Duplex 2205 Stainless (UNS S31803 / S32205)
Twice the yield strength of 316 with far better chloride stress-corrosion resistance — the standard duplex for offshore, seawater and sour-service bolting.
What Duplex 2205 is.
Duplex 2205 is a 22 percent chromium, 5 percent nickel, 3 percent molybdenum stainless steel with a nitrogen addition, balanced to solidify as roughly half ferrite and half austenite. The mixed structure gives it a 65 ksi minimum yield, about double that of 316, together with resistance to chloride pitting and stress-corrosion cracking that austenitic grades cannot match.
S32205 is the tighter-chemistry version of S31803 with higher nitrogen and molybdenum minimums; most modern bar is dual certified. ASTM A1082 governs 2205 bolting. We machine studs, bolts and nuts from certified solution-annealed bar and supply them to A1082 with heat traceability.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.030 |
| Manganese | Mn | — | 2.00 |
| Phosphorus | P | — | 0.030 |
| Sulfur | S | — | 0.020 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 22.0 | 23.0 |
| Nickel | Ni | 4.5 | 6.5 |
| Molybdenum | Mo | 3.0 | 3.5 |
| Nitrogen | N | 0.14 | 0.20 |
Values per ASTM A1082/A1082M-16(2021) Tables 1 and 4 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| UNS | Tensile strength, min (ksi) | Yield strength, min (ksi) | Elongation, min (%) | Hardness, max |
|---|---|---|---|---|
| S31803 | 90 | 65 | 25 | 30 HRC / 290 HBW |
| S32205 | 95 | 65 | 25 | 30 HRC / 290 HBW |
Values per ASTM A1082/A1082M-16(2021) Tables 1 and 4 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Solution annealed at 1900 ± 25 °F and water quenched.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.030 |
| Manganese | Mn | — | 2.00 |
| Phosphorus | P | — | 0.030 |
| Sulfur | S | — | 0.020 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 21.0 | 23.0 |
| Nickel | Ni | 4.5 | 6.5 |
| Molybdenum | Mo | 2.5 | 3.5 |
| Nitrogen | N | 0.08 | 0.20 |
Values per ASTM A1082/A1082M-16(2021) Tables 1 and 4 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Specifications that apply.
How Duplex 2205 ships from Houston.
- Full-thread studs and stud bolts
- Hex and heavy hex bolts
- Socket head cap screws
- Hex nuts in the same alloy
- Threaded rod
- Machined components from certified bar
Duplex 2205 fasteners we make.
Every item is manufactured to your drawing or standard in Duplex 2205, imperial or metric, with an EN 10204 3.1 certificate.
What is duplex 2205?
Duplex stainless steels combine ferrite and austenite in roughly equal amounts. The ferrite phase brings strength and resistance to chloride stress-corrosion cracking; the austenite brings toughness and general corrosion resistance. 2205 is the general-purpose duplex: with a pitting resistance equivalent number of about 35 it outperforms 316 in seawater and brines, and its 65 ksi yield lets designers use smaller fasteners or higher loads. Toughness is good down to about −50 °F, below which the ferrite becomes brittle.
S31803 or S32205?
S32205 is a narrower chemistry inside the S31803 range, with chromium at 22 percent minimum, molybdenum at 3.0 percent and nitrogen at 0.14 percent. Those minimums guarantee the corrosion resistance the alloy is bought for; S31803 material at the bottom of its ranges can fall short. A1082 sets a 95 ksi tensile for S32205 against 90 for S31803. Specify S32205 unless a legacy document calls for S31803.
Handling and heat treatment limits
Duplex bolting is supplied solution annealed and must stay that way. Any hot work, welding or stress relief between about 700 and 1800 °F risks sigma-phase precipitation, which destroys toughness and corrosion resistance. We machine from annealed bar and do not heat treat after threading. Keep service temperature below 570 °F.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade or alloy marking 32205 or 31803 (A1082 Table 5) and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
Recent Duplex 2205 jobs.
Super Duplex 2507 Stainless (UNS S32750)
25 Cr super duplex with a PREN above 40 — 116 ksi tensile and 80 ksi yield for the most aggressive seawater, sour and chloride bolting.
ASTM A1082 bolting · ASTM A276 / A479 bar · ASTM A182 F55Super Duplex Zeron 100 (UNS S32760, F55)
The copper-tungsten super duplex with a guaranteed PREN of 40 — the F55 bolting grade for North Sea, Gulf of Mexico and West African offshore projects.
ASTM A193 / ASME SA-193ASTM A193 Grade B8M Class 1 (316 Stainless)
316 stainless bolting with molybdenum for chloride and pitting resistance — offshore, marine, chemical and coastal plant fasteners.