ASTM A789 S32906 Super Duplex Stainless Steel Pipe
ASTM A789 S32906 Super Duplex Stainless Steel Pipe: Properties & Equivalents
Complete material data for ASTM A789 S32906 super duplex stainless steel pipe, covering chemical composition, mechanical and thermal properties, international equivalents, and application guidance.
Hot working, cold working, machining, welding (GTAW, GMAW, SMAW, SAW), forming
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ASTM A789 S32906 Super Duplex Stainless Steel Pipe Introduction
ASTM A789 UNS S32906 is a super duplex stainless steel with a mixed microstructure of ferrite and austenite, providing an excellent combination of high strength and outstanding corrosion resistance. Its high chromium, molybdenum, and nitrogen content yields a Pitting Resistance Equivalent Number (PREN) typically above 42, making it ideal for aggressive chloride-containing environments such as seawater, chemical process streams, and sour oil and gas applications. The alloy is designed for seamless and welded pipe intended for general corrosive service. It displays good weldability and formability while maintaining toughness down to sub-zero temperatures. The balanced composition suppresses harmful sigma phase formation during fabrication, ensuring reliable performance in demanding service conditions.
ASTM A789 S32906 Super Duplex Stainless Steel Pipe Chemical Composition
Typical chemical composition in accordance with ASTM A789/A789M for UNS S32906. Single values are maximum unless otherwise indicated. The balance of the composition is iron. Minor variations are permissible within the standard limits to optimize the ferrite–austenite balance and corrosion resistance.
| Chemical Element | Standard Value | Remarks |
|---|---|---|
| Carbon (C) | max 0.030 | |
| Silicon (Si) | max 0.80 | |
| Manganese (Mn) | 0.80 - 1.50 | |
| Phosphorus (P) | max 0.030 | |
| Sulfur (S) | max 0.020 | |
| Chromium (Cr) | 28.0 - 30.0 | Key element for corrosion resistance |
| Nickel (Ni) | 5.8 - 7.5 | Austenite stabilizer |
| Molybdenum (Mo) | 1.50 - 2.60 | Enhances pitting resistance |
| Nitrogen (N) | 0.30 - 0.40 | Increases strength and pitting resistance |
| Iron (Fe) | Balance |
ASTM A789 S32906 Super Duplex Stainless Steel Pipe Thermal and Electrical Physical Properties
Typical physical properties for solution-annealed UNS S32906 super duplex stainless steel. These values are representative for engineering calculations and may exhibit slight variations depending on exact composition and heat treatment condition. Data at room temperature unless otherwise indicated.
| Performance Item | Standard Requirement Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.8 | g/cm³ | 20 °C |
| Elastic Modulus (E) | 200 | GPa | 20 °C |
| Shear Modulus (G) | 77 | GPa | 20 °C |
| Poisson's Ratio (ν) | 0.30 | - | 20 °C |
| Thermal Expansion Coefficient (α) | 10.5 | 10⁻⁶/K | 20 - 100 °C |
| Thermal Expansion Coefficient (α) | 11.5 | 10⁻⁶/K | 20 - 200 °C |
| Thermal Expansion Coefficient (α) | 12.5 | 10⁻⁶/K | 20 - 300 °C |
| Thermal Conductivity (λ) | 15 | W/(m·K) | 20 °C |
| Thermal Conductivity (λ) | 17 | W/(m·K) | 100 °C |
| Thermal Conductivity (λ) | 19 | W/(m·K) | 200 °C |
| Thermal Conductivity (λ) | 21 | W/(m·K) | 300 °C |
| Specific Heat Capacity | 500 | J/(kg·K) | 20 °C |
| Electrical Resistivity (ρₑ) | 0.8 | μΩ·m | 20 °C |
ASTM A789 S32906 Super Duplex Stainless Steel Pipe Mechanical Properties
Minimum mechanical properties required by ASTM A789/A789M for S32906 super duplex stainless steel pipe at room temperature. Tests are performed on solution-annealed material. The listed values represent the standard requirements; actual values may be higher and can vary with product form and pipe wall thickness.
| Performance Item | Standard Required Value | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | min. 750 | MPa (ksi) | Room temperature, longitudinal direction |
| Yield Strength (0.2% offset, ReH) | min. 550 | MPa (ksi) | Room temperature, longitudinal direction |
| Elongation (A) | min. 25 | % | Gauge length 50 mm (2 in.) or 4D |
| Brinell Hardness | max. 310 | HBW | As per ASTM E10, typical load 3000 kgf |
| Rockwell C Hardness | max. 32 | HRC | As per ASTM E18 |
ASTM A789 S32906 Super Duplex Stainless Steel Pipe Completely Equivalent Material Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A789/A789M | S32906 (UNS S32906) | Seamless and welded ferritic/austenitic stainless steel tubing |
| European Union | EN 10088-1, EN 10088-3, EN 10216-5, EN 10217-7 | X2CrNiMoN29-7-2 (1.4477) | Sheet, plate, seamless and welded tubes |
| International | ISO 9328-5:2018 | X2CrNiMoN29-7-2 | Stainless steels for pressure purposes – technical delivery conditions for seamless tubes |
| China | GB/T 20878-2007, GB/T 1220-2007, GB/T 3280-2015 | 022Cr29Ni7Mo2N (S32906) | Wrought stainless steel bars, plates, strips |
ASTM A789 S32906 Super Duplex Stainless Steel Pipe Application Introduction
S32906 super duplex stainless steel pipe excels in environments where high strength and excellent resistance to pitting, crevice corrosion, and stress corrosion cracking are required. Its primary use is in chloride-rich media such as seawater, brine, and chemical process fluids. The material is also suitable for sour service in oil & gas production complying with NACE MR0175/ISO 15156. Typical applications range from thin-walled heat exchanger tubes to thick-walled subsea piping.
Product Applications: Seamless and welded heat exchanger tubes, Hydraulic and instrumentation tubing, Seawater lift pipes and risers, Flue gas desulfurization scrubber piping, Chemical injection lines
Processed into products: Tube-to-tubesheet joints in heat exchangers, Pipe spools and fittings (elbows, tees, reducers), Flanges (weld neck, blind, spectacle blind), Valve stems and bodies for corrosive media, Pump shafts and sleeves in seawater service, Dual-certified pipe for pressure vessels
Application industries: Chemical Processing (nitric acid, chlorides, organic acids), Oil & Gas (subsea manifolds, topside piping, downhole tubing in sour wells), Desalination (reverse osmosis high-pressure piping, evaporator tubes), Marine Engineering (seawater cooling systems, fire water lines, pump columns), Pulp & Paper (digester tanks, liquor heaters)
ASTM A789 S32906 Super Duplex Stainless Steel Pipe Closely Related/Similar Substitute Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA/Global | ASTM A790/A789 | S32750 (UNS S32750, 2507) | Super duplex with PREN >40, higher strength but lower workability than S32906 |
| USA/Global | ASTM A790/A789 | S32760 (UNS S32760, Zeron 100) | Super duplex with W and Cu addition, PREN >40, good for aggressive media |
| USA/Global | ASTM A240/A789 | S32550 (UNS S32550, Ferralium 255) | Duplex with lower Cr but higher Cu, good corrosion resistance, lower cost |
| European Union | EN 10088-3 | X2CrNiMoN25-7-4 (1.4410) | Super duplex, similar PREN but different Cr-Ni-Mo balance |
| Japan | JIS G 3459 | SUS329J4L (UNS S32550) | Not a full equivalent; lower corrosion resistance than S32906 |
Notes:
For best corrosion performance, solution annealing to achieve the optimal ferrite–austenite ratio (close to 50/50) and rapid cooling after welding are essential. Avoid prolonged exposure in the temperature range 600–950°C to prevent sigma phase embrittlement. Subject to customer–supplier agreement, supplementary testing such as intergranular corrosion test per ASTM A262 Practice E or critical pitting temperature per ASTM G48 Method A may apply. Manufacturing processes must ensure sound welded joints with low heat input to preserve the duplex structure.
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