What is Seamless Duplex Steel UNS S31803 Pipe?
A Seamless Duplex Stainless Steel Pipe UNS S31803 (Duplex 2205 family, W.Nr. 1.4462) is supplied to ASTM A790 / ASME SA790 with the general requirements of ASTM A999 / ASME SA999, and ordered by NPS and schedule (or actual OD and wall) to ASME B36.10M. S31803 is the original designation of the 2205 family — still specified by legacy projects and existing plant standards — while S32205 is the tighter-composition variant added later.
The roughly 50/50 ferrite–austenite structure gives the grade its high yield strength and its resistance to chloride stress corrosion cracking. The standards, grade comparison and substitution notes below give the numbers you need to keep an S31803 designation — or to justify a change.
Ordering the other form? UNS S31803 seamless tube (ASTM A789) is on the same standards family. Also available: the UNS S32205 seamless pipe page.
We supply this product as a China-based stockist and supplier: common sizes are quoted from stock, the balance is sourced mill-direct from qualified producers, and the material test certificate is issued for the heat actually supplied. Availability, condition and price are confirmed at quotation rather than published as a fixed list. Every supply can be evidenced before you order — ask for a redacted MTC of a comparable delivery and photographs of the material offered.
Key Advantages of Seamless Duplex Stainless Steel Pipes
Strength and chloride resistance
A790 Table 3 requires a minimum yield strength of 450 MPa and a minimum tensile of 620 MPa for S31803, with 25 % elongation and a maximum hardness of 290 HBW — roughly twice the yield strength of austenitic 304L/316L at comparable general corrosion resistance.
Chloride stress corrosion cracking
A790 names resistance to stress corrosion cracking as the emphasis of the ferritic/austenitic family; the duplex structure is the reason. As with every duplex selection, the actual medium, temperature and chloride content decide the operating window.
S31803 and S32205 — two designations inside the Duplex 2205 family
Both UNS numbers are sold as “Duplex 2205 / 1.4462”, and both share the same minimum yield strength. What the standards actually separate is the composition window — and through it, the consistency of corrosion performance:
| Requirement (room temperature) | UNS S31803 | UNS S32205 |
|---|---|---|
| Cr, % | 21.0–23.0 | 22.0–23.0 |
| Mo, % | 2.50–3.50 | 3.00–3.50 |
| N, % | 0.08–0.20 | 0.14–0.20 |
| Tensile strength, min | 620 MPa (90 ksi) | 655 MPa (95 ksi) |
| Yield strength, min | 450 MPa (65 ksi) | 450 MPa (65 ksi) |
| Elongation, min | 25 % | 25 % |
| Hardness, max | 290 HBW (30 HRC) | 290 HBW (30 HRC) |
| PREN from minimum composition | ≈ 30.5 | ≈ 34.1 |
Where S31803 remains the right buy: drawings and standards that name it, spare parts for existing plants built with S31803, and orders where the fabricator has qualified the weld procedure for that designation. Where S32205 wins: new corrosion-limited designs that benefit from the tighter Cr/Mo/N window. Material certified to S32205 may be certified to both designations where it meets every requirement of each grade — the MTC must state which certification(s) apply, and a substitution from a specified S31803 needs the designer’s approval, not just a supplier’s suggestion.
Temperature behaviour — separate the three things “max temperature” gets mixed up with
- Prolonged exposure above about 280 °C. Duplex 2205-type microstructures change on long exposure at elevated temperature and impact strength falls. The producer datasheet (Alleima SAF™ 2205) advises contacting the producer before continuous service above this level. The classic 475 °C embrittlement sits above it.
- Design-code allowables. Published ASME B31.3 design stresses for UNS S31803/S32205 run from 207 MPa at 38 °C to about 185 MPa near 300 °C (Alleima datasheet, ASME B31.3 table). Your allowable stress must come from the code edition you build to.
- Low-temperature toughness. Producer data show good Charpy-V impact energy down to about −50 °C for solution-annealed material — but an impact requirement is not automatic. If you need it, specify the test temperature, specimen orientation and acceptance energy at enquiry.
- Corrosion-limited service. In aqueous chloride duty the medium, temperature, chloride level, crevices and flow decide the operating window — usually well below any strength-based limit. Seawater and H₂S service need case-by-case assessment (see the applications note below).
Sources: Alleima SAF™ 2205 datasheet (UNS S31803/S32205) for the temperature notes and B31.3 stress figures; ASTM A790/A789 for the mechanical requirements. None of these numbers is a blanket service guarantee.
Seamless construction — what it does and does not guarantee
Seamless pipe is made from a solid billet by hot working and cold finishing, so there is no longitudinal weld seam in the wall. That is a real difference from welded pipe and the reason seamless is specified in many standards. It is not by itself a pressure rating and not a blanket guarantee of a uniform structure:
- Pressure capability comes from the specified OD, wall thickness and tolerance, delivered condition, design temperature, the design code and the inspection performed — none of which the word “seamless” sets.
- Structure and cleanliness follow the mill’s melting and annealing practice. Material is sourced from qualified mills whose practice is verified by the tests on the MTC, not by the manufacturing route alone.
Standards on this page, and what each one governs
- ASTM A790 / ASME SA790 — product specification: chemistry (Table 2), tensile and hardness (Table 3), manufacture, heat treatment, testing.
- ASTM A999 / ASME SA999 — general requirements referenced by A790 (tolerances, lot definitions, test frequency, certification).
- ASTM A789 / ASME SA789 — the tubing standard of the same family; covered on the UNS S31803 seamless tube page.
Technical Specifications of Duplex Stainless Steel UNS S31803
Product standard: ASTM A790 / ASME SA790 — chemistry (Table 2), tensile and hardness (Table 3), manufacture, heat treatment and testing. General requirements — dimensional tolerances, lot definitions, test frequency and certification — come through ASTM A999 / ASME SA999, referenced by A790.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| S31803 | 2205 / Duplex 2205 | 1.4462 | X2CrNiMoN22-5-3 | SUS329J3L | 022Cr22Ni5Mo3N |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. See the grade designation index.
Chemical Composition (A790 Table 2)
The composition limits below are the acceptance limits of ASTM A790 Table 2, verified on the ladle (heat) analysis. They are not typical values and not our guarantee band — the actual analysis of the heat you receive is reported on the MTC, and product analysis tolerances follow ASTM A480/A480M.
| UNS designation | C | Mn | P | S | Si | Ni | Cr | Mo | N | Fe |
|---|---|---|---|---|---|---|---|---|---|---|
| UNS S31803 | ≤ 0.030 | ≤ 2.00 | ≤ 0.030 | ≤ 0.020 | ≤ 1.00 | 4.50–6.50 | 21.0–23.0 | 2.50–3.50 | 0.08–0.20 | balance |
| UNS S32205 | ≤ 0.030 | ≤ 2.00 | ≤ 0.030 | ≤ 0.020 | ≤ 1.00 | 4.50–6.50 | 22.0–23.0 | 3.00–3.50 | 0.14–0.20 | balance |
Ladle analysis limits in weight % from ASTM A790 Table 2 (maxima unless a range is given); the same limits appear in the other product specification under a different table number. Iron is the balance of the analysis, not a specified limit. Copper and other elements are not specified for these two grades. These are acceptance limits verified on the heat analysis; product analysis tolerances are those of ASTM A480/A480M. The actual analysis of your heat is reported on the material test certificate.
Mechanical Properties (A790 Table 3)
Dual-phase structure gives S31803 its strength: A790 Table 3 requires a minimum yield of 450 MPa with a minimum tensile of 620 MPa, 25 % elongation and a maximum hardness of 290 HBW — about twice the yield of austenitic 304L/316L.
| Tensile strength, min | Yield strength, min | Elongation in 2 in. / 50 mm, min | Hardness, max |
|---|---|---|---|
| 620 MPa (90 ksi) | 450 MPa (65 ksi) | 25 % | 290 HBW / 30 HRC |
Basis: ASTM A790 Table 3
These are the acceptance minima of the standard, tested per lot on specimens from the heat. Typical mill results run well above them; the measured values for your lot are reported on the certificate. Hardness is a maximum requirement of the standard, not a typical value. Note the S32205 yield figure: A790 Table 3 keeps the minimum at 65 ksi (450 MPa), the same as S31803 — it is A789 Table 4 for tube that raises S32205 to 70 ksi (485 MPa). Do not quote the tube figure on a pipe order.
Physical Properties (typical)
These physical properties highlight the material’s ability to perform reliably under a wide range of conditions.
| Density | Specific heat capacity | Thermal conductivity | Thermal expansion, mean | Modulus of elasticity | Electrical resistivity |
|---|---|---|---|---|---|
| 7.8 g/cm³ (at 20 °C) | 480 J/(kg·°C) (at 20 °C) | 14 → 20 W/(m·°C) (20 → 400 °C) | 13.0 → 14.5 ×10-6/°C (30–100 → 30–400 °C) | 200 → 180 GPa (20 → 300 °C) | 0.74 µΩ·m (at 20 °C) |
Typical values for the UNS S31803/S32205 (Duplex 2205) family, quoted from the Alleima SAF™ 2205 datasheet, which covers both designations. They describe the alloy family, not the acceptance criteria of your order — physical properties are not tested per lot unless you ask.
Size & Tolerance (A999, in./mm)
Outside diameter tolerance — ASTM A999/A999M, applied through ASTM A790
| NPS designator | Over nominal OD | Under nominal OD |
|---|---|---|
| 1/8 to 1½, incl. | +1/64 in. (0.4 mm) | −1/32 in. (0.8 mm) |
| Over 1½ to 4, incl. | +1/32 in. (0.8 mm) | −1/32 in. (0.8 mm) |
| Over 4 to 8, incl. | +1/16 in. (1.6 mm) | −1/32 in. (0.8 mm) |
| Over 8 to 18, incl. | +3/32 in. (2.4 mm) | −1/32 in. (0.8 mm) |
| Over 18 to 26, incl. | +1/8 in. (3.2 mm) | −1/32 in. (0.8 mm) |
| Over 26 to 34, incl. | +5/32 in. (4.0 mm) | −1/32 in. (0.8 mm) |
| Over 34 to 48, incl. | +3/16 in. (4.8 mm) | −1/32 in. (0.8 mm) |
Wall thickness tolerance
Minimum wall: at any point, not more than 12.5 % under the nominal wall thickness specified.
Maximum wall (over nominal), by size and t/D ratio:
| NPS designator | t/D ratio | Permissible excess over nominal wall |
|---|---|---|
| 1/8 to 2, incl. | all ratios | +20.0 % |
| 3 to 18, incl. | t/D ≤ 5 % | +22.5 % |
| 3 to 18, incl. | t/D > 5 % | +15.0 % |
| 20 and larger, seamless | t/D ≤ 5 % | +22.5 % |
| 20 and larger, seamless | t/D > 5 % | +15.0 % |
Lengths: random lengths as normally supplied; pipe ordered to specific cut lengths is held to +1/8 in. (about 3 mm), −0. Pipe dimensions follow ASME B36.10M for the schedule ordered.
Tolerances per ASTM A999/A999M, the general requirements specification referenced by ASTM A790 (§ General Requirements). Inch dimensions are the standard units; metric values are equivalents shown for convenience. Always work from the current edition of the standards for acceptance.
What the certificates show — S32205-certified heats, indicative ranges
These figures are not a specification and they are not S31803 limits. They are the ranges seen on EN 10204 3.1 material test certificates for Duplex 2205 heats that were certified to S32205, passed on by us as the supplier. In the table below, “Specified limit” is the S32205 requirement from ASTM A790 Table 2 — the Cr 22.0–23.0 and tensile 655 MPa values on this page are S32205 limits, not S31803 ones. S31803 is the wider window (Cr 21.0–23.0, Mo 2.5–3.5, N 0.08–0.20) with a 620 MPa tensile minimum; material meeting the S32205 window also meets S31803, which is why the two designations share production heats — but that overlap is not by itself evidence for a dual certificate. Grade designation and any dual certification must be supported by the applicable requirements and recorded on the actual manufacturer’s certificate. Any substitution of S31803 by S32205 requires the designer’s approval.
| Heat analysis (weight %) — S32205-certified heats | Indicative delivered range | S32205 specified limit (A790 Table 2) | Basis |
|---|---|---|---|
| C | 0.021 – 0.022 | ≤ 0.030 | ASTM A790 Table 2 |
| Si | 0.69 – 0.75 | ≤ 1.00 | ASTM A790 Table 2 |
| Mn | 1.05 – 1.11 | ≤ 2.00 | ASTM A790 Table 2 |
| P | 0.021 – 0.022 | ≤ 0.030 | ASTM A790 Table 2 |
| S | 0.001 | ≤ 0.020 | ASTM A790 Table 2 |
| Cr | 22.6 – 22.7 | 22.0 – 23.0 (S32205) | ASTM A790 Table 2 |
| Ni | 4.82 – 4.85 | 4.50 – 6.50 | ASTM A790 Table 2 |
| Mo | 3.35 – 3.38 | 3.00 – 3.50 | ASTM A790 Table 2 |
| N | 0.17 – 0.18 | 0.14 – 0.20 | ASTM A790 Table 2 |
| Fe | balance | balance | ASTM A790 Table 2 |
| Property | Typical delivered range | Minimum requirement | Basis |
|---|---|---|---|
| Tensile strength | 675 – 685 MPa | 620 MPa | ASTM A790 Table 3 |
| Yield strength, 0.2 % offset | 480 – 510 MPa | 450 MPa | ASTM A790 Table 3 |
| Elongation in 50 mm | 28 – 29 % | 25 % | ASTM A790 Table 3 |
| PREN from the heat analysis | 36.5 – 36.6 | no minimum in the standard | calculated |
| Ferrite content | recorded where the order requires it, typically 40 – 60 % | per order | certificate |
Condition recorded on the same certificates: solution annealed at 1050 °C and water quenched, then delivered annealed, pickled and passivated — inside the heat-treatment range the standard sets for this grade.
Test coverage recorded on those certificates: heat analysis, tensile, ferrite content, flattening, hydrostatic test, eddy-current test and dimensional and visual examination, each entered as pass. An item absent from a certificate was either not required by the standard for that order or not added as an optional acceptance criterion — it cannot be inferred that the material failed it. A redacted copy of a comparable certificate, with purchaser details removed, can be sent before you order. The ranges above describe production experience, not an acceptance criterion — what you can enforce is the standard plus whatever is written into your order.
Industrial Applications of UNS S31803 Seamless Pipe
S31803 pipe is a candidate material in offshore oil and gas piping, chemical process lines, desalination systems, marine structures and pulp and paper equipment — in particular where existing plants, drawings or approved specifications already name UNS S31803. See the note below before treating any of these as settled.
Oil and Gas Industry
Offshore platforms
Subsea pipelines
Manifolds, risers, and flowlines
Chemical Processing Industry
Heat exchangers
Pressure vessels
Chloride-rich processing equipment
Marine and Desalination Systems
Seawater piping systems
Reverse osmosis (RO) desalination plants
Cooling water pipelines
Pulp and Paper Industry
Digesters
Bleaching systems
Chemical storage tanks
Quality Assurance and Inspection
Inspection and testing — what the standard requires and what is ordered separately
Lists that read “every product undergoes everything” hide the two questions a buyer actually has: what am I paying for by default, and what must I specify as an acceptance criterion. The matrix answers both:
| Item | Basis | Frequency / extent | Status | Reported as |
|---|---|---|---|---|
| Ladle (heat) analysis | ASTM A790 Table 2 limits | Per heat | Standard | EN 10204 3.1 MTC |
| Tension test, room temperature | ASTM A790 Table 3, sampled per ASTM A999/A999M | Per lot | Standard | 3.1 MTC |
| Hardness test | ASTM A790 Table 3: ≤ 290 HBW / 30 HRC | Per lot | Standard | 3.1 MTC |
| Hydrostatic test or non-destructive electric test | ASTM A790 | Each pipe — one of the two, as agreed on the order | Standard | Test record on the MTC |
| Dimensional and visual examination | ASTM A999/A999M tolerances | Each length | Standard | 3.1 MTC |
| Impact test (Charpy V) | Not in ASTM A790 | Specify test temperature and acceptance energy | Optional — agree at enquiry | Test report |
| Positive material identification (PMI) | Not in ASTM A790 | Per piece or sampled — state which | Optional | PMI report |
| Intergranular corrosion test | ASTM G28 Method A or B, as specified (test method for Ni-base and high-alloy stainless, not the duplex-specific route) | Per lot | Optional — agree method and acceptance criterion at enquiry | Test report |
| Pitting / crevice corrosion test | ASTM G48 Method A or B | Per lot | Optional — agree method and acceptance criterion at enquiry | Test report |
| Intermetallic phase (sigma) test | ASTM A923 (Methods A/B/C — the duplex-specific route) | Per lot | Optional — agree method and acceptance criterion at enquiry | Test report |
| Third-party inspection or witnessing | The agency’s own scope | As agreed | Optional — carried out and reported by the agency, not by us | Agency report; EN 10204 3.2 where required |
Frequency and lot definitions follow ASTM A999/A999M as referenced by ASTM A790. Tell us at enquiry which optional items are acceptance criteria for your project — they usually cannot be added after the material is produced.
Documents, traceability and delivery
- Material test certificate. EN 10204 3.1 as standard, issued by the producing mill for the heat actually supplied and stating grade, heat number, chemical analysis, tensile results, dimensions, condition and the tests performed.
- 3.2 certificate and witnessed inspection. On request. These are performed and signed by the third-party agency — nominated by you or proposed by us — and are not a certificate issued by our company.
- Traceability. Heat number is marked on each length and carried onto the MTC, so a piece can be traced back to its heat. Inspection records held by the mill for your order can be passed on where you need them.
- Marking and packing. Grade, size, standard and heat number stencilled or tagged; ends protected; packed for sea freight. Special marking, tagging or packing against your specification on request.
- Documents and photographs before you order. On request we can send a redacted MTC for a comparable order, dimensional inspection records, and photographs of the actual material being offered, so the paperwork can be checked before the order is placed.
UNS S31803 seamless pipe — specification summary
Seamless duplex stainless steel pipe in UNS S31803 (Duplex 2205 family, EN 1.4462) to ASTM A790 / ASME SA790, with the general requirements of ASTM A999/SA999, supplied as a China-based stockist and supplier.
| Material | UNS S31803 / Duplex 2205 family / W.Nr. 1.4462 |
|---|---|
| Product standard | ASTM A790 / ASME SA790 (general requirements: ASTM A999/SA999) |
| Ordered by | NPS and schedule, or actual OD and wall (ASME B36.10M) |
| Tensile requirement (RT) | ≥620 MPa tensile, ≥450 MPa yield, ≥25% elongation, ≤290 HBW (A790 Table 3) |
| Condition | Solution annealed and pickled (or bright annealed), per A790 |
| PREN | Calculated per heat from the ladle analysis; standard sets no minimum |
| Documentation | EN 10204 3.1 MTC standard; 3.2 / witnessed inspection on request |
| Availability | Confirmed at quotation; price on request |
UNS S31803 seamless pipe — purchasing FAQ
Why buy S31803 when S32205 exists?
Three normal reasons: drawings or an approved specification that name S31803, spare parts for plants built with it, and projects where the fabricator’s weld procedures are qualified for that designation. Where none of these binds, S32205 gives a tighter composition window for new corrosion-limited designs.
Can S32205 be substituted for a specified S31803?
Only with the designer’s approval. A heat meeting every requirement of both grades may be dual certified — the MTC must state which certifications apply. We do not substitute silently; if substitution is proposed it is documented for your approval.
How is PREN confirmed for my heat?
PREN = %Cr + 3.3 × %Mo + 16 × %N from the ladle analysis on the MTC. From the minimum S31803 composition the calculation gives about 30.5; typical heats run higher. The standard sets no PREN minimum for S31803.
Which tests are standard and which are optional?
Standard: ladle analysis, tension and hardness per A790 Table 3, hydrostatic or non-destructive electric test on each pipe, dimensional and visual examination. Optional (specify at enquiry): Charpy impact, PMI, IGC, G48, 3.2 certificate, witnessed inspection.
What sizes can you actually supply?
NPS and schedule to ASME B36.10M, or actual OD and wall. Stock and mill sourcing are confirmed in the quotation together with MOQ and lead time.
Ready to Request a Quotation?
Send the NPS and schedule (or actual OD and wall), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
