2205 stainless steel is a dual-phase iron alloy with roughly 50 percent austenite and 50 percent ferrite by volume in the as-supplied condition. It is the most widely specified member of the duplex stainless steel family and serves as the reference material against which both standard duplex grades and super duplex grades (PREN ≥ 40) are compared. The "2205" designation refers to the nominal composition: 22 percent chromium, 5 percent nickel, with molybdenum and nitrogen additions that determine the corrosion-resistance ceiling. The same alloy is designated UNS S31803 (original 1980s composition envelope) and UNS S32205 (a tighter modern composition envelope) in the North American system, and EN 1.4462 / X2CrNiMoN22-5-3 in the European system. All three designations refer to the same material in practice, with S32205 representing today's mill-supplied composition.
A standard 304L or 316L austenitic stainless steel is single-phase: 100 percent face-centered-cubic austenite. A standard 430 ferritic stainless steel is also single-phase: 100 percent body-centered-cubic ferrite. Each phase has trade-offs. Austenite has good ductility and toughness but limited strength and stress-corrosion-cracking sensitivity in chloride. Ferrite has high strength and chloride-SCC resistance but poor low-temperature toughness. The dual-phase 2205 microstructure combines the better properties of each: yield strength roughly twice that of 316L (450 MPa minimum vs 170 MPa for 316L), Charpy toughness retained down to -46 °C, and chloride-SCC resistance equivalent to ferritic grades. The 35 to 55 percent ferrite-content range mandated by NORSOK M-630 is the engineering control point: too little ferrite and the strength advantage is lost; too much ferrite and toughness drops below the 45 J at -46 °C floor.
| Property | Minimum value | Test method |
|---|---|---|
| 0.2% Yield strength (Rp0.2) | 450 MPa (65 ksi) | ASTM E8 |
| Ultimate tensile strength (Rm) | 620 MPa (90 ksi) | ASTM E8 |
| Elongation A5, min | 25% | ASTM E8 |
| Hardness, max | 293 HBW (32 HRC NACE limit) | ASTM E18 / E10 |
| Charpy V-notch at -46 °C, min | 45 J (NORSOK M-630) | ASTM E23 |
| Density | 7.80 g/cm³ | |
| Modulus of elasticity | 200 GPa (29 Msi) | |
| Coefficient of thermal expansion (20 to 100 °C) | 13.0 × 10−&sup6;/°C | |
| PREN (typical heat) | 34 to 36 | %Cr + 3.3×%Mo + 16×%N |
| Critical Pitting Temperature (CPT) | 22 to 28 °C | ASTM G48 Method A |
Full elemental composition is documented on the 2205 stainless steel chemical composition page. Spec-by-spec mechanical limits and ferrite-content envelope are on duplex 2205 properties.
| Grade | UNS | Family | PREN | Yield (MPa) | Use case |
|---|---|---|---|---|---|
| 304L | S30403 | Austenitic | 19 | 170 | Indoor, low-chloride |
| 316L | S31603 | Austenitic | 26 | 170 | Mild marine, food, pharma |
| 2205 | S31803 / S32205 | Duplex | 35 | 450 | Chemical processing, oil & gas low-CO2, moderate-chloride seawater |
| Ferralium 255 | S32550 | Super duplex | 40 | 550 | Severe sour, brine, chemical, subsea |
| Super Duplex 2507 | S32750 | Super duplex | 43 | 550 | Highest PREN among standard super duplex grades |
| Zeron 100 | S32760 | Super duplex | 41 | 550 | W-bearing variant, similar duty to Ferralium 255 |
Where 316L falls short on chloride pitting (CPT 1 to 6 °C), 2205 holds at CPT 22 to 28 °C with PREN 35. Where 2205 falls short above 30 to 35 °C chloride service or in NACE-restricted sour-gas, super duplex grades like Ferralium 255 with PREN ≥ 40 take over. Direct comparison detail on Ferralium 255 vs Duplex 2205 (2205).
2205 stainless steel is available in every wrought form covered by the standard ASTM family:
2205 is engineered for moderate-aggression service. It is the WRONG choice when: chloride exceeds typical seawater concentration combined with service above 30 °C; sour-gas H2S partial pressure exceeds the NACE MR0175 envelope for standard duplex (typically > 10 kPa H2S); reducing acids dominate (HCl, dilute H2SO4, phosphoric); or service temperature is sustained above 280 to 320 °C where 475 °C embrittlement and sigma-phase precipitation become controlling. In these envelopes, super duplex grades (PREN ≥ 40) such as Ferralium 255 (S32550), SAF 2507 (S32750), or Zeron 100 (S32760) are specified. For very-high-temperature service (above 600 °C), nickel-base alloys (Inconel 625, Hastelloy C-276) replace duplex stainless entirely.
Per-heat EN 10204 type 3.2 MTC (third-party witnessed) covering chemistry per ASTM A479 / EN 10088-3, mechanical properties per ASTM E8 specimen sketch, hardness traverse, ferrite-content point count per ASTM E562 with grid sketch, Charpy V-notch energy at the qualifying temperature, NACE MR0175 / ISO 15156-3 conformance with Table A.13 reference, and traceability back to the melt heat number. NORSOK M-630 MDS D45 conformance and NORSOK M-650 manufacturer QTR available on request.
Need 2205 stainless steel bar, plate, pipe, fittings, flanges, forgings, or fasteners? Email info@torqbolt.com or WhatsApp +91-22-66157017 with form, dimensions, quantity, ASTM/EN spec, MTC level (3.1 / 3.2). NACE MR0175 sour-service stamp on every heat. NORSOK M-650 QTR (MDS D45) on request. Per-heat EN 10204 type 3.2 MTC included with every consignment.
