2205 duplex stainless steel is 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 stainless steel presents its unique advantages in composition, properties and application forging. In its composition, the elements of iron, chromium, nickel and molybdenum are precisely proportioned to give this stainless steel excellent corrosion resistance and high strength. The microstructure of this alloy consists of two phases, austenite and ferrite, the coexistence of which not only enhances the mechanical properties but also improves its resistance to stress corrosion cracking.
2205 Duplex Stainless Steel Composition
2205 duplex stainless steel is usually composed of 22% chromium, 2.5% molybdenum, 4.5% to 6.5% nickel, 0.14% to 0.20% nitrogen, as well as a small amount of carbon (C ≤ 0.030%), silicon (Si ≤ 1.00%), manganese (Mn ≤ 2.00%), phosphorus (P ≤ 0.030%), and sulphur (S ≤ 0.020%) and other elements.
| C | Mn | Si | P | S | Cr | Mo | Ni | N | |
|---|---|---|---|---|---|---|---|---|---|
| 2205 | 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 |
* Maximum, unless range is indicated
2205 Duplex Stainless Steel Mechanical Properties
| Tensile Strength (Mpa) Min | Yield Strength (Mpa) Min | Elongation (%) | Hardness (HRC) Max | |
|---|---|---|---|---|
| 2205 | 655 | 485 | 25 | 30 |
2205 Duplex Equivalent Grades
- UNS S32205
- DIN 1.4462
- EN X2CrNiMoN 22-5-3
- JIS SUS 329J3L
- GB 00Cr23Ni5Mo3N
2205 Stainless Steel Physical Properties
| Physical Properties | Data |
|---|---|
| Density, g/cm3 (lb/in3) | 7,83 (0.283) |
| Melting point, ℃ (°F) | 1385-1440 (2525-2630) |
| Magnetic | Yes |
| Electrical resistivity, μΩ·m | 0,85 (20 ℃) (68 °F) |
| 0,90 (100 ℃) (212 °F) | |
| 0,95 (200 ℃) (392 °F) | |
| 1,0 (300 ℃) (572 °F) | |
| Specific heat capacity, J/(kg·K) | 470 (20 ℃) (68 °F) |
| 500 (100 ℃) (212 °F) | |
| 530 (200 ℃) (392 °F) | |
| 560 (300 ℃) (572 °F) | |
| Thermal conductivity, (W/m·K) | 15,0 (20 ℃) (68 °F) |
| 15,9 (100 ℃) (212 °F) | |
| 17,0 (200 ℃) (392 °F) | |
| 18,0 (300 ℃) (572 °F) | |
| Modulus of elasticity, Gpa | 190 (20 ℃) (68 °F) |
| 180 (100 ℃) (212 °F) | |
| 175 (200 ℃) (392 °F) | |
| 171 (300 ℃) (572 °F) | |
| Mean coefficient of thermal expansion, (10-6/K) | 13,5 (20-100 ℃) (68 °F – 212 °F) |
| 14.0 (20-200 ℃) (68 °F – 392 °F) | |
| 14.6 (20-300 ℃) (68 °F – 572 °F) |
2205 Duplex Stainless Steel Properties
- 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
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
Forms
| Form | Standard |
|---|---|
| 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 |
Disadvantages of 2205 Suplex Stainless Steel
- Higher processing difficulty, due to the high strength and hardness of 2205 stainless steel, its processing is relatively complex and requires the use of specialized processing equipment and processes. This increases the processing cost and time, and the technical level of the operator also has high requirements.
- The surface is easily damaged, the surface of 2205 stainless steel is more susceptible to scratches and wear, which may affect its aesthetics and corrosion resistance. Therefore, appropriate protective measures need to be taken in the process of use, such as avoiding the use of hard objects or sharp tools for scratching, regular cleaning and maintenance.
- Higher cost, 2205 stainless steel uses a large amount of precious metal elements such as nickel and molybdenum in its production, leading to its relatively high cost. This may limit its use in some cost-sensitive application scenarios.
- Difficult to weld, Although 2205 stainless steel has good weldability, specific welding processes and techniques are required to prevent problems such as thermal cracking and phase separation during the welding process. If it is not welded properly, it may affect its mechanical properties and corrosion resistance.
- Phase separation problem, due to its two-phase structure, 2205 stainless steel may have phase separation problems in some specific environments. Phase separation may lead to a decline in material properties, affecting its service life and safety. Therefore, special attention needs to be paid to the influence of environmental factors in the process of use, and take corresponding protective measures.
- Restricted range of application, compared with austenitic stainless steel, 2205 stainless steel application universality and versatility is slightly inferior. For example, its use temperature must be controlled within a certain range (usually -50F/+600F), beyond which the application may be limited.
- Relatively low plastic toughness, although the plastic toughness of 2205 stainless steel is better than that of ferritic stainless steels, it still falls short of austenitic stainless steels. This may affect its performance in certain applications where high plastic toughness is required.
316L vs 2205 Duplex Stainless Steel
Composition
The 2205 material is a duplex stainless steel consisting of 22% chromium, 3% molybdenum and 5-6% nickel, along with nitrogen. This material combines the advantages of austenitic and ferritic stainless steel, with excellent corrosion resistance, strength and toughness. The 316L material is a kind of austenitic stainless steel, which contains 16-18% chromium, 10-14% nickel and 2-3% molybdenum, and does not contain the element of carbon, so it is also known as low carbon stainless steel.
Properties
- Corrosion resistance: 2205 material has excellent corrosion resistance due to its duplex structure, especially in the chloride environment. This makes it has a wide range of applications in marine engineering, chemical, petrochemical and other fields. In contrast, although the 316L material also has good corrosion resistance, but in some specific environments, such as high concentration of chloride solution, its corrosion resistance may not be as good as 2205 material.
- Strength and toughness: 2205 material has high strength and toughness, especially at low temperatures. This allows it to excel in applications where high stress and impact forces need to be withstood. While 316L also has good strength and toughness, it may not perform as well as 2205 in certain extreme conditions, such as low temperatures or high-stress environments.
- Processing performance: 316L material in the process of processing has good plasticity and welding performance, easy to process into a variety of shapes and sizes. The 2205 material, due to its duplex structure, may require more attention and skill during machining to ensure the best possible results.
Price
Because 2205 duplex stainless steel contains more precious metal elements and the production process is more complicated, its price is usually higher than 316L stainless steel.
2205 Duplex Specifications
- 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