| Intergranular cracking properties of 304 austenitic stainless steel, particularly its welding region, have been evaluated by exposing C-ring specimen to polythionic acid. Effects of stress relief annealing temperature, cooling rate, and applied stress have been closely investigated. The results obtained are as follows. The stress corrosion cracking of 304 austenitic stainless steel is preferred at intergranular boundary and normal to the direction of tensile stress. The cracking of welding region happens in heat affected zone where grain is coarsened. When stress relief annealing is carried out, the efficiency is significant at 1050℃ furnace cooling or water quenching, at 850℃ furnace cooling. Preventing SCC in polythionic acid, furnace cooling is better than air cooling in all heat treatment. As the applied stress has higher value, the incubation period is shorter, so one must design and heattreat to lessen applied streess and residual stress. Plotting applied stress against log time-to-failure, knee of the plot appears. The stress of this point is similar to the stress which is shown by boiling 42% MgCl₂ Solution. |
|
