duplex steel

Material Range

duplex steel

Duplex grades have a ferritic-austenitic microstructure that combines many of the beneficial properties of ferritic and austenitic stainless steels. The duplex microstructure also contributes to high strength and high resistance to stress corrosion cracking. Duplex stainless steels are characterized by high chromium content (20.1–25.4%) and low nickel content (1.4–7%) compared to austenitic grades. The low nickel content makes duplex grades more price stable. Molybdenum (0.3–4%) and nitrogen are added to improve corrosion resistance, while nitrogen also increases strength. Due to their ferrite content the duplex grades are magnetic.

Characteristics

Austenitic Stainless Steels generally have good corrosion resistance, good impact toughness and are considered straightforward to fabricate and weld. More highly alloyed austenitic stainless steels are available, such as XM-19 and 254SMO, with improved corrosion resistance due to their added chromium and molybdenum. However, in order to retain the required austenitic microstructure, it is necessary to increase the nickel content too, which helps to raise their cost.

Ferritic Stainless Steels are resistant to stress corrosion cracking, have good strength but the more commonly used grades are less alloyed and therefore less corrosion resistant.

Duplex Steel were developed to exploit the desirable properties of both austenitic and stainless steels, namely high strength; excellent corrosion resistance; resistance to stress corrosion cracking and value for money compared with more expensive super austenitic stainless steels and nickel-based alloys. Although nominally a 50:50 mix, in practice, the ferrite content can vary between 35-55% and still achieve acceptable properties. The microstructure appears as grains or islands, of austenite within a matrix of ferrite.

applications

Duplex Stainless Steel serves many different applications in these industry categories:

  • Chemical Process
  • Petrochemical
  • Oil & Gas
  • Pharmaceutical
  • Geothermal
  • Sea Water
  • Water Desalination
  • LNG (Liquefied Natural Gas)
  • Biomass
  • Mining
  • Utilities
  • Nuclear Power
  • Solar Power

Grades

DUPLEX 2205

Duplex 2205 is a two-phase, ferritic, austenitic 22% chromium, 3% molybdenum, 5 to 6% nickel alloyed stainless steel. It is the most widely used duplex stainless steel grade and is characterized by high yield strength, double that of the standard austenitic stainless steel grades, Excellent in most caustic environments.

 

DUPLEX 2304

Duplex 2304 is a 23% chromium, 4% nickel, molybdenum-free duplex stainless steel whose structure is a balance of ferritic and austenitic. It has general corrosion resistance similar or better than Alloys 304L and 316L but with yield strength nearly double that of austenitic stainless steels, Suitable for applications covering -50ºC/+300ºC temperature range.

● Resistance to pitting and crevice corrosion

● Improved machinability and weldability 

DUPLEX 2202

Duplex 2202, or DX2202, is an austenitic-ferritic stainless steel. It offers users general resistance to corrosion that is comparable to Type 304L. Some of the other key characteristics of Duplex 2202 include. Improved mechanical strength,

 ● Service temperature range of -50 °C to 300°C, Stress corrosion resistance that is often double other austenitic stainless steels

DUPLEX 2507

Duplex 2507, is a commonly used super duplex stainless steel. Also sold as Alloy 2507, this alloy is used in situations where exceptional strength and corrosion resistance are in demand. Some of the applications and industries that utilize Duplex 2507 include  Chemical process industries.

● Heat exchangers, vessels, and piping, Desalination plants and other saltwater applications.

● Power industry FGD systems & Offshore platforms including fire-fighting systems.

DUPLEX S32950

S32950 stainless steel is a duplex stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition.

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