Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > Special welding > Laser welding

Process Research on Fiber Laser-MIG Hybrid Welding Medium Thickness Aluminum

Author HuPeiPei
Tutor WangChunMing
School Huazhong University of Science and Technology
Course Materials Processing Engineering
Keywords Fiber laser Laser-MIG hybrid welding Medium thickness plate Aluminum alloy
CLC TG456.7
Type Master's thesis
Year 2011
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Medium thickness aluminum plate were widely used in weapon, ship, car and high speed train industries and laser-MIG hybrid welding technology was one of the most efficient techniques in medium thickness aluminum manufacture. Fiber laser was a potential dominator in laser application market. Accordingly, high power fiber Laser-MIG hybrid welding technique was employed to systematically research the process, microstructure and weld properties of aluminum alloy ZL114.The potential penetration ability of laser-MIG hybrid welding technology could be better exploited by using arc leading welding direction (AL) and larger absolute value of defocused length. On the contrary of laser leading direction (LL), when AL was employed, laser will shoot at a deeper position located in the concave weld pool and penetrate through deeper length of liquid metal made by the arc. As a result of different laser shooting position, AL was more suitable than LL in acquiring deeper penetration with larger absolute value of defocused length. Excessive arc current or laser power will deteriorate the weld collapse tendency while the former one do more and the latter one will lead to additional serious evaporation.Fine grain and defects free weld could be gained by using Al-Si wire rather than Al-Mg or Al-Mn wire. Grain was rougher for Al-Mg wire in compared with Al-Si wire while rougher grain and much more irregular pores or inclusions for Al-Mn wire. There was no essential difference in microstructure among the very three kind wires while quantities of needle-like pores in eutectic area and some evident burning for Al-Mg wire, less eutectic for Al-Mn wire than Al-Si wire.Stronger tensile strength and better elongation could be obtained by using Al-Si wire rather than Al-Mg or Al-Mn wire. Tensile fracture will occur in base material for Al-Si wire with defects free and perfect weld shape, which was owing to different stress bearing microstructure, that is, Al-Si eutectic for weld but solid solution for base material while the former one is stronger than the latter one in the same stress condition. Either the black oxide film on weld or small metallurgical pores in weld won’t deteriorate the weld tensile strength. Larger cross section area, stronger welds tensile strength in certain range.8mm aluminum alloy ZL114 was successfully jointed in optimized process by one scan without groove. Good weld shape and inside defects condition met some aerospace industry requirement. The joint strength was stronger than base material. The achievements confirmed excellent feasibility and adaptability of fiber laser-MIG hybrid welding medium thickness aluminum.

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