Analysis Of Droplet Transfer Behavior In Double-wire Three-arc Welding And Research On Weld Formation Mechanism

GMAW has been widely applied in the field of modern industrial production,such as in aerospace and shipbuilding,because of its advantages of high efficiency,high quality and low consumption.However,in the process of traditional GMAW,it usually increases the heat input of welding even though this welding method is able to enhance the deposition rate of welding,which would lead to the decline of mechanical property of welding line.Thus,this produces a contradiction that constrains the application in practical production of the traditional welding method of GMAW.Therefore,in this paper,the author is going to carry out a directed study about the a kind of all-new welding process—Tri-Arc DE,which is capable of not only generating M-arc between the wire for welding and the base metal,but also producing the M-arc among wires for welding,featuring its high deposition rate and low heat input.But since of its shortcomings,for instance,the generation of a relatively much splashes in the welding process and lack of stability,this kind of welding method has never witnessed wide promotion in the market.For this reason,this study,which is designed to have a thorough exploration about its drop transfer as well as its mechanism of formation of weld,is bound to be of great significance in terms of the improvement of this processes method.In this paper,the researcher conducts a study in regard to the surfacing technology of the welding method of Tri-Arc DE.In first place,the researcher builds up a welding system,and a high speed photography and waveform synchronous acquisition system.By virtue of these two systems,the research is capable of not only completing the weld test of Tri-Arc DE,but also keeping a real time observation about the characteristics of drop transfer in the process of welding,as well as obtaining the corresponding characteristic parameters of the electric signal.On the basis of analyzing the operating principle of its power supply and the control principle of its current pulse shape,a weld test system of Tri-Arc DE is constructed and is further improved in the later stage.In addition,the theory of static equilibrium is applied to study the major acting force of molten drop.The results show that the main acting forces of molten drop include:the gravity,the force of plasma jet,the electromagnetic force that promote the molten drop transition,the surface tension and the spot pressure that prevent the drop transfer.With the increase of M-arc current,the drop transfer change from the mix transfer of short circuiting transfer and spray transfer to globular transfer,and then to projected transfer and finally to spray transfer.While the gradual increase of pulse frequency,the droplet transfer frequency gradually decreases,which is followed by several drops per pulse,one drop per pulse,and one drop within several pulses,the most ideal transfer form is one drop per pulse.Afterwards,the paper lays its emphasis on the study of the effect of pulse peak current on drop transfers through separately studying the current peak of different pulse,and the different forms of drop transfer under the pulse peak time.And the research findings demonstrate that with rise of peak pulse current of M-arc,the transfer modes of molten drop will also change,and the different mode of metal transfer is equipped with different current fluctuation.Also,with the gradual decrease of pulse peak time of M-arc,the modes of drop transfer.When it is at 41.7 ms of the pulse peak time,it is several drops per pulse,when it is at 33.3 ms,the mode of drop transfer is converted into one drop per pulse,and when it is at 27.8 ms,and it changes into one drop within several pulses.In the end,the researcher conducts a study about the mechanism of the formation of weld in terms of different M-arc pulse currents,impulse frequency,wire feed rate and welding speed.And the results indicate:the formation of weld is turned out to be the best when the M-arc pulse current is 90 A,the impulse frequency is 166 Hz,the wire feed rate is 7 m/min and the welding speed is 14 mm/s.