Characteristics degradation of gas transmission pipeline steel welded joints due to long-term operation

摘要

The mechanical and electrochemical properties of different zones of welding joint of 17H1S pipe line steel after 30 years of service were investigated. It was established that long-term service causes a decrease of plasticity and impact toughness, especially of the heat affected zone metal. The weld metal revealed synchronous decrease of strength, hardness and brittle fracture resistance. Operated material revealed a general regularity of the potential shift to the negative direction for all zones of welded joint in comparison with those in the initial state. For the base metal, the potential shifts least, and, for the weld metal, it shifts most. So, selective corrosion can be localized on the weld metal with the increase of gas transmission pipelines service time.