Operational performance and metal droplet formation in pulsed-shielded metal arc underwater welding

Abstract

Underwater Shielded Metal Arc Welding (SMAW) is highly affected by the welding depth. The arc and molten metal in contact with the surrounding environment cause operational and metallurgical challenges regarding arc stability, metal transfer, gas formation, high-cooling rates, and diffusible hydrogen uptake. The hydrostatic pressure causes losses in consumable fusion efficiency, constricts the arc, increases the number of short-circuit events, and consequently decreases the welded joint’s process quality. In the present study, the novel approach of pulsed welding current is applied to wet shielded metal arc welding and is operational characteristics are evaluated in detail. Automated welding using an arc-voltage control system was used to obtain reproducible results. For the pulse conditions, two values of pulse current combinations, taking 140 A as the mean value, were set (Δ I of 40 A and 80 A). The same pulse and base duration were chosen, giving pulsing frequencies of 2.5 Hz and 25 Hz. The voltage and current signals were acquired and the short-circuit numbers and melting rates were calculated by processing the data stability factors. As a result, it was possible to weld with lower average welding currents through pulsed-current technology. This new approach can improve the stability of the wet SMAW process and contribute to obtaining better-quality welds without any changes for the underwater welder.