Process Research And Mechanism Analysis Of TA2 Thin Plate Tandem TIG Welding

Titanium,as a kind of green and high-quality structural material,is often used in aerospace,petrochemical and seawater desalination fields.Because the arc is stable and easy to realize automation,TIG welding is the most used way of titanium and titanium alloys welding.However,TIG welding has a low penetration and is prone to form undercut,hump and incomplete welding defects during high-speed welding.Although high-energy beam welding can effectively improve the speed of welding and avoid the occurrence of defects such as undercut,hump and lack of penetration,high capital costs are involved,which makes it difficult to apply.This paper aims at solving problems of high speed welding.By observing the profile and dynamic image of weld pool based on high-speed photography,the behavior of weld pool could be analyzed.And using Tandem TIG welding can prevent defects and improve welding speed,which has important theoretical significance and engineering application value for high speed TIG welding and improving welding efficiency.The results show that the backflow pool is the main reason for the formation of undercut and hump bead.According to the mechanism of forming undercuts and hump defects,we put forward the method to prevent the defects.One weld gun was put forward which can heat and melt parent metal,and another is put backward,which can prevent the defects.By observing the profile and dynamic image of weld pool based on high-speed photography,the behavior of weld pool could be analyzed.The mechanism of Tandem TIG welding to restrain undercut and hump defects was revealed.By studying the maximum welding speed that can be obtained by different inter-electrode distance,current ratio and current sum,this paper reveals the mechanism of increasing penetration depth of TIG welding and the inhibitory effect of auxiliary arc on the backflow pool and the stirring effect on the pool are expounded.The technological reference for selecting welding parameters of TIG welding is also proposed.Based on the study of arc morphology and current and voltage waveforms and high-speed photography,the morphology and dynamic image of the melting pool were observed,and the behavior of the melting pool was analyzed.The research results of this paper have been applied in the actual production of the titanium welded pipe.When the welding speed is 5m/min,the mechanical properties and technological properties of the titanium welded pipe meet the requirements and realize the high-speed welding of the titanium welded pipe.