Volgograd State Technical University (Volgograd, Russia):

V. F. Petrova, Cand. Eng., Associate Prof., “Materials Technology” Dept., e-mail: val.petrova7@mail.ru
A. A. Guseva, Student, “Materials Technology” Dept., e-mail: aguseva20@yandex.ru

In the study of thick-walled seamless pipes, instability of toughness and heterogeneity of the microstructure and microhardness were revealed after a single hardening and after high tempering. The effect of repeated heat treatment of thick-walled oil and gas pipelines on their structure and impact strength is studied. It was revealed that double thermal treatment leads to a more uniform distribution of structural components and a decrease in grain size. More dispersed than in the initial state, the ferrite-cementite mixture with a more uniform distribution of carbon increases the stability of supercooled austenite during quenching and allows for a more uniform tempering sorbitol. The formation of a fine-grained structure provides the required toughness.

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