ASME SA789 UNS S32304 Lean Duplex Stainless Steel Tube

Inside ASME Section II Part A, SA-789 / SA-789M covers seamless and welded duplex stainless tubing for general service. UNS S32304 is the 2304-type lean duplex: chromium 21.5–24.5%, nickel 3.0–5.5%, molybdenum only 0.05–0.60%, nitrogen 0.05–0.20%, and copper 0.05–0.60%, with carbon ≤0.030%. It is the lean duplex most often compared with 304/316 on cost while offering duplex strength and better chloride SCC resistance than those austenitics in many waters.

SHH STEEL can produce and supply ASME SA789 UNS S32304 lean duplex stainless steel tube as seamless product and as welded product with no filler metal, in typical heat-exchanger OD × wall sizes, with EN 10204 3.1 MTCs that report ladle chemistry including the copper range and the OD-dependent tensile result required by Table 4. Dual SA-789/A789 marking is available when requested; this page stays ASME-first for Code purchases.

High-manganese lean alternatives include SA789 S32101 and SA789 S32001. Mainstream 22Cr duplex is SA789 S32205. Seawater PREN ≥40 duty belongs on SA789 S32750. Plate: A240 / SA240. Hub: SA789/SA789M.

Table 1 sets heat analysis. Molybdenum stays very low (0.05–0.60%), and copper is a required range rather than an ellipsis. Product analysis, when ordered, follows Section 8 through A1016/A1016M. Sulfur and phosphorus maxima are 0.040% — looser than on some sister duplex rows.

Mid-range PREN with Cr ≈23, Mo ≈0.3, N ≈0.12 gives PREN ≈ 25.9. That lean-band estimate reflects the low molybdenum; nitrogen and chromium do most of the pitting work. SA-789 publishes no PREN minimum for S32304.

Table 4 splits S32304 by outside diameter, not by wall — a different split from S32101/S32003. Lot rules follow Section 9; properties do not apply below 1/8 in. OD or 0.015 in. wall.

For OD 1 in. [25 mm] and under: tensile 100 ksi [690 MPa] min, yield 65 ksi [450 MPa] min, elongation 25%, hardness shown as HV 290 max with HBW/HRC ellipses on that row. For OD above 1 in.: tensile 87 ksi [600 MPa] min, yield 58 ksi [400 MPa] min, elongation 25%, hardness 290 HBW / 30 HRC / 290 HV. Source: ASME BPVC.II.A-2023 SA-789 Table 4. State OD on the PO so the correct row applies.

ASME SA-789 allows S32304 to be furnished as seamless tube or as welded tube made with no filler metal in the longitudinal seam. After welding, the finished tube is heat-treated as a whole under Table 2, and marking must state the manufacture route together with average or minimum wall so receiving inspection can match each length to the purchase order and the mill test certificate.

Seamless lots take a flaring test requiring at least 10% inside-diameter expansion on one end of one tube per lot. Welded lots take a flange test on one end of one tube per lot plus reverse flattening on a specimen from each 1500 ft [450 m] of finished tubing. Tension and hardness tests apply to both routes on the Section 9 lot basis. SHH STEEL produces both seamless and welded SA789 S32304 and records the route on stencil and EN 10204 3.1 MTC.

Dimensional supply for ASME SA789 S32304 uses tube language — outside diameter × wall thickness (average wall unless the order specifies minimum wall) and, commercially, BWG / gauge — rather than ASME B36.19 pipe schedules as the primary size story. Section 3 ordering information should include quantity, seamless or welded, grade, OD and wall, length, optional product analysis, hydro or NDE preference, and the specification designation.

Ovality provisions in clause 12.2 apply to thin-walled tubes as defined in Table 5. Source: ASME BPVC.II.A-2023 SA-789 Table 5. SHH STEEL quotes OD × wall or BWG and average-versus-minimum wall explicitly on every S32304 enquiry.

Because Table 4 tensile floors also depend on whether OD is above or below 1 in., write OD clearly on every line item for S32304.

ASME SA-789 UNS S32304 is the governing designation. The commercial name 2304 usually points here, but confirm the UNS and product standard before accepting a substitute certificate.

Do not treat 2304 as interchangeable with high-Mn lean grades or with 2205 without a materials review.

Table 2 requires S32304 at 1700–1920 °F [925–1050 °C] with rapid cooling in air or water — a lower temperature window than the 1870–2010 °F band used for S32205.

Direct quench after hot forming is allowed for seamless tubes when temperature stays at or above the minimum. SHH STEEL ships only Table 2 heat-treated SA789 S32304 with the record on the MTC.

S32304 targets lean-duplex chloride SCC resistance above 304/316 at lower alloy cost than 2205, with estimated PREN near 25.9. It is not a mid-30s PREN substitute for SA789 S32205 and not a seawater PREN ≥40 grade like SA789 S32750.

Respect SA-789’s prolonged elevated-temperature embrittlement warning and the 475 °C ferrite-embrittlement mechanism. Keep continuous-service temperature inside lean-duplex engineering limits.

S32304 (2304) tube is widely specified for water systems, mild process exchangers, and cost-sensitive duplex projects where full 2205 molybdenum is not required. Match the OD-dependent tensile row and the written UNS.

For high-Mn lean chemistry see SA789 S32101; for 2205 see SA789 S32205.

Fabrication welds typically use lean-duplex or 2304-matching fillers under a qualified WPS; the mill welded SA-789 seam stays autogenous. Low molybdenum means ferrite balance differs from 2209-on-2205 practice — qualify on S32304 heats.

Control heat input, cool promptly, and clean after welding. SHH STEEL can discuss filler families; the fabricator owns WPS/PQR under the applicable Code.

Standard mill delivery for ASME SA789 S32304 is heat-treated and pickled or otherwise descaled, leaving a clean surface free of excessive mill scale and suitable for inspection under Section 13. A slight amount of oxidation is not considered scale. Bright annealing under protective atmosphere, specified Ra on the bore or OD, or light polish are agreement items that must be written into the purchase order.

When a fouling-sensitive or hygienic exchanger specification quotes an Ra maximum, treat that limit as a commercial finish overlay on top of SA-789 product requirements, not as automatic with the grade stamp. SHH STEEL supplies the standard descaled heat-treated finish as default and quotes special finishes against the written enquiry for S32304.

Base ASME SA-789 testing for S32304 includes heat analysis to Table 1, tension and hardness tests to Table 4, flaring (seamless) or flange plus reverse-flattening (welded) tests on the lot basis in Section 9, and either hydrostatic testing or nondestructive electric testing of each length. The manufacturer may choose hydro versus NDE unless the purchase order fixes the method. For hydrostatic calculation, SA-789 substitutes 64000 (441.2) for the A1016 default factor.

Marking under Section 14 must indicate seamless or welded identity and average or minimum wall in addition to A1016/A1016M requirements. SHH STEEL’s EN 10204 3.1 MTC ties heat number, chemistry, tensile/hardness, heat treatment, and test method to each length so receiving inspection can clear the shipment against the PO.

S32304 tube leaves SHH STEEL bundled, end-protected, and tagged for export or domestic delivery according to the length mix on the order. Bundle tags repeat the ASME SA789 grade, seamless or welded identity, OD × wall (or BWG), heat number, and PO reference so site receiving can check the shipment without opening every certificate packet first.

Export packing can be bare bundles, wrapped bundles, or wooden-cased lengths for bright-finished or small-bore material. We ship under the Incoterms and destination documents named on the order acknowledgment, with the MTC pack accompanying or preceding the cargo as agreed at quotation.

SHH STEEL produces and supplies ASME SA789 UNS S32304 as manufactured 2304-type lean-duplex Code Book tube, reporting copper and the OD-dependent tensile row honestly on the EN 10204 3.1 MTC. We do not relabel it as 2205.

If mid-30s PREN is required, we quote SA789 S32205. If high-manganese lean chemistry is written, we quote SA789 S32101. Dual marking is available on request.

SHH STEEL can produce and supply ASME SA789 UNS S32304 stainless steel tube against the edition, manufacture route, and finish named on your enquiry. The capability table below summarizes sizes, routes, and documents we regularly quote, followed by the Stock / Available sizes map for heat-exchanger and general-service planning, including the OD split that drives Table 4.

Stock / Available sizes — SHH STEEL regularly enquires and produces SA789 S32304 in heat-exchanger bands such as OD about 12.7–50.8 mm with common BWG / metric walls, and can extend into larger Table 5 OD groups on agreement. Cut lengths, U-bends, and end prep are quoted against the PO. We do not publish fictitious warehouse tonnages; send OD × wall, length, seamless or welded preference, and quantity for a production and near-stock reply.

To enquire, list ASME SA789 UNS S32304, seamless or welded, OD × wall (average or minimum), length, quantity, test preferences, and any dual-marking or third-party need.

ASME SA789 UNS S32304 is the 2304-type lean duplex tubing grade for Code and general service when duplex strength is needed without 2205-class molybdenum. SHH STEEL produces and supplies seamless and welded (no filler metal) SA789 S32304, heat-treated per Table 2, tested per Section 9, and certified on EN 10204 3.1 MTCs. State OD clearly so the correct Table 4 tensile row applies. For technical follow-up, contact admin@steelspecs.com.