Residual stresses of LTT welds in large-scale components

Abstract

Residual stresses of welds become more and more important influencing cold cracking as well as the fatigue life of welded components. Low transformation temperature (LTT) filler materials offer the opportunity to alter the residual stresses already during the welding process by means of adjusted martensite phase transformation temperature (M S). In the current paper, welding residual stresses are studied putting the focus on M S while joining heavy steel sections with a thickness of 20 and 25 mm, respectively. The residual stress state was determined at the top surface using X-ray diffraction as well as in the bulk by neutron diffraction. The results compare the residual stresses present in a conventional weld and LTT welds when multi-pass welding of large-scale components was applied. Repeated phase transformation in the case of the LTT weld is more vital for the residual stresses present in the real-life-like joints. This accounts for the top surface in longitudinal direction but is most pronounced for the bulk of the welds. Detrimental tensile residual stresses are mainly reduced in the bulk in comparison to a conventional filler wire even in multi-pass welds of thick steel sections.