Hydrogen Embrittlement Behavior and Mechanism of Low Carbon Medium Manganese Steel Gas Metal Arc Welding Joints

The hydrogen embrittlement behavior of two low-carbon medium manganese steel welding joints was elucidated using a slow strain rate tensile experiment, hydrogen permeation experiment, and hydrogen concentration test. The fracture starting position becomes heat-affected zone (HAZ) after hydrogen charging. The hydrogen concentration of HAZ is higher than weld material (WM) for two welding joints after hydrogen charging for both 1 h and 2 h. The hydrogen embrittlement susceptibility of the welding joint with high hydrogen concentration, which contains about 0.03 Ti in both WM and HAZ, is larger than the welding joint that does not contain Ti. When the hydrogen charging time of the Ti-contained welding joints increases from 1 h to 2 h, the fractography of WM changes from small shallow dimples (hydrogen enhanced localized plasticity) to quasi-cleavage and cleavage (hydrogen enhanced decohesion), and the fractography of HAZ changes from quasi-cleavage (hydrogen enhanced decohesion) to intergranular (hydrogen enhanced decohesion).