Keyword: «ferrite-pearlite microstructure»

A comprehensive study of the destruction of the heating system parts has been carried out: the weld connecting the heater register pipe to the plug in order to determine the causes of the failure. The purpose of the work is to identify the causes of the destruction of the plug of the heating register. Optical and electron microscopy, chemical analysis, and metallography have been used to evaluate the structure, chemical composition, and macro-microstructure of the fracture surface of a part of the heater's heating register. It was found that the destruction of the weld connecting the pipe of the heater register to the plug occurred as a result of the internal high stress of the seam metal and the plug, as well as as a result of the high pressure generated by the expansion of water inside the heater register due to its freezing.

Currently, there is a tendency to increase the proportion of accidents on main gas pipelines due to the corrosion instability of the pipeline material. The article presents the results of studies of the damaged section of the gas pipeline used in the conditions of the North. Chemical composition studies and visual inspection of the external and internal sides of the provided gas pipeline fragment were carried out. The structures of the base metal and the defect-prone area with a through hole are investigated. The structure of the main material of the pipe under study is fine-grained, slightly striped, ferrite-pearlite. In the area closer to the defect, the structure is coarse-grained, with a Widemannstatt formation. Numerous traces of deformation and corrosion pits have been identified, indicating a brittle structure and dynamic loads during operation.