Modelling of gas jet effect on the melt pool movements during deep penetration laser welding

Abstract

A modelling of the induced melt pool movements during iron deep penetration welding by CW Nd–YAG laser beam is developed, with the aim of studying the effect of inert gas jet on the liquid metal flow. The keyhole shape is calculated as a function of the operating parameters and the derived boundary conditions on the keyhole walls are used, by applying a solidification model, to calculate the frontiers of the assumed stationary molten pool. The vapour flow generated inside the keyhole, the surface tension and the recoil pressure are considered as the mechanisms producing the melt pool movements, and the evolution of the interfaces between the keyhole, the molten pool and the surrounding air is simulated by the multiphase volume of fluid method. We demonstrate, in accordance with the experimental observations, that an important stirring effect is generated inside the melt pool, and moreover by extending the modelling to the study of the effect of 45° inert gas projection at 100 m s−1 on the metallic liquid pool, it is shown that a more uniform flow is obtained.

Explanation of penetration depth variation during laser welding under variable ambient pressure

“…[23][24][25] It is interesting to note that our simulations show a similar behavior even if the influence of IB, as pointed out in Ref. 6, or the difference in the magnitude of friction force on melt induced from uprising metallic vapor jet, as pointed out in Ref.…”

“…Without loss of generality, two different pressures, vacuum (0 bar) and atmospheric pressure (1 bars) are used as the ambient pressure in LW process, respectively. Both the IB effect 23 and frictions effect of vapor plume 24,25 are neglected in numerical modeling, since we intend to give an explanation of penetration depth variation that well supports most of LW processes. The process parameters used in the simulations of LW under atmospheric pressure and vacuum are the same.…”

A Review on Melt‐Pool Characteristics in Laser Welding of Metals

“…e friction force, which is induced on the melt-pool wall, results in a drag force expelling the flow towards the surface. e other main driving forces for the molten material in the melt-pool result from surface tension, recoil pressure, and buoyancy forces [5,85,94]. By solving a combination of the Navier-Stokes, energy conservation, and ideal gas equations, using the finite volume method, it was confirmed that using a gas jet during deep penetration laser welding results in better weld joints because the melt flow in the melt-pool is enhanced.…”

“…Amara and Fabbro [94] modeled the fluid flow in the melt-pool, considering the interaction between the vapor and the liquid and between the liquid and the air. Fabbro et al [95] showed that the escaping vapor, which is generated in the keyhole, creates friction forces, which, in turn, play an important role in fluid flow in the melt-pool.…”

Monitoring of deviation status of incident laser beam during CO2 laser welding processes for I-core sandwich construction

“…Some numerical researches focused on the correlation between keyhole and laser-induced plasma plume were also developed to supplement the experimental observation and analysis. Amara and Fabbro [10] established a model of the induced melt pool movements during iron deep penetration welding. They found that the vapor flow generated inside the keyhole and that the surface tension as well as the recoil pressure are considered as the mechanisms producing the melt pool movements.…”