Structure and Fatigue Durability of 09mn2si Pipe Steel after Long-Term Operation in Far North Conditions

摘要

A comprehensive study of the structure and fatigue durability of the 09Mn2Si steel used for constructing the Mastakh-Berge-Yakutsk main gas pipeline (taken from the linear part with an outer diameter of 530 mm and a wall thickness of 7mm) after 37 years of operation is carried out. A comparative analysis of the results obtained for the emergency stock steel is made. It is shown that long-term operation does not give rise to a substantial redistribution of cementite. Deformation aging is slightly expressed, and it is manifested through the precipitation of finely dispersed carbides in the grain bulk. The revealed structure degradation practically does not make sense under static tension or hardness measurement. At the same time, under cyclic testing, the microstructure degradation occurring during long-term operation results in a fatigue lifetime decrease, especially at the stage of crack initiation.