Relation between the Fatigue and Fracture Ductile-Brittle Transition in S500 Welded Steel Joints

The formation and propagation of cracks occur through irreversible dislocation movements at notches, material defects, grain boundaries. Since this process is partly thermally controlled, the resistance to low temperatures increases. This slows both fatigue initiation crack propagation. From recent experimental data, it can be seen that growth accelerated below transition temperature (FTT) correlates with ductile-brittle (DBTT) found by well-known fracture mechanics tests, i.e., Charpy impact, toughness, CTOD. Hence, study investigates relation between FTT DBTT in S500 high-strength steel base welded joints using growth, toughness tests as well scanning electron microscopy. an almost constant decrease rate determined decreasing test even DBTT. At −100 °C, about half observed room for weld metal.