Study of Residual Stress Effect on Hydrogen Diffusion of X-groove Flat Butt Welded Joints

Abstract

Abstract-Ships are usually large-welded structures, and residual stress would inevitably occur in the welding process. At present, high-strength steel has been more and more widely used in ship structures, and it has high sensitivity to residual stress. At the same time, in the high temperature during the welding process, the hydrogen-containing compound in the arc welding is decomposed into monoatomic hydrogen, which is dissolved in the molten pool in a large amount. Uneven weld residual stresses in such structures can promote the diffusion and accumulation of hydrogen in the steel, resulting in excess hydrogen at the weld joint. This behavior can lead to hydrogen embrittlement, threatening the safety and reliability of the ship's structure. In this study, a three-dimensional finite element analysis thermodynamic model for the flat butt welding joints of high-strength steel was established, the welding process was simulated, and the distribution law for the welding residual stress field was obtained based on the thermal elastic-plastic theory. Then the sequential coupling calculation of hydrogen diffusion was performed by defining the welding residual stress field of flat butt welding joint of high strength steel as the pre-defined field, and the hydrogen diffusion behavior under the welding residual stress field was obtained based on the theory of residual stress-induced hydrogen diffusion. The results show that the welding residual stress level decreases rapidly with the increase of the weld distance. The welding residual stress affects the hydrogen diffusion behavior, hydrogen is enriched in the zone where the residual stress is high, and the heat affected zone is the region with high residual stress. These results could provide theoretical support for ensuring the safety and reliability of large ship structures.