Experiment Study On Resistance Brazing Welding Prcedure Of Cantctor Based On Metallic Electrode

In this paper, to the research of Noark which is "Autonomously produce electrical contact of low-voltage apparatus switch", experimental study on three kinds of solders including BAg72Cu, BAg60CuZn and BAg15CuP and three welding parameters including welding current,welding time and welding pressure was conducted. So that the best solder material and optimal parameters can be determined. Meanwhile by comparing the quality of electrical contactors of Schneider, Siemens and Noark to give further methods to enhance braze welding quality.First, by analysis orthogonal test, the better parameters of three kinds of solders can be chose. During the three welding parameters, the main parameter that affects welding quality is welding current, then is welding time, the last one is welding pressure; Secondly by using single factor rotation method to draw the law curves between shear strength, the ratio of brazing area and three welding parameters. And by comparing the law curves to determine the best solder which is BAg60CuZn and the optimum parameters is that welding current: 60%(7.5kA), welding time: 91 cycle(1820ms), welding pressure: 2.0MPa(1.57kN). The electrical contactor that produced with selected solder and parameters can meet the production standards. And we found ultrasonic nondestructive tester is not sensitive to rosin joint, so the suggestion is to use ultrasonic nondestructive tester and mechanical property tester to test braze welding quality.Using optical microscopy (OM) and scanning electron microscopy (SEM) to compare the quality of electrical contactors of Noark,Schneider and Siemens . The comparison contains metallurgical structure, microstructure, and component of phase composition and diffusion of elements. The experiment showed the weld interface of electrical contacts from Schneider and Siemens have less defects and the diffusion is much better than that of Noark and the former generated peak-like tissue which is good for mechanical property, but the latter generated a small amount of cloud-like organization. By analysis the law of the base metal dissolving to deposite solder, we can conclued that the different organizations is caused by different cooling speed. By analysis of component of phase composition showed the burning loss of Noark is more than that of Schneider and Siemens. And organization of the former is mainly eutectic structure but the latter is mixture of solid solution and eutectic structure, so the ability to force temperature is worse. By comparison and analysis, the improvement is: careful preparation before welding including closed assembly gap and oxide clean-up completely, reduce the cooling rate, by cooling with pressure; by pulse current, the first current is for warm-up, the second current is for welding; regular cleaning equipment, by cooling and cleaning the electrodes.