Alloy 2205 (UNS S32205 Duplex F60 (UNS31803 Duplex F51))
Alloy 2205 is a 22% Cr duplex stainless steel, supplied in the solution annealed condition. As a duplex stainless steel, it combines the desirable aspect of properties of both austenitic and ferritic grades. The high chromium, molybdenum and nitrogen contents results in a Pitting Resistance Equivalent number (PREN) of 33-34, providing pitting and crevice corrosion resistance superior to Alloy 316L or Alloy 317L austenitic stainless steels in almost all corrosive media. Due to its excellent corrosion properties, it is well-suited to environments containing chlorides and hydrogen sulphide, for use in oil and gas extraction from sour wells, in refineries and in process solutions contaminated with chlorides.
It also has good erosion fatigue properties as well as lower thermal expansion and higher thermal conductivity than austenitic steels. The yield strength is about twice that of austenitic stainless steels, allowing a designer to save weight and make the alloy more cost competitive when compared to Alloy 316L or Alloy 317L.
Chemical Composition
| Cr | Ni | Mo | Co | Nb (+Ta) | Ti | V | W | Cu | C | Mn | N | Si | P | S | Fe | Al | |
| Min | 22.00 | 4.50 | 3.00 | 0.14 | 0.20 | ||||||||||||
| Max | 23.00 | 6.50 | 3.50 | 0.03 | 0.20 | 0.70 | 0.03 | 0.02 | Bal |
Mechanical Properties:
| 0.2% Proof Stress | 450 N/mm2 | 91.4ksi |
| Tensile Strength | 655 N/mm2 | 123.3ksi |
| Elongation, 5.65√S0 | 25% | |
| Reduction of area | 45% | |
| Hardness (Brinell) | <270 | |
| Impact Strength (Room Temp) | 80J (av) | |
| Impact Strength (-46°C) : Longitudinal | <100mm 80J | |
| 100-260mm 45J (35J min) | ||
| >260mm For info only | ||
| Impact Strength (-46oC) : Transverse | 50-260mm 45J (35J min) | |
| >260mm For info only | ||
Notes:
- Testing shall be carried out in accordance with ASTM A370 or EN ISO 6892-1 (tensile), EN ISO 6506-1 (hardness)
- Minimum properties quoted (tested at room temperature in a longitudinal direction)
- Testing performed on each melt of material per heat treatment batch
- Hardness shall be in accordance with NACE MR 1075
- ASTM G48A corrosion test (at 25°C) No pitting and < 3.0g/m2 weight loss
- Ferrite content 40-55%
- Microstructure certified free from grain boundary carbides, sigma, chi and laves phases
Physical Properties:
| Density (Kg/m3) | 7810 |
| Magnetic Permeability (20°C) | <50 |
| Young’s Modulus (kN/mm2) | 190 |
| Specific Electrical Resistance, 20°C (µΩ.m) | 0.85 |
| Mean coefficient of thermal expansion, 20-300°C (m/m/oC) | 11 x 10-6 |
| Specific Heat, 20°C (J/kg.K) | 400 |
| Thermal conductivity, 20°C (W/m.K) | 15 |