ASTM A789 UNS S31260 Duplex Stainless Steel Tube

ASTM A789 / A789M covers seamless and welded ferritic/austenitic stainless steel tubing for general corrosion service with particular emphasis on stress corrosion cracking resistance. UNS S31260 is a tungsten-bearing duplex listed in A789/A789M-24 Table 1 with carbon ≤0.030%, chromium 24.0–26.0%, nickel 5.5–7.5%, molybdenum 2.5–3.5%, nitrogen 0.10–0.30%, copper 0.20–0.80%, and tungsten 0.10–0.50%. The W + Mo + Cu combination lifts crevice and pitting resistance relative to plain Cr-Ni-Mo duplex grades at a similar chromium level, while the duplex microstructure still delivers roughly double the yield of annealed 300-series austenitics.

SHH STEEL can produce and supply ASTM A789 UNS S31260 duplex stainless steel tube as seamless and welded product (welded without filler metal) in the usual heat-exchanger and process OD × wall / BWG band, with EN 10204 3.1 mill test certificates reporting ladle chemistry and the tensile plus hardness set. Dual A789 / SA789 marking is issued only when both standards are named on the purchase order. See the grade family on the A789/A789M hub.

Shop names for this chemistry include DP3 and S31260 duplex tube; they do not replace the UNS grade on the stencil. Compare with sister A789 S31200 (no W/Cu), workhorse A789 S32205, and tungsten-bearing super duplex A789 S32760 when PREN and seawater crevice demands step up. Matching plate chemistry is ordered under A240, not this tube specification.

Heat analysis for UNS S31260 must meet A789/A789M-24 Table 1. Product analysis, when ordered, follows A480/A480M annex tolerances (carbon product-analysis tolerance does not apply when the specified maximum is 0.04% or less).

For W-bearing grades the screening PREN form often used in the duplex community is Cr + 3.3(Mo + ½W) + 16N. At mid-range (Cr 25, Mo 3.0, W 0.30, N 0.20) that estimate is about PREN ≈ 38–39 — high in the standard duplex band and approaching super duplex territory, which is why S31260 shows up on chloride-process enquiries that outgrow 2205 but do not yet need S32750/S32760. Copper supports resistance in some reducing acids; confirm against your actual media rather than the label alone.

Tensile and hardness floors are prescribed in A789’s tensile/hardness table (Table 4 in recent editions). Those figures were not present in the public A789/A789M-24 sample excerpt; the values below come from older publicly circulated Table 4 reprints and should be reconfirmed against the edition on your purchase order.

The 65 ksi yield floor is typical of standard duplex tube and already roughly doubles annealed 304/316 yield, which is why designers thin the wall when switching from austenitic tube. Hardness is capped at 290 HBW / 30 HRC — keep cold reduction and quench practice inside the mill procedure so the MTC does not fail hardness while still meeting tensile.

A789 Section 5 allows seamless or welded manufacture with no filler metal added. Seamless S31260 is usually hot-finished then cold-drawn to final size; welded tube is roll-formed from matching strip and autogenously welded, then typically cold-worked and re-annealed so the seam matches parent-metal properties.

Seamless lots take a flaring test (minimum 10% ID expansion); welded lots take a flange test plus reverse flattening every 1500 ft [450 m]. Tension and hardness sampling apply to both routes. SHH STEEL produces and supplies both seamless and welded A789 S31260 against the route on the enquiry, with EN 10204 3.1 coverage of chemistry and mechanicals for the lengths shipped.

Default wall basis is average wall; specify minimum wall on the order when that is the design basis. OD and wall are tube callouts (metric or inch × wall / BWG). General dimensional rules sit in A1016/A1016M unless A789 overrides them.

State avg versus min wall explicitly when converting from a pipe schedule — the mill ticket and hydro test pressure both depend on that choice. SHH STEEL confirms OD × wall, length, and finish before reserving the heat.

UNS S31260 is known in the market as DP3 and appears under the same UNS in sister ASTM pipe and plate documents. Product-form tables differ, so do not swap an A789 tube heat for an A790 pipe heat without checking the applicable mechanical and HT tables.

Call out SA789 when ASME Code stamping is mandatory; dual stencil only on request. Plate: A240. Tube family hub: A789/A789M.

A789/A789M-24 Table 2 sets UNS S31260 at 1870–2010 °F [1020–1100 °C] with rapid cooling in water or by other means. Seamless tube may be quenched directly after hot forming while still at or above the minimum solution temperature, as an alternate to a final furnace anneal.

Rapid cooling limits time in the sigma nose (roughly 700–1000 °C) where intermetallics nucleate quickly in Mo- and W-bearing duplex. The scope of A789 also warns that these steels are susceptible to embrittlement if used for prolonged periods at elevated temperatures — including 475 °C (885 °F) ferrite embrittlement from spinodal decomposition between about 400 and 500 °C. S31260 is therefore a corrosion-and-strength tube grade for aqueous and moderate-temperature service, not a continuous high-temperature alloy. SHH STEEL supplies it solution-annealed and quenched per Table 2.

S31260 is specified when chloride SCC resistance and a higher pitting/crevice margin than basic duplex are needed, but full super duplex is not yet justified. Tungsten and copper alongside Mo push crevice performance above plain A789 S31200 and often above A789 S32205 at comparable chromium, which is why DP3-type tube appears in chemical-process and some offshore utility circuits.

It is still not a drop-in for seawater crevice duties written around PREN ≥40 super duplex such as A789 S32750 or A789 S32760. Use heat-certificate chemistry for any PREN screen, and qualify against your chloride, temperature, and pH — not against a brochure band alone.

Typical service includes chemical-process heat-exchanger and cooler tube, chloride-bearing process lines, desalination and brine-handling circuits that need more than 2205 but not necessarily 2507, and selected oil-and-gas utility tubing. The duplex yield strength supports thinner walls versus 316L in pressure design.

Avoid prolonged holds in the 400–500 °C embrittlement band and careless soaks through the sigma window during fabrication or coating cure. SHH STEEL produces and supplies A789 S31260 for the sizes and test extras your enquiry lists.

Autogenous A789 welded tube must meet parent heat treatment and mechanicals without filler. Fabrication welds that do use filler typically take matching or overalloyed duplex consumables with controlled heat input and interpass temperature so ferrite–austenite balance stays inside the qualified window.

Re-anneal and rapid quench after heavy hot work if the procedure requires restoration of phase balance. Keep stress-relief and bake cycles out of the sigma and 475 °C bands unless a qualified procedure says otherwise. SHH STEEL can discuss typical WPS ranges when fabrication is in scope.

Standard finish is solution-annealed and pickled (or equivalently descaled). Bright anneal or light OD/ID polish is available by agreement for cleaner exchanger or inspection surfaces. Passivate after pickling or after field welding in chloride service, and remove carbon-steel tooling contamination before commissioning. Finish route is stated on the quotation and MTC.

Each tube takes hydro or NDE electric test; lots take tension, hardness, and flaring (seamless) or flange plus reverse flattening (welded). Heat analysis is on the MTC; product analysis and extra corrosion/ferrite tests are order options. SHH STEEL issues EN 10204 3.1 as standard and 3.2 with third-party attendance on request, with lot identity per A789 Notes 1 and 2.

Bundles or cases with end protectors, waterproof wrap, and tags repeating heat, size, and standard. Cut lengths and U-bends use length-grouped or purpose-built packing. FOB/CFR/CIF/EXW as named; export set includes 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 S31260. Mill chemistry, tube making, solution anneal, testing, and documents are coordinated to the PO — production capability, not a trader-only offer.

Choose SHH STEEL when you need a clear seamless-or-welded option, EN 10204 3.1 traceability, and a supplier who understands W-bearing duplex metallurgy (sigma risk, 475 °C embrittlement, PREN screening with the W term) rather than a generic stainless stockist.

SHH STEEL can produce and supply ASTM A789 UNS S31260 duplex stainless steel tube against the edition, size, and finish on your enquiry. Capability and Stock / Available sizes maps follow.

Stock / Available sizes

Quoted against a practical production-and-stock enquiry range — not a frozen SKU list with published tonnages. Treat the table as a supply map for enquiry.

Include edition (if known), seamless or welded, OD × wall (avg/min), length, finish, extras, and port on the enquiry. Sister A789 S32205 and A789 S32760 can be quoted on the same request when the project mixes duplex classes.

ASTM A789 UNS S31260 is a tungsten- and copper-bearing duplex stainless tube grade for chloride-service heat exchangers and process lines that need more crevice margin than basic duplex without stepping fully into super duplex. SHH STEEL produces and supplies seamless and welded S31260 to the A789 anneal and test regime with EN 10204 3.1 documentation. For sizes, dual marking, or a comparison with A789 S32205 or A789 S32760, contact admin@steelspecs.com.