Abstract
GMA welding process with synchronized control system consisting of a pulsed arc current waveform with cyclical variation of wire feed rate has been developed on the base of computer simulation. In the ultra-narrow gap (less than 5 mm gap) welding process, as the welding wire melting behavior is controlled by low frequency pulsated arc current waveform, the arc generating at the wire tip can be widely oscillated in the direction of thickness. The arc heat pole is dominated by wire melting tip position in consumable electrode welding process, and the arc heat distribution can be changed by this wire tip behavior. The wire melting tip position is represented by wire extension which is a function of wire feed rate and wire melting rate. In order to more-adequately control the arc heat distribution, this report describes synchronized control process between wire feed rate and pulse current waveform in the ultra-narrow gap GMA welding. The important control factor in the newly proposed process is phase shift θ between pulse current waveform and wire feed rate pattern. Firstly, the non-steady state simulation of the wire melting behavior is developed in the case that both arc current and wire feed rate change periodically with low frequency. From simulation results of wire tip behavior under various phase sifts and wire feed rates and pulse conditions, the adaptive welding conditions can be found effectively. Secondly, the synchronized control of welding was carried out under adaptive welding conditions. From the experimental results, it was verified that the arc heat distribution was effectively controlled with the phase shift method expected by numerical simulation thus adequate penetration shapes were obtained in the proposed welding process.
