Investigation of welded joints of long-term operated gas pipeline controllable rolled X70 steel

The complex properties (mechanical, microstructure, and electrochemical) of controllable rolling X70 steel pipes the main gas pipeline with a diameter 1420 mm after an operation for 20 years emergency reserve pipe similar period storage were studied. Taking into account specified heterogeneity caused by technological effect on rolling, it is difficult to draw unequivocal conclusions about operational work changes in condition welded joints investigated pipes. It was established that operating loads did not significantly affect characteristics base metal joints. Electrochemical (corrosion potential, hydrogen recovery anodic curves slopes) long-term operated different manufacturers (Ukraine, France) stock NS4 solution are similar. Due high impact viscosity at standard temperature conditions, characterized satisfactory resistance against breaking.