Stabilization of the process of mechanized pulsed-arc welding

Abstract

The main disadvantage of the mechanized arc welding process in shielding gases with short circuits is the spatter during melting of the electrode metal and its transfer to the weld pool, which affects the productivity of the process, reducing it. Its elimination is possible through the implementation of the controlled transfer of molten electrode metal into the weld pool. The implementation of such a transfer and the control of the processes that take place in the arc gap to a large extent determine the conditions for the qualitative formation of the deposited metal, the stability of the process, the magnitude of the loss of electrode metal and the manufacturability of the processes of arc welding in shielding gases. At the present stage of development of welding technologies, controlled transfer of electrode metal is possible due to the pulsed nature of arc burning. In this case, one of the main methods for increasing the efficiency of the process is to limit the maximum value of the short circuit current by increasing the inductive resistance of the welding circuit.
 The research aimed to determine the effect of the rate of rising of the welding current during a short circuit on the stability of the welding arc. It was found that an increase in the current growth rate, starting from 1.23 kA/s to 50 kA/ s, leads to a decrease in the average duration of short circuits by at least 10 times. At the same time, the average frequency of short circuits increases by more than 2 times, from 36...38 s-1 to 80...86 s-1. The reason for this is the increase in the values of the electrodynamics’ Lorentz force, the action of which leads to the compression of the liquid metal bridge of the drop (pinch effect) due to an increase in the short circuit current. At the same time, there is a violation of the stability of the pulse process, and this is reflected in an increase in the average frequency of arc breaks by more than 30 times from 0.33 s-1 to 10 s-1. An increase in the energy parameters of the welding process led to a decrease in the average frequency of short circuits (2...3 times) and their average duration (2 times). The reason for this should be considered a change in the type of transfer of liquid metal – the welding process with short circuits has turned into a mixed process in which, along with short circuits, a droplet transfer of electrode metal is observed.