Current waveform effects on CMT welding of mild steel

Distributions of CMT periods and short circuit times are established by analyzing the electrical waveforms and metal transfer images sensed simultaneously under different welding conditions so as to evaluate the process stability for CMT welding of mild steel. Concentrated distributions for both CMT periods and short circuit times are observed in the whole adjustable range of boost current from 250 A to 320 A, indicating that changing the boost current doesn't disturb the regularity and stability of CMT welding process obviously. With the boost duration ranging from 1.6 ms to 3.6 ms, the welding process is very regular and stable, and beyond this range, the process becomes unstable. The average CMT frequency changes very little with welding parameters, and fall in a narrow ranges from 80.1 Hz to 90.1 Hz. The deposition rate, average wire feed speed and droplet size increase with increasing boost current or boost duration, even the preset wire feed speed is kept constant. As the boost current or boost duration increases, the weld width and penetration increase noticeably, and the reinforcement varies very little.