Investigation of failure behavior of ferritic-austenitic type of dissimilar steel welded joints

摘要

Dissimilar metal welded joints are integral parts of modern-day power and process plant equipments. Among the various types of material combinations, welded joints of ferritic grade carbon-manganese steel and austenitic stainless steels are very common in nuclear and chemical industries. Due to the difference in coefficients of thermal expansion, mechanical strength and fracture properties between the two materials, suitable welding electrodes for buttering and weld regions are selected in order to avoid a drastic gradient in the above properties across the welded region and hence, to avoid significant welding distortions. The weld joint is therefore a complex combination of different materials with presence of heat affected and carbon depleted zones due to the welding process. Investigation of fracture behavior of these types of joints is very important from point of view of design and safety analysis. In this work, the fracture behavior of a dissimilar metal welded joint has been studied through testing of single-edged notched bend type of specimens with initial cracks machined at different locations. The behavior of crack propagation and crack path are investigated and the critical location of the joint is identified through scanning electron microscope investigation. The fracture resistance behavior is also predicted using finite element analysis which incorporates the Gurson-Tvergaard-Needleman's constitutive model and the simulation results are compared with those of experiment and available data from literature.