Investigation Of Dual Beam High Brightness Laser Welding Of Aluminum Alloy With T Joint

The background of this research is the national aircraft manufacture. The mainresearch object is the dual beam laser welding technology of aluminum fuselage. Thedual beam laser welding technology has been presented on aircraft commercialaluminum alloys (6056-T6511stringer/6156-T4skin) and the third generation of Al-Lialloys (2099-T83stringer/2060-T8skin).The systemic study of this paper mainlyincludes three aspects as follows. The first is about dual beam laser welding devicesof T type joints. The second is about surface treatment of aluminum alloy. And thethird is about dual beam laser welding technology of T type joints on aluminum andaluminum lithium alloy.In order to conduct the research of dual beam laser welding technology of T jointof aluminum alloy, T type dual beam laser welding device has been designed andintegrated. Two high brightness laser YLS-6000fiber laser and DC040Disc laserhave been used as the T type joint of dual beam welding power source. The cantilever3D NC machine tool designed by ourselves has been used as motion control subject.Vacuum adsorption platform have been adopted as the locating datum of skin. Thewelding device integrates all necessary functional units, which comprises the outerlight path, the wire feeding system, the protective gas system, the protection of anoptical element and the fixture. The successful development of the equipment has laida good hardware foundation for the next step research of dual beam laser weldingtechnology.The special structure and cooling condition of T type joint of aluminum andaluminum lithium makes porosity rate of the laser welds much higher than the otherjoints. In order to solve porosity problems of the T type joint, the features anddistribution of the pores in the weld have been studied. The study shows that themajority of stomata distributed along V shaped region of the fusion line, and thedistribution of large pore is more rules. The reason about the distribution of bubble isdirectly related to those factors, such as bubble formation, growth, hindered andmoving path. To solve the pore in weld, the ways mainly rely on the decreasing sourceand welding process optimization.To remove the oxide film on the surface of aluminum alloy, chemical or mechanical methods have usually adopted as pre-welding treatment. But the filmprocessing method has low efficiency, environmental pollution and long perioddocking process. Referred to the principle of crushing effect of arc on film, thisresearch puts forward a method of using small value of reverse current combined withthe swing arc cleaning of oxide film on aluminum alloy surface. This methodovercomes the problem of traditional arc reversal of tungsten electrode, unevensurface cleaning, not enough width of cleaning and the large heat impact on parentmetal. This pre-treatment method has been presented on6156-T4aluminum alloy and2060-T8aluminum lithium alloy. The surface microstructure of aluminum alloy hasbeen observed after surface treatment. The composition of oxygen and tungstenelement has been analyzed. And the arc shape characteristics of cleaning process areobserved and analyzed by high speed camera. To test the effect of oxide film dislodge,dual beam welding experiment has been presented in this paper. And the porosity inweld is also detected. The results show that weld porosity in6156-T4aluminum is0.01%when the metal cleaned by cathode atomization. And the weld porosity in2060-T8aluminum lithium alloy is about0.05%. Pores are uniformly distributed inthe weld and their size is very small.The dual beam laser system has been used as experimental platform. The methodof swing arc has been adopted to clean the oxidation film. Dual laser weldingexperiment has been presented on6056-T6511/6156-T4aviation commercialaluminum alloys. Influence of process parameters included laser power, defocus, wirespeed, wire position, laser incident angle and welding speed on weld forming of the Ttype joint and the relationship of mutual matching of each parameters have beenstudied in this paper. Because of the influence of T type weld on skin performance isdirectly related to the performance of fuselage parts, this paper also studies the law ofdifferent depth affect the weld tensile properties of skin. The general trend is that theweld penetration was negative linear correlation with the skin stretch performance.2099-T83/2060-T8is a new third generation of high strength aluminum lithiumalloy. Thermal crack is another important problem encountered in laser welding ofhigh strength aluminum lithium alloy. The reason and the distribution of hot crackhave been studied in this paper. The results show that the sensitivity of crack in weldcan be decreased by optimizing the groove size and increasing the volume ratio offiller material. The research on dual beam laser welding of airplane fuselage panelhas animportant reference value to the large aircraft project, which is the major concern ofour country now. At the same time, this study also provides technical and theoreticalbasis for dual beam laser welding used in aircraft manufacturing.