Interaction between the laser beam and keyhole wall during high power fiber laser keyhole welding

Abstract

The crucial factor of laser welding is the laser energy conversion. For a better understanding of the process, the interaction process between the laser beam and keyhole wall was investigated by observing the keyhole wall evaporation during high-power fiber laser welding. The results show that the evaporation vapor, induced by the laser beam, discretely distributed on the keyhole wall. A tiny 'hollow' zone was observed at the spot center-action region on the FKW. The evaporation vapor induced by the spot center moved downward along the front keyhole wall (FKW) with a period of about 0.3~0.75 ms, which indicates that the keyhole formation is reminiscent of a periodical laser drilling process on the FKW. The evaporation vapor on the keyhole wall suggest the assumption that the laser energy coupling mode in the keyhole was multiple-reflection, and the keyhole depth was mainly determined by the drilling behavior induced by the first absorption on the FKW.

Effect of alloy element on weld pool dynamics in laser welding of aluminum alloys

“…Various methods have been adopted to explore the dynamic behavior inside weld pool in laser material processing 18 – 21 . High speed camera was adopted to observe the movement of molten metal in the weld pool with a specially designed structure 18 , 19 , 22 . In this method, a glass sheet and a steel sheet were arranged side by side, and their interface was irradiated by laser.…”

Influence of oscillating magnetic field on the keyhole stability in deep penetration laser beam welding

“…The incidence angle α between the keyhole front and laser beam axis, is significantly higher in the case without EMF, as shown in Figure 5. The incidence angle has a major impact on the absorption coefficient [23]. This, together with other factors, plays an important role on the welding depth.…”

Progress and perspectives of in-situ optical monitoring in laser beam welding: Sensing, characterization and modeling

“…Furthermore, the conventional optical-sensing techniques can provide only minimal depth information and may be blinded by the intense emission of metallic plasma and spatters. To gain insight into the process dynamics phenomena including the shape and geometry of the capillary (keyhole) in the weld bead, some novel monitoring methods including X-ray imaging technique [97]- [110], inline coherent imaging [111]- [117] and metal-glass "sandwich" imaging [118]- [123] have been proposed and achieved excellent results in laser beam welding. Next sections, we summarize and analyse the research progress of the novel monitoring techniques.…”

“…The observation results revealed the the formation mechanisms of the spatter and bubble and then discussed the relationship between the spatter and bubble formation. Zou et al [123] used the metal-glass sandwich imaging method to observe the laser-induced intense evaporation vapor on the keyhole wall, in order to analysis the interaction processes between the laser beam and keyhole wall.…”