Technology Research And Quality Analysis Of Single Mode Fiber Laser Scanning Welding Of T2 Copper

Copper,with an outstanding conductivity,is often used as the main material of circuit components of new energy vehicles.Welding is an important part of the application of copper.In recent years,the research of using laser to weld copper has been widely concerned.However,due to the special physical properties of copper,it is easy to have welding defects such as poor weld formation,spatter and porosity in laser welding,which is dramatically harmful for application and further studies of laser welding technology of copper.According to the actual engineering application requirements,T2 copper is used as the research object,single-mode fiber laser is used for welding test,and the welding process monitoring,welding quality and conductive performance are studied for laser scanning welding under conventional linear welding and different scanning trajectories(“O”,“8”,“∞”),in order to seek the best path and optimal parameter combination of copper laser welding,and provide important test basis and theoretical guidance for the promotion and application of laser welding of copper parts.The research work is mainly carried out from the following aspects:(1)The technical difficulties and research status of laser welding for copper are summarized.The working principle of laser scanning welding are introduced.A test platform for laser welding of copper was built,and a quality testing scheme was designed.(2)The images of laser welding process were collected by high-speed photography,and the metal splash images were processed by MATLAB to obtain the metal splash area parameters under different welding paths,so as to analyze the influence of different welding paths on the stability of laser welding process.The results show that compared with conventional laser welding,choosing the correct laser scanning trajectory can restrain metal spatter better.Among them,the average splash area curve of the “O” scanning trajectory is only 116.4357 pixels,without abnormal large particle splash,and the welding process is of high stability.(3)The influence of welding path on copper laser welding quality and conductivity is analyzed by surface morphology observation,mechanical property detection,metallographic test,porosity detection,conductivity detection,etc.The results show that compared with conventional linear welding,selecting the correct laser scanning trajectory can greatly increase the weld melting width,improve weld forming,inhibit porosity,improve the softening phenomenon of weld joints,and improve the tensile strength and conductivity of welds.Among them,the “O” scanning trajectory specimen weld forming quality is good,the effect of improving the weld softening phenomenon is good,the porosity is the lowest,and the tensile strength(234MPa)and conductivity(71.79 m S/m)can reach 97.5% and 91.5% of the base metal,respectively.Based on the analysis of metal spatter,welding quality and conductivity during the welding process,the “O” scanning trajectory is the best welding path among several welding paths.(4)Based on the “O” scanning trajectory design response surface test,a reasonable and reliable response surface model and the best process parameters are obtained: laser power1301 W,scanning frequency 253 Hz,scanning amplitude 1.1mm,the conductivity of the welding specimen under the combination of parameters can reach 78.715 m S/m,which is very close to the conductivity of the base material,and the welded specimen has excellent conductivity.(5)Through the welding and quality inspection of copper parts,it is proved that the “O”scanning trajectory can be applied to laser welding of copper parts with different specifications,models,welding methods and weld shapes after the process parameters are optimized for specific parts.