Evaluation of the Effect of the Water in the Contact Tip on Arc Stability and Weld Bead Geometry in Underwater Wet FCAW

Abstract:

Underwater wet flux cored arc welding – FCAW – is an important process employed to repair marine structures with the advantages of not handling the components off the water and offers higher productivity in comparison to other conventional welding process. Under the water, wet welding activities are performed with lower stability, due to the pressure of the water surrounding the arc column and the presence of water in the gap between the contact tip and the electrode, which promotes poor electrical contact. In the present work, to compare the process stability of underwater wet FCAW with self-shielded electrode, welds were carried out using a special torch, which keeps the contact tip dry under the water. A two-level factorial design was used for experimentation and an Analysis of Variance was conducted to validate the results. Current coefficient of variation was used as the stability index. Welds performed with the torch have shown better-shaped beads and more stable arc in comparison to beads deposited with no mechanical barrier between water and the contact tip.

Key-words:
Underwater FCAW; Welding torch; Arc stability