3D modeling of the hydrogen distribution in X80 pipeline steel welded joints

The distribution of diffusion hydrogen in the welded joints of high-strength X80 pipeline steel was investigated using finite element method. Using ABAQUS software, hydrogen diffusion in X80 pipeline steel welded joint was studied in consideration of the inhomogeneity of the weld zone, and temperature-dependent thermo-physical and mechanical properties of the metals. The effects of preheating procedure and welding heat input on the hydrogen diffusion behavior were studied. Three-dimensional finite element models were developed and coupled thermo-mechanical-diffusion analyses under different welding conditions were performed. It is found that the postweld residual hydrogen exhibits a non-uniform distribution across the welded joint. A maximum equivalent stress occurs in the immediate vicinity of the weld metal. The heat affected zone has the highest hydrogen concentration level, followed by the welding zone and the base metal. Both preheating and increasing heat input are effective in reducing the diffusion hydrogen content remaining in the weld zone for the X80 pipeline steel welded joints.