Study On The Characteristics Of High Power Dual Beam Laser And Laser-TIG Hybrid Welding Of Aluminum Alloy

Aluminum alloys with low density, high strength, high plasticity, corrosion resistance, easy to process and a series of excellent characteristics have become the preferred materials of structure lightweight design such as aerospace and high speed trains and other vehicle. Traditional TIG and MIG arc welding method is still currently aluminum alloy structure of welding manufacturing processing methods, but due to the relatively low energy density of arc, the welding speed of arc is slow and the heat input is high, in solving the structure welding deformation, thermal damage, the welding efficiency promotion of welding engineering problems encountered technical bottlenecks. The welding method(laser and laser arc hybrid welding) with high energy density of laser deep penetration welding with characteristics of high welding speed, small thermal damage of material, small welding deformation, attract more and more attention in aluminum alloy welding research field. Previous research found that one of the main problems of the aluminum alloy laser deep penetration welding is bad appearance of weld with a characteristis of the surface shape of the weld is rough and the weld depth fluctuations large. Another major problem is that the weld is easy to produce many keyhole induced pores, especially in non-penetration welding.The generation of these defects is related to the fluctuation of the keyhole. How to give full play to the advantages of laser deep penetration welding and to solve the problem of the welding defects caused by the sharp fluctuations in the welding of aluminum alloy is the key problem in this paper.This paper takes the 5A06 aluminum alloy as the research material, using 6k W disc laser generator, systematically studied the influence of the key welding parameters of the single beam welding, dual beam laser welding, single beam laser-TIG arc hybrid welding, dual beam laser-TIG arc hybrid welding four welding methods with deep penetration welding characteristics on weld shape and porosity, and the forming elements including the weld surface forming, penetration fluctuation, depth to width ratio of weld and weld porosity ratio were compared. The results show that with the same welding parameters, compared with single beam laser welding, the welding surface forming of dual beam laser is more uniform, the weld reinforcemen is smaller, the volatility of weld reinforcemen of dual beam laser welding is about 30%~40% of that of the single beam laser welidng; The penetration depth and width to depth of weld in dual beam laser welding is about 50%~80% of that of single beam laser welding; Both of the single beam and dual beam laser deep penetration welding exist penetration fluctuation and the volatility is about 20%~40% of the mean penetration in the two forms of laser welding. In the aspect of the formation of weld, Single beam laser-TIG arc hybrid welding and double beam laser-TIG arc hybrid welding have similar rules.Through the analysis of the relationship between the porosity and the shape of the weld, the relationship between the porosity and the weld shape was found, which was closely related to the ratio of the weld depth to width. For the single beam welding, double beam welding, single beam laser-TIG arc hybrid welding and double beam laser-TIG arc hybrid welding, the bigger ratio of depth to width of the weld, the more serious the porosity.When the ratio of depth to width of four welding methods is not more than 0.8, the ratio of porosity can be controlled below 3%.Based on the effects of key welding parameters on weld shape and porosity, the dynamic informations of keyhole, plasma and spatter in the process of single beam welding, dual beam welding, single beam laser-TIG arc hybrid welding and dual beam laser-TIG arc hybrid welding were collected with a high speed camera, the acquired image information were processed and analysed with MATLAB software. Results show that the keyhole and the plasma in the process of the four kinds of welding method are all always in the state of irregular cyclical fluctuation, compared with the fluctuation process composed of brith, growth, maintaince, shrink, annihilation in single beam laser welding and single beam laser-TIG hybrid welding, the keyhole in dual beam laser welding and dual beam laser-TIG hybrid welding also still exist the process of separation and merging, Under the condition of the same welding parameters, the average opening area of keyhole in dual beam welding is about 2 times of that of the single beam laser welding, the coefficient of variation of the volatility of keyhole opening area is about 50% of that of the single beam laser welding, the the average fluctuation cycle of the keyhole is about 1.5 times of that of the single beam laser welding; The same rules is also reflected in the variation of plasma, with the same welding parameters, the cycle from brith to annihilation of the plasma in dual beam laser welding is about 1.5 times of that of the single beam laser welding, the coefficient of variation of plasma area in single beam laser welding is about 50% of that of the single beam laser welding; For the welding spatter, dual beam laser welding splash particles is smaller and more homogeneous. The characteristics of keyhole and plasma in the process of single beam laser-TIG arc hybrid welding and dual beam laser-TIG arc hybrid welding respectively have similar laws with single beam laser welding and dual beam laser welding.