Gazprom Transgaz Samara, Samara, Russia:

D. V. Zhukov, Head of the Database Maintenance Group

Samara National Research University named after Academician S. P. Korolev, Samara, Russia:
A. A. Melnikov, Cand. Eng., Associate Professor, Dept. of Metal Technology and Aviation Materials Science

Samara National Research University named after Academician S. P. Korolev, Samara, Russia¹ ; Siberian State Industrial University, Novokuznetsk, Russia²:
S. V. Konovalov, Dr. Eng., Prof., Chief Researcher, ONIL-4 Laboratory¹, Vice-Rector for Research and Innovation², e-mail: Konovalov@sibsiu.ru

Research and Development Manufacturing Enterprise “Valma”, Samara, Russia:
M. O. Dmitrieva, Engineer

Investigations of transverse cracks in a longitudinal weld of a main gas pipeline pipe are presented, and the reasons for the formation of defects are analyzed. A comparative analysis of the results of in-line diagnostics and additional non-destructive testing with the actual parameters of cracks in microsections was carried out. The microhardness of the weld metal was measured in the crack zone and at a distance of up to 20 mm from it in both directions, which showed the presence of residual stresses in the region of the crack tip. The methods of optical and electron scanning microscopy were used to study the crack zone with the determination of the chemical composition of the weld base metal and inclusions in the crack zone. The results obtained made it possible to classify defects as “cold cracks” that formed in the weld metal after a long period of operation and developed further according to the stress corrosion cracking mechanism.

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