FEM calculation and effect of diffusion hydrogen distribution in the fusion zone of super-high strength steel

The distribution of diffusion hydrogen in the welding zone of super-high strength steel is calculated by using finite element method (FEM). The finite element program of diffusion hydrogen calculation in the welding zone is worked out. In the program, the effects of welding heat input (E), temperature and surface-escaping coefficient of hydrogen etc., are taken into account. Microstructure and crack morphology in the fusion zone and effect of diffusion hydrogen on crack is analyzed. Crack originated in the fusion zone and propagated parallel to the fusion interface or turned into the weld metal. Hydrogen accumulates seriously near the fusion zone, particularly at the root fusion zone. This is one of importance reasons to produce crack in the welding zone. The test results and analysis indicate that welding heat input should be controlled about E=16.0 kJ/cm to prevent crack producing and propagating for HQ130 super-high strength steel.