Application of Magnetic NDT Methods to Evaluate the Stress-Strain State of the Individual Zones of Welded Joints

Abstract

An extensive network of trunk pipelines, existing and under construction, working under hard environmental conditions necessitates the development of non-destructive testing techniques to be applied to diagnosing a current state of pipes and welded joints in the process of production and use. This paper reports on the results of the microstructural analysis and the study of the mechanical and magnetic properties of the different zones of welded joints (base metal, heat-affected zone material and weld material) in tube steels Х70 and Х80 made by controlled rolling. The effect of various loading conditions on the magnetic characteristics of the metals of the three zones is studied. Magnetic parameters uniquely characterizing the variation of the stress-strain state of the individual zones of a welded joint (the weld, the heat-affected zone, the base metal) in a certain range of applied stresses have been ascertained.