ASTM A789 UNS S32900 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 S32900 is an older duplex listing with heat limits of carbon ≤0.08%, chromium 23.0–28.0%, nickel 2.5–5.0%, and molybdenum 1.00–2.00% in A789/A789M-24 Table 1 — and notably no nitrogen range (ellipses in Table 1). Higher allowed carbon and the absence of a nitrogen minimum distinguish it from modern N-strengthened duplex grades such as A789 S32205.

SHH STEEL can produce and supply ASTM A789 UNS S32900 duplex stainless steel tube as seamless and welded product (welded without filler metal) in typical OD × wall / BWG sizes, with EN 10204 3.1 mill test certificates. Dual A789/SA789 marking only when both standards are on the order. Hub: A789/A789M.

Often associated with early Type 329 / 1.4460-family discussions; confirm UNS because Cr bands overlap other grades. Plate: A240.

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

No nitrogen requirement in Table 1 (ellipses). Carbon max 0.08% is much higher than the 0.030% max on most modern A789 duplex grades. Mid-range PREN without N credit (Cr 25.5, Mo 1.5, N≈0) is only about PREN ≈ 30 — and real heats may vary widely across the broad Cr window.

Tensile and hardness floors come from older A789 Table 4 reprints; the public A789/A789M-24 sample did not include that table. Reconfirm on the PO edition.

Older Table 4: 90/70 ksi, 20% elong, 271 HBW / 28 HRC — hardness cap lower than most sister grades.

A789 Section 5 allows seamless or welded manufacture with no filler metal added. Seamless S32900 tube is typically hot-finished then cold-drawn to final OD and wall; welded tube is roll-formed from matching strip and autogenously welded, then usually cold-worked and re-annealed so the seam meets parent-metal heat treatment and mechanical floors.

Seamless lots take a flaring test (minimum 10% inside-diameter expansion); welded lots take a flange test plus a reverse flattening test on a specimen from each 1500 ft [450 m] of finished tubing. Tension and hardness sampling apply to both routes. SHH STEEL produces and supplies both seamless and welded A789 S32900 against the route named on the enquiry, with EN 10204 3.1 coverage of chemistry and mechanicals.

Average wall is the default under A789; specify minimum wall on the order when that is the design basis. Outside diameter and wall are ordered as tube sizes (metric or inch OD × wall / BWG). General dimensional requirements sit in Specification A1016/A1016M unless A789 states otherwise.

When converting a pipe schedule into tube wall, state clearly whether acceptance is average or minimum wall — the two are not interchangeable on the mill ticket. SHH STEEL confirms OD × wall, length, and finish before the heat is reserved.

Historical Type 329 associations exist in commerce; certify to UNS S32900 on A789 orders.

Hub: A789/A789M. Prefer A789 S32205 for modern 2205-class duties unless the datasheet freezes S32900.

A789/A789M-24 Table 2 lists UNS S32900 at 1700–1750 °F [925–955 °C]. Rapid cooling in water or by other means applies unless Table 2 states a different quench (for example air cool on some grades). Seamless tube may be quenched directly after hot forming while at or above the minimum solution temperature where that alternate is allowed.

Rapid cooling limits time in the sigma-forming window (roughly 700–1000 °C). A789’s scope warns that these steels are susceptible to embrittlement if used for prolonged periods at elevated temperatures, including 475 °C (885 °F) ferrite embrittlement. SHH STEEL supplies S32900 in the heat-treated condition required by Table 2.

S32900 provides duplex SCC resistance relative to 300-series austenitics, but the lack of a nitrogen minimum and the wide Cr band make PREN and crevice performance less predictable than modern N-alloyed duplex. Prefer A789 S32205 or A789 S32750 when a defined modern PREN floor is mandatory.

Replacement and legacy-spec tube where S32900 / Type 329 is frozen, and selected chemical duties that still name this UNS. New greenfield chloride designs usually migrate to S32205 or super duplex.

SHH STEEL produces and supplies A789 S32900 when the enquiry names it, and can quote modern alternatives alongside.

Autogenous A789 welded tube must meet parent anneal and mechanicals without filler. Fabrication welds that use filler typically take matching or overalloyed duplex/super duplex consumables with controlled heat input and interpass temperature so ferrite–austenite balance stays qualified. Re-anneal after heavy hot work when required; keep bake and stress-relief cycles out of the sigma nose and the 400–500 °C embrittlement band unless a qualified procedure says otherwise.

Standard delivery is solution-annealed and pickled (or otherwise descaled) so the passive film can form uniformly. Bright-annealed or lightly polished OD/ID finishes are available by agreement when the exchanger or hygienic duty needs a smoother bore. Passivation after pickling or after fabrication welding is good practice in chloride service; remove carbon-steel tooling contamination before commissioning. SHH STEEL states the finish route on the quotation and on the MTC.

Each A789 tube takes either a nondestructive electric test or a hydrostatic test. Mechanical sampling covers tension, hardness, and flaring for seamless or flange plus reverse flattening for welded, with full heat analysis on the mill test certificate. Product analysis and supplementary corrosion or ferrite tests are added when the purchase order asks for them. SHH STEEL issues EN 10204 3.1 as standard and arranges third-party inspection / 3.2 when the enquiry names an agency, with lot identity per A789 Notes 1 and 2.

Tube is typically packed in hexagonal bundles or plywood cases with end protectors and waterproof wrapping for ocean freight, with bundle tags repeating heat number, size, and standard. Cut-to-length exchanger tube may be boxed by length group; U-bends travel in purpose-built crates when ordered. SHH STEEL ships FOB, CFR, CIF, or EXW under the Incoterm on the order, with commercial invoice, packing list, and the EN 10204 3.1 or 3.2 certificate set.

SHH STEEL produces and supplies ASTM A789 UNS S32900 — including the unusual 1700–1750 °F anneal window and the no-nitrogen Table 1 chemistry — with EN 10204 3.1 documents. Production capability, not trader-only.

We warn buyers when a “duplex” enquiry would be better served by S32205 unless S32900 is contractually required.

SHH STEEL can produce and supply ASTM A789 UNS S32900 against the edition, size, and finish route named on your enquiry. The capability table below summarizes what we regularly quote, followed by the Stock / Available sizes map.

Stock / Available sizes

SHH STEEL quotes S32900 tube against a practical production-and-stock enquiry range rather than a frozen warehouse SKU list with published tonnages. Availability of any single line on a given week depends on mill drawing and inbound schedule — treat the table as a supply map for enquiry.

When you send an enquiry, include the ASTM edition if known, seamless or welded, OD × wall (avg or min), length, finish, test extras, and destination port. Sister grades such as A789 S32205, A789 S31200, and A789 S32750 can be quoted on the same enquiry when the project mixes duplex classes.

ASTM A789 UNS S32900 is covered here as duplex stainless steel tube under the A789 seamless-and-welded duplex tubing specification. SHH STEEL produces and supplies seamless and welded S32900 to the A789 heat-treatment and test regime with EN 10204 3.1 documentation. For sizes, dual marking, or grade comparisons, contact admin@steelspecs.com.