阴APP导航

It has been widely acknowledged that fracture toughness of ferritic weld metal deposited with a gas shielded flux core arc welding (FCAW-G) process is typically lower than those obtained with other arc welding processes. Several commercially available flux cored arc welding electrodes were evaluated for their Charpy V-Notch (CVN) toughness and fracture toughness properties. Fracture toughness behavior was investigated using crack tip opening displacement (CTOD) testing. Microhardness measurements in the notch region of the multi-pass weld metal was correlated to microstructure variations produced by the varied thermal cycling experienced by the different regions in a multipass weld. The average hardness at the notch region showed a direct correlation to the resistance of the weld metal to crack propagation. The influence of alloying elements and tramp elements on the fracture toughness properties of the weld metal was assessed. Carbonitride forming elements were found to be the most potent to reducing fracture toughness. Fractography of a modified wire composition to minimize the effect of cleavage initiators shows a transition from stable to unstable crack propagation at - 50C. EBSD shows significant reduction in plasticity around the crack tip between fracture toughness samples broken at -40C and -60C also indicating a transition from ductile to brittle behavior at -60C.