Research On Droplet Transfer And Arc Behavior Of P-GMAW With Narrow Gap Of Swing Arc

In recent years,thick plates and medium plates are more and more widely used in welding engineering with the enlargement of equpment in fields of oil and gas Pipeline,nuclear power,marine engineering and pressure vessel.Narrow gap welding,which can improve welding efficiency and reduce welding cost,is more and more popular in practical engineering.This paper has systematically analyzed the arc behavior and metal transfer of waving arc narrow gap P-GMAW welding,and has specially studied the short circuit transfer behavior of all-position welding.(1)The arc behavior,metal transfer and arc characteristics of narrow gap swing arc P-GMAW during the down-hand welding are studied.The mathematical model of wire extension and welding current is established to figure out the relationship between arc behavior and welding current.The analysis shows that when TPS3200 digital welding machine is used as the welding supply,the welding current is directly affected by the arc behavior in the welding process,especially in the peak stage of welding current.When the groove angles is changed into 8 °and 20 °,the arc behavior and metal transfer are observed to be affected by the angle of narrow gap groove,and they are affected more obviously when the welding torch approaches to the side wall.The effect of arc behavior on welding current is studied by changing the side wall,which shows that the welding current is changing greatly w:ith the change of side wall,especially at the peak stage of current.And the mechanical analysis of the droplet shows that the arc shape is the main factor affecting the d:irection of metal transfer.(2)The influence factors of short circuit transfer on narrow gap swing arc P-GMAW during the down-hand welding are studied.It is found that the relative position of the oscillation center and groove center o f welding gun during down-hand welding,the swing amplitude of welding gun and the arc length are the main factors that affect the short-circuit transfer.And the distribution law and the affecting reasons are analyzed by using the statistical principle.(3)The influence factors on the short-circuit transfer of narrow gap swing P-GMAW in vertical welding and over-head welding are analyzed.During vertical welding,the force analysis of molten pool is firstly carried out and the vertical down welding is selected for the application of practical engineering.The experiment shows that the short circuit transition of welding current and welding speed have some effect on the short circuit transfer of vertical welding,and the reasons have been explained.Through the mechanical analysis of molten pool and droplet,it is found that the weld in over-head welding is obviously thicker than that of horizontal welding and vertical welding.Therefore,the adjustment range of welding parameters is narrow.The effect of arc length on short-circuit transfer has also been studied,which shows that it is difficult to ensure the welding quality while the short circuit transfer is controlled.