Laser Welding Of Al Alloy With Activating Flux

Aluminum alloys are widely used in many fields of National defense and economic construction due to its high specific strength, corrosion resistance, electrical conductivity and thermal performance advantages. As an efficient high-energy beam welding method, laser welding has technical and economic advantages in joining and welding of aluminum alloy structures. However, due to aluminum alloy’s high reflectivity of laser and high thermal conductivity, laser welding of aluminum alloy faces many problems, such as low thermal efficiency, low weld penetration, poor weld appearance caused by aluminum alloy’s high reflectivity of laser. Recently, the characteristics of A-TIG welding that can largely increase the weld penetration provide a new method to solve the problems in laser welding of Aluminum alloy. In this study, activating welding technology is used in laser welding of aluminum alloy, in order to solve the problems in laser welding of aluminum alloy and increase weld penetration.The effects of different activating fluxes on weld penetration, weld appearance, microstructure of Aluminum alloy laser welding are investigated. The double-component and a multi-component activating flux formula that can improve weld appearance and increase weld penetration are developed. The laser welding process parameters of Aluminum alloy are optimized and the effects of defocus amount, weld speed, laser power and coating quantity of flux on weld penetration are studied. The mechanism of improving weld penetration increased by activating flux is also studied.The results showed that oxides can significantly increase the weld penetration while fluoride can improve weld appearance and reduce the weld width and porosity. By using the developed double-component flux NaF+Ni2O3, the6013Aluminum alloy plates of thickness1.8mm can be welded with full penetration, good weld appearance and no porosity defects under conditions of CO2laser power3.5kW and weld speed0.3m/min. By using the developed multi-component activating flux AF1(12.0%V2O5+81.4%NaF+6.6%Cr2O3), a2.130mm penetration is achieved under following conditions:weld speed1m/min, Nd:YAG laser power2kW, defocus amount-1mm and the coating quantity of flux12.5mg/cm2. It is found that weld penetration grows as the coating quantity of flux increases. Based on the analysis of chemical composition of different positions of weld bead, activating flux did not change the chemical composition of weld bead. The experiment that AF1activating flux increased the temperature of the point5mm away from the center of weld bead from110℃to133℃showed that activating flux increased the laser absorptivity of Aluminum alloy, so that the weld penetration is improved.