inferred through microstructure analysis, micro hardness and conductivity test, tensile test, EDS and high-speed video. Then the effects of diffrernt brazing temperature, different brazing time and different joint clearance were discussed respectively, and the best process parameters can be found.SiO2、Cr2O3、ZnF2、CaF2can increase the penetration effectively. Oxide is superior to the fluoride in increasing the weld penetration. Weld depth width ratio is bigger and the shape of weld is better when the plates were welded with oxide. Arc voltage in the region of the fluxes would increase significantly and the voltage would increase as well as the coating quantity of fluxes. Because the conductivity of fluxe is low and it needs higher voltage to forme the electric channels and maintain the stable arc. The more coating quantity, the higher arc voltage would get.The best coating quantity of SiO2is0.8mg/cm2. When the coating quantity is lower than the critical value, the penetration would increase obviously as well as the coating quantity. When the coating quantity is more than the critical value, the penetration would change barely. Deviation ratio and the penetration of weld would decrease with the increasing of the offset of fluxes. The penetration of weld which was coated with fluxe on both sides is bigger than the weld which was coated with fluxe on single side.Observe the shape of arc in the region of fluxes through high-speed camera. It’s found that the shape of arc change barely. Basing on the changing law of arc voltage, it’s inferred that there are anode spots on the surface of plates because of the fluxes. Current will be more concentrated because of the anode spots and the weld penetration would be increased with the more concentrated heat.In the experiment of A-TIG butt welding, it can get the best weld seam with the optimum fluxes and the optimum process (Current is200A and welding speed is120mm/min). The weld seam has no defects and the tensile strength (233MPa) is more than85%of the base metal. The hardness and conductivity of weld is low, but it is better than the weld seams with other weld process. The fluxes can reduce the influence of heat. The combination property of the weld with the optimum fluxes is better than the weld seam with other fluxes.In the experiment of vacuum brazing, it’s found that brazing temperature, brazing time and joint clearance has a little effect on hardness and conductivity. The hardness of reacting region is higher than the hardness of base metal and brazing seam. The conductivity of brazing seam is a little bigger than the conductivity of base metal. It can get the best tensile strength (273MPa) with the optimum process (Brazing temperature is830℃,brazing time is10min and joint clearance is0.2mm). Each region of the joint with the optimum process has relatively high hardness and it can insure the good conductivity of brazing joint.