Seamless Duplex Tubes
Seamless duplex stainless steel tube for the three duplex grades we supply — UNS S31500 (3RE60, lean duplex), UNS S31803 and UNS S32205. Tube in this category is made to ASTM A789 / ASME SA789, with the general requirements of ASTM A1016 / ASME SA1016M, and is ordered by exact outside diameter and wall thickness — stating average or minimum wall — plus cut length.
Which grade you need depends on the duty, not on a ranking: S32205 is the tightened-composition 2205 designation; S31803 is the original, wider-window designation still named by legacy projects, drawings and approved plant standards; S31500 is a lean duplex with a deliberate silicon addition, specified for hot chloride and process service where 316L is not enough but full seawater-grade duplex is not required. Any substitution between grades needs the designer’s approval and must be recorded on the actual manufacturer’s certificate.
Choose the grade
Duplex seamless tube — ASTM A789 / ASME SA789 (general requirements ASTM A1016 / ASME SA1016M). Requirements below are specification minima; values are per the standard edition shown on each product page.
| Grade | Type | Standard | Composition (key elements, %) | Tensile / Yield, min | PREN (min–typical) | Where it fits |
|---|---|---|---|---|---|---|
| S31500 (3RE60) | Lean duplex | ASTM A789 / A790 | Cr 18.0–19.0 · Ni 4.3–5.2 · Mo 2.50–3.00 · N 0.05–0.10 · Si 1.40–2.00 | TS ≥ 630 MPa · YS ≥ 440 MPa | ≈ 28–30 | Hot chloride, pulp & paper, process water where 316L is insufficient |
| S31803 | Duplex 2205 | ASTM A789 / A790 | Cr 21.0–23.0 · Ni 4.5–6.5 · Mo 2.5–3.5 · N 0.08–0.20 | TS ≥ 620 MPa · YS ≥ 450 MPa | ≈ 30.5–35 | Legacy designs and approved standards that name S31803 |
| S32205 | Duplex 2205 | ASTM A789 / A790 | Cr 22.0–23.0 · Ni 4.5–6.5 · Mo 3.0–3.5 · N 0.14–0.20 | TS ≥ 655 MPa · YS ≥ 485 MPa | ≈ 34.1–36 | Heat exchangers and new corrosion-limited designs; tighter window |
PREN = %Cr + 3.3 × %Mo + 16 × %N, calculated per heat; ASTM A790 / A789 set no PREN minimum for these grades. PREN is a screening index, not a corrosion rate or service-life prediction. Minimum yield differs between forms: S32205 is 450 MPa as A790 pipe and 485 MPa as A789 tube.
Looking for the other form? See the Seamless Duplex Pipes (ASTM A790) category.
What to send for a quotation
- Grade and UNS designation (S31500, S31803 or S32205)
- Governing standard and edition (for example ASTM A790-24 / ASME SA790)
- Outside diameter and wall (or NPS and schedule for pipe) — state average or minimum wall for tube
- Length: fixed cut length, random or mill lengths
- Quantity and required delivery date
- Delivery condition: solution annealed; pickled / passivated as required
- Inspection: standard tests plus any acceptance tests (for example ASTM A923 or G48) and their criteria
- Certification documents: EN 10204 3.1 as standard; 3.2 or third-party witnessing on request
- Service conditions (medium, temperature, chloride content, H₂S) where design-basis advice is needed
Minimum order quantity and lead time are confirmed on enquiry against the ordered grade, size and quantity. Availability, condition and price are confirmed at quotation rather than published as a fixed list.
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