ESSC & DUPLEX 2019

**Abstract:** In the design of steel structure, the avoidance of brittle fracture is of great importance as e.g. steel bridges are exposed to low temperatures and fatigue loads. In the supplementary rules for the design of stainless steel structures in the European standard EN 1993-1-4 as part of the Eurocode 3-familiy, toughness requirements for stainless steels are given. However, the toughness requirements for duplex stainless steels are insufficient. Due to this fact, first investigations have been carried out on various duplex stainless steel base materials and welded specimens based on the fracture mechanic based concept of EN 1993-1-10. The results have been transformed into the general approach used in EN 1993-1-10, which was originally developed for carbon steel considering the structural detail of a welded longitudinal attachment with a semi elliptical surface crack at the weld toe. The results show that the investigated duplex stainless steels show a very good toughness behaviour and that the EN 1993-1-10 model can be transformed for application of duplex stainless steels. The paper also discusses the influence of the plate thickness for some duplex grades on the sub-zero temperature Charpy V impact toughness. **Keywords:** Duplex stainless steel, steel construction, fracture toughness, impact toughness, choice of steel material.