F51 duplex stainless steel: standards, composition and properties
UNS S31803, 1.4462
F51 is the ASTM A182 forging of duplex UNS S31803, the original designation of 22Cr-5Ni-3Mo-N stainless, with about half ferrite and half austenite, twice the yield strength of 316L and high resistance to chloride stress corrosion cracking. In plate, bar and pipe the same material appears as S31803; in EN, as 1.4462. Today's 2205, with a narrower composition range and a higher minimum PREN, is S32205 (F60), which has its own page.
One composition, several standards
The name changes with the product form. When specifying, cite the standard, grade and class.
| Form | ASTM/ASME | Grade/class | EN | ABNT/others |
|---|---|---|---|---|
| Plate, coil, strip | A240 / SA-240 | S31803 | EN 10088-2, EN 10028-7 (1.4462) | JIS G4304/G4305 SUS329J3L; NORSOK M-630 MDS D45 |
| Bar and section | A276; A479 / SA-479 | S31803 | EN 10088-3; EN 10272* (1.4462) | NORSOK M-630 MDS D47 (A479) |
| Forging and flange | A182 / SA-182 | F51 (S31803) | EN 10222-5*, EN 10250-4* (1.4462) | NORSOK MDS D44; ASME B16.5 group 2.8* |
| HIP part (powder metallurgy) | A988 / SA-988 | S31803 | n/a | n/a |
| Seamless and welded pipe (piping) | A790 / SA-790 | S31803 | EN 10216-5 (seamless), EN 10217-7* (welded) | NORSOK MDS D41 |
| Pipe welded with filler metal | A928 / SA-928 | S31803 | n/a | NORSOK MDS D42 |
| Heat exchanger tube | A789 / SA-789 | S31803 | EN 10216-5 (1.4462) | NORSOK MDS D48 |
| Welding fittings | A815 / SA-815 | WPS31803 (CRS for MSS) | EN 10253-4* (1.4462) | NORSOK MDS D43 |
| Casting | A890 (general use); A995 / SA-995 (pressure) | 4A = CD3MN (J92205) | EN 10213 / EN 10283: 1.4470 GX2CrNiMoN22-5-3 | NORSOK MDS D46 |
| Welding consumable | AWS A5.9 / A5.4 / A5.22 | ER2209, E2209-xx, E2209Tx | EN ISO 14343: 22 9 3 N L | ASME IX: P-No. 10H Gr 1 |
| Detrimental phase testing | A923 | Methods A, B, C | n/a | ISO 17781* (alternative used in O&G) |
Material certified as S32205 (F60) meets orders for S31803 (F51), but not the other way around: when the project requires a minimum PREN of ~34, specify F60. In NORSOK M-630 the D41–D48 sequence (22Cr) comes from Rev. 2; D47 confirmed in Rev. 5 for A479 S31803/S32205.
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7222.30.00* | 7222.30 | 7222.30.0024 | 7222 30 51 |
| Hot-rolled bar | 7222.11.00 | 7222.11 | 7222.11.0059 | 7222 11 11 |
| Plate (> 10 mm, width ≥ 600 mm) | 7219.21.00 | 7219.21 | 7219.21.0020 | 7219 21 10 |
| Seamless pipe | 7304.41.90 | 7304.41 | 7304.41.6045 | 7304 41 00 |
| Welded pipe | 7306.40.00 | 7306.40 | 7306.40.5085 | 7306 40 80 |
| Flange and fitting | 7307.21.00 | 7307.21 | 7307.21.5000 | 7307 21 00 |
Class in Dustre's NCM table (INF 004): stainless steel.
*: US and EU codes are for reference; confirm with your customs broker. NCM codes with * were checked by Dustre against the current NCM, outside the INF 004 table. HS = first 6 digits of the NCM.
Chemical composition by standard (%)
The ranges of each standard side by side, to see where they differ.
| Standard | C | Mn | P max | S max | Si max | Cr | Ni | Mo | N | Others |
|---|---|---|---|---|---|---|---|---|---|---|
| UNS S31803 (A240, A182 F51, A790) | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 21.0–23.0 | 4.5–6.5 | 2.5–3.5 | 0.08–0.20 | n/a |
| A890 / A995 4A (CD3MN, J92205) | 0.030 | 1.50 | 0.040 | 0.020 | 1.00 | 21.0–23.5 | 4.5–6.5 | 2.5–3.5 | 0.10–0.30 | Cu 1.00 |
| EN 1.4462 X2CrNiMoN22-5-3 (EN 10088, EN 10216-5) | 0.030 | 2.00 | 0.035 | 0.015 | 1.00 | 21.0–23.0 | 4.5–6.5 | 2.5–3.5 | 0.10–0.22* | n/a |
| EN 1.4470 GX2CrNiMoN22-5-3 (cast) | 0.030 | 2.00 | 0.035 | 0.025 | 1.00 | 21.0–23.0 | 4.5–6.5 | 2.5–3.5 | 0.12–0.20* | n/a |
| JIS SUS329J3L | 0.030 | 2.00 | 0.040 | 0.030 | 1.00 | 21.0–24.0 | 4.5–6.5 | 2.5–3.5 | 0.08–0.20 | n/a |
| AISI 329 / S32900 (comparison, NOT 2205) | 0.08 | 1.00 | 0.040 | 0.030 | 0.75 | 23.0–28.0 | 2.0–5.0* | 1.0–2.0 | not specified | n/a |
Mechanical properties by standard
Minimum values at room temperature, in the stated delivery condition.
| Standard and condition | YS min | UTS | Elong. | RA | Hardness |
|---|---|---|---|---|---|
| FORGINGS | |||||
| A182 F51 (S31803), solution annealed | 450 MPa (65 ksi) | 620 MPa min (90 ksi) | 25 % | 45 % | not specified in the table* |
| ROLLED | |||||
| A240 S31803, solution-annealed plate | 450 MPa (65 ksi) | 620 MPa min (90 ksi) | 25 % | n/a | 293 HBW / 31 HRC* max |
| A479 / A276 S31803, bar | 450 MPa | 620 MPa min | 25 % | n/a | 290 HBW max* |
| EN 10088-2 1.4462, quarto plate (P) | 460 MPa | 640–840 MPa | 25 % | n/a | n/a |
| EN 10088-3 1.4462, bar | 450 MPa | 650–880 MPa | 25 % | n/a | 270 HB max* |
| PIPE, FITTINGS AND CASTINGS | |||||
| A790 / A789 S31803, pipe/tube | 450 MPa | 620 MPa min | 25 % | n/a | 290 HBW / 30 HRC* max |
| EN 10216-5 1.4462, seamless pipe | 450 MPa | 640–880 MPa | 22 %* | n/a | KV 40 J at -40 °C* |
| A890 / A995 4A (CD3MN), cast | 415 MPa (60 ksi)* | 620 MPa min (90 ksi) | 25 % | n/a | n/a |
| EN 10213 1.4470, cast | 420 MPa* | 600–800 MPa* | 20 %* | n/a | n/a |
F51 (S31803) vs. F60 (S32205): what is the difference
S31803 is the original designation of 22Cr duplex; with the wide Cr, Mo and N ranges (N min. 0.08 %), a heat could come out with a PREN near 30. S32205 was created to pin 2205 at the top of the range: Cr 22.0–23.0, Mo 3.0–3.5 and N 0.14–0.20, minimum PREN ~34, and a higher minimum UTS (655 vs. 620 MPa). Almost all plate, bar and pipe today ships dual-certified S31803/S32205. S32205 (F60) material can be accepted where S31803 (F51) is ordered, but not the other way around.
Heat treatments required by the standards
| Standard | Delivery condition | Temperature |
|---|---|---|
| A240 / A790 / A789 (S31803) | Solution annealed + rapid cooling (water or other fast medium) | 1020–1100 °C (1870–2010 °F) |
| A182 F51 | Solution annealed + liquid quenched | 1020 °C min (1870 °F) |
| A276 / A479 | Solution annealed + rapid cooling | 1020 °C min* |
| A815 WPS31803 | Solution annealed + water quenched (mandatory after forming/welding) | 1020–1100 °C |
| A890 / A995 4A | Solution annealed + water quenched; or furnace cool to ≥ 1010 °C, hold 15 min and quench | 1120 °C min (2050 °F) |
| EN 10088 / EN 10216-5 (1.4462) | Solution annealed (+AT) + water or forced air | 1020–1100 °C (Outokumpu); 1050–1100 °C (DEW)* |
Variants in the family
| Variant | Standards | Difference | YS / UTS |
|---|---|---|---|
| S31803 / F51 | A240, A479, A790, A182 F51 | Original range: Cr 21–23, Mo 2.5–3.5, N 0.08–0.20 | 450 / 620 MPa |
| S32205 / F60 | A240, A479, A790, A182 F60 | Restricted range: Cr 22–23, Mo 3.0–3.5, N 0.14–0.20; min. PREN ~34 | 450 / 655 MPa |
| Cast 4A (CD3MN, J92205) | A890, A995, EN 1.4470 | Mn 1.50 max, N up to 0.30, Cu 1.00; higher solution annealing | 415 / 620 MPa |
| Lean duplex 2304 (S32304) / 2101 (S32101) | A240, A790 | Little or no Mo; cheaper, PREN ~24–26 (does not replace 2205 in chlorides)* | 400–450 / 600–650 MPa* |
| Super duplex 2507 (S32750, F53) | A240, A182 F53, A790, A995 5A | 25Cr-7Ni-4Mo-0.3N; PREN ≥ 40, for seawater | 550 / 795 MPa |
| AISI 329 (S32900) | A240, A789/A790 | Old 25Cr-2/5Ni-1.5Mo duplex without controlled N; NOT equivalent to 2205 | 485 / 620 MPa |
Corrosion, PREN and temperature
- PREN (Cr + 3.3 Mo + 16 N): ~35 typical; at the standard minimum, ~30.5 for S31803 (for S32205/F60, ~34).
- Pitting and crevice corrosion: CPT in 6 % FeCl3 (G48) around 35 °C (Rolled Alloys; Tubacex cites 45 °C)*. Good in moderate chlorides; for natural seawater use super duplex.
- Chloride stress corrosion cracking: far superior to 304/316L austenitics, one of the main reasons for its use.
- Temperature: ASME (II-D) limits use to 316 °C (600 °F); below −29 °C (−20 °F) the code requires Charpy impact testing*. Above ~300 °C, 475 °C embrittlement (alpha prime phase) occurs; DEW limits it to 350 °C.
- Sigma and nitrides: precipitate in the ~700–950 °C range* in poorly cooled solution anneals, high-heat-input welds or thick sections; they collapse toughness and pitting resistance (see A923).
- NACE MR0175 / ISO 15156-3: solution annealed and rapidly cooled, 35–65 % ferrite, no hardness limit; accepted up to 232 °C with pH2S ≤ 10 kPa (0.1 bar). NACE MR0103: up to 28 HRC.
Tests required for duplex (ASTM A923, G48)
- A923 Method A: NaOH etch and metallographic examination for intermetallic phases; used only for acceptance (a poor result leads to Method B or C).
- A923 Method B (Charpy): -40 °C; min. 54 J (40 ft-lbf) in base metal and HAZ, 34 J (25 ft-lbf) in weld metal (S31803, J92205).
- A923 Method C (FeCl3): 25 °C for base metal and 22 °C for weld, 24 h, max. loss 10 mdd (1.0 g/m²). There is no criterion for the J92205 casting in this table.
- ASTM G48: Method A (pitting) or E (CPT) in 6 % FeCl3; the temperature and criterion come from the project or from NORSOK, not from G48. O&G projects usually accept up to 4.0 g/m² in welds*.
- NORSOK M-630 / ISO 17781: besides G48, they require low-temperature Charpy and ferrite content in qualification; values per the MDS and project revision*.
- Ferrite measurement: ferrite control (typically 35–65 % in base metal and 30–70 % in weld*) is required in O&G and sour service.
Welding
| Item | Usual practice |
|---|---|
| Consumable | ER2209 (AWS A5.9), E2209-15/16/17 (A5.4), E2209T0/T1 (A5.22); EN ISO 14343 22 9 3 N L. Higher Ni than the base metal to balance ferrite. |
| ASME IX classification | P-No. 10H, Group 1 |
| Preheat | Not needed (only dry the part) |
| Interpass | 150 °C max (100 °C in thin sections or by project requirement)* |
| Heat input | ~0.5–2.5 kJ/mm; DEW recommends 1–3 kJ/mm*. Too low gives excess ferrite, too high gives sigma. |
| Gas | TIG: Ar or Ar + 2 % N2; root purge with Ar or Ar + N2 |
| PWHT | No stress relief is done; only full solution annealing when the standard requires it (e.g. A815 fittings) |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
International equivalents
| System | Designation |
|---|---|
| UNS | S31803; equivalent casting J92205 |
| ASTM forging | F51 (S31803) |
| ASTM casting | Grade 4A / CD3MN (A890, A995) |
| EN / W.Nr. | X2CrNiMoN22-5-3 / 1.4462; cast GX2CrNiMoN22-5-3 / 1.4470 |
| JIS | SUS329J3L |
| GB | 022Cr22Ni5Mo3N (S22253)* |
| BS / AFNOR / SIS (old) | 318S13 / Z3CND22-05Az / SS 2377 |
| ABNT | No confirmed designation of its own in NBR 5601; UNS/ASTM is used* |
| Trade names | SAF 2205 (Alleima), Forta DX 2205 (Outokumpu), ATI 2205, UR 45N |
SUS329J3L has Cr up to 24 % and N min. 0.08 %, so it is closer to S31803, not S32205. None of the '329' designations without the J3L suffix correspond to 2205.
Typical applications
| Form or industry | Where it is used |
|---|---|
| Offshore oil and gas | Process piping, manifolds, F51 flanges, vessels and separators |
| Chemicals and petrochemicals | Heat exchangers (A789), tanks, chloride-bearing lines |
| Pulp and paper | Digesters, liquor and bleaching tanks |
| Chemical tankers | Cargo tanks and heating coils |
| Pumps and valves | Cast 4A bodies, shafts and stems in A479 bar |
| Water and sanitation | Desalination (parts not exposed to hot seawater), effluent piping |
| Structures | Bridges, fasteners and structures where the high YS is used to reduce thickness |
Frequently asked questions
Is 2205 the same as 329 or '329A' stainless?
No. AISI 329 (UNS S32900) is an old 23–28Cr duplex with 1–2 % Mo and no specified nitrogen. '329A' is not a recognized UNS, ASTM or JIS designation. The confusion comes from the Japanese SUS329J3L, which is the JIS equivalent of 2205. When buying, order by UNS S31803/S32205 or F51/F60.
Is F51 the same as 2205?
Partly. F51 is S31803, the original designation of 2205. Today's 2205 is S32205 (F60), with higher minimum Cr, Mo and N (PREN ~34) and higher minimum strength (655 vs. 620 MPa). F60 material meets F51 orders, but F51 does not meet F60.
What is the difference between A890 4A and A995 4A?
The composition (CD3MN) is the same. A890 is for general-purpose castings; A995 is for pressure parts (valves, pumps) and enters ASME as SA-995.
Up to what temperature can I use F51?
ASME limits S31803 to 316 °C (600 °F) because of 475 °C embrittlement. At low temperature, common use goes down to about -40/-50 °C with proven Charpy values.
