Study On Impurity Problems In Preparation Of Cesium Salt Aluminum Flux And The Problem In Oxidation Of Molten Solder

Aluminum brazing has the advantages of high precision,can be molded at once and green pollution-free,so it has been widely used in scientific research and actual production.And the researches related to brazing flux and solder are growing.In this paper,the influence of Fe and Si impurities on the properties of cesium salt aluminum flux and the oxidation of molten solder in aluminum alloy brazing were studied.The main research work and achievements are as follows:?1?High purity CsF-AlF₃ flux,CsF-AlF₃ flux with Fe impurity?0.2wt%?and CsF-AlF₃ flux with Si impurity?0.5wt%?were prepared by wet synthetic technology.Then,the properties of these three fluxes were compared.The results showed that Fe or Si impurity can't change the phase compition,melting point and microstructures.But the Fe impurity will reduce the spreading performance and brazing performance of CsF-AlF₃ flux at 1060 and 6061 aluminum alloy.However,the Si impurity does not change the spreading performance and brazing performance of CsF-AlF₃ flux.In addition,the contents of Fe and Si in the CsF-Al F₃ fluxes prepared by replacing the high-purity raw materials with low-purity raw material individually were tested.The results showed that the low-purity raw materials mainly lead to the increase of Fe content in the flux,while the content of Si element had no obvious increasement.?2?A series of experiments about the oxidation of molten Zn-Al solder during simulated brazing process were carried out.The results showed that the weight increasement of Zn-15Al solder covered with CsF-AlF₃ flux is much bigger than that of Zn-15Al solder with no flux.And Zn-15Al solder with CsF-AlF₃ flux covered formed a layer of a layer loose slag-like substance after oxidation,and it was consisted of oxide film and residual flux after reacting.It is found that CsF-AlF₃flux can effectively remove the solder oxide film,but it can't inhibit the secondary oxidation of solder.The high temperature oxidation experiments of Zn-08Al solder,Zn-15Al solder and Zn-22Al solder at different temperatures showed that the oxidation degree of Zn-Al solder didn't change significantly with the increase of brazing temperature.While at the same oxidation temperature,the oxidation degree of Zn-22Al solder is higher than that of Zn-15Al and Zn-08Al brazing alloys,which is mainly because that its composition is far away from Zn-Al eutectic point.