| Aluminum alloy is used extensively in automobile,train,aerospace and other industrial fields due to its unique performance characteristics.Laser-arc hybrid welding technology combines the advantages of laser and arc,and has unique advantages in aluminum alloy welding.As an important part of advanced joining technology,laser-arc hybrid welding process not only ensures the final quality,but also needs guarantee certain production efficiency.Improving the speed of laser-induced arc hybrid welding is an important way to improve the production efficiency and a powerful measure to control the heat input of welding.However,the improvement of welding speed is bound to affect the welding stability,and defects such as porosity will appear in the welding,which seriously restricts the optimization and improvement of high-speed welding performance of aluminum alloy.Therefore,it is of great theoretical significance and engineering practical value to study the process characteristics of laser-TIG hybrid high speed welding of 6061 aluminum alloy,obtain the generation mechanism and control measures of porosity defects,and analyze and study the softening behavior of the joint on this basis,and realize the high-speed and high-quality welding of laser-TIG hybrid high speed welding of 6061 aluminum alloy.In this paper,the porosity sensitivity and softening behavior of the laser induced arc hybrid high speed welding joint of 6061 aluminum alloy were studied by using Nd:YAG pulse laser and the hybrid welding platform developed and designed by the laboratory of the research group.The research results confirmed that under the experimental conditions of this study,the welding formation and protection effect of 6061 aluminum alloy high-speed welding were better by laser induction.In the case of a certain welding speed,the influence of four position parameters including the defocusing,the distance between heat sources,the shielding gas flow and the tungsten pole extension length were analyzed,and a stable welded joint was obtained.There are two types porosity defects inside aluminum alloy laser induced TIG hybrid welding: hydrogen porosity and process porosity.Hydrogen porosity can be controlled through good protection measures,and the process porosity is related to the stability of keyhole.Process porosity has irregular shape and different size,which can be better controlled to keep dynamic balance of keyhole.The matching experiments of welding speed and energy output control parameters were designed,the influence of laser pulse excited current,laser pulse duration,pulse frequency and arc current on the welding process stability and keyhole state was systematically studied,the control measures of porosity were explored,and the porosity rate of joint was effectively reduced through reasonable experimental design.6061 aluminum alloy welded joint has HAZ softening zone owing to heat treatment strengthening,by comparing the different welding speed(1m/min,2m/min,3m/min)of the joint microstructure,phase composition,element distribution and mechanical performance,found that with the increase of welding speed the welding heat input is effective controlled,the joint microstructure is refined,the dissolution of the black precipitate decreases,the width of fusion zone and heat affected zone narrow,the element damage degree is reduced,which make the joint performance is improved,the joint strength can reach to 77% of base metal or more,and alleviate the degree of softening joint.The simulation of hybrid welding temperature field verifies the improvement of welding speed,which significantly reduces the width of the heat affected zone of the welded joint and refines the weld grain.Finally,the porosity defects are effectively suppressed under the high welding speed,and the welded joints with excellent properties are obtained. |
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