Metallographic study of gas pipeline steel with local defect

A sample of steel from a gas pipeline with a local defect in the form of a corrosion ulcer has been studied. Possible causes of its formation were analyzed based on the operational conditions and operating modes of the gas pipeline. Chemical analysis showed that the pipe material was steel 09G2S. According to metallographic studies, it was found that the distribution of the ferritic and pearlite phases in the plane of the inner surface of the pipe was uneven. The joint location of significant areas occupied only by ferrite or only by perlite was noticed. Such a pronounced banding of the microstructure at the inner surface of the pipe may be the cause of the formation of local defects on the steel in places of accumulation of the aqueous phase of increased mineralization and the constant contact of the surface with it.