Study On Brazing Process Of Al-(Sn-xZn)

This paper selects aluminum rich reserves as raw materials by electrochemical polishing,soldering process and preparation method of Al-（Sn/Zn）solder joints.In the testing process of brazing parameters;substrate and solder interconnection mechanism are discussed;effect of different Zn content on properties of brazed joints,the brazing joints a series of mechanical properties and corrosion resistance test,obtained the following conclusions:1.In this study,the surface treatment process of electrochemical polishing was used to prevent the oxidation of aluminum substrate in the surface pretreatment,and to eliminate the mechanical damage on the substrate surface.Based on the experiment on the composition of the polishing liquid and polishing temperature,the control time and voltage in voltage 15 V,5min surface polishing quality best 10 degrees,not only solves the problem of toxic Cr⁶⁺ traditional electrochemical polishing in the waste liquid,and greatly improve the aluminum surface smoothness and corrosion resistance,provides an ideal raw material for the follow-up test.2.by soldering,on Al-Sn（xZn）brazed joint preparation method and the preparation parameters related in the insulation system,when the temperature is low,the solder dissolution is not obvious,unable to realize the welding,high temperature oxidation,solder will obviously affect the welding quality,with the holding time prolonged,the aluminum substrate diffusion phenomenon increased to 9min is relatively stable,no longer with time increased,obtained at 280 Deg.C for 9min is the best preparation process;10h aging treatment on the brazed joint after aluminum plate longitudinal diffusion tendency is obvious,that when treatment can be treated as a way to improve the brazing quality;on the combination of brazed joint interface the Sn-Zn solder found extremely obvious diffusion and dissolution phenomenon,with the increase of Zn content,the Al will be a lot of substrate from substrate into solder Zn-Al-Sn solid solution is formed at the interface,and the strength of brazed joint increases with the increase of Zn content.Meanwhile,the thickness of the solid solution layer increases.3.The prepared Al-（Sn-xZn）brazing joints of salt leaching test and electrochemical corrosion test,salt leaching experiment in the process of brazing brazing seam produced a large number of bubbles,the bubble rate increased significantly with the increase of Zn content;12h after removing the connector,the aluminum substrate is dark,brazing seam exists some white insoluble precipitates.The weight loss measurement,Sn-20 Zn brazing joint loss rate is the highest,up to 18.3%;the energy spectrum analysis and scanning electron microscope,the white precipitate of Zn（OH）₂,along the vertical incision joint surface corrosion,section Sn-5Zn and Sn-9Zn observation showed that the surface corrosion layer is thin,with a small amount of deep corrosion pits;and the Sn-20 Zn surface is thicker but porous corrosion layer,composed of a large number of pits,single shallow pits.The results show that the corrosion resistance of brazed joint is decreased with the increase of Zn content.The potentiodynamic polarization curves of different salt solutions were obtained.The results showed that the corrosion resistance of Cl^- was the strongest,SO₄^2- times,and the corrosion of NO₃^- was the weakest.