Investigation Of Pulse MIG Welding Process Of 5a06 Aluminum Alloy Using Multi-strands Composite Wire

Aluminum alloy has been widely used in the automotive,aerospace and marine industries due to its light weight,high specific strength,corrosion resistance and good weldability.Therefore,more and more researchers have focused on how to weld aluminum alloy efficiently and obtain good welded joint as well.Gao Ding,Alan Thomas Mayr and Hao Feng used multi-strands composite wire firstly in China to explore high-efficiency welding processes.However,the research on multi-strands composite wire are mainly focused on thick steel plates.The study on this new wire used in aluminum alloy has not been reported yet.Therefore,in this study,the threestrands/seven-strands aluminum alloy composite wire were used to study its droplet transfer characteristics and its welding stability.The welded joints with the best mechanical properties were compared with pulse MIG and TIG welded joints using common welding wire.The results of pulse MIG welding droplet transfer test of multi-strands composite wire show that the welding of three-strands composite wire is better than that of sevenstrands composite wire,and the single-pulse MIG welding method is better than doublepulse MIG welding method.The main contents of this study are shown as follows:(1)The single-pulse MIG welding droplet transfer type using three-strands composite wire is projected transfer,the transition mode is a drop of one pulse,the droplet is a regular spherical shape,the spatter is less,while seven-strand composite wire is explosion transition during single-pulse MIG welding and results in more splashes;The transitional type of the three-strands composite wire in the strong as well as weak pulse group of the double-pulse MIG welding is projected transfer,but in the strong pulse group,droplets of three-strands composite wire are difficult to polymerize due to the fast pulse frequency,these drops are irregular when entering molten pool so that causing a lot of splashes.(2)Three-strands composite wire used in single-pulse and double-pulse MIG welding produced fewer pores compared with using seven-strands composite wire,it has a good macroscopic shape and no obvious welded defects such as splashes;It is difficult for seven-strands wire to aggregating and forming a spherical shape under the effect of large electromagnetic and centrifugal force in single or double-pulse MIG welding.What's more,it is easy for drops to diverge under the effect of metal vapor so that the transition type is explosion transfer,which is the reason why more pores and spatter can be observed.The optimal weld parameter of single-pulse MIG welding used aluminum alloy three-strands composite wire was obtained.The comparison between pulse MIG welding of three-strands composite wire and pulse welding of common wire shows that:the best welding process of three-strands composite wire can refine grains,and it makes the grain size change slowly from weld zone to fusion zone.It is beneficial to reduce the softening of the heat affected zone compared with the traditional fusion welding method.The average hardness of pulse MIG welded joints using three-strand composite wire is about 89.3 MPa,the tensile strength is about 89.7% of the base metal,which is better than that of single-pulse MIG using common wire.In addition,the welded joint properties of single-pulse MIG welding using this new wire is smilar to that of TIG welding(about 93% of pulse TIG),while the welding efficiency of pulse MIG is almost4 times higher than that of TIG.