Influence of steady magnetic field on dynamic behavior mechanism in full penetration laser beam welding

To study influence from external static magnetic field on dynamic behavior interaction between laser beam and EH36 steel, four cases with different magnetic strength (0 mT, 15 mT, 25 mT and 30 mT) are designed to capture high-speed image series of full penetration laser welding through quartz glass. It can be observed that: (1) Part of laser welding energy is compacted in bottom of weld pool to increase penetration and bottom width of bead geometry; (2) Eruption cycle and intensity (height 2.125 mm, width 1.75 mm) of vapor plume are both weakened; (3) Inhomogeneity and fluctuation of energy distribution are prominently dropped off; (4) Cooling period is delayed to reduce thermal gradient, depression area of the final profile is also reduced. Meanwhile, a polynomial model is developed to reveal relationship between thermal density and distance along the weld center. Therefore, external steady magnetic field has influence on dynamic behavior mechanism (weld pool, vapor plume, energy homogeneity, cool down stage) and even the final morphology, while 15 mT is an optimal value of the magnetic strength in these four cases. It can be concluded that selecting an appropriate magnetic field strength is helpful to stabilize laser process and improve welding quality.