Study On MIG Welding Process Of Magnesium Alloy

In present study, direct current (DC) pulsed MIG welding and alternating current (AC) pulsed MIG welding are developed by adding a pulse rework current and negative current, based on traditional DC pulsed MIG welding. AZ31B plates are welded with these two processes separately. The microstructure, mechanical property and hardness were investigated by the metal phase microscopy, scanning electron microscope, tensile testing machine and hardness instrument after welding. The detachment of droplets and arc shape is documented with high-speed-camera. The result shows below.1. DC pulsed MIG welding that we used is formed by adding a pulse rework current based on traditional DC pulsed MIG welding. Continuous weld beads can be obtained. The range of parameters is still narrow, and the parameters can not match with each other easily. Globular transfer form can only be realized. The average ultimate tensile strength of weld beads is 96% of base metal and the average elongation is 58% of base metal.2. AC pulsed MIG welding is formed by adding a pulse rework current and a negative current. A stable welding procedure and continuous joints can be obtained. When this process is used, not only the welding procedure is stable under a wide range of welding parameters, but also the parameters can be matched with each other easily. The most important factors for MIG welding are negative electrode (EN) ratio and pulse rework current Two metal transfer forms of globular and pulse transfer can be realized. The average ultimate tensile strength of weld beads is 97% of base metal; the average elongation is 78% of base metal; the average contraction is 199% of base metal.3. The deformation and residual stress of weld bead are studied using AC pulsed MIG welding process. There are several results. The deformation paralleled to weld bead expands. The deformation perpendicular to weld bead shrinks. For the stress paralleled to weld direction on the weld bead, it is compression stress at arc side. It is tension stress at weld bead. For the stress perpendicular to weld direction, it is compression stress at arc side. For the stress on the midnormal line of weld, it is tension stress at weld bead and it is compression stress at HAZ.