:: DOI: https://doi.org/10.2118/201291-MS
Abstract
High strength steel pipes internally clad with Ni superalloys are components widely used in the oil and gas industry, with distinguished application in the production of rigid steel risers. The joining of clad pipes is carried out through a girth welding process, in which the joint is totally filled with a filler material similar to the internal clad. However, depending on mechanical strength of the pipe substrate, an undermatching condition is created. Thus, a critical weaker region results in the welded joint, where loads and plastic deformations will occur preferentially. In view of this problematic, this work aims to apply an alternative approach as a method of joining clad steel pipes, whereby an overmatching condition is achieved in the joint. This technique is carried out through a double-sided weld, which enables the use of steel filler wire in the joint filling externally, preserving the internal cladding through an inside diameter weld with a CRA filler wire. A C-Mn API X-65 steel pipe, metallurgically cladded with Inconel 625 was used in the study. For joining the pipes, modern welding techniques as GMAW CCC (Controlled Short-Circuit) and GTAW with dynamic wire feeding were applied. The developments showcased weld beads with excellent surface appearance and without welding defects, fact verified by internal videoscopy and cross section macrography. Energy Dispersive X-ray Spectometry (EDS) indicated low iron dilutions, around 2,7% in weight, on the internal weld bead surface. The double-sided welding methodology produces favorable conditions to reach joint properties equalization, enabling the employment of steel filler wire in joint filling, in addition to preserving the internal clad and its corrosion properties.
Reference
RIFFEL, K.; GONÇALVES E SILVA, R. H.; CARVALHO, L.; KEJELIN, N.. An Efficient Alternative for Joining Internally Clad Pipes Using Innovative Welding Techniques and Equipment. Society of Petroleum Engineers. 2020, October 21. doi:10.2118/201291-MS