MECHANICAL AND METALLURGICAL CHARACTERIST ICS OF STRESS-TEST OF PIPELINE WELDED OF THERMOMECHANICALLY TREATED STEEL

The paper is devoted to an analysis of mechanical and metallurgical co nsequences of a stress-test applied to a welded joint of a pipeline ma nufactured from spirally welded pipes of thermomechanically rolled ste el grade StE 480.7 TM. The pipeline was welded as a whole using basic vertical down electrodes without application of preheating and additio nal heat treatment. During the stress-testing, an irreversible integra l deformation of 1 parts per thousand was attained on the circumferenc e of the pipes. The result of the testing was a change in distribution of the localized internal stresses and an increase of working safety and reliability of the pipeline system. After making this test, neithe r microcracks nor other types of defects were detected in welded joint s of the StE 480.7 TM steel grade.