ASTM A789 UNS S31500 Duplex Stainless Steel Tube

ASTM A789 / A789M is the specification for seamless and welded ferritic/austenitic stainless steel tubing for general corrosion service, with particular emphasis on resistance to stress corrosion cracking. UNS S31500 under that standard is a silicon-bearing duplex with heat limits of carbon ≤0.030%, chromium 18.0–19.0%, nickel 4.3–5.2%, molybdenum 2.50–3.00%, silicon 1.40–2.00%, manganese 1.20–2.00%, and nitrogen 0.05–0.10% per A789/A789M-24 Table 1. The elevated silicon and modest chromium set it apart from 2205-class material: it was developed historically for urea and nitric-acid related duties where Si helps, while still offering duplex SCC resistance and higher yield than 300-series austenitics.

SHH STEEL can produce and supply ASTM A789 UNS S31500 duplex stainless steel tube as seamless and welded product (no filler metal on welded), in typical heat-exchanger and process OD × wall / BWG sizes, with EN 10204 3.1 mill test certificates covering ladle chemistry and tensile plus hardness acceptance. Dual A789/SA789 marking is available only when both names are on the purchase order. Browse the family on the A789/A789M hub.

Market names include 3RE60 and S31500 duplex tube; they never replace the UNS on the stencil. Sister pages worth comparing include workhorse A789 S32205, lean A789 S32304, and higher-Cr A789 S31200. Plate of related chemistry is ordered on A240.

Heat analysis must meet A789/A789M-24 Table 1 for UNS S31500. Product analysis uses A480/A480M annex tolerances when ordered (carbon product-analysis tolerance does not apply at C max ≤0.04%).

Mid-range PREN = Cr + 3.3Mo + 16N with Cr 18.5, Mo 2.75, N 0.08 is about PREN ≈ 29 — lower than 2205-class S32205 and closer to the upper lean / lower standard duplex transition. Silicon is intentionally high (1.40–2.00%), which is the metallurgical signature of this grade versus other A789 duplex entries. Do not assume seawater crevice capability from the duplex label alone; verify against process media.

Tensile and hardness requirements come from A789’s tensile/hardness table (Table 4 in recent editions). That table was absent from the public A789/A789M-24 sample; figures below are from older Table 4 PDF reprints and must be reconfirmed on the PO edition.

Note the 30% elongation floor — higher than the 25% used for many sister duplex grades — and the slightly lower tensile/yield pair (92/64 ksi) versus S32205’s 95/70 ksi in those same older copies. Hardness remains capped at 290 HBW / 30 HRC.

Manufacture is seamless or welded with no filler metal (A789 §5). Seamless S31500 is typically extruded or pierced then cold-finished; welded tube is formed from strip and autogenously welded, then usually cold-worked and re-annealed so the seam meets parent requirements.

Flaring (≥10% ID expansion) applies to seamless lots; flange plus reverse flattening (every 1500 ft / 450 m) applies to welded lots. SHH STEEL produces and supplies both routes for A789 S31500 with EN 10204 3.1 documentation of chemistry and mechanicals.

Average wall is the default; call minimum wall on the order when required. Sizes are tube OD × wall / BWG under A1016/A1016M general rules unless A789 states otherwise.

State avg versus min wall when converting schedules. SHH STEEL confirms size and finish before heat reservation.

UNS S31500 is widely known as 3RE60 and aligns with EN 1.4424 (X2CrNiMoSi18-5-3) in European lists. Product-form tables differ across tube, pipe, and plate — check the applicable standard before substituting.

Dual A789/SA789 only on request. Plate: A240. Hub: A789/A789M.

A789/A789M-24 Table 2 lists UNS S31500 at 1800–1900 °F [980–1040 °C] with rapid cooling in water or by other means — a lower anneal window than 2205-class grades. Seamless tube may be quenched directly after hot forming at or above the minimum solution temperature.

Rapid quench still matters: Mo-bearing duplex can form sigma if cooled slowly through ~700–1000 °C, and all duplex grades in A789 carry the scope warning about embrittlement after prolonged elevated-temperature use, including 475 °C (885 °F) ferrite embrittlement. S31500 is an aqueous/process corrosion grade, not a continuous high-temperature alloy. SHH STEEL supplies it solution-annealed and quenched per Table 2.

S31500 is chosen for chloride SCC resistance versus 304/316 and for Si-assisted performance in selected nitric and urea-related environments, not for maximum PREN. Mid-range PREN ≈29 sits below A789 S32205 and well below super duplex A789 S32750.

Do not substitute S31500 into a seawater crevice or high-PREN datasheet written around 2507-class alloys. Match the Si-bearing chemistry to the process fluid; when general chloride pitting is the driver and Si is not required, A789 S32205 or lean options may be the better commercial choice.

Historic and current uses include urea-plant and nitric-acid related heat-exchanger and process tube, chemical-plant coolers where Si duplex is specified by name, and general chloride-SCC-resistant service where the datasheet already freezes S31500 / 3RE60. Higher yield than 316L supports wall reduction in pressure design.

If the datasheet simply says “duplex” without naming S31500, confirm whether 2205-class S32205 was intended before ordering this Si grade. SHH STEEL produces and supplies A789 S31500 to the enquiry size and test scope.

A789 welded tube is autogenous (no filler). Fabrication welds that use filler typically take matching duplex consumables with controlled heat input so ferrite–austenite balance stays qualified. Re-anneal and quench after heavy hot work when the procedure requires it; keep bake and stress-relief cycles out of the sigma and 475 °C bands unless qualified otherwise.

Standard delivery is solution-annealed and pickled. Bright anneal or light polish is available by agreement. Passivate after pickling or field welding in corrosive service; remove carbon-steel contamination before commissioning. Finish is stated on the quote and MTC.

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

Hex bundles or cases with end caps, waterproof wrap, and heat/size tags. Cut lengths and U-bends packed by length group or in purpose crates. Shipped FOB/CFR/CIF/EXW with invoice, packing list, and 3.1/3.2 certificates.

SHH STEEL is a Shanghai stainless manufacturer and exporter that produces and supplies duplex tube including ASTM A789 UNS S31500. We coordinate chemistry, tube making, the lower 1800–1900 °F anneal window, testing, and documents to the PO — production capability, not trader-only stock photo offers.

Buyers come to SHH STEEL for S31500 when the datasheet names 3RE60 / S31500 specifically and they need seamless or welded tube with EN 10204 3.1 traceability from a mill-aware exporter who understands Si duplex versus 2205.

SHH STEEL can produce and supply ASTM A789 UNS S31500 duplex stainless steel tube against the edition, size, and finish on your enquiry.

Stock / Available sizes

Quoted as a practical production-and-stock enquiry range, not a frozen tonnage SKU list.

List edition, seamless/welded, OD × wall (avg/min), length, finish, and port. Sister A789 S32205 can be quoted alongside when the project compares Si duplex with 2205.

ASTM A789 UNS S31500 is the Si-bearing duplex stainless tube grade (3RE60 family) for process duties that specify elevated silicon along with duplex SCC resistance and strength. SHH STEEL produces and supplies seamless and welded S31500 to the A789 anneal and test regime with EN 10204 3.1 documentation. For availability or a comparison with A789 S32205, contact admin@steelspecs.com.