PSI - Issue 20

Nikolay I. Golikov / Procedia Structural Integrity 20 (2019) 161–166

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Nikolay I. Golikov / Structural Integrity Procedia 00 (2019) 000 – 000

remained in the trench. According to the results of measurements, the level of RWS in the circumferential weld reaches 210 MPa at a distance of 15 mm from the center of the seam, which is 65% of the yield strength. The chemical analysis of the steel pipes has revealed that steel of two different grades, 09Mn2Si (pipe 2) and 17Mn1Si (pipe 1), were used. Figure 2 demonstrates that the RWS distribution is not symmetrical towards the weld center. The asymmetry of the RWS distribution may be explained by the different chemical composition and mechanical properties of the pipes. The destruction site of the welded joint was located in the heat-affected zone of the pipe No. 1. A high level of circumferential RWS was found exactly in pipe No. 1 (Fig. 2). Thus, the site of the destruction was exposed to the action of tensile circumferential RWS commensurate with the yield strength of 17Mn1Si steel. This destruction is an example of the brittle failure of a welded joint at high tensile RWS.

Fig. 2. Distribution of RWS in the circumferential butt weld of the second coil of the gas pipeline with a diameter of 530 mm.

Fig. 3. Dependence of the impact strength of welded joints of the underwater crossing on test temperature of the samples.

In the work of Golikov et al. (2016), was described that in 2013, two welded joints of the underwater crossing of the main gas pipeline across the river Lena, which was put into operation in 2005, were destroyed. When inspecting the incident site, two sections of the pipe failure were detected. The welded joint on the first section was destroyed; the second section was with incomplete failure along the welded joint at the site of the installed cast iron weight. The rout scours were located at the site of the destruction of the welded joints of the underwater crossing with pipe