Cementite decomposition in the oil pipelines metal
Background Cementite (Fe3C) is one of the basic phases of oil pipeline steels. The mechanical properties of oil pipeline steels depend on the quantity of cementite. Aims and Objectives To determine the quantity of Fe3C in the metal of oil pipelines after long-time (33 years) operation. Methods X-ray analysis based on the interpretation of the diffraction lines. Results Cementite decomposition results in the release of a certain number of carbon atoms, part of which comes in the tetrahedral caverns of the body-centered cubic lattice of the ferrite. There is determined the amount of Fe3C in the oil pipelines metal (14ГН steel) after long-time operation. The results obtained show that after the 33 years of exploitation 15 % of the 14ГН steel cementite is decomposed.