2205 duplex stainless steel is by far the most used and well-known Duplex grade within the Duplex family. It is a Molybdenum and Nitrogen alloyed stainless steel with general corrosion resistance similar to 904L, but with yield strength nearly double that of austenitic stainless steels, the high chromium, molybdenum and nitrogen contents provide corrosion resistance superior to 316/316L and 317L common austenitic stainless steels.
2205 Duplex Characteristics
- High yield strength – roughly twice of Austenitic stainless steel
- The most widely used duplex stainless steel grade, around 60%
- Outstanding resistance to stress corrosion cracking, crevice, pitting, erosion, and general corrosion in severe environments
- 2205 is not suggested for operating temperatures above 300°C and below -50°C
- The high strength of 2205 results in its machinability slower, like cutting, forming, bending
- Good weldability
- 2205 is not the same as S31803, but very close, in many instances, it is an alternative
2205 Duplex Chemical Composition (% Max)
2205 duplex stainless steel contains 22% chromium, 5% nickel, 3.2% molybdenum and other alloying elements such as nitrogen and manganese, approximately 40-50% ferrite.
| C | Mn | Si | P | S | Cr | Mo | Ni | N | |
|---|---|---|---|---|---|---|---|---|---|
| 2205 (S31803) | 0.03 | 2.0 | 1.0 | 0.03 | 0.02 | 21.0 – 23.0 | 2.5 – 3.5 | 4.5 – 6.5 | 0.08 – 0.20 |
| 2205 (S32205) | 0.03 | 2.0 | 1.0 | 0.03 | 0.02 | 22.0 – 23.0 | 3.0 – 3.5 | 4.5 – 6.5 | 0.14 – 0.20 |
2205 Duplex Mechanical Properties
| Tensile Strength (Mpa) Min | Yield Strength (Mpa) Min | Elongation (%) | Hardness (HRC) Max | |
|---|---|---|---|---|
| 2205 (S31803) | 620 | 450 | 25 | 30 |
| 2205 (S32205) | 655 | 485 | 25 | 30 |
2205 Duplex Equivalent Grades
| AISI | UNS | DIN | EN | JIS | GB |
|---|---|---|---|---|---|
| 2205 | S31803/S32205 | 1.4462 | X2CrNiMoN 22-5-3 | SUS 329J3L | 00Cr23Ni5Mo3N |
2205 Stainless Steel Physical Properties
| Density | Melting Point | Specific Heat | Thermal Conductivity | Coefficient Of Expansion | Electrical Resistivity | Elastic Modulus |
|---|---|---|---|---|---|---|
| G/Cm3 | （℃） | [J/(Kg·K)] 0~100 ℃ | [W/(M·K)] 100 ℃ | （ 10-6/K ）0~100 ℃ | （ NΩ.M | KN/Mm2 |
| 7.80 | 1398~1427 | 450 | 16.3 | 13.7 | 850 | 200 |
Corrosion Resistance
Excellent resistance to localized corrosion including intergranular, pitting and crevice corrosion. The grade is also resistant to SCC at temperatures of up to about 150°C. It has similar resistance to seawater as grade 904L.
- High resistance to stress corrosion cracking (SCC) in chloride-bearing environments
- High resistance to stress corrosion cracking (SCC) in environments containing hydrogen sulfide
- High resistance to general corrosion, pitting corrosion, and crevice corrosion
- High resistance to erosion corrosion and corrosion fatigue
Heat Treatment
Duplex 2205 stainless steel heat treatment temperature range is 1020 to 1100°C, and cool rapidly. 2205 grade cannot be hardened by thermal treatment but does work harden.
Heat Resistance
The high chromium content of duplex stainless steels that protects against corrosion, causes embrittlement at temperatures over about 300°C.
At low temperatures, duplex stainless steels have better ductility than the ferritic and martensitic grades. Duplex grades can readily be used down to at least -50°C.
Machining
The machinability of this grade is low due to its high strength. The cutting speeds are almost 20% lower than that of grade 304.
Fabrication
The fabrication of this grade is also affected by its strength. Bending and forming of this grade requires equipment with a larger capacity. The ductility of grade 2205 is lesser than austenitic grades; therefore, cold heading is not possible on this grade. To carry out cold heading operations on this grade, intermediate annealing should be carried out.
Welding
2205 Duplex stainless steels have good weldability. All standard welding processes can be used. They are not quite as easily welded as the austenitic grades but low thermal expansion in duplex grades reduces distortion and residual stresses after welding. Common welding methods are:
- MMA, SMAW (Shielded Metal Arc Welding)
- TIG, GTAW (Gas Tungsten Arc Welding)
- MIG, MAG, GMAW (Gas Metal Arc Welding)
- FCAW (Flux-Cored Arc Welding)
- PAW (Plasma Arc Welding)
- SAW (Submerged Arc Welding)
The general recommendation for shielding and plasma gas is pure Argon (TIG/PAW). An addition of 1–2% nitrogen in the shielding gas for TIG and PAW methods will improve the corrosion resistance in the weld. As backing/purging gas the general recommendation is Formier gas (90% N2 and 10% H2), pure Argon could also be used but the addition of nitrogen enhances the corrosion resistance of the weld. When material thickness requires more than one run, the interpass temperature has to be below 150oC. The general filler metal recommendation for steel grade 2205 can be 2101, 2304 and 2507.
Welding without filler metal not followed by post-weld heat treatment will reduce the corrosion resistance and is therefore not recommended. Welding against other steel grades is also possible when suitable filler metal and shielding/backing gas is used.
Typical Applications
- Chemical processing
- Transport and storage
- Oil and gas exploration and processing equipment
- Marine and other high-chloride environments
- Pulp & Paper digesters
- Liquor tanks and paper machines
2205 Duplex Specifications
| Seamless Tube: | EN 10216-5, NFA 49-217 |
| Seamless And Welded Tube: | ASTM A789 |
| Seamless And Welded Pipe: | ASTM A790 |
| Flanges And Valves: | ASTM A182 |
| Fittings: | ASTM A182; A815 |
| Plate, Sheet And Strip: | ASTM A240, EN 10088-2 |
| Bar And Shapes: | ASTM A276, A479, EN 10088-3 |
| Forged Billets | EN 10088-3 |
- ASTM A789, ASME SA789 – Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service
- ASTM A790, ASME SA790 – General Requirements for alloy and Stainless Steel Pipe
- ASTM A240/ASME SB240, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications
- ASTM A480, Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip
- EN 10088-2, Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion-resisting steels for general purposes
- EN 10088-3, Stainless steels. Technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products of corrosion-resisting steels for general purposes
- EN 10088-4, Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion-resisting steels for construction purposes
- EN 10088-5, Stainless steels. Technical delivery conditions for bars, rods, wire, sections and bright products of corrosion-resisting steels for construction purposes
- ASTM A249, Standard Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes
- ASTM A213, Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes
- ASTM A312, Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes