Parametric study on AC square waveform welding

Abstract The quality and productivity of submerged arc welding (SAW) products are significantly influenced by the power source characteristics (i.e., direct current or alternating current power source). One of the latest developments in the SAW power sources is alternating current (AC) square. The square waveform provides fast polarity reversal from positive to a negative peak which resolves the problem of arc extinguish that occurs during polarity cross-over in sine or triangular waveform. This paper presents the parametric study of AC square waveform arc SAW of heat resistant steel. The effects of change in process variables, namely frequency, electrode negative (EN) ratio, current, and welding speed, on the process outcomes such as bead width, penetration depth, deposition rate, and flux consumption rate are observed through experimentation. All the outcomes follow a non-linear trend except deposition rate, which follows almost a linear trend with the variation in welding current. The bead width, penetration depth, and deposition rate increased with the increase of current, whereas the bead width decreased with the rise of EN ratio and welding speed. The deposition rate follows an increasing trend with an increased EN ratio and a decreasing trend with welding speed. A similar observation is noticed in the case of penetration depth which increases with the increase of welding speed and decreases with the increases of EN ratio. Concerning each parameter studied, the flux consumption rate shows a parabolic variation, i.e., first increases and then falls. The frequency does not have much impact on the process outcomes. A comparison of AC welds with those obtained with direct current is presented concerning the attributes mentioned above. The parametric study results in this investigation are corroborated with the physics of the process to make them more useful for industrial application. The key finding of this investigation is that the AC square arc welding can maintain penetration at a higher welding speed, which significantly improves the productivity.