Stress Corrosion of X80 Pipeline Steel Welded Joints by Slow Strain Test in NACE H2S Solutions

The X80 pipeline steel was welded with the way of submerged arc welding. The SST (slow strain test) of the welded joint samples in the air, NACE (National Association of Corrosion Engineers) solution (no H2S) NACE solution (saturated H2S) was performed to research the sensibility index of SCC (stress corrosion cracking) I-scc. The morphologies of the welded joint fractures and the fracture modes were observed with SEM (scanning electron microscope), and the fracture chemical compositions were analyzed with EDS (energy dispersive spectrometer), respectively. The fracture mechanisms of the welded joints were discussed. The results show that sensibility index of SCC in the air is not obvious, the fracture is dimple, and the mode of fracture is ductile fracture. The sensibility index of SCC in NACE solution (no H2S) is 13.21%, the stress corrosion is not obvious. The sample fracture shows quasi cleavage+dimple, and the fracture mode is toughness+brittle rupture. The sensibility index of SCC in NACE solution (saturated H2S) is 56.94%, the plastic loss is the most serious, appearing an obvious stress corrosion tendency, and there is no obvious necking phenomenon. The fracture mode is brittle fracture, and the sample fracture has a high sulfur concentration, prompting S to a aliquation of crisp crystal in the welded zone, and making its mechanical properties worsen.