Estudio del comportamiento de la soldadura en una tubería API 5L X52 expuesta en ambiente salino, con los procesos GTAW con electrodo ER70S-6 y SMAW con electrodo E7010

Abstract

This project analyzes the behavior of two type of welds on an API 5L X52 pipeline, that was exposed to a saline environment under the ASTM B117 standard. The applied welds were GTAW with ER70S-6 electrode and SMAW with E7010 electrode, which were made with and without preheating the base material, the qualification of these was done by the API 1104 requirements. The extracted specimens were submitted to flexion effort and prepared according to ASTM G1 and ASTM G39 standard, the applied flexion loads were 10%, 50% and 80% of the base material elastic limit. The corrosion essay was performed on a 2016 hours period, with inspections and data collection each 168 hours. The corrosion rate for every analyzed weld variation was calculated with the obtained data in the experimental process. The rate was presented in a range from 0,68621[𝑚𝑚/𝑎ñ𝑜] to 0,81935[𝑚𝑚/𝑎ñ𝑜]. The corrosion rate from each welding process was compared by an ANOVA statistical analysis under the ASTM G16 standard and a descriptive analysis, the results did not present greater differences, therefore, we could not choose one weld process that mitigates the corrosive process. When examining the macrographs, it was determined that on every process the edge of weld that limits with the heat-affect zone presents more affectations as result of the corrosion. In the micrographs, it was determined that the corrosion product of the pearlite acts as an anode in front of the ferrite that has a cathodic behavior in the corrosion process, for this reason, more corrosion is evident in the HAZ, due to it is higher perlite dispersion on the ferritic matrix.