Toughness requirements should be derived for the structural situation of interest as they will be strongly affected by applied loads and possible flaw dimensions. However, for general use of this type of steel, TWI work has suggested a Charpy requirement of 40J up to a wall thickness of 50mm at the minimum operating temperature.
C S Wiesner, 'Toughness requirements for duplex and super duplex stainless steels'. Duplex Stainless Steels '97. Proceedings of the 5th World Conference. Maastricht, The Netherlands, 21-23 October 1997. Book 2, p.979-990. Zutphen, KCI Publishing, 1997.