Effects of PTFE on operational characteristics and diffusible H and O contents of weld metal in underwater wet welding

Abstract

For this paper, oxidizing rutile type tubular wires were developed by using polytetrafluoroethylene (PFTE) as a flux ingredient in concentrations up to 21 %. The welds were carried out in a flat position at a depth of 0.5m by using both negative (DCEN) and positive electrodes (DCEP). Welding electrical signals were acquired and processed to determine process characteristics voltages, and quantify the occurrence of short-circuit and arc extinction. The influence of flux composition on weld bead shape and its hydrogen and oxygen contents were also evaluated. For both polarities, welding current increased with the addition of PTFE to the flux probably because it required more energy to melt and dissociate. The additions of PTFE also increased bead penetration and reinforcement and reduced the width as well as the H and O contents in the weld metal. These results were more pronounced with DCEN. Weld porosity was not observed for all formulations. Therefore, tubular wires with PTFE additions to the flux may have potential operational advantages for underwater welding including the reduction of weld metal oxygen and diffusible hydrogen contents particularly when used with DCEN.