Study On Ultrasonic Aiding Resistance Brazing Process For WC-Co/BeCu

It is hard to get good strength of joints and properties of beryllium copper simultaneously using traditional welding methods to weld hard alloy and beryllium copper because of great differences of physics and chemistry properties between hard alloy and beryllium copper. It is easy to seriously soften beryllium copper using fusion welding methods while hard to get a ideal joint using brazing methods.Processes of ultrasonic vibration aiding resistance brazing for WC-Co/BeCu were investigated in this paper using scanning acoustic microscope, scanning electron microscopy, vickers hardness tester etc, mainly discussed influences of time, pressure parameter etc on brazing quality, determinated the microconstituent of brazing seam, analysed the cause of softening of beryllium copper, finally, Consided the shear strength of the joint and the hardness of beryllium copper comprehensively, executed the process optimization and proposed a ultrasonic vibration aiding resistance brazing process for WC-Co/BeCu.The experiment results show that, the acoustic cavitation and the acoustic streaming effect of ultrasonic can prompt the filler metal to wet the base metal and get rid of the air bubble in liquid filler metal, improved brazing quality. Compare against the traditional resistance brazing method, the join rate of brazing seam will increase more than 35 percents and the shear strength of joint will increase 40 percents approximately when using ultrasonic vibration aiding resistance brazing method for WC-Co/BeCu.When using ultrasonic vibration aiding resistance brazing method, with the increase of power up time, the temperature will raise and the remained time of high temperature will increase too, that would reinforce the effect of ultrasonic vibration for filler metal wetting base metal, it results the join rate of brazing seam and the shear strength of joint improving; but, when the power up time being too long, it will results the filler metal running off because the temperature is too high for brazing, filler metal running off would result the shear strength of joint declined; With the increase of the pressure, the shear strength of joint increased to maximum and then decline. Experiment proves that, pressure on 2MPa around is suitable for brazing.When using Ag-Cu-Zn-Cd filler metal for ultrasonic vibration aiding resistance brazing for WC-Co/BeCu, microstructure composition of brazing seam consists ofαphase, which is rich in Cu and Zn, andβphase, which is rich in Ag and Cd. Theαphase exists in globular form and theβphase in branching form.The main cause of beryllium copper softening is that, beryllium copper occured recovery when it is heated, the grain will grow up, that would result grain boundary reinforcement effect depress. The higher temperature and longer heating time, the more serious of beryllium copper softening.Experiment proves that, using large current short time of rapid heating mode for ultrasonic vibration aiding resistance brazing for WC-Co/BeCu can get good shear strength of joint and hardness of beryllium copper. When using current I=1.5(reference quantity of equiment), time t=1s to experiment, the average shear strength of joint is 241MPa, the hardness of beryllium copper in brazing center is 185HV, where the beryllium copper is the most serious soften, and its soften range is about 2mm.