Comparison of underwater wet welding performed with silicate and polymer agglomerated electrodes

Abstract

Conventional basic electrodes varnished and basic electrodes agglomerated with polymer in underwater wet welding in a simulated depth of 10 m were compared. A hyperbaric tank was used for depth simulation and a gravity welding device for making the bead on plate welds. Bead on plate welds were deposited with welding currents of 100, 120, 140, 160 and 180 A with DCEN and DCEP polarities, in order to evaluate the arc stability through a non-dimensional statistical index. The welding current which showed better stability level in both polarities was chosen to evaluate weld bead morphology, weld metal porosity, weld metal oxygen and diffusible hydrogen levels. A methodology was used to correlate the heat input and short-circuit frequency with the weld bead morphology. It was observed a direct relation with the weld metal oxygen and penetration and an inverse relation of the weld metal oxygen with the diffusible hydrogen. Electrodes agglomerated with polymer showed higher penetration values than conventional electrodes in both polarities and lowest diffusible hydrogen levels in the DCEP polarity. It was observed lower levels of weld metal porosity for the electrodes agglomerated with polymer in comparison to conventional electrodes. This result was related to lower levels of porosity found in the droplets formed at the tip of the electrodes agglomerated with polymer.