Modelling physical phenomena of welding processes

Abstract

One factor of decisive importance when the suitability for work, in specific conditions, of parts welded in austenitic–ferritic steels is considered, is that of ferrite content in the weld. The content of ferrite should be therefore specified precisely, and should reflect the type of the part and its working conditions. Ferrite is required in the weld because of the effect that this phase has on the tensile strength, yield stress, resistance to dynamic loading, resistance to creep, stress and intercrystalline corrosion, resistance to thermal cracking, to sigma-phase formation, and to the generation of ‘475°C brittleness’. The very strict limitation imposed on the content of ferrite in austenitic–ferritic structures, is a function of the conduct of the process. Accordingly, strict control must be exercised not only over the basic and additional materials, but also over the thermal conditions under which the process of welding is conducted.