Stainless duplex steels (SDS) are characterised by increased yield limit, satisfactory toughness, sufficiently high corrosion resistance and good weldability. The extensive application of these materials in welded structures is determined by a high yield limit (twice the yield limit of austenitic steels) so that it is possible to decrease the metal requirement of the structure, and also by high corrosion resistance and relatively low cost (Table 1). The process of fusion welding of SDS has a significant effect on the microstructure of the welded joint. In welding, the SDS have the ferritic structure at temperatures close to the solidus temperature, structural transformations take place with further cooling of the metal and HAZ and this has a strong effect on the mechanical properties and corrosion resistance. As a result of the large volume of the investigations, it was possible to improve the quality of welded joints in SDS. A new generation of these steels is characterised by high properties of welded joint.
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