The Influence of Service Life and Corrosive Environment on the Crack Growth Resistance of the Welded Joints of Pipe Steel

This paper presents investigation results of the service life and the corrosive environment influence on the crack growth resistance of welded joints in X60 API 5L pipe steel, commonly used in gas main pipelines. Using the fracture mechanics approaches, which are sensitive to the influence of the different operational factors in the material, the crack growth resistance in the base metal, heat-affected zone (HAZ), and metal weld was established and compared. It was found that the material of the HAZ has the lowest fatigue and corrosion-fatigue fracture resistance. Degradation changes in the steel enhance this tendency. Comparative studies were carried out in air and in the NS4 solution simulating neutral underground water.