Modified active control of metal transfer and pulsed GMAW of titanium

Conventional pulsed gas metal arc welding (GMAW-P) achieves stable and repeatable spray transfer by using correct pulse parameters. Because the optimal pulse parameters depend on welding parameters, technology is needed to improve the robustness of the transfer process respective to the variations in welding parameters. To resolve this problem, active control technology is proposed to ensure a desirable and repeatable metal transfer mode, i.e., one drop per pulse (ODPP) mode. It uses a peak current lower than the transition current to prevent accidental detachment and takes advantage of the downward momentum of the oscillating droplet to enhance the detachment. When the droplet moves toward the weld pool, the current is switched to peak level and the combination of increased electromagnetic detaching force and downward momentum ensures detachment. Hence, the metal transfer process becomes controllable and robust against variations in welding parameters. However, in order to ensure the combination of increased electromagnetic force and downward momentum, the oscillation process must be monitored. In this study, a modified method is proposed in which the droplet starts to oscillate by first moving toward the weld pool. As a result, the detaching pulse can be applied after a very short period of time and the combination of increased electromagnetic force and downward momentum is guaranteed. Thus, the control system is simplified and the metal transfer's robustness is further improved. This modified active control technology has been used to weld titanium.