| High magnesium aluminum alloy has the characteristics of low density,high specific strength and good resistance to seawater corrosion,and has been widely used in aluminum alloy hull panels.At present,TIG welding,MIG welding and Double-sided MIG welding are mainly used for hull panel welding.When TIG or MIG welding is used,the welding heat input is large,which leads to serious deformation of components after welding,easy to produce porosity defects at the weld position,and serious decline in mechanical properties of welded joints.When Double-sided MIG welding is used,it was necessary to clean the root from the back side,which cannot achieve single-pass welding and forming,the production efficiency is slow,which seriously affects the widespread use of aluminum alloy in shipbuilding.In order to improve the porosity defects in the current welding process and increase the production efficiency,used Double Wire Pulse MIG welding(DW-MIG)for marine grade 5083 aluminum alloy welding.Firstly,the arc characteristics and droplet transition of DW-MIG welding were analyzed using a high-speed camera and synchronized Electric signal acquisition system.The formation of the weld bead was analyzed under different welding currents.Within the designed range of welding parameters,the arc of the front and trail wires were deflected towards the center of the two wires,and the droplets mainly transfer mode was “one droplet per pulse”.Due to the mutual interference of the front and trail wires,short-circuiting occured during the welding process,causing unstable moments.It was found that as the current of the front wire was increased from 100 A to 160 A and the current of the trail wire was increased from 40 A to 100 A,the weld penetration and width increased,the wetting angle increased from 90° to 120°,and the spreadability improved,resulting in enhanced weld formation.Secondly,the 5083 aluminum alloy plates docking test were conducted to examine the effects of welding parameters on the weld morphology,porosity rate,metallographic structure,and mechanical properties,and the DW-MIG welding process parameters were optimized.It was found that when the current of the front wire was increased within the range of 120 A to 150 A,the porosity rate of the weld first decreased and then increased.Similarly,when the current of the trail wire was increased within the range of 50 A to 80 A,the porosity rate of the weld increases after 60 A.Moreover,as the welding speed was increased within the range of 50 cm/min to 80 cm/min,the porosity rate of the weld increased after 60 cm/min.When the front wire current was 140 A,the trail wire current was 60 A,and the welding speed was 60 cm/min,the tensile strength of the welded joint was 300.8MPa,reaching 84% of the tensile strength of the base metal,which was considered the optimal welding parameter.Finally,a three-dimensional arc model and droplet-molten pool model of DW-MIG welding were established.Compared with Single-wire Pulsed MIG welding,the arc of DW-MIG welding had a velocity component in the horizontal direction,which reduced the velocity component in the vertical direction.The arc had a smaller pressure on the surface of the test plate but a larger area of action,which can better melt the metal.The molten pool of Double-wire Pulsed MIG welding was longer,and with the continuous fall of droplets,the surface of the entire melt pool showed periodic changes in a "wave" shape.There were three small eddy currents inside the weld pool,which were located below the front wire arc,between the two welding wires,and at the tail of the weld pool,which promotes the flow of the melt pool and reduced porosity defects. |
