329 (S32900) Duplex Stainless Steel Plate & Coil
329 (S32900) Duplex Stainless Steel Plate & Coil - High Strength, Superior Corrosion Resistance
329 (UNS S32900) duplex stainless steel plate and coil offering a balanced ferritic-austenitic microstructure, combining high mechanical strength with excellent resistance to stress corrosion cracking and pitting. Conforms to ASTM A240.
Hot rolling, cold rolling, forming, welding (with appropriate filler), machining
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329 Duplex Stainless Steel Plate & Coil Introduction
UNS S32900 (329 duplex stainless steel) is a low-carbon, molybdenum-bearing dual-phase stainless steel with approximately equal parts ferrite and austenite. It delivers significantly higher yield strength than standard austenitic grades, typically exceeding 485 MPa, along with good ductility and toughness. Its key advantage lies in outstanding resistance to chloride-induced stress corrosion cracking (SCC) and superior pitting resistance in aggressive environments, making it ideal for chemical processing, marine applications, and heat exchangers. The material is supplied as hot- or cold-rolled plate and coil, usually in the solution-annealed and descaled condition.
329 Duplex Stainless Steel Plate & Coil Chemical Composition
The composition of 329 duplex stainless steel is controlled to provide a balanced ferrite–austenite phase ratio and to ensure adequate corrosion resistance through molybdenum and chromium additions.
- Carbon is kept low to avoid intergranular carbide precipitation.
- Molybdenum improves pitting and crevice corrosion resistance.
- Chromium and nickel are balanced to achieve the desired two-phase microstructure.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.08 | |
| Manganese (Mn) | ≤ 1.00 | |
| Silicon (Si) | ≤ 0.75 | |
| Phosphorus (P) | ≤ 0.040 | |
| Sulfur (S) | ≤ 0.030 | |
| Chromium (Cr) | 23.0 – 28.0 | Key element for corrosion resistance |
| Nickel (Ni) | 2.5 – 5.0 | Austenite stabiliser |
| Molybdenum (Mo) | 1.0 – 2.0 | Enhances pitting resistance |
| Nitrogen (N) | Not specified | Not required; may be present as residual |
329 Duplex Stainless Steel Plate & Coil Thermal & Electrical Physical Properties
Physical properties are typical for 329 duplex stainless steel in the annealed condition and may vary slightly with manufacturing route and exact composition. These values are intended for design guidance.
- Thermal expansion is lower than austenitic grades, reducing thermal stress in welded structures.
- Thermal conductivity is higher than austenitic grades, improving heat transfer.
| Property | Typical Value | Unit | Condition / Temperature Range |
|---|---|---|---|
| Density (ρ) | 7.80 | g/cm³ | Room temperature |
| Elastic Modulus (E) | 200 | GPa | Room temperature (tension) |
| Shear Modulus (G) | 77 | GPa | Room temperature (calculated) |
| Poisson's Ratio (ν) | 0.30 | – | Room temperature |
| Thermal Expansion Coefficient (α) | 13.0 | x10⁻⁶ /°C | 20 – 100°C (68 – 212°F) |
| Thermal Conductivity (λ) | 15.0 | W/m·K | At 100°C |
| Specific Heat Capacity (cp) | 460 | J/kg·K | At 20°C |
| Electrical Resistivity (ρ_e) | 0.80 | μΩ·m | Room temperature |
329 Duplex Stainless Steel Plate & Coil Mechanical Properties
Mechanical properties are based on ASTM A240/A240M requirements for plate, sheet, and strip. The high yield strength of duplex 329 provides design advantages, allowing thinner sections compared to austenitic stainless steels.
- Bend tests apply to material ≤ 9.5 mm (3/8 in.) thickness.
- Elongation values depend on specimen gauge length (2 in. or 50 mm).
- Hardness is not specified in the standard; typical values are given for reference only.
| Property | Specified Value | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | ≥ 620 (90) | MPa (ksi) | Room temperature |
| Yield Strength (ReH, 0.2% offset) | ≥ 485 (70) | MPa (ksi) | Room temperature |
| Elongation (A) | ≥ 20 | % | In 50 mm (2 in.) – thickness ≤ 4.8 mm (0.1875 in.) |
| Elongation (A) | ≥ 15 | % | In 50 mm (2 in.) – thickness > 4.8 mm (0.1875 in.) |
| Bend Test (180°) | Bend diameter = specimen thickness | For thickness ≤ 9.5 mm (3/8 in.) |
329 Duplex Stainless Steel Plate & Coil Completely Equivalent Material Standards & Substitutable Grades
| Country / Region | Standard | Grade / Designation | Remarks |
|---|---|---|---|
| USA | ASTM A240/A240M | S32900 (329) | Original specification; chemical and mechanical requirements match exactly. |
| Japan | JIS G4304 | SUS329J1 | Chemically identical to S32900; widely accepted as a direct equivalent. |
329 Duplex Stainless Steel Plate & Coil Application Introduction
329 duplex stainless steel (S32900) is chosen for components that require high strength combined with excellent resistance to stress corrosion cracking and localised corrosion. The material can be formed, welded, and machined using standard duplex procedures.
Product Applications: Coiled tubing and pipe, Welded plate heat exchangers, Baffle plates and tube sheets, Structural sections for aggressive environments, Wire mesh and screens
Processed into products: Flanges and fittings, Bolting (studs, nuts), Pump impellers and casings, Valve bodies and internals, Agitators and shafts
Application industries: Oil & gas – offshore pipelines, separators, heat exchangers, Chemical processing – pressure vessels, reactors, storage tanks, Marine engineering – pump shafts, seawater handling systems, Pulp & paper – digesters, bleaching equipment, Desalination – evaporators, brine heaters
329 Duplex Stainless Steel Plate & Coil Recommended Similar / Alternative Materials
| Country / Region | Standard | Grade / Designation | Remarks |
|---|---|---|---|
| Europe | EN 10088-2 / EN 10088-3 | 1.4460 (X3CrNiMoN27-5-2) | Contains deliberate nitrogen addition (0.05–0.20%). Higher strength and slightly different phase balance but similar corrosion resistance. |
| USA | ASTM A240 | S31803 / S32205 (2205) | Mid-range duplex stainless steel with lower Cr (22–23%) and higher Ni (4.5–6.5%) plus nitrogen. Offers better weldability and toughness; widely used as an all-round duplex grade. |
| China | GB/T 4237 | 0Cr26Ni5Mo2 (obsolete) | Old Chinese designation with similar nominal composition to 329; now mostly superseded by nitrogen-alloyed grades. |
Notes:
Welding: Matching or slightly over-alloyed filler metal (e.g., ER2209) is recommended. Heat input and interpass temperature must be controlled to maintain phase balance and corrosion resistance.
Heat treatment: Solution annealing is mandatory after hot forming or welding; fast cooling (water quench) avoids detrimental sigma phase precipitation.
Surface condition: Supplied in No.1, No.2D or No.2B finish depending on thickness and processing route.
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