Duplex grades

Duplex grades

Outokumpu duplex stainless steels offer an excellent combination of strength and corrosion resistance, meaning you can significantly reduce material thickness and cost in a host of applications.

Our duplex innovation is unmatched in the industry and our offering covers a full palette of duplex stainless steels for use in diverse industries and applications. 

The high mechanical strength of duplex grades is a result of the duplex microstructure and the alloying with nitrogen. This high strength gives opportunities for reducing both weight and cost as a thinner material can be used. Low nickel content of the duplex grades makes them price stable.

The duplex grades LDX 2101® and 2304 are referred to as lean duplex grades. Typical applications are storage tanks, bridges, water heaters and reinforcement bars. The corrosion resistance is comparable to the standard austenitic grades like 4301 and 4404 respectively or high alloyed ferritics like 4521.

Grades 2507 and 4501 are regarded as super duplex grades. They are highly alloyed and have a corrosion resistance comparable to high performance austenitics like 254 SMO®. Typical applications for super duplex are desalination plants, seawater systems, flue-gas cleaning, umbilicals, storage tanks and pressure vessels.

By lowering total material weight, you also lower transportation and assembly costs, reducing environmental impacts even further – making duplex stainless steel a genuine material of the future.  

Put our expertise to work for you.
Check Stainless steel finder to browse available grades, product forms and dimensions and surface finishes by product form.

Product properties

Duplex grades have a ferritic-austenitic microstructure, with a phase balance of approximately 50% ferrite and 50% austenite. Duplex grades combine many of the beneficial properties of ferritic and austenitic stainless steels. The duplex microstructure contributes to the high strength and high resistance to stress corrosion cracking.

Other characteristic properties of duplex grades include good abrasion and erosion resistance, good fatigue resistance, high-energy absorption and low thermal expansion.


Duplex stainless steels generally have good weldability and can be welded using most of the welding methods used for austenitic stainless steels:

  • Shielded metal arc welding (SMAW)
  • Gas tungsten arc welding TIG (GTAW)
  • Gas metal arc welding MIG (GMAW)
  • Flux-cored arc welding (FCW)
  • Plasma arc welding (PAW)
  • Submerged arc welding (SAW)
  • Laser welding
  • Resistance welding
  • High-frequence welding

Find an Outokumpu sales office near you to get the printed version of the Outokumpu Welding Handbook

Corrosion resistance

Duplex stainless steel grades are superior to standard austenitics with regard to stress corrosion cracking resistance, and duplex grades are also good in a number of acidic and alkaline environments.

Outokumpu's duplex offering is unique: for a given austenitic stainless steel grade there is a duplex counterpart that not only provides similar corrosion resistance but also twice the strength.

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Mar 15, 2019