The Research On Weld Forming Of A31B Magnesium Alloy In Non-consumable Double Electrode GMAW Process

The welding performance of AZ31 B magnesium alloy is poorer. In the conventional MIG welding process, in condition of smaller current, the surface tension and density are small so that the droplet can easily grow up and hard to break away from welding wire to make droplet transition unstable to produce spatters, leading to incomplete penetration and poor weld; In condition of larger current, the heat input of base metal is large so that welding bead subsidence even burn through can easily disappear to prevent weld forming. So, 2.3 mm AZ31 B magnesium alloy is welded by non-consumable DE-GMAW in this paper. Non-consumable DE-GMAW can decrease the size of droplet and increase the transition frequency of droplet while reducing the heat input of base metal to realize the stable and less spatter welding process of magnesium alloy and obtain the weld with high quality and favorable forming.In order to get the welding seam of magnesium alloy with high quality and favorable forming, arc stability, the transition characteristics of droplet, welding technology and the problems disappeared are studied and analyzed in this paper.First of all, non-consumable DE-GMAW experiment operational platform is established, including the experiment operational system and welding electrical signal data acquisition system. Experiment operational system has realized the welding of AZ31 B magnesium alloy and regulation of welding technology parameters. Welding electrical signal data acquisition system has realized real-time and synchronous acquisition of multiple electrical signal in the welding process to be displayed on the computer to more intuitively obtain the information of current and voltage.Secondly, the non-consumable DE-GMAW experiment on the magnesium alloy is carried out. Making use of the obtained current and voltage data to analyze the stability of welding arc and the transition characteristics of droplet. The effect of welding technology parameters on the stability of welding arc and transition of droplet is studied to provide practical experience for optimization of process parameters. The non-consumable DE-GMAW surfacing experiment is carried out on the basis of stable arc and droplet transition. The effect of welding technology parameters on the welding forming is studied to obtain the matched welding electric parameters and geometric position relationship of welding torches to achieve the good forming.Finally, the microstructure analysis and mechanical properties test is carried out on the surfacing weld. Researching the effect rules of welding technology parameters on the quality of weld. Further optimizing the welding process parameters to improve the quality of weld to obtain the surfacing bead with high quality and good forming. The best welding technology parameters obtained through a great deal of experiment is: the total current of 225 A, bypass current of 140 A, welding voltage of 21 V, welding speed of 2.8 m/min.The experimental results show that non-consumable DE-GMAW is a high efficient method to weld the magnesium alloy, which can achieve high speed welding of magnesium alloy and welding bead with high quality and favorable forming.