Hydrogen effusion from high strength weld metal

Constant heating rate hydrogen thermal analyses were carried out for weld metals with tensile strengths in the range 490 - 1000 MPa. It was found that the hydrogen diffusion rate in the highest strength weld metal is lower by a factor of five than that in a lower strength variant. The hydrogen diffusion behaviour varied greatly between weld metal and wrought steel. Finite difference analyses indicated that this difference can be attributed to the changes in the interaction energy between a trap site and hydrogen. Using the analysis it was possible to determine apparent diffusion rates at temperatures from 20 to 300 degrees C and explain satisfactorily the effect of plastic deformation on hydrogen diffusion in a steel.