Optimization of waveform parameters for high speed CMT welding of steel

A series of high speed CMT welding tests were conducted on Q235 steel at a wire feed speed of 5 m/min and a welding speed of 1.8 m/min. The effect of waveform parameters on welding process, weld bead appearance was researched by means of orthogonal test. The causes for unstable welding process at high welding speed were analyzed. The results showed that the wing order: peak wire feed speed, boost current duration (tp) and boost current (Ip). With unsuitable welding parameters (including expert welding parameters in CMT power source), periodic “wire adhesion” phenomenon which led to uneven weld bead appearance and severely undercut occurred frequently in high speed CMT welding. The “wire adhesion” phenomenon was caused by high peak wire feed speed, droplet drag and low temperature of thin liquid metal layer in front of the weld pool. Wire adhesion phenomenon was eliminated and sound weld bead appearance was obtained by properly matching the above three waveform parameters.