High corrosion resistance, durability, formability, ease of use and low maintenance requirements – these are just a few of the characteristics that make duplex stainless steels the material of choice for industrial applications.

The Duplex Formula

Stainless steels are alloyed steels that have a chromium content greater than or equal to 10.5% and a carbon content less than or equal to 1.2%, with iron as the main element.

Aperam duplex stainless steels typically contain:

  • 21 – 26% chromium,
  • 2 – 7% nickel,
  • 0 – 4% molybdenum,
  • 0.1 – 0.3% nitrogen, and
  • Only 0.02% carbon.

Two-Phase Microstructure

Duplex is a family of stainless steel grades that contain a mix of austenitic (γ) and ferritic (α) phases. While the ferritic phase provides the strengthening, the austenitic lattice enables ductility and toughness. 

It’s this two-phase structure that gives duplex stainless steels an elevated yield strength. In fact, duplex stainless steels are nearly twice as strong as austenitic grades. This mixed structure also means duplex have good resistance to both stress corrosion cracking and intergranular corrosion, all while maintaining a sufficient level of ductility. Furthermore, duplex’s low nickel content and high strength enable the use of thinner sections, bringing significant cost benefits to the end user. 


  • Elevated yield strength
  • Good resistance to both stress corrosion cracking and intergranular corrosion
  • Maintains sufficient level of ductility
  • High strength
  • Thinner sections for significant cost benefits


  • Desalination and Water Treatment (waste water treatment, Drinking water systems)
  • Oil & Gas (refinery, flexible, oil platform, transportation)
  • Transportation (cargo ships, tanker trucks, trains and trams)
  • Equipment (piping, tanks, pressure vessels, heat exchangers, tubes)
  • Building & Construction (roofing, façades, bridges)

Norsok Approvals

Aperam has received NORSOK approval (M-650 & M-630) for its DX2507 (EN 1.4410/ASTM S32750) superduplex grade in flat stainless steel products (up to 8 mm thick in 1.5 m wide for hot-rolled coils and sheets and up to 5.6 mm in 1.5 m wide for cold-rolled material).

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