Duplex stainless steel

Both the low nickel content and the high strength (enabling thinner sections to be used) give significant cost benefits.

[6] Duplex steels are used extensively in the offshore oil and gas industry for pipework systems, manifolds, risers, etc.

Duplex stainless is widely used in the industry because it possesses excellent oxidation resistance but can have limited toughness due to its large ferritic grain size, and they have hardened, and embrittlement tendencies at temperatures ranging from 280 to 500 °C, especially at 475 °C, where spinodal decomposition of the supersaturated solid ferrite solution into Fe-rich nanophase (

), accompanied by G-phase precipitation, occurs,[13][14][15] which makes the ferrite phase a preferential initiation site for micro-cracks.

[16] Duplex stainless steel grades must be cooled as quickly as possible to room temperature after hot forming to avoid the precipitation of intermetallic phases (Sigma phase in particular) which drastically reduce the impact resistance at room temperature as well as the corrosion resistance.