329 stainless steel – UNS S32900
First-generation 25Cr-4Ni-1.5Mo duplex stainless steel
First-generation duplex, with no specified nitrogen and carbon up to 0.08%, so it has more ferrite (typically 55–75%) and the weld HAZ loses toughness and corrosion resistance; the PREN is ~26–35 (typically ~30). Caution: in the Brazilian market "329", "329A" or "329LN" is used loosely for bars that may be true 329 (S32900/1.4460) or, in practice, duplex 2205 (S31803/S32205, 1.4462, whose JIS name is SUS329J3L); these are different materials and the order must cite the UNS and the standard.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | S32900 |
| W.Nr./EN | 1.4460 – X3CrNiMoN27-5-2 (approximate equivalent, with N) |
| DIN | X8CrNiMo27-5 (old designation) |
| JIS | SUS329J1 |
| Trade names | AISI 329, Sanmac 329 |
| Others | S32950 / A182 F52 is a variant with N (not the same). SUS329J3L = 2205 and SUS329J4L = super duplex: they are not equivalents of 329 |
Standards by product form
| Form | Standard |
|---|---|
| Bar | EN 10088-3 (1.4460); ASTM A276/A479 subject to availability |
| Forging | No grade of its own in ASTM A182 (F52 = S32950) |
| Plate | ASTM A240 – S32900 |
| Tube | ASTM A789 / A790 – S32900 |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7222.30.00 | 7222.30 | 7222.30.0024 | 7222 30 51 |
| Hot-rolled bar | 7222.11.00 | 7222.11 | 7222.11.0059 | 7222 11 11 |
| Plate (> 10 mm, width ≥ 600 mm) | 7219.21.00 | 7219.21 | 7219.21.0020 | 7219 21 10 |
| Seamless pipe | 7304.41.90 | 7304.41 | 7304.41.6045 | 7304 41 00 |
| Welded pipe | 7306.40.00 | 7306.40 | 7306.40.5085 | 7306 40 80 |
| Flange and fitting | 7307.21.00 | 7307.21 | 7307.21.5000 | 7307 21 00 |
Tariff class: stainless steel (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
ASTM A240 / A789 (UNS S32900)
| Element | Range (%) |
|---|---|
| C | ≤ 0.08 |
| Mn | ≤ 1.00 |
| P | ≤ 0.040 |
| S | ≤ 0.030 |
| Si | ≤ 0.75 |
| Cr | 23.0 – 28.0 |
| Ni | 2.0 – 5.0 |
| Mo | 1.00 – 2.00 |
| Fe | balance |
Mechanical properties
Solution annealed (ASTM A240 plate; 1.4460 bar per EN 10088-3)
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 485 MPa (A240) / ≥ 450 MPa (1.4460 bar) |
| Tensile strength | ≥ 620 MPa |
| Elongation | ≥ 15% (A240) / ≥ 20% (bar) |
| Hardness | ≤ 269 HB (A240) / ≤ 260 HB (bar) |
| Charpy (1.4460 bar, 20 °C) | ≥ 85 J |
Typical physical properties
| Property | Value |
|---|---|
| Density | 7.8 g/cm³ |
| Modulus of elasticity | 200 GPa |
| Thermal conductivity (20 °C) | 15 W/m·K |
| Thermal expansion (20–100 °C) | 13.0 µm/m·K |
| Ferrite (solution annealed) | 55 – 75% (typical) |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Recommended continuous use up to ~250 °C (475 °C embrittlement of the ferrite, aggravated by the high ferrite content); low-temperature toughness inferior to 2205. |
| Heat treatment | Supplied solution annealed (≈ 950–1,050 °C, typical) and water quenched. Not hardenable by heat treatment. |
| Welding | Weldability inferior to N-bearing duplex grades: the HAZ tends to become almost fully ferritic. Use AWS ER2209/E2209 and, in severe corrosive service, solution anneal after welding. No preheat; interpass ≤ 150 °C. |
| Machining | Similar to 2205: lower than 316, requires carbide tooling and continuous cutting. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Pump shafts and components
- Heat exchangers and tubes in chloride media
- Equipment for nitric acid and oxidizing solutions
- Valve parts and stems
- Pulp and paper industry components
Alternatives: For new designs prefer 2205 (S32205/F60), tougher and weldable with PREN ~35; for seawater, super duplex F53/F55. Use 329 only to replace an existing part.
329 stainless steel: complete guide
What 329 stainless steel is
329 belongs to the family of special stainless steels, in the duplex group. It is a two-phase ferrite-austenite steel developed before the addition of nitrogen: with 23 to 28% chromium but little nickel and molybdenum, it has more ferrite than 2205 and a heat-affected zone that embrittles on welding. That is why it was replaced by 2205 in most applications, remaining in nitric acid exchangers, pulp and replacement parts.
329 or 2205: do not confuse them
In the Brazilian market the designations "329", "329A" and "329LN" are often used for 2205 (S31803 / S32205), and JIS itself calls 2205 SUS329J3L. 329 proper is UNS S32900 (JIS SUS329J1, EN 1.4460), with less nickel and molybdenum and no nitrogen. The only safe way to buy is by UNS and product standard, checked on the 3.1 certificate.
Mechanical properties
Solution annealed, ASTM A240 requires a minimum yield strength of 485 MPa, minimum tensile strength of 620 MPa, minimum elongation of 15% and maximum hardness of 269 HBW; in bar per EN 10088-3 (1.4460) the minimum yield strength is 450 MPa with 20% elongation.
Welding
Without nitrogen, the heat-affected zone becomes almost fully ferritic and brittle; welding is possible in thin sections, with nickel over-alloyed ER2209 consumable, low heat input and interpass of up to 150 °C, but for welded constructions 2205 is the choice.
Corrosion and applications
With a PREN of 26 to 35, 329 resists pitting and, above all, chloride stress corrosion cracking better than 316L, and the high chromium gives it good performance in nitric acid and oxidizing media. It is not indicated for seawater or hydrochloric acid. Applications: nitric acid heat exchangers and condensers, pulp equipment, pump shafts and parts in moderate chloride media and replacement of old equipment.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, solution annealing in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of 329 stainless steel?
Per ASTM A240 / A789 (UNS S32900): C ≤ 0.08; Mn ≤ 1.00; P ≤ 0.040; S ≤ 0.030; Si ≤ 0.75; Cr 23.0 – 28.0.
Which standards cover 329 stainless steel?
Bar: EN 10088-3 (1.4460); ASTM A276/A479 subject to availability. Forging: No grade of its own in ASTM A182 (F52 = S32950). Plate: ASTM A240 – S32900. Tube: ASTM A789 / A790 – S32900.
Up to what temperature can 329 stainless steel be used?
Recommended continuous use up to ~250 °C (475 °C embrittlement of the ferrite, aggravated by the high ferrite content); low-temperature toughness inferior to 2205.
Which materials can replace 329 stainless steel?
For new designs prefer 2205 (S32205/F60), tougher and weldable with PREN ~35; for seawater, super duplex F53/F55. Use 329 only to replace an existing part.
