Duplex stainless steel · 22Cr-5Ni-3Mo-N
UNS S32205 Forgings ASTM A182 F60 · EN 1.4462 · Alloy 2205. Melted, forged, ring-rolled, heat-treated and machined on one site in Jiangyin, China.
UNS S32205 is the tightened, nitrogen-enhanced version of 22% chromium duplex stainless steel, carried in ASTM A182 as forging grade F60. It gives roughly double the proof strength of 316L with far better resistance to chloride pitting and chloride stress corrosion cracking, and it is the default choice for seawater-cooled heat exchangers, sour gas hardware and pulp digester components.
We forge it from our own steel. The electric arc furnace, ladle furnace and vacuum oxygen decarburisation route holds carbon and nitrogen where S32205 needs them, and the part never leaves the works between the melt and the certificate.
- UNS
- S32205
- ASTM A182
- F60
- EN
- 1.4462 · X2CrNiMoN22-5-3
- Also known
- Alloy 2205, 318S13 (BS), SS 2377, SUS 329J3L
- Tensile min
- 655 MPa / 95 ksi (A182 F60)
- Yield min
- 450 MPa / 65 ksi
- PREN
- approx. 34 min, approx. 36 nominal
- Forge at
- 1150 to 950 °C
- Anneal
- 1020 to 1100 °C, water quench
- Max ring OD
- 6,000 mm
- Max piece
- 30,000 kg
- Lead time
- 20 to 60 days
Grade identity and equivalents
S32205 began as a commercial refinement of S31803. Producers found that aiming at the upper end of the original 22Cr duplex ranges gave consistently better pitting resistance, and that narrower window was registered separately. ASTM A182 lists it under the identification symbol F60, described as 22 chromium, 5.5 nickel, 3 molybdenum, modified with nitrogen, grade 2205.
On dual certification. Every composition that satisfies S32205 also falls inside the wider S31803 ranges, so heats are routinely certified to both numbers. The reverse does not hold. An S31803 heat sitting at 21.4% Cr or 2.7% Mo cannot be re-stamped as S32205, and a purchase order that says S31803 will not automatically bring you S32205 material. If your design calculation assumed PREN 35, specify S32205 or A182 F60 explicitly.
| System | Designation | Note |
|---|---|---|
| UNS | S32205 | Dual-certifiable with S31803 |
| ASTM A182 / A182M | F60 | Forged flanges, fittings, valves and parts. F51 is S31803 |
| ASTM bar and plate | A479 S32205, A276 S32205, A240 S32205 | Plate values differ from forging values, see Table 3 |
| EN number | 1.4462 | Shared with S31803 in most European stock |
| EN name | X2CrNiMoN22-5-3 | |
| Old British BS | 318S13 | |
| Swedish SS | 2377 | |
| Japanese JIS | SUS 329J3L | |
| Trade names | Alloy 2205, SAF 2205 | Alleima quotes SAF 2205 at nominally 22Cr, 5Ni, 3.2Mo, 0.18N |
Chemical composition
Three figures separate S32205 from S31803: chromium 22.0 minimum instead of 21.0, molybdenum 3.0 minimum instead of 2.5, and nitrogen 0.14 minimum instead of 0.08. Those three minima are what buy the extra pitting resistance, and nitrogen also speeds austenite reformation in the heat affected zone during welding.
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N | |
|---|---|---|---|---|---|---|---|---|---|---|
| S32205 A182 F60 | min | – | – | – | – | – | 22.00 | 3.00 | 4.5 | 0.14 |
| max | 0.030 | 2.00 | 1.00 | 0.030 | 0.020 | 23.00 | 3.50 | 6.5 | 0.20 | |
| S31803 A182 F51 | min | – | – | – | – | – | 21.0 | 2.5 | 4.5 | 0.08 |
| max | 0.030 | 2.00 | 1.00 | 0.030 | 0.020 | 23.0 | 3.5 | 6.5 | 0.20 |
Mechanical properties
Forging and plate acceptance values are not the same number, and the difference catches people out. ASTM A182 F60 requires 95 ksi tensile. Flat rolled 2205 to ASTM A240 is commonly quoted at 621 MPa. If a drawing calls out 620 MPa on a forging, it has most likely been copied from a plate data sheet.
| Property | ASTM A182 F60, forgings | 2205 flat rolled, for comparison |
|---|---|---|
| Tensile strength, min | 655 MPa (95 ksi) | 621 MPa |
| Yield strength 0.2% proof, min | 450 MPa (65 ksi) | 448 MPa |
| Elongation, min | 25% in 2 in. or 4D | 25% in 50 mm |
| Reduction of area, min | 45% | not specified |
| Hardness, max | per order | 31 HRC / 293 HB |
Section size governs the result. Published duplex figures come mostly from thin product. In a heavy forged section the quench rate at mid-wall decides the ferrite balance and the toughness, so the test location, orientation and sampling depth matter as much as the grade. We agree these in the enquiry, together with any requirement for ASTM A923 intermetallic phase screening or ASTM E562 ferrite point counting, rather than after the part is on the press.
Physical properties
| Property | Value |
|---|---|
| Density | 7,800 kg/m³ |
| Elastic modulus | 190 GPa |
| Mean thermal expansion, 0 to 100 °C | 13.7 µm/m·°C |
| Mean thermal expansion, 0 to 315 °C | 14.2 µm/m·°C |
| Thermal conductivity at 100 °C | 19 W/m·K |
| Specific heat, 0 to 100 °C | 418 J/kg·K |
| Electrical resistivity | 850 nΩ·m |
| Magnetic response | Ferromagnetic |
The expansion coefficient sits well below that of austenitic stainless, which is why duplex distorts less during welding and why bolted and clamped joints hold load better through thermal cycles.
Corrosion behaviour
Pitting and crevice attack
Pitting resistance is compared by the pitting resistance equivalent number, PREN = Cr + 3.3Mo + 16N. With molybdenum held at 3.0% minimum and nitrogen at 0.14% minimum, S32205 lands at about 34 even on a worst-case analysis and about 36 at nominal composition. The critical pitting temperature is around 35 °C. Resistance in most environments is clearly better than 316, 316L and 317L.
That figure is the honest boundary of the grade. For warm aerated seawater, or for crevices under deposits in chloride service, a super duplex such as A182 F53 or A182 F55 carries the margin that 2205 does not.
Stress corrosion cracking
This is usually the reason the grade is chosen. Standard 300-series stainless begins to crack in chlorides not far above 60 °C, while 2205 is reported resistant to chloride stress corrosion cracking at 150 °C. In chloride-bearing process and cooling water it replaces 316L on durability rather than on first cost.
Intergranular attack
Carbon is capped at 0.030% and the high nitrogen content restores austenite quickly after welding, so sensitisation is not the problem it is in older ferritic-austenitic steels. Mill products are evaluated against ASTM A923 and are supplied free of harmful levels of intermetallic phase.
Sour service
22Cr duplex is used in moderately sour wells, but the acceptance is set by NACE MR0175 and ISO 15156-3, which impose combined limits on temperature, hydrogen sulphide partial pressure, chloride content, pH, hardness and cold work. Those conditions apply together, not one at a time. Our valve and wellhead forgings are supplied to API 6A and NACE MR0175 / ISO 15156 where the order calls for it; send us the environmental envelope and we will confirm against the current edition before we quote.
Temperature limits and phase stability
Duplex steels are sensitive to time at temperature in two separate bands, and both of them sit inside the range a forging passes through on its way out of the press.
| Range | What happens | Consequence |
|---|---|---|
| 705 to 980 °C 1300 to 1800 °F | Sigma phase precipitates, fastest at about 807 °C | Loss of room-temperature ductility and of corrosion resistance |
| 345 to 525 °C 650 to 980 °F | Alpha prime forms in the ferrite, the classic 475 °C embrittlement | Limits continuous service to below about 315 °C |
| Above 300 °C | Brittle micro-constituents precipitate on extended exposure | Grade performs well below 300 °C |
| Below −50 °C | Ductile to brittle transition | Not suitable for continuous service at those temperatures |
The practical reading for a forge shop is simple. Get through the sigma band quickly on heating, do not let a section sit in it on cooling, and never substitute a sub-critical stress relief for the full solution anneal.
How we melt, forge and heat treat it
Most Chinese forging suppliers buy billet. This works starts at the furnace, which matters for a nitrogen-alloyed duplex grade more than for most steels: the nitrogen window of 0.14 to 0.20% is narrow, and it is easier to hit it in the ladle than to discover it on an incoming certificate.
Melting
- Electric arc furnace, 25 t. Primary melting for carbon, alloy, stainless and duplex grades.
- Ladle furnace, 25 t and 50 t. Desulphurisation, alloy trim and temperature control before casting.
- Vacuum oxygen decarburisation, 30 t and 60 t. The route used for stainless, duplex and low-carbon grades, where carbon has to come down without losing chromium and where nitrogen has to be held to a specified band.
- Maximum heat size 60 t, so a single ingot can carry a 30 t finished forging with the yield loss accounted for.
- Electroslag remelting, 3 t and 6 t under protective atmosphere, available when cleanliness or segregation control is specified.
Forging
Heat uniformly to 1120 to 1150 °C. Do not forge below 950 °C, and reheat as often as the shape requires. Hammer forging is preferred and dies are given generous radii. Starting too hot risks hot tearing and surface checking; finishing too cold drives deformation into the weaker, less ductile ferrite and can crack it, while also parking the piece in the sigma range. Coarse grinding marks on the billet are a known initiation site on high-chromium alloys, so conditioning is done before the first heat, not after.
- 6,300 t hydraulic open-die press for heavy cogging, upsetting, large discs and blocks.
- 4,000 t and 2,000 t presses for shafts, ring preforms and medium sections.
- Radial-axial ring mills at 6 m, 3 m and 1 m maximum outside diameter.
- Hammers from 750 kg to 5 t for drawing out, blocking and small batch work.
Solution annealing
Every S32205 forging is solution annealed in the 1020 to 1100 °C range. The aim point is 1065 °C, held at least 10 minutes or 30 minutes per inch of thickness, followed by a mandatory water quench. Heat-up is deliberately rapid so that second phases have no time to form, and the piece is cooled below 370 °C as fast as the section allows. Furnace cooling and air cooling are not options here; they produce mechanical and corrosion properties that will not pass.
The alloy has very little strength at annealing temperature, so long and thin work is fixtured or supported. Fourteen heat-treatment furnaces are on site, including high-temperature car-bottom units and two well-type furnaces 15,000 mm deep by 1,500 mm diameter, which allow long shafts to be hung and quenched vertically instead of being laid down and distorting.
Machining
Machinability is lower than austenitic stainless because the strength is higher. Cutting speeds run roughly 20% below grade 304. Feeds come down only slightly. Rigid setups, sharp positive-geometry inserts and plenty of coolant do more for tool life here than conservative speeds alone. Our shop runs vertical lathes to 5,000 mm swing, horizontal lathes to 1,600 mm by 14,000 mm, CNC machining to 2,000 mm by 10,000 mm and deep-hole drilling to 1,600 mm by 10,000 mm.
Welding
Use 2209 type consumables: AWS A5.9 ER2209 bare wire for GMAW, GTAW and submerged arc, AWS A5.4 E2209 covered electrodes for SMAW, and AWS A5.22 E2209-T0-1 or E2209-T1-1 flux cored wire. Welding without filler leaves excess ferrite and is avoided. Argon shielding with up to 2% nitrogen is normal; oxygen and hydrogen additions lower weld toughness. Typical heat input is 0.8 to 1.8 kJ/mm for GMAW and 0.8 to 2.0 kJ/mm for GTAW on light gauges, rising to 1.8 to 2.2 kJ/mm for submerged arc with a highly basic flux. Acid fluxes intended for 18-8 stainless must not be used.
Product forms and size envelope
The limits below are set by real equipment on this site, not by a sales brochure. Each figure names the machine that produces it.
| Product | Size limit | Set by |
|---|---|---|
| Seamless rolled rings | OD 50 mm to 6,000 mm | 6 m radial-axial ring mill; upset-and-punch route below mill range |
| Forged rings, contoured and gear ring blanks | to OD 6,000 mm | 6,300 t press and ring mills |
| Forged flanges, A182 F60 | weld neck, blind, slip-on, socket weld, lap joint, orifice, swivel, long weld neck | ASME B16.5, B16.47, API 6A |
| Shafts, spindles, stepped and eccentric shafts | to 14,000 mm turned length | C61160 horizontal lathe; 15 m well furnace for vertical quench |
| Discs, tube sheets, blocks, covers | to 5,000 mm machined diameter | 5,000 mm vertical turning lathe |
| Bored cylinders, sleeves, bushings, hollow shafts | to 1,600 mm dia × 10,000 mm | CNC deep-hole drilling machine |
| Valve bodies, bonnets, stems, seat rings, spools, nozzles, manifolds | per drawing | API 6A, NACE MR0175 / ISO 15156 where specified |
| Single piece weight | to 30,000 kg | 60 t heat size, 6,300 t press |
| Minimum order | 10 kg, no minimum piece count | |
| Lead time | 20 to 60 days | Depends on melt scheduling and machining content |
Where these parts end up
- Heat exchange and desalination. Tube sheets, shell rings, covers and forged tube in brackish and chloride-bearing cooling water. The classic 2205 duty.
- Oil and gas. Wellhead and Christmas tree components, manifolds, spools, risers and moderately sour downhole hardware.
- Chemical and petrochemical. Separators, crystalliser parts, flanges and fittings in chloride-contaminated streams, and in dilute sulphuric and organic acid service.
- Pulp and paper. Digester components, liquor tank parts and paper machine rolls.
- Marine and shipbuilding. Shafts, rolls, wheels and structural forgings in splash-zone chloride exposure.
- Rotating equipment. Pump and compressor shafts, gearbox components, turbine parts, air and nitrogen compressor internals.
- Valves. Bodies, bonnets, stems, seat rings and blocks for ball, gate, globe, check and plug valves.
Testing and certification
- Chemical and mechanical testing to ASTM A182 or A479 as the order requires, with low-temperature Charpy on request.
- Ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388, class and quality level per specification.
- Ferrite content by ASTM E562 point count or ferritescope.
- Intermetallic phase screening to ASTM A923 where contractually required.
- Corrosion testing on request, including ASTM A262 Practice E and ASTM G48 Method A.
- PMI, hardness survey, dimensional report, PT and MT as specified.
- Certification to EN 10204 3.1 or EN 10204 3.2 with third-party witness.
- Works approvals held with CCS, BV, DNV, LR and NK.
Request a quotation
Send a drawing, or just the grade, the form, the dimensions, the quantity and the standard you have to satisfy. If the material selection is still open we will tell you honestly when 2205 is enough and when it is not.
Jiangyin Jiangnan Metal Co., Ltd.
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province 214423, China
T +86 189 2135 9659
E sales@steelforgepieces.com
Common questions
Is UNS S32205 the same as ASTM A182 F60?
Yes. F60 is the identification symbol that ASTM A182 assigns to UNS S32205. The F prefix marks a forging grade.
What is the difference between S32205 and S31803?
S32205 is the narrower specification: Cr 22.0 to 23.0 against 21.0 to 23.0, Mo 3.0 to 3.5 against 2.5 to 3.5, N 0.14 to 0.20 against 0.08 to 0.20. S32205 material can carry both numbers; S31803 material cannot be upgraded.
Why does one source say 620 MPa and another 655 MPa?
Because they describe different products. ASTM A182 F60 forgings are accepted at 95 ksi, or 655 MPa, minimum tensile. Flat rolled 2205 is quoted at 621 MPa. Yield is effectively the same at 450 MPa.
What is the PREN of UNS S32205?
About 34 at the minimum composition and about 36 at nominal, using Cr + 3.3Mo + 16N.
Can 2205 be used in seawater?
In cold or brackish chloride water, yes, and it is used there constantly. In warm aerated seawater its critical pitting temperature of about 35 °C leaves no margin, and super duplex is the correct selection.
Does a 2205 forging have to be solution annealed?
Yes, at 1020 to 1100 °C with a water quench. There is no safe lower temperature at which a stress relief can be substituted, because intermetallic phases form across the whole band below the annealing range.
Is 2205 magnetic?
Yes. Roughly half the structure is ferrite, so duplex grades are ferromagnetic, unlike 304 and 316.
What is the maximum service temperature?
About 300 °C for sustained service, with 475 °C embrittlement limiting practical use to below roughly 315 °C. The lower limit is about −50 °C.
What is your minimum order?
10 kg, with no minimum piece count. Lead time runs 20 to 60 days depending on melt scheduling and machining content.
References
- ASTM A182 / A182M, identification symbol F60, UNS S32205, composition and mechanical requirements. Summarised at Ferrobend.
- Rolled Alloys, 2205 Duplex Stainless Steel Data Book, bulletin 1101USe. Forging temperatures, solution annealing practice, sigma and alpha prime behaviour, PREN, welding consumables and parameters.
- International Molybdenum Association, Shop Sheet 101, Hot forming and heat treatment of duplex stainless steels.
- AZoM, Stainless Steel, Grade 2205 Duplex (UNS S32205). Composition comparison, physical properties, CPT, machining and service temperature limits.
- Langley Alloys, What are duplex grades F51, F53, F55, F60 and F61? Relationship between A182 grade numbers and UNS designations.
- Alleima, SAF 2205 billet data sheet. Nominal analysis and European designations.