ASTM A789 UNS S32750 Duplex Stainless Steel Tube For Offshore Subsea
ASTM A789 UNS S32750 super duplex stainless steel tube is a premium-grade product designed for the most demanding industrial applications. With a higher chromium, molybdenum, and nitrogen content than standard duplex grades (e.g., 2205/S31803), UNS S32750 offers superior strength and exceptional corrosion resistance, particularly in aggressive chloride-containing environments.
This tube is manufactured in accordance with ASTM A789, covering both seamless and welded ferritic/austenitic stainless steel tubing for general corrosion-resistant and high-temperature service.
Available Sizes – ASTM A789 UNS S32750 Tube
| Parameter | Range |
|---|---|
| Outer Diameter (OD) | 6.0 mm – 219 mm (1/8″ – 8″) |
| Wall Thickness (WT) | 0.5 mm – 15 mm |
| Length | Customized (up to 12 meters or as required) |
| Type | Seamless / Welded (cold finished) |
| End Finish | Plain end, beveled end, threaded, or grooved |
Note: For larger diameters (> 8″), refer to ASTM A790 UNS S32750 pipe.
Key Features of ASTM A789 UNS S32750 Super Duplex Tube
| Feature | Description |
|---|---|
| Ultra-High Strength | Minimum yield strength ≥ 550 MPa (80 ksi) – significantly stronger than 2205 and 316L |
| Exceptional Corrosion Resistance | Outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) |
| High PREN Value | PREN ≥ 40 – suitable for seawater and high-chloride environments |
| Chloride & Sour Service | Excellent performance in offshore, subsea, and H₂S-containing environments |
| Good Weldability | Weldable with proper filler metal (e.g., 2507/P100) and qualified procedures |
| Wide Temperature Range | Serviceable from -50°C to 300°C depending on application |
| Cost-Effective Alternative | Lower cost than nickel-based alloys (e.g., Inconel) while offering comparable or superior performance in many environments |
Chemical Composition (%, ASTM A789 UNS S32750)
| Element | UNS S32750 Requirements |
|---|---|
| Carbon (C) | ≤ 0.030 |
| Silicon (Si) | ≤ 0.80 |
| Manganese (Mn) | ≤ 1.20 |
| Chromium (Cr) | 24.0 – 26.0 |
| Nickel (Ni) | 6.0 – 8.0 |
| Molybdenum (Mo) | 3.0 – 5.0 |
| Nitrogen (N) | 0.24 – 0.32 |
| Copper (Cu) | ≤ 0.50 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.020 |
| Iron (Fe) | Balance |
Mechanical Properties (Typical)
| Property | Value |
|---|---|
| Tensile Strength | ≥ 800 MPa (116 ksi) |
| Yield Strength (0.2% offset) | ≥ 550 MPa (80 ksi) |
| Elongation | ≥ 15% |
| Hardness (HRC) | ≤ 32 |
| Density | 7.8 g/cm³ |
PREN = %Cr + 3.3 × %Mo + 16 × %N
UNS S32750 PREN: ≥ 40 (typically 42 – 45)
UNS S32750 vs Other Grades
| Grade | Type | Yield Strength (MPa) | PREN | Relative Cost | Best For |
|---|---|---|---|---|---|
| 316L | Austenitic | ≥ 170 | 24 – 26 | Low | Mild corrosive environments |
| 2205 / S31803 | Standard Duplex | ≥ 450 | 30 – 38 | Medium | General industrial, brackish water |
| UNS S32750 | Super Duplex | ≥ 550 | ≥ 40 | High | Seawater, offshore, chemical processing |
Which one to choose?
316L – Basic corrosion resistance, low cost, non-magnetic.
2205 / S31803 – Good balance of strength, corrosion resistance, and cost.
S32750 – Maximum performance for extreme environments – offshore, subsea, high-chloride, and sour service.
Applicable Standards
| Standard | Description |
|---|---|
| ASTM A789 | Seamless and welded ferritic/austenitic stainless steel tubing |
| ASME SA789 | Boiler and pressure vessel code |
| ASTM A790 | Seamless and welded pipe (larger diameters) |
| EN 10216-5 | European standard for duplex steel tubes |
| EN 10217-7 | Welded duplex steel tubes |
| NACE MR0175 / ISO 15156 | Suitable for sour service (H₂S environments) |
| API | Applicable for oil and gas industry |
| Industry | Typical Applications |
|---|---|
| Oil & Gas (Offshore & Subsea) | Umbilicals, control lines, hydraulic lines, subsea manifolds, and flowlines |
| Chemical & Petrochemical | Heat exchangers, pressure vessels, reactor piping, and process tubing |
| Marine & Shipbuilding | Seawater cooling systems, ballast water treatment, and desalination plants |
| Pulp & Paper | Bleaching systems and digesters in aggressive environments |
| Water Treatment | Reverse osmosis (RO) high-pressure tubing, brine handling |
| Flue Gas Desulfurization (FGD) | Scrubber systems in power plants |
| Pharmaceutical & Food | High-purity and corrosion-resistant applications |
FAQ – ASTM A789 UNS S32750 Super Duplex Tube
Q: What is the difference between UNS S32750 and UNS S32760?
A: Both are super duplex grades. S32760 typically contains small amounts of tungsten (W) and copper (Cu), offering slightly better corrosion resistance in certain environments. S32750 is more common in ASTM A789 tubing applications.
Q: Is UNS S32750 suitable for seawater applications?
A: Yes. With PREN ≥ 40, S32750 is specifically designed for seawater and high-chloride environments, including offshore and subsea applications.
Q: Can UNS S32750 tube be welded?
A: Yes, but requires proper filler metal (e.g., 2507/P100) and qualified welding procedures. We recommend consulting our technical team for specific welding parameters.
Q: Is UNS S32750 magnetic?
A: Yes, due to its ferrite content (approximately 40-60%), S32750 is magnetic – unlike fully austenitic grades like 316L.
Q: What is the difference between ASTM A789 and ASTM A790?
A: ASTM A789 covers tubing (typically smaller diameters up to 8″), while ASTM A790 covers pipe (larger diameters). Both can be used for UNS S32750.
Q: Do you provide cutting and tube processing services?
A: Yes, we offer custom cutting, beveling, bending, and end finishing per your requirements.
Please provide your required size (OD × WT), quantity, length, and delivery port. Our team will reply within 24 hours with a competitive price and technical datasheet.
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