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Materials/Metals and alloys/Stainless steels

Duplex stainless steels

stainless-duplex

4 materials across 1 types

About duplex stainless steels

Duplex and super duplex stainless steels (2205, 2507): strength, pitting resistance and limits, with sources.

Duplex stainless steels combine austenite and ferrite in roughly equal parts. They are stronger than austenitic grades and resist chloride stress-corrosion cracking better, but they embrittle if held at high temperature for long.

At a glance

  • Highest yield strength: Duplex stainless steel 2205 reaches 895 MPa. Lowest: Lean duplex stainless steel 2304 starts at 400 MPa. (4 of 4 grades have a sourced value.)
  • Highest tensile strength: Super duplex stainless steel 2507 reaches 1,000 MPa. Lowest: Lean duplex stainless steel 2304 starts at 600 MPa. (4 of 4 grades have a sourced value.)

Ranges run across the conditions each source reports (temper, heat treatment, form), measured at room temperature where the source says so.

How they compare

The same measurements for every material in the collection. A range means the grade has values under several conditions; "at least" means the source gives a specified minimum. "no data" means no sourced value yet. For ranked tables, open a benchmark.

Duplex stainless steels: how the grades compare
MaterialYield strengthTensile strengthDensityYoung's modulusThermal conductivityMelting point
Duplex stainless steel 2205structural alloy at least 450 MPa655 to 965 MPa7.8 to 7.82 g/cm³190 to 200 GPa14 to 15 W/(m·K)1,385 to 1,441 °C
Super duplex stainless steel 2507corrosion-resistant structural alloy at least 530 MPa750 to 1,000 MPa7.8 g/cm³200 GPa14 W/(m·K)no data
Lean duplex stainless steel 2304structural alloy at least 400 MPa600 to 820 MPa7.8 g/cm³200 GPa16 W/(m·K)no data
Lean duplex stainless steel 2101 (UNS S32101)Lean duplex stainless steel for general process service, with high strength and chloride stress corrosion cracking resistance at lower nickel at least 450 MPaat least 650 MPa7.8 g/cm³200 GPa16 to 18 W/(m·K)1,385 to 1,443 °C

What these materials are made of

Composition by weight, as printed in the sources for each grade (the first constituents listed).

Composition of each grade
MaterialMain constituents
Duplex stainless steel 2205Fe balance · Cr 22 to 23% · Ni 4.5 to 6.5% · Mo 3 to 3.5% · N 0.14 to 0.2% · C up to 0.03% · Mn up to 2%
Super duplex stainless steel 2507Fe balance · Cr 25% · Ni 7% · Mo 4% · N 0.3% · C up to 0.03% · Mn up to 1.2%
Lean duplex stainless steel 2304Fe balance · Cr 21.5 to 24.5% · Ni 3 to 5.5% · Mo 0.05 to 0.6% · N 0.05 to 0.2% · Cu 0.05 to 0.6% · C up to 0.03%

Where they are used

Uses
UseGrades
Chemical process vessels, piping and heat exchangersDuplex stainless steel 2205
Oil and gas production tubing, flowlines and heat exchangers in sour serviceDuplex stainless steel 2205
Marine propellers, shafts, rudders, pumps and valvesDuplex stainless steel 2205
Subsea umbilicals and offshore oil and gas tubingSuper duplex stainless steel 2507
Seawater cooling tubing and desalination pressure vesselsSuper duplex stainless steel 2507
Propeller shafts and high-load parts in seawaterSuper duplex stainless steel 2507
Process heat exchangers and piping where chlorides are presentLean duplex stainless steel 2304
Pulp and paper digester preheaters and evaporatorsLean duplex stainless steel 2304
Oil and gas coolers, piping and flowlines on and offshore, and offshore rig tensioning systemsLean duplex stainless steel 2304
Chemical process pressure vessels, piping and heat exchangersLean duplex stainless steel 2101 (UNS S32101)
External stiffeners on an FGD absorber towerLean duplex stainless steel 2101 (UNS S32101)
Screw conveyor shaft in a mechanical pulping millLean duplex stainless steel 2101 (UNS S32101)

When each grade fits

Best use and weak spots of each grade
MaterialBest forWeakest at
Duplex stainless steel 2205Chloride-bearing and sour service where 300-series steels crack, in welded pipe, tube, sheet and plate (ATI, Alleima)Extended exposure at 343 to 530 C (475 C embrittlement), welds made with straight chromium filler, and sour service above 232 C (ATI, Alleima)
Super duplex stainless steel 2507Chloride-bearing seawater, subsea and sour oil and gas service that needs high strength and pitting resistance, in solution-annealed tube, bar and forgingsProlonged exposure above 250 °C, which lowers impact strength, and hydrogen-induced cracking in cathodically protected subsea steel
Lean duplex stainless steel 2304Chloride-bearing process piping and heat exchangers, pulp and paper equipment, and strength-limited structures where 304 or 316 would crack or be too weak (Alleima, ATI)Exposure above about 315 C (600 F), where 475 C embrittlement can follow (ATI); prolonged exposure above 280 C (Alleima); weld metal without an overmatched filler (ATI)
Lean duplex stainless steel 2101 (UNS S32101)Chloride-bearing process equipment where a 300 series grade is too weak or too prone to chloride stress cracking, and nickel cost matters: the grade gives about double the 0.2 % yield of 304 and 316 and no SCC in the boiling CaCl2 U-bend testUse above about 300 °C: Atlas says held above 300 °C the grade embrittles and only a full solution anneal restores it, and no space-environment data (radiation, outgassing, cryogenic toughness) were found