Effect of longitudinal alternating magnetic field on the dynamic behaviour and joint properties of laser scanning welding of T2 red copper
摘要
To address the issues of high reflectivity and poor stability in laser welding of T2 red copper, this study aimed to combine non-contact magnetic field with laser welding, proposing an alternating magnetic field-assisted laser welding technique. Furthermore, the approach combined theoretical analysis and experimental research to establish a thermal-fluid coupling numerical model and conduct experiments to explore the effect of an alternating magnetic field on the weld quality of laser scanning welding of T2 red copper. The results indicated a high consistency between numerical simulations and experimental results regarding the weld geometry. The introduction of the alternating magnetic field increased weld pool temperature, fluid flow velocity, weld pool width and depth, and keyhole depth. It also weakened the distortion degree of the keyhole wall, decreased the oscillation amplitude of the deep penetration keyhole, and improved the stability of the weld pool. When the alternating magnetic field with a frequency of 50 Hz and a strength of 40 mT, the temperature rise rate, weld pool width, weld pool depth, keyhole depth reached their respective maximum values of 8.438 K/ms, 1.29 mm, 1.51 mm, 0.95 mm, representing significant improvements of 3.76%, 11.21%, 7.86%, 49.6% respectively, compared without an alternating magnetic field. The variance of the keyhole depth achieved its minimum value of 0.012 m2, representing significant reductions of 47.83%, compared without an alternating magnetic field. Additionally, the application of the alternating magnetic field also further suppressed metal vapor plasma eruptions, improved the weld surface morphology, refined the grain structure, and enhanced the mechanical properties and electrical conductivity of the weld joint. When the alternating magnetic field with a frequency of 50 Hz and a strength of 40 mT, the microhardness, tensile strength, and electrical conductivity reached their respective maximum values of 72.2 HV, 275 MPa, and 75.96 mS/m, representing significant enhancements of 22.37%, 58.05%, and 15.56%, respectively, compared without an alternating magnetic field. The average value and standard deviation of the metal vapor/plasma area achieved their minimum values of 1045.2 pixels and 336.23 pixels, representing significant reductions of 31.98% and 15.38%, respectively, compared without an alternating magnetic field. The introduction of the alternating magnetic field can effectively enhance the coupling efficiency of laser energy during the laser welding process of T2 red copper, optimize the weld pool dynamics, and significantly improve the welding stability and joint quality. The application of the alternating magnetic field provides a new research direction for improving the process performance of laser welding of T2 red copper.