Double-Sided Welding as an Alternative for Joining Internally Clad Pipes

Abstract

High strength steel pipes internally clad with nickel (Ni) superalloys are components widely used in the oil and gas industry in the production of rigid risers. The joining of clad pipes is carried out through a girth welding in which the joint is totally filled with a material similar to the internal clad. However, depending on a substrate’s mechanical strength, an undermatching condition is created. This work aims to develop and parameterize a double-sided welding as an alternative method of joining steel clad pipes, enabling the application of steel wire as filler metal. An American Petroleum Institute (API) X-65 pipe cladded with Inconel 625 was used as a sample. In order to reduce the girth welding difficulties, modern welding techniques, such as gas metal arc welding with controlled metallic transfer (GMAW CCC), and gas tungsten arc welding with dynamic wire feeding (GTAW-DF), were applied along with internal pipe inspection by videoscopy. Developments showcased welding beads without macroscopic defects and good appearance in the entire circumference. Chemical composition tests indicated low iron dilutions, around 2.8% in weight, on the internal Inconel 625 weld.