Research On Pore Sensitivity And Control Process Of Aluminum Alloy In Horizontal Welding

For the manufacture of large-scale aluminum alloy welding structures,if the traditional method is adopted,the welding process have the characteristics of easily deformed,the low efficiency,and the large space occupied,the accuracy is difficult to guarantee.The tank of the aerospace heavy-load rocket is manufactured by the vertical assembly welding,which can effectively reduce the deformation of the structure and ensure the accuracy of welding,but there is a large number of horizontal welding seam in this process,it can occurs easily the porosity defects near the upper side of the weld seam.The problem of the porosity defects stomata in the horizontal welding of aluminum alloys is studied from two aspects,which includes the internal factors of the material and the external factors of the welding process.An effective welding wire cleaning process was proposed,and the influence of the content of oxide film on the surface porosity of aluminum alloy welding was pointed out.The porosity of argon arc welding and helium arc welding was compared.The mechanism of the formation of pore,and the numerical simulation method was used to study the bubble behavior in the weld pool.Firstly,the experiment of the wire cleaned by different cleaning process proves that the wire cleaned by arc can effectively decrease the oxide film on the surface of the wire and reduce the pore sensitivity.According to the cathode cleaning action,a process method for cleaning the oxide film on the surface of aluminum alloy wire by arc is proposed.The study on the relationship between the content of oxide film on the wire surface and the porosity shows that the pore sensitivity is positively related to the content of the oxide film.The formation mechanism of porosity is analyzed.The generation of pores needs to meet three conditions,namely the nucleation conditions of the bubbles,growth conditions and floating conditions.Compared to the flat welding,the horizontal welding in aluminum alloy welding is more likely to occur forming defects and porosity defects.In the comparison of argon arc welding and helium arc welding,helium tungsten arc welding can achieve the same welding penetrates with smaller current.And there is fewer porosity defects and there is no macroscopic pore.The larger welding currents in argon tungsten arc welding can reduce the porosity of the weld seam.The experimental method is difficult to study the influence of driving force in the molten pool on the bubble behavior,the bubble behavior in weld pool was investigated by numerical simulation.The mechanism of action of electromagnetic force on bubble behavior was also revealed.The force acting on the bubble in the molten pool is complex.The movement of bubble in weld pool is not simply a straight floating,but it is a swinging floating.The speed of floating bubble is related to its diameter.At the same time,there is also fusion and consolidation of bubbles in the molten pool.The state of the bubble in the horizontal welding pool is different from that of the flat welding,and the floating process is more likely to be hindered.Compared with argon arc welding,the bubble in helium arc weld pool has a lateral movement.The force analysis of the bubble in the molten pool reveals that electromagnetic force direction of flow can promote the escape of bubbles.And the bigger the electromagnetic force is in the molten pool,the faster the bubble floats,and the greater the tendency is for lateral movement.