Study On Mechanism And Process Of Fiber Laser-MAG Hybrid Welding

With the wide application of large thick walled workpiece in heavy-duty machinery,large steel structure,shipbuilding,the welding problem has become a hot spot of research.Laser-MAG hybrid welding-as an effective new welding technology,which has been paid great attention to,can be used to solve the problem of welding of thick wall workpiece.The interaction between the laser and the arc is mainly manifested in the fact that the laser changes the MAG arc power conduction mechanism,and the arc plasma and the laser-induced plasma energy are coupled to each other.The high-speed imaging can be used to observe the change of arc morphology more directly.During the experiment,the influence of laser on the different transition modes(short circuit transition and jet transition)of MAG welding was studied by using MAG welding small and high current,180 A and 300 A respectively.Through the high-speed image and electrical signal,arc morphology and droplet transfer changes were observed before and after the introduction of laser,and giving the theoretical explanation of laser-MAG hybrid welding mechanism.Then,a series of research about the influence of the main process parameters(laser power,welding current,defocus amount,distance between laser and wire,welding speed and relative position of laser and arc)on the weld formation of laser-MAG hybrid seam were carried out with 10 mm thick Q345 B steel plate,which can provide a theoretical basis for optimizing the hybrid welding process.The process study of root pass welding with hybrid welding on 10 mm thick Q345 B steel with Y-shaped groove(blunt edge 4mm,symmetrical groove angle of 45°)was carried out,and the experimental results showed that the formation of hybrid weld was good with such process parameters,as the laser power PL=3.5k W,arc current range I=240~300A,welding speed Vw=600~1000mm/min.In the actual welding production,as there is a problem that the assembly precision is poor,so the research of the adaptability of the laser-MAG hybrid welding technology to the assembly gap and the misalignment will be carried out.Under severe assembly error with the gap range of 0 to 2mm and the misalignment range of 0 to 2mm,we will study the forming law of hybrid weld with such main parameters PL=3.5kW,I=270A,VW=800mm/min of the laser-MAG hybrid welding process.The macrostructure and microstructure of the weld seam of laser-MAG hybrid welding were observed,the cross section geometry of the hybrid weld is different from that of single laser welding and MAG welding.In the direction of weld penetration,there is laser-arc action zone and laser action zone.The mechanical properties of the hybrid weld are tested by hardness test,tensile test,bending test and impact test.The influence of laser-MAG hybrid welding process on mechanical properties of welding seam was studied.