Influência dos parâmetros de soldagem sobre as características de revestimentos de liga de níquel aplicados em aços API 5L Gr B pelo processo arco submerso.

Abstract

The need for exploration of heavier oils, in ever deeper wells and more aggressive environments has caused failures due to corrosion of materials with large economic and environmental losses. Therefore the aim of this study was to evaluate the influence of welding parameters on geometry (ratio of height to width - R/L), dilution (D), Iron content, % Fe, and hence corrosion resistance of Ni alloy overlays (Hastelloy-276) applied by welding on C-Mn steels. Submerged Arc welding process was used with pulsed and conventional current using nickel alloy wire electrode (Ni-Cr-Mo-4) with 1.14 mm diameter as filler metal. A segments of API 5L Gr B steel pipe with 18 mm thickness and 290 mm internal diameter was used as substrate. To relate the influence of the variables mentioned with the desired responses design of experiments technique with application of factorial design at two levels was used. The factorial design was used only in the stage of isolated welding beads. Subsequent steps consisted of overlay with 3 welding pass in plan position and inside of the pipe in rotation movement with the torch stopped. In this case it was also being evaluated mainly % Fe and corrosion resistance. For isolated beads in the pulsed current mode, dilution values were obtained from 3.6% to 22.26% and values of R / L from 0.23 to 0.67, being the most satisfactory result of 12.76% and 0.28 for D and R / L respectively. For isolated beads in the conventional current method,dilution values ranged from 9.62% to 23.19%, with R / L ranging from 0.21 to 0.60, being the most satisfactory result of 11.81% and 0.28 for D and R / L. At overlays with three passes, have been achieved better results in the corrosion resistance with conventional current mode, and the variable “distance from the contact tip to the workpiece, DBCP”, had the greatest influence on results.