Simulation of plasma dynamics in a keyhole during laser welding of metal with deep penetration

Abstract

Physical processes occurring in the keyhole during the deep-penetration laser welding of aluminium, where evaporation, ionization and formation of near-surface low-temperature plasma can take place, are studied theoretically. Equations of radiation gas dynamics including the equilibrium model of plasma, description of laser radiation transport and absorption are solved. Numerical calculations of plasma cloud propagation processes in aluminium vapour are performed in a one-dimensional approach. The minimum radiation power necessary to maintain this cloud is found. The effect of radiation trapping by plasma due to self-absorption in the optically thick plasma layer is revealed. The simulation results are of interest for a qualitative understanding of the processes in the keyhole plasma.

Comparative study on the behavior of keyhole in analogy welding and real deep penetration laser welding

“…Huang et al (2017) theoretically studied the correlation among the surface area, the volume of the keyhole, the welding speed and the surface tension coe cient, believed that the surface tension controlled the oscillation period of the keyhole. Bedenko et al (2010) conducted one-dimensional simulation research on the dynamics of keyhole plasma during laser welding, pointed out that the keyhole plasma has a periodic shielding effect on laser radiation, which makes the absorption of laser energy by workpiece materials alternately attenuate or stop, resulting in the pressure and temperature oscillations. Pang et al (2016) proposed a mathematical model to describe the dynamic coupling behavior of keyhole and weld pool, pointed out that the surface tension has a great in uence on the period of keyhole depth oscillation.…”

Formation and influence mechanism of keyhole-induced porosity in deep-penetration laser welding based on 3D transient modeling

“…Much research focused on modeling dynamic keyhole behavior [9][10][11], thermal and strain field in laser welding [12,13], laser absorption mechanisms of material [14][15][16] and laser plasma behavior of laser welding [17]. Some research were carried out on keyhole-induced porosity by modeling.…”

Numerical Modelling Of Thermal And Structural Phenomena In Yb:YAG Laser Butt-Welded Steel Elements

“…In the case of laser welding a "keyhole" is created with ionised vapour that absorbs the laser beam power. The beam is afterwards transferred to the walls of the "keyhole" forming the fusion zone [12][13][14]. Moreover, the impact of concentrated heat source on the material causes high temperature gradients as well as different heating and cooling conditions, contributing to the formation of various structures in the weld and heat affected zone, which leads to different mechanical properties [6,10].…”