Estudo da influência da soldagem de diferentes corpos de provas de aço inox 316l através do processo de soldagem GTAW orbital autógena

Abstract

Oil industries are one of the most important in the world, since they feed the main energy matrixes, collaborate in the production of essential goods in various sectors of the economy, in addition, move a wide production chain, drive technological development, and job creation. Production units need to operate underwater valves by opening and closing them, which control the production flow. They are managed through a hydraulic control system where the lines are small diameter tubes, which receive cathodic protection when submerged and hydraulic fluids are non-corrosive. They usually use hydraulic power, delivered from the surface via an umbilical. Most subsea developments also require injection of chemicals, e.g. for controlling internal wax formation, scaling, hydrates and corrosion. In subsea applications, the leakage of hydraulic control fluids and treatment chemicals will often be unacceptable both from the environmental and the operational points of view. Consequently, a high reliability joining technique is required for the small diameter hydraulic/chemical injection tubing and associated fittings. The present study aims to conduct the study of the influence of welding of different 316L stainless steel specimens through the autogenous orbital GTAW welding process. The work was carried out through a case study in a company X, using AISI 316L austenitic stainless-steel pipe from different manufacturers as test specimens, using specific parameters predefined in the welding procedure specification (WPS) to map and understand the possible causes of non-repeatability of the welding program, proposing improvements in the process, such as a work system. Metallographic characterization and mechanical tests were conducted, to identify which characteristic in the raw material could be contributing to the need to change the welding current, in addition, analysis of the Schaeffler diagram, the chemical composition of the test specimens and the results of heat input were also essential for the elaboration of the results achieved. The results indicated that, in fact, there is a difference in the weldability of samples of specimens from different manufacturers, thus showing the complexity of the welding process for small diameter pipes and showing the importance of controlling the raw materials used and the implementation of a work system. In this way, it is essential to separate the raw material by supplier during its receipt and handling in production.