Study of “Re-Melt” Temper Bead and Polarity Effects on Porosity in the Under Freshwater Wet Welds

Abstract

The objective of this work was to discuss the influence of electrode polarity on bead-on-plate (BOP) welds and re-melt temper bead on the pores behavior in the weld bead section of bead-on-grove (BOG) and bead-on-bead (BOB) welds. The welds were made with E6013 electrode at 50 and 100 meters of water depth. Researchers recommend the use of direct current electrode negative DCEN for wet welding. The justifications are to prevent electrode holder electrolytic corrosion and performance improvement. On the other side, some researchers said that no significant variations should be expected while another researcher affirms that depending on the region (Mexican Golf or North Sea) where the welding will be performed, inverse polarity DCEP produces better results. In this work, a gravity feed welding system was used in a hyperbaric chamber with 200 m pressure capability to simulate the wet welds. Visual analysis, arc stability, porosity and pores location in the weld metal enable to evaluate the polarity influence. The results showed significant differences between the two polarities. DCEP produced better bead appearance and higher arc stability than DCEN. Consequently it presented less porosity and best porosity location than DCEN. Additionally, it is was observe that in multi-pass welds (BOG and BOP) the weld bead made previously is partially “re-melted” by the following bead and the pores were in this region were removed or significantly reduced. It is believed then that pores position in the weld section is important information in such welds.