On The Characteristics Of Nd: YAG Laser-Short Circuiting Transfer GMA Hybrid Welding

In this paper, a 2000W continuous wave Nd:YAG solid state laser and a short-circuiting transfer GMA hybrid welding system was used, and the characteristics of it were studied. The influences of welding parameters on the weld shape, the stability of welding process and spattering were verified. Through the use of high-speed photography, arc analyzer as well as arc spectrum analyzer, the roles of laser on droplet detachment, molten pool flow field, arc shape and stability in Nd:YAG laser-short circuiting transfer GMA hybrid welding process were studied.The experiments showed that the laser-short circuiting transfer GMA hybrid welding process could effectively improve the weld shape, increase the frequency of droplet transfer, enhance the stability of the welding process and reduce spatter. By changing the angles of the heat sources, while the laser was oblique and the welding wire was vertical to the work piece, spattering could be further depressed. The hybrid welding process could also significantly increase the welding speed and inhibit weld humping.By analyzing the characteristics of the laser-short circuiting transfer GMA hybrid welding process, it is verified that laser played a leading role on the increase of weld penetration; laser increased the temperature of molten pool and reduced the surface tension of molten metal; laser also increased the radiant intensity of the arc plasma, and the arc energy concentrated more on the surface and the center of the molten pool,which raised the temperature at the central region, and increased the gradient of surface tension of the whole molten pool; The surface flow velocity of the molten pool of laser-short circuiting transfer GMA hybrid welding process was much higher than that of the conventional GMAW, which led to a wider bead, deeper penetration depth and smaller reinforcement and wetting angle.The "wavy flow" between the arc and the laser key hole on the surface of the molten pool caused by short circuiting as well as the higher flowing speed of the process reduced the arcing time T₃, and short-circuiting time T₁. So it increased the frequency of droplet transfer obviously.Due to the interaction between laser and arc in the laser-short circuiting transfer GMA hybrid welding process, it reduced the surface tension of the molten metal, increased the dimensions of the molten pool, mitigated the bursting force acted on the molten pool surface during the explosion of the liquid bridge and reduced spattering compared to conventional short circuiting welding process However, when Laser was vertical and welding wire was oblique to the work piece surface of the hybrid process, and during the necking of the liquid bridge at short circuiting period, the sliding of the molten droplet to the wire tip, ultimately created spattering caused by the explosion of the liquid bridge and swang the liquid bridge metal forward and form spattering. But when laser was oblique and the welding wire was vertical to the work piece, the sliding of the molten metal droplet had not been observed. After the droplet transfered to the pool, it flowed backward immediately to the back of the pool and formed less spattering.Finally, based on the understanding of the characteristics of the laser-short circuiting transfer GMA hybrid welding process and the requirements of products, we have successfully applied the laser-short circuiting transfer GMA hybrid welding process to the welding of cylinder to cap of a vibration absorber. for heavy vehicle. By ensuring the strict requirements of weld quality, high pressure air tightness and welding deformation of the work piece, the process fulfilled the requirements and improved welding efficiency by more than 100%. After completing the laboratory test siage it laid a foundation for the application of the technology in the practical engineering productions.