Welding metallurgy of stainless steels

Stainless steels (SS) are irreplaceable materials in many industrial applications due to their excellent combination of mechanical and chemical properties. Oil & Gas extraction, petrochemical and urea industry, kitchen utensils, cutlery, surgical instruments and implants, bridges, aircraft, rail cars, monuments and sculptures are only some examples where SS are used. But it is also true that the success of stainless steels is due to the development and study of joining techniques such as fusion welding and solid-state welding. Stainless steels are characterized by good weldability provided that proper recommendations are followed. Secondary phases may precipitate with detrimental effects on corrosion resistance and mechanical properties. For a fixed geometry, a sound SS welded joint is thus the result of an optimization of process parameters that may differ for each welding method, e.g., arc-welding, high power density welding or friction stir welding. This chapter is aimed at describing the fundamentals of welding metallurgy with reference to the main families of stainless steels such as austenitic, ferritic, martensitic and duplex steels. Welded joints of dissimilar materials will also be briefly treated. Finally, modelling of the evolution of secondary phases under isothermal and non-isothermal conditions will be described in detail.