High-Temperature Heat-Treatment of the Welded Joints of Du300 Austenitic Pipelines at 900°C

The high-temperature heat treatment of the welded joints of Du300 austenitic pipelines on straight sections and lead-aways, welded joints of Du300 pipelines to pipe connections for equipment and fittings and welded joints in the zones of construction walkways is described. It was implemented in the welded joints in a real Du300 pipeline and full-scale mockup of a Du300 pipeline and the pipe connections of the intake manifold in an operating power-generation unit of the Leningradskaya NPP with an RBMK-1000 reactor, which was shut down for midlife repairs. The technology suppresses the sensitization of the metal in the near-joint zone to below the proneness toward intercrystallite corrosion cracking under stress (coefficient of potentiodynamic reactivation below 1%) and decreases the residual stresses by 70–80%.