Study On Brazing Technology For LY12 Aluminum Alloy At Middle-range Temperature

The technology for brazing LY12 aluminum alloy at middle-range temperature by means of the improved CsF-AlF3 non-corrosive flux matching Ag-Al-X-Y, Al-Si-Y(l) and Al-Si-Y(2) filler metal is presented in this thesis. The defects including the over-heated structure of base metal and the lower corrosion resistance of brazed seam, which usually take place during brazing process, could be eliminated completely.After the sound brazed joint of LY12 alloy at middle-range temperature is obtained, further detailed analysis of the brazing parameters reveals that the optimized joint can be produced at the brazing temperature 496~503℃, dwell time 15min and the lap area 60~70 mm 2 following with cooling to 450℃ in the furnace and then to room temperature in air. The brazed joint meets the need of the required mechanical properties.It is the core point to accomplish the brazing LY12 alloy well at middle-range temperature that the improved CsF-AIFs non-corrosive flux can remove easily the complicated oxide film on the surface of LY12 aluminum alloy. From the research on the mechanism of the improved brazing flux CsF-AlF3 removing the oxide film of LY12 alloy, it is found that the compound CsF plays a key role in removing the oxide film. The high activation of the brazing flux is related to the presence of compound NR^F, NH4A1F4 as well as other melted salts. That is, the ability to remove the oxide film by theflux can be enhanced owing to the impacts of above compounds. In addition, the formation of HF is the key cause to the initiation and acceleration of the reaction and heightens the ability to remove oxide film by dissolving.Through the application of brazing technique at middle-range temperature in Al/Cu tube and the characteristics of the improved CsF-AlF3 brazing flux it could be formulated that the improved brazing flux CsF-AlF3 will possess potential utilization and broad prospects in other fields.Based on the research in this thesis, it could be confident to say that the brazing technique of aluminum and its alloys at middle-range temperature is about to have better application.