ASTM A789 UNS S31803 Duplex Stainless Steel Tube

ASTM A789 / A789M covers seamless and welded ferritic/austenitic stainless steel tubing for general corrosion service with particular emphasis on chloride stress corrosion cracking resistance. UNS S31803 is the older “2205-family” duplex listing with heat limits of carbon ≤0.030%, chromium 21.0–23.0%, nickel 4.5–6.5%, molybdenum 2.5–3.5%, and nitrogen 0.08–0.20% in A789/A789M-24 Table 1. Many purchase orders still say S31803 even though the tighter nitrogen-and-chromium window of UNS S32205 was introduced later to guarantee the corrosion performance people associate with modern 2205; both grades remain separate rows in A789 and both get their own page here.

SHH STEEL can produce and supply ASTM A789 UNS S31803 duplex stainless steel tube as seamless and welded product (welded without filler metal) in the usual heat-exchanger and process OD × wall / BWG band, documented on EN 10204 3.1 mill test certificates. Dual A789/SA789 marking is available only when both standards are named on the order. See the A789/A789M hub for the full duplex tube family.

Commercially S31803 is still called 2205, 1.4462, or duplex 2205 tube — but if your datasheet needs the tighter S32205 chemistry, order A789 S32205 by UNS, not by the shop nickname alone. Lean options such as A789 S32101 and super duplex A789 S32750 sit on either side of this mid-range duplex. Plate: A240.

Heat analysis must meet A789/A789M-24 Table 1. Product analysis follows A480/A480M annex tolerances when ordered.

Compared with S32205, S31803 allows a wider chromium band that bottoms at 21.0% and a nitrogen minimum of only 0.08% (S32205 requires Cr 22.0–23.0% and N 0.14–0.20%). Mid-range PREN = Cr + 3.3Mo + 16N at Cr 22, Mo 3.0, N 0.14 is about PREN ≈ 34, but a heat sitting at the low-N / low-Cr corner of S31803 can screen noticeably lower — which is exactly why many corrosion specs migrated to S32205. Always read the heat certificate, not only the UNS label.

Tensile and hardness floors are in A789’s tensile/hardness table (Table 4 in recent editions). The public -24 sample lacked that table; values below are from older Table 4 reprints and should be reconfirmed on the PO edition.

Note that older copies list S31803 at 90 ksi tensile versus 95 ksi for S32205 — another reason not to treat the two UNS numbers as identical on a design datasheet. Yield at 65 ksi still roughly doubles annealed 304/316.

A789 §5: seamless or welded with no filler metal. Seamless lots take flaring (≥10% ID expansion); welded lots take flange plus reverse flattening every 1500 ft [450 m]. Both routes are solution-annealed per Table 2. SHH STEEL produces and supplies both seamless and welded A789 S31803 with EN 10204 3.1 coverage.

Average wall default; minimum wall when specified. Tube OD × wall / BWG under A1016/A1016M unless A789 overrides.

State avg versus min wall when converting pipe schedules. SHH STEEL confirms size before heat reserve.

S31803 shares the EN 1.4462 / 2205 marketplace with S32205; they are not chemically identical. Confirm which UNS the project freezes.

Dual A789/SA789 on request. Prefer A789 S32205 when the corrosion spec needs the tighter window. Plate: A240.

A789/A789M-24 Table 2: UNS S31803 at 1870–2010 °F [1020–1100 °C], rapid cool in water or equivalent. Direct quench after hot forming is allowed for seamless tube at or above the minimum solution temperature.

Quench practice limits sigma in the ~700–1000 °C window. A789’s scope warns of embrittlement after prolonged elevated-temperature use, including 475 °C (885 °F) ferrite embrittlement. S31803 is an aqueous corrosion-and-strength grade, not a creep alloy. SHH STEEL supplies it solution-annealed and quenched.

S31803 delivers classic duplex chloride SCC resistance and mid-range pitting performance when the heat sits near the middle of the chemistry window. Heats at the low-Cr / low-N corner can underperform the corrosion reputation of “2205,” which is why many EPC specs now name A789 S32205 explicitly.

Against lean duplex such as A789 S32304 it offers more Mo and typically higher PREN; against super duplex A789 S32750 it is a clear step down for seawater crevice duty. Screen with heat-certificate PREN and project chloride limits.

Oil-and-gas process and utility tube, chemical-plant heat exchangers, desalination and brine systems, pulp-and-paper liquor lines, and general chloride-SCC-resistant service where the datasheet still freezes S31803. Higher yield than 316L supports thinner walls.

If the project language says “2205 to S32205,” do not ship S31803 without written approval. SHH STEEL produces and supplies A789 S31803 — and can quote S32205 on the same enquiry when you want the tighter grade.

Autogenous A789 welded tube must meet parent anneal and mechanicals. Fabrication fillers are usually matching 2209-type duplex with controlled heat input and interpass temperature. Re-anneal after heavy hot work when required; avoid sigma and 475 °C soaks during bake cycles.

Annealed and pickled standard; bright anneal or light polish by agreement. Passivate after pickling or field welding; remove carbon-steel contamination before chloride service.

Hydro or NDE per tube; tension, hardness, flaring or flange + reverse flattening per lot; heat analysis on MTC. Product analysis and extra corrosion tests on order. EN 10204 3.1 standard; 3.2 on request.

Bundles or cases with end protectors, waterproof wrap, and heat/size tags. FOB/CFR/CIF/EXW with invoice, packing list, and 3.1/3.2 certificates.

SHH STEEL produces and supplies ASTM A789 UNS S31803 duplex tube from Shanghai as a manufacturer-exporter — coordinating melt chemistry, tube making, anneal, test, and documents to the PO, not as a trader-only middleman.

We help buyers decide whether S31803 or S32205 is the grade the corrosion spec actually needs, and we quote seamless or welded with EN 10204 3.1 traceability either way.

SHH STEEL can produce and supply ASTM A789 UNS S31803 duplex stainless steel tube against the edition, size, and finish on your enquiry.

Stock / Available sizes

Practical production-and-stock enquiry range — not a frozen tonnage SKU list.

State whether the project allows S31803 or requires A789 S32205. List OD × wall, avg/min, length, finish, and port.

ASTM A789 UNS S31803 remains a widely ordered 2205-family duplex tube grade, but it is not chemically identical to A789 S32205. SHH STEEL produces and supplies seamless and welded S31803 to the A789 anneal and test regime with EN 10204 3.1 documentation, and can quote S32205 when the tighter window is required. Contact admin@steelspecs.com.