ASTM A240 329 (S32900) Duplex Stainless Steel Pipe
ASTM A240 329 (S32900) Duplex Stainless Steel Pipe: Properties, Composition & Applications
Complete material guide for ASTM A240 329 (S32900) stainless steel pipe: chemical composition, mechanical and physical properties, equivalent grades, and typical applications in chemical, marine, and energy industries.
Hot rolling, cold rolling, welding, forming, machining
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ASTM A240 329 Duplex Stainless Steel Pipe Introduction
ASTM A240 329 (UNS S32900) is a duplex stainless steel characterized by a mixed microstructure of austenite and ferrite, providing a combination of high strength and excellent corrosion resistance.
- High resistance to stress corrosion cracking and pitting.
- Significantly higher yield strength compared to standard austenitic grades like 304/316.
- Good weldability and formability in the annealed condition.
- Used in chemical processing, heat exchangers, and marine environments.
It is typically supplied in the solution annealed and pickled condition.
ASTM A240 329 Duplex Stainless Steel Pipe Chemical Composition
The chemical composition of 329 (S32900) is specified in ASTM A240. All values are maximum unless a range is shown.
- High chromium and molybdenum ensure strong pitting and crevice corrosion resistance.
- Nitrogen is limited to maintain a balanced duplex microstructure.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.08 | Max |
| Manganese (Mn) | ≤1.00 | Max |
| Phosphorus (P) | ≤0.040 | Max |
| Sulfur (S) | ≤0.030 | Max |
| Silicon (Si) | ≤0.75 | Max |
| Chromium (Cr) | 23.0 – 28.0 | Range |
| Nickel (Ni) | 2.5 – 5.0 | Range |
| Molybdenum (Mo) | 1.0 – 2.0 | Range |
| Nitrogen (N) | ≤0.10 | Max |
ASTM A240 329 Duplex Stainless Steel Pipe Physical Properties
Typical physical properties of 329 duplex stainless steel at room temperature, unless otherwise stated. These values are for general reference and can vary slightly with product form.
- Lower thermal expansion than austenitic grades reduces thermal stress in service.
- The material is magnetic due to its ferrite phase.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.7 | g/cm³ | at 20 °C |
| Elastic Modulus (E) | 200 | GPa | at 20 °C |
| Shear Modulus (G) | 77 | GPa | at 20 °C (calculated) |
| Poisson's Ratio (ν) | 0.3 | — | at 20 °C |
| Thermal Expansion (α) | 11.0 | 10⁻⁶/K | 20–100 °C |
| Thermal Conductivity (λ) | 15 | W/(m·K) | at 20 °C |
| Specific Heat Capacity | 500 | J/(kg·K) | at 20 °C |
| Electrical Resistivity (ρe) | 0.80 | µΩ·m | at 20 °C |
ASTM A240 329 Duplex Stainless Steel Pipe Mechanical Properties
Mechanical properties for S32900 in solution annealed condition at room temperature. Tensile and yield values are minimum, elongation is minimum, hardness is maximum.
- Yield strength is nearly twice that of typical austenitic stainless steels.
- Hardness values reflect the annealed duplex state.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | ≥550 | MPa | Room temperature |
| Yield Strength (Rp0.2) | ≥450 | MPa | Room temperature, 0.2% offset |
| Elongation (A) | ≥15 | % | Gauge length 50 mm (2 in) or proportional |
| Hardness (HBW) | ≤297 | HBW | As per ASTM A240 |
| Hardness (HRC) | ≤31 | HRC | As per ASTM A240 |
ASTM A240 329 Duplex Stainless Steel Pipe Direct Equivalent Grades & Substitute Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A240/A240M | 329 (UNS S32900) | Original specification; this is the primary designation. |
| — | — | — | No other national standards have an exact equivalent grade. |
ASTM A240 329 Duplex Stainless Steel Pipe Application Introduction
329 (S32900) duplex stainless steel pipe is suitable for demanding environments where both high mechanical strength and resistance to chloride-induced stress corrosion cracking are required. It can be fabricated by welding (using appropriate duplex filler), cold forming, and machining.
Product Applications: Process piping and seamless/welded tubes, Shell-and-tube heat exchangers, Pressure vessels and storage tanks, Condenser tubes, Offshore platform piping systems, Clad plate for equipment
Processed into products: Pipe spools, elbows, and flanges, Heat exchanger tube bundles and tubesheets, Welded pipe joints and fittings, Valve bodies and seats, Expansion joints and bellows, Acid-resistant piping components
Application industries: Chemical and Petrochemical Processing, Oil and Gas (Offshore & Onshore), Marine Engineering and Shipbuilding, Desalination Plants, Power Generation (Heat Exchangers), Pulp and Paper Industry
ASTM A240 329 Duplex Stainless Steel Pipe Similar or Alternative Duplex Stainless Steels
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10088-2 | 1.4460 (X3CrNiMoN27-5-2) | Similar Cr-Ni-Mo base, but higher Ni (4.5–6.5%) and controlled N (0.05–0.20%). Practical substitute with slightly different properties. |
| USA | ASTM A240 | S32950 (UNS S32950) | Higher molybdenum (2.5–3.5%) and nitrogen (0.15–0.35%) for improved pitting resistance. |
| USA | ASTM A240 | S32205 (UNS S32205) | Standard duplex 2205 with 22–23% Cr, 4.5–6.5% Ni, 3.0–3.5% Mo. Offers higher strength but different microstructure balance. |
| USA | ASTM A240 | S32750 (UNS S32750) | Super duplex 2507: significantly higher corrosion resistance (PREN > 40) due to increased Mo and N. |
Notes:
Welding: Use matching or over-alloyed duplex filler metals (e.g., ER2209 or E2209). Preheat is generally not required. Post-weld heat treatment is rarely applied but can be performed for stress relief.
Corrosion Testing: When specified, intergranular corrosion resistance can be verified per ASTM A262 Practice E.
Magnetic Properties: The material is strongly magnetic due to its ferritic phase, which can be used for identification but requires consideration in certain designs.
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