Study And Application Of Hybrid Modes In Low-power Laser+Arc Hybrid Welding

As a new welding technique with high quality, laser+arc hybrid welding process has received significant attentions all over the world for its particular advantages, such as the large welding penetration, high welding speed, less deformations and good bridging ability for relatively large gaps, etc. Since the laser-arc hybrid welding technology was conducted firstly by Steen and Eboo in1979, researchers have been making great amount of investigations on the hybrid welding technology due to the increments of weld penetration, welding efficiency, and capacity of gap tolerance. However, most researches investigate the effect of laser power, arc current or the distance between laser beam and TIG electrode barely, and the both effection is ignored. So it’s necessary to do further research on the interaction between the parameters and to study their differences for the different hybrid modes and lay a solid foundation to improve the laser/arc hybrid welding technology.In this paper, the character of low power YAG laser+arc hybrid welding on AZ31B magnesium alloy is investigated. The main conclusions can be drawn as follws.1. The Laser leading hybrid welding mode (Laser-tungsten inert gas (Laser-TIG) and TIG leading hybrid welding mode (TIG-Laser) were utilized in magnesium alloy welding process. Experimental results show that, there is a decided difference in the change regularities of the penetration depth with the changes of welding parameter in different welding modes, and then that, the interaction between the welding parameters is defferent. The penetration depth increases firstly and then decreases with the Dla increasing from1mm to7mm in TIG-Laser hybrid welding mode while that decreases monotonously with Dla in Laser-TIG hybrid welding mode. The value of Dla for achieving the maximum penetration depth varies with the arc current in TIG-Laser hybrid welding mode. However, this law does not exist in Laser-TIG hybrid welding mode.2. A dimensionless parameter Ψ was introduced to indicate the change in the melting energy of different hybrid welding modes. The increase percentage of melting efficiency remains at around20%in Laser-TIG hybrid welding mode while that fluctuates acutely and achieves the maximal value (about53.14%) at the arc current of120A in TIG-Laser hybrid welding mode. 3. Welding mode has a great effect on the change regularities of the penetration depth. The different plasma behaviors and characteristics of molten pool are the fundamental reasons for the differences in penetration depth.4. Combining the different change regularities of tow different hybrid welding modes and welding materials, welding thickness and welded structures, the eminent welding joint of plate and T-structure of AZ31B magnesium alloy welded by low-power laser+TIG arc hybrid can be obtained. Experimental results show that, Laser-TIG hybrid mode compared to TIG-Laser hybrid mode is more conducive to weld magnesium alloy sheet and the T-structure welding, that can still get a good molding in the high-speed welding conditions and there is no energy fluctuation and no burn, holes and other defects..