ASME SA789 UNS S32101 Lean Duplex Stainless Steel Tube

Under ASME Section II Part A, SA-789 / SA-789M is the Code Book product standard for seamless and welded duplex stainless tubing for general service. UNS S32101 is a lean duplex built around very low nickel (1.35–1.70%), high manganese (4.0–6.0%), chromium 21.0–22.0%, molybdenum 0.10–0.80%, nitrogen 0.20–0.25%, and copper 0.10–0.80%, with carbon ≤0.040%. Nitrogen at the top of the lean band and manganese replacing much of the nickel are the metallurgical idea behind this row.

SHH STEEL can produce and supply ASME SA789 UNS S32101 lean duplex stainless steel tube as seamless product and as welded product with no filler metal in the seam. Typical heat-exchanger OD × wall sizes are quoted regularly, and every certified length ships with an EN 10204 3.1 MTC covering ladle chemistry — including Mn, N, and Cu — plus the wall-dependent tensile result and the Table 2 heat-treatment record. Dual SA-789/A789 marking is available when requested; this page remains ASME-led for Code purchases.

Among lean duplex sisters, SA789 S32001 is also manganese-rich but with a wider nickel band and lower nitrogen floor; SA789 S32304 (2304-type) runs higher nickel and little manganese enrichment; SA789 S32003 adds more molybdenum. Mainstream 22Cr remains SA789 S32205; seawater PREN ≥40 duty goes to SA789 S32750. Plate: A240 / SA240. Hub: SA789/SA789M.

Table 1 sets the heat analysis. Note carbon ≤0.040% — slightly higher maximum than the 0.030% cap on many sister duplex rows — and the narrow nickel window 1.35–1.70%. Product analysis, when ordered, follows Section 8 through A1016/A1016M using A480/A480M tolerances. Copper and the manganese range are required reporting elements on this grade.

Mid-range PREN using %Cr + 3.3×%Mo + 16×%N with Cr ≈21.5, Mo ≈0.45, N ≈0.225 gives PREN ≈ 26.6. Nitrogen’s 16× multiplier is doing real work on this lean chemistry; molybdenum stays modest. SA-789 publishes no PREN minimum for S32101 — the estimate is from stated chemistry only.

Table 4 splits S32101 by wall thickness, and the thin-wall row is notably strong for a lean duplex. Lot rules follow Section 9; properties do not apply below 1/8 in. OD or 0.015 in. wall.

For wall 0.187 in. [5.00 mm] and under: tensile 101 ksi [700 MPa] min, yield 77 ksi [530 MPa] min, elongation 30% min. Above that wall: tensile 94 ksi [650 MPa] min, yield 65 ksi [450 MPa] min, still 30% elongation. Hardness max is 290 HBW / 30 HRC / 290 HV on both rows. Source: ASME BPVC.II.A-2023 SA-789 Table 4. Design allowables live in Section II Part D.

S32101 under SA-789 may be furnished seamless or welded. Welded tube uses no filler metal; the seam is autogenous and the tube is heat-treated after welding. Marking must identify the route and the wall basis (average or minimum).

Flaring (10% minimum ID expansion) is required on seamless lots. Welded lots require flange testing and reverse flattening on each 1500 ft [450 m] of finished tubing. SHH STEEL manufactures both routes for SA789 S32101 and prints the route on stencil and certificate.

Buyers should order OD × wall and length in tube terms, stating whether wall is average or minimum. Table 5 of SA-789 governs OD, wall, and cut-length tolerances by diameter group; clause 12.2 addresses thin-wall ovality beyond the basic OD band.

Source: ASME BPVC.II.A-2023 SA-789 Table 5. Because S32101 tensile floors change at 0.187 in. wall, the ordered wall thickness also decides which mechanical row applies — another reason to write wall clearly on the PO.

ASME SA-789 UNS S32101 governs this article. Lean-duplex trade brands that market similar low-nickel, high-manganese concepts are not automatic substitutes unless the mill certifies this UNS to SA-789 Table 1 and Table 4.

Keep the UNS on the purchase order so a high-Mn lean grade is not confused with 2304-type S32304.

Table 2 lists S32101 at a minimum of 1870 °F [1020 °C], quenched in water or rapidly cooled by other means — a minimum-temperature style row rather than a closed band like many sister grades.

Direct quench after hot forming is allowed for seamless tubes when temperature stays at or above that minimum. Rapid cooling protects phase balance on this nitrogen-strengthened lean duplex. SHH STEEL ships only Table 2 heat-treated SA789 S32101 with the record on the MTC.

Estimated PREN near 26.6 from mid-range chemistry puts S32101 in the lean duplex pitting band — helped by nitrogen, limited by low molybdenum. Chloride SCC resistance should still beat 304 in many waters, but it is not a substitute for SA789 S32205 or SA789 S32750 when PREN in the mid-30s or 40+ is specified.

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

S32101 is chosen for lean-duplex tube duty that values high strength (especially in thinner walls) and low nickel cost. Typical homes are water systems, mild process coolers, and Code general-service tubing where the datasheet names this UNS.

For higher molybdenum lean chemistry see SA789 S32003; for 2304-type see SA789 S32304; for 2205 see SA789 S32205.

Tube-to-tubesheet and attachment welds on S32101 typically use lean-duplex fillers under a qualified WPS; the mill welded SA-789 product itself remains autogenous with no filler in the longitudinal seam. High manganese and elevated nitrogen change weld-pool behaviour and ferrite balance relative to low-manganese 2205 practice, so procedures should be qualified on representative S32101 heats rather than borrowed unchecked from S32205 PQRs.

Control heat input, limit interpass temperature, cool the HAZ promptly to limit intermetallics, and clean thoroughly after welding. SHH STEEL can discuss filler families commonly used with this lean duplex; the Code-stamped fabricator owns the WPS and PQR under the applicable vessel or piping Code.

Default delivery for ASME SA789 S32101 is heat-treated and descaled or pickled so the tube is free of excessive mill scale and suitable for inspection under Section 13. A slight amount of oxidation is not treated as scale. Bright anneal under protective atmosphere or Ra-controlled bore/OD finishes need a written agreement on the order and are quoted as commercial overlays on the SA-789 product.

SHH STEEL does not assume special finishes with the grade stamp alone. Call bright, polish, or Ra limits out on the enquiry so the quotation for SA789 S32101 matches the exchanger or process specification that will receive the tube.

Heat analysis, wall-appropriate tension and hardness, flare or flange tests, reverse flattening for welded tube, and hydro or NDE on every length form the base program. Hydrostatic factor 64000 (441.2) applies. Manufacturer selects hydro versus NDE unless the PO locks the method.

Marking shows seamless or welded and wall basis. SHH STEEL 3.1 MTCs link heat, chemistry, mechanicals, heat treatment, and test method for receiving clearance.

Bundles leave SHH STEEL tagged with ASME SA789, UNS S32101, seamless or welded identity, OD × wall, heat number, and purchase-order reference, with end protection matched to the length mix so receiving can verify the shipment before opening every certificate packet.

Export packing options include wrapped bundles and wooden cases for bright-finished or small-bore material. Incoterms and document flow follow the order acknowledgment, and MTC packs accompany or precede cargo as agreed at quotation.

SHH STEEL produces and supplies ASME SA789 UNS S32101 as manufactured lean-duplex Code Book tube, reporting the narrow nickel window, high manganese, and wall-dependent tensile row honestly on the EN 10204 3.1 MTC. We do not relabel S32101 as 2205 or as 2304.

If PREN must rise into the mid-30s, we quote SA789 S32205. If the drawing wants 2304-type chemistry, we quote SA789 S32304. Dual marking and third-party inspection are available on request.

SHH STEEL can produce and supply ASME SA789 UNS S32101 lean duplex tube to the edition, route, and finish on your enquiry. Capability and Stock / Available sizes follow.

Stock / Available sizes — Common enquiry bands include OD about 12.7–50.8 mm with usual BWG / metric walls; larger Table 5 groups by agreement. Because tensile floors change at 0.187 in. wall, state wall clearly. No invented tonnage lists — send OD × wall, route, and quantity for a firm reply.

List ASME SA789 UNS S32101, seamless or welded, OD × wall, wall basis, length, and quantity on the enquiry.

ASME SA789 UNS S32101 is the high-manganese, very-low-nickel lean duplex tubing grade with wall-dependent tensile floors that can reach 101/77 ksi in thinner walls. SHH STEEL produces and supplies seamless and welded (no filler metal) SA789 S32101, heat-treated at 1870 °F min, tested per Section 9, and certified on EN 10204 3.1 MTCs. Write wall thickness clearly so the correct Table 4 row applies. For technical follow-up, contact admin@steelspecs.com.