Fiber Laser Welding And Numerical Simulation Of20Mn2Pipe

As a structural metallic material which possesses satisfactory weldability,20Mn2iswidely used in welding manufacture of automobile shock absorber pipes. Researchs onwelding method of automobile shock absorber pipes at home and abroad mainly concentrateon friction welding and so on. At present there is no correlational research reports about fiberlaser welding of20Mn2pipe. Laser welding, active laser welding and laser-TIG hybridwelding on20Mn2pipes have been conducted. Microstructure and property of welded jointare analysed by optical metallurgical microscope, scanning electron microscope,microhardness tester, tensile tester and Energy Disperse Spectroscopy(EDS). In addition,welding temperature field and stress field are analogue simulated by finite element software.First of all, microstructure and property of laser welded joints on20Mn2pipes withdifferent laser powers, welding speeds and defocus amounts are studied. It shows that themaximum weld depth and width of weld are respectively4.56mm and2.48mm when the laserpower is2400W, the welding speed is7.3mm/s and the defocus amount is0mm. When thelaser power is1200W, the welding speed is7.3mm/s and the defocus amount is0mm, themaximum value of microhardness is382.4HV1.0. The main microstructure of weld is lathmartensite. The main microstructure of heat affected zone are ferrite, pearlite, bainite and lathmartensite.Based on laser welding experiment, orthogonal experiment of active laser welding on20Mn2pipe is conducted. Through analysis, the best ratio of surfactant is36.36%SiO2,36.36%TiO2,9.09%Cr2O3and18.18%NaF. When this surfactant is used, the depth of weldincreases24.9%, the microhardness increases21.8%, the maximum value of tensile strengthand ductility are respectively827.9MPa and13.9%. There is O and Si in the weld whichcompletely consistent with the theory of surfactant increasing depth of weld.Secondly, microstructure and property of laser-TIG hybrid welded joints on20Mn2pipewith different laser powers and welding currents are studied. It shows that when the laserpower is2500W and the welding current is80A, the maximum value of weld depth is4.28mm. The laser power has little influence on width of weld. When the welding current is40A and the laser power is1300W, the minimum value of weld width is1.68mm, themaximum value of microhardness is372.6HV1.0. The main microstructure of weld is also lathmartensite. The main microstructure of heat affected zone are ferrite, pearlite, bainite and lathmartensite as well.Finally, the temperature field and stress field analogue simulation of laser welding andlaser-TIG hybrid welding on20Mn2pipe are conducted by finite element software. Then, thesimulation results are compared with experimental results. It shows that the temperature fieldand stress field distribution of laser welding and laser-TIG hybrid welding are similar. But themaximum value of laser weld temperature and von mises are2401℃and215.9MPa. The maximum value of laser-TIG hybrid weld temperature and von mises are2766℃and216.5MPa. The simulation and experimental results of weld macroscopical morphology arebasically the same.