Study of improvement of gap tolerance in laser MIG arc hybrid welding of aluminium alloy

Abstract

Hybrid welding combining YAG laser or fibre laser with MIG arc was carried out on aluminium alloy, and the effects of setup conditions of a laser beam and a wire, and the laser beam parameters on wire melting phenomena and gap tolerance in butt joint were investigated. It was found that, in order to obtain a deeper penetration, the laser beam should be separated from the wire with a distance at which there was no direct interaction between a laser beam and a droplet during its transfer. On the contrary, in order to get a wider gap tolerance for a butt joint, for example, it was better for the laser beam to be set to cross with a wire over 2 mm so that the laser beam could directly irradiate on the wire surface to melt it. As a result, the arc current could be decreased so efficiently that the molten pool size formed by MIG is decreased and the gap tolerance increased.In the case of the utilization of a fibre laser, it was found that the wire melting phenomena were affected by the laser beam parameters such as the beam diameter and the defocused conditions when welding was not done at a focal position. It was clarified that even at the same laser beam diameter on the work surface, the wire melting phenomena could be different under the different defocused conditions. In the defocused conditions where the focal position was over the work surface, the molten droplet on the wire tip evaporated more easily than the case where the focal position was within the work surface.From the viewpoint of laser absorption by the wire or the molten droplet, according to an arc phenomenon approach, it was found that about 10% of laser energy was absorbed during hybrid welding when the laser beam was directly irradiated on the wire surface.

The effect of fit-up geometry on melt flow and weld quality in laser hybrid welding

“…However, the melt is accelerated and redirected around the laser-created keyhole. 10,12 The melt is accelerated by the arc's magnetic field and gas shear force 19 (directly and via acceleration of the transferring droplet) and by the keyhole boiling recoil pressure. From high speed imaging, typical trajectories were estimated, see Fig.…”

“…High speed imaging has enabled the study of drop transfer and the keyhole conditions for steel 10,11 and aluminum. 12,13 It has been established that the recoil pressure from keyhole evaporation can drive the melt into the gap. 10 Different situations have been classified 13 dependent on the presence of a gap, the torch arrangement, and the corresponding drop flight and heat and mass transfer.…”

Interaction between laser-induced plasma/vapor and arc plasma during fiber laser-MIG hybrid welding

“…However, previous research has concentrated on the optimization of welding parameters and the improvement of weldability of particular materials [8][9][10][11][12]; only a few studies have been conducted on the mechanisms of hybrid welding. Simulations and statistical analysis have also been used to examine the hybrid welding process [13][14].…”

Comparative Study of Laser-Arc Hybrid Welding for AA6082-T6 Aluminum Alloy with Two Different Arc Modes

“…Therefore, it is becoming an important welding technology for joining aluminum alloys, especially for laser-pulsed MIG hybrid welding (LPMHW) [12][13][14]. Compared with laser welding and arc welding, previous research proved that LPMHW has several advantages, such as: higher welding speed [15], deeper weld penetration [16], narrower heat-affected zones [17], better gap bridging ability [18], less residual stress [19], and superior mechanical properties [20]. Meanwhile, some research pointed out that welding deformation due to high heat input was still unignorable, and that spatter could not be completely eliminated due to the droplet transfer mode [21,22], which was determined by the arc characteristic of pulsed MIG welding.…”