STUDY OF STRUCTURAL-PHASE STATE AND INTERNAL STRESSES IN ZONES OF DEFORMATION LOCALIZATION OF HEAT-RESISTANT STEEL SAMPLES

A study of metal samples from exploited and damaged sections of steam pipelines made of 0.12С-1Сr-1Mo-1V steel after deformation to the formation of zones of stable localization of deformations by the method of electron microscopy was carried out. Specimens without exploitation, after exploitation, but not damaged, and specimens after exploitation before destruction were investigated. As a result of the studies carried out for each sample, the phase composition was determined (qualitatively and quantitatively), and the following parameters of the fine structure were calculated: volume fractions of structural components of steel, scalar r and excess r_± dislocation density, curvature-torsion of the crystal lattice c, amplitude of internal stresses (shear stress and long-range stresses). All quantitative parameters of the fine structure are determined both in each structural component of steel, and in general for each sample. The structure of the metal of all specimens after deformation before the formation of zones of stable localization of deformations consists of a ferrite-pearlite mixture, and for specimens after operation before fracture only of unfragmented and fragmented ferrite. Ferrite, which occupies the bulk of the material, is present both unfragmented and fragmented. For all samples, the ratios r ≥ r_±, c = c_pl, s_L ≥ sd were calculated, which indicate whether there is a danger of the initiation of microcracks in metal samples. For specimens without operation and after operation without damage in zones of stable localization of deformations, these conditions are met, and for specimens after operation until destruction they are not met.

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