MICROSTRUCTURAL AND MECHANICAL PROPERTIES IN THE WELD BEAD OF THE API X-52 STEEL PIPELINE

摘要

One of the greater problems encountered in the petroleum industry including refineries and crude oil and natural gas extraction and transportation is related with the nature of the weld joining. Therefore, this work was aimed to characterize the weld beads based in the microstructure that might resemble those produced by inadequate welding. The chemical composition and mechanical properties of the weld bead, heat affected zone and the base metal were studied using SEM energy dispersive analysis (EDS) and SSRT-Slow strain rate test, respectively. Second phase particles formed by large and small globular inclusions and some irregular particles were observed. Iron oxide, Mn, Si, Al, Ca, and Mo, were the main chemical elements detected in the small inclusions. Ultimate tensile strength obtained from the SSRT tests were 395, 250, 225 MPa, for the specimens tested in air, NACE solution saturated with H2S at room temperature, and NACE solution saturated with H_2S at 50℃ respectively.