Preparation Of Nano Aluminum Potassium Aluminum Fluoride Flux

Aluminum and Al-alloys are widely used in areas such as mechanism, electron, household electrical appliances, space appliances, and so on. The function of aluminum brazing flux is to clear oxidation film on the surface of Al-alloys and to reduce boundary tension between molten filler and base metal so that molten filler and base metal can be moistened and brazing can be achieved. Aluminum brazing flux, mainly including chloride brazing flux and fluoride brazing flux, are widely studied at home and abroad. In this paper, one kind of aluminum brazing flux was investigated firstly by X-ray diffraction (XRD) and X-ray fluorescence analysis, the result shows that the flux are composed of chloride including BaCl₂, KC1, AlCl₃ and NaF.Secondly, potassium fluoaluminate eutectic brazing fluxes were prepared from aluminum chloride, potassium fluoride and hydrofluoric acid by chemical precipitation method. The properties of soldering flux were investigated by differential scanning calorimeter (DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), brazing ability measurement, the result obtained shows: The average grain size of flux powder is 25-40 run and the grain is diamond-shaped, the melting point of flux is 551℃,the main and secondary phase is K₂ALF₅·H₂O and KAlF4.The effect of disperser on conglobation of aluminum soldering flux powder is studied then. The result shows that conglobation of aluminum soldering flux powder can be improved by PEG addition. On the basis of results obtained above, the preparation processing was studied by orthogonal test, optimal process conditions were found as follows: concentration of aluminum chloride is 1mol/L, reaction temperature is 40 ℃, and reaction time is 2 hour. And another optimal process conditions: concentration of aluminum chloride is 1.5 mol/L, reaction temperature is 40 ℃, and reaction time is 1 hour.Aluminum brazing flux, prepared by various means including mechanical means, water cooked method, sintering method, smelting method and chemical precipitation method, were prepared. The properties of these fluxes were investigated by differential scanning calorimeter (DSC) and brazing ability measurement. The result shows that fluxes prepared by chemical precipitation method have a better brazing ability and lower melting point.The relation between microstructure of soldered joint and mechanical properties of nanometer aluminum brazing flux were studied. LF21 aluminum was brazed by butt brazing joint method. The sample prepared was investigated by tensile-strength test, metallographic examination, SEM. The result obtained shows: The tensile-strength of reaches 146.2MPa , microstructure of soldered joint are mainly a (Al) and a (Al) + Si binary eutectic phase, the fracture features are gliding fracture with quasi-cleavage crack mode.Chemical analytical method were used to analyse the percentage composition of K, Al, F in soldering flux, the results were tested by energy spectrum examination. The results obtained shows that chemical analytical method can analyse the percentage composition of K, Al, F in soldering flux accurately...