Multiaxial Forging of Super Duplex Steel

Abstract

The investigated super duplex steel belongs to the group of stainless steels which exhibits an austenitic-ferritic microstructure with a phase fraction of about 50% austenite and 50% ferrite. The alloy shows excellent general corrosion resistance as well as a good resistance against stress corrosion cracking, corrosion fatigue and erosion corrosion. Due to these outstanding properties, the super duplex alloy is used in components for sea or waste water applications and in the offshore and chemical industry. In addition, the investigated super duplex steel exhibits a good weldability and a high strength in comparison to pure austenitic steel grades In order to optimize the production process and to provide a suitable microstructure to satisfy the customer’s requirements multiaxial forging test at various temperatures were performed in the Gleeble Maxstrain system. The force and the displacement after each anvil stroke were measured and used to distinguish the mechanical behaviour in the forging process at different thermal conditions. The recorded force and displacement is also compared with a multi step compression test to show the influence of change in the deformation direction. A certain number of samples were exposed an in-situ heat treatment after the deformation while other samples were immediately quenched after the forging to preserve the deformed microstructure, which was measured by optical microscopy and electron microscopy. Furthermore, electron back scatter diffractions scans were applied to characterize the degree of dynamic recrystallization during the forging process.