Hydrogen-assisted degradation at weld joint of the SA 336 F3V steel for a hydroprocessing refinery

摘要

The hydrogen attack resistance for the special regions in heat affected zone(HAZ) of the SA 336 F3V steel prepared by both applying the welding simulation thermal cycles and practical welding was evaluated after exposure to hydrogen of 45.0 MPa at 600 deg C for 100 approx 600h. The reistance to hydrogen attack (HA) was the lowest at the fusion layer and decreased as the peak temperature of the heat affected zone (HAZ) raised. These were resulted from the increase of the bubble density ratio along the grain boundaries, which was resulted in the reduction of grain boundary area to be precipitated carbide due to grain coarsening. The resistance to hydrogen attack was high in the order of base metal, weld deposit, HAZ and fusion boundary. It was found from the present study that the resistance to HA the each region was closely related with a kind and stability of the precipitated carbides.