Kozak O. Influence of corrosive environment on intensity of fracture pipeline steels of main oil and gaze pipeline

. The Dissertation gives justification and solution to scientific and technical task which is in determination of pipeline steels corrosion and fatigue fracture candidness being interrelated with the parameters of physical and mechanical state of metals and mechanisms of working corrosive medium impact. It has been experimentally proved that internal fraction of metals enables to qualitatively evaluate the level of pipe steel 17Г1С degradations during its operation. For all testing environments (laboratory air, distilled water, modal solution of water, modal solution of water condensate 3% aqueous solution NaCl) the parameters of cyclic longevity of operational steel 17Г1С are lower in comparison with non-operational steel. However if the period of crack initiation decreases only 10-20% then recession period of crack propagation is 17-20%. Longevity of pipes made from steel 17Г1С with the additives of rare-earth metals increases of the stage of fatigue crack propagation of the expense growth of cy-clic failure ductility Kfc as compared with the commotional steel. In the case of welded joints study has been shown that the material of the sections of thermal influence of welded joints repaired specimens made of steel 17Г1С are more sensible to brittleness as compared with the material from the section of thermal influence of output specimens.