Development Of Activating Flux For A-TIG Welding Of Stainless Steel And Carbon Steel And Research On Weld Microstructure And Properties

Tungsten Argon Arc Welding（TIG）is a kind of welding technology widely used in practical projects.This kind of welding technology can obtain excellent performance welds.It is often used to weld stainless steel,carbon steel,non-ferrous metal,aluminum alloy,high strength steel and other materials.At the same time,There are many defects in this welding method,such as shallow penetration of one-time welding,low deposit rate of weld metal,small thickness of single pass welding plate（generally used for less than 3 mm thickness）,large heat input,large thermal deformation,multi-layer multi-pass welding with groove when welding thick plate,TIG welding is also sensitive to some trace elements in the base metal.For a long time,experts and scholars have been working on a welding method and process that can greatly improve the penetration and make full use of the advantages of TIG welding.In recent years,A-TIG welding has attracted the attention of welding experts and scholars all over the world.It is a new and efficient welding method.This method is to coat the surface of welded plate with an active agent（MnO₂,Al₂O₃,SiO₂ and Mixture with halides）before the beginning of welding.In the process of welding,activator can change the flow pattern of welding arc shrinkage pool,and ultimately lead to a substantial increase in welding penetration.The one-time penetration of A-TIG welding is about three times as deep as that of traditional TIG welding.It can penetrate 3-8mm plate at one time without groove.At the same time,the weld is well formed,and the surface is smooth without arc pits and welding nodules.The use of activator will not cause adverse effects on the weld interior.The comprehensive properties of welded joints are good.The requirements and standards of carbon steel and stainless steel can be met when welding.In this project,the effects of activator type,welding current and welding speed on weld penetration and comprehensive properties of welded joints were studied through experiments.The main active agents studied in this paper are SiO₂,TiO₂,MnO₂,La₂O₃,Cr₂O₃,Y₂O₃,Fe₂O₃ and MgO.Because the oxidizing elements in halides corrode stainless steel,they are removed.Firstly,the influence of each single component activator on weld penetration was studied,and then orthogonal comparative experiments were carried out.After a lot of experiments,a series of activator formulations were developed to increase weld penetration most obviously.In the subsequent A-TIG welding experiments,the activator uses these formulations to study the microstructure of the weld,the macro-metallographic,micro-metallographic,mechanical properties and corrosion properties of the welded joints.Finally,the advantages of A-TIG welding process can be clearer by comparing with the welds and welded joints obtained by conventional TIG welding.By comparing and analyzing the experimental results,it is found that the A-TIG welding method can not only significantly increase the weld penetration,but also improve the mechanical properties of the welded joints.There are no welding defects such as porosity,slag inclusion,cracks,arc pits,welding nodules and undercut in both macro and micro metallographic phases,and the micro-structure composition is more uniform than that in conventional TIG welding and good corrosion resistance.During the welding process,the arc shrinkage is obvious,the molten pool opens and flows violently,the temperature gradient decreases,and the shape of the molten pool is deep and narrow.This lays a foundation for the practical application of A-TIG welding in engineering projects.A-TIG welding can not only reduce welding cost but also improve welding efficiency.At the same time,it can also enhance the comprehensive properties of welded joints,and has a good development prospect in the future welding market.