Study On Heat And Mass Transfer Behaviors During Filler Powder Laser Welding

Filler powder laser welding can fill the molten material into the welding seam in real time,so the gap margin of the weld can be improved.In industrial production,the width of the weld gap may gradually change,which makes it necessary to adjust the powder feeding rate to fill the weld gap.Therefore,the influence mechanism of powder feeding rate on the heat and mass transfer process of filler powder laser welding is studied,which provides theoretical basis for the monitoring strategy of adaptive filler powder laser welding.This paper takes the powder feeding rate as the research point,and systematically studies the heat and mass transfer behaviors in filler powder laser welding,including the plasma behavior,the keyhole behavior and the molten pool behavior.The main research work is as follows:The experimental observation platforms of the heat and mass transfer behavior on the surface and inside of the keyhole were built,and the information of the plasma,the keyhole and the molten pool were collected simultaneously.Under the condition of single factor increasing of powder feeding rate,the experimental platforms were used to observe the change rules of heat and mass transfer behaviors.The results show that as the powder feeding rate increased,the emission spectral intensity and electron temperature of the plasma decreased,and the electron density,atomic density and inverse bremsstrahlung absorption coefficient increased;The keyhole depth and surface temperature of the molten pool decreased,and the keyhole area increased.By analyzing the correlation between plasma behavior and keyhole,molten pool behavior,some conclusions were drawn.In this experiment,the increase of the atomic density of plasma plume was the main factor affecting the increase of the keyhole area,and the atomic density was linearly correlated with the keyhole area.The particle density and the inverse bremsstrahlung absorption coefficient of the plasma increased,attenuating the laser beam energy,resulting in the decrease of the laser energy absorption of the molten pool and the bottom wall of the keyhole,which reduced the keyhole depth and the surface temperature of the molten pool.In addition,the correlation between the emission spectral intensity of plasma and the keyhole depth was analyzed and found to be exponentially correlated.