ASTM A789 UNS S32760 tube is a super duplex stainless steel tube specification for general corrosion-resistant and high-strength applications. UNS S32760 (also known as Zeron 100 or EN 1.4501) is a high-performance super duplex grade offering a balanced austenitic-ferritic microstructure with enhanced alloying additions of tungsten and copper.
This grade delivers approximately twice the yield strength of common austenitic grades like 316L, combined with exceptional resistance to chloride stress corrosion cracking (SCC), pitting, crevice corrosion, and erosion corrosion. The addition of tungsten and copper provides superior performance in aggressive sour service (H₂S), seawater, and acidic environments.
These tubes are widely used in offshore oil & gas, subsea systems, heat exchangers, hydraulic instrumentation lines, desalination plants, and chemical processing where the highest level of corrosion resistance and mechanical strength is required.
Key Features
| Feature | Description |
|---|
| Standard | ASTM A789 / ASME SA789 |
| Grade | UNS S32760 (EN 1.4501 / Zeron 100 equivalent) |
| Type | Super Duplex Stainless Steel |
| Construction | Seamless and welded |
| Microstructure | Austenitic + Ferritic (≈50/50 dual-phase) |
| Yield Strength | ≥550 MPa (~2× 316L, 20% higher than 2205) |
| PREN | ≥40 (excellent pitting resistance) |
| Corrosion Resistance | Superior against SCC, pitting, crevice, erosion |
| Temperature Range | -50°F to 600°F (-46°C to 316°C) |
| Magnetic | Yes |
| Special Alloying | Tungsten (W) + Copper (Cu) for enhanced performance |
Equivalent Designations
| Standard | Grade |
|---|
| ASTM | UNS S32760 |
| EN | 1.4501 (X2CrNiMoCuWN25-7-4) |
| Trade Name | Zeron 100 (Rolls-Royce) |
| DIN | X2CrNiMoCuWN25-7-4 |
| BS | 2507 with Cu + W |
| NORSOK | MDS D48 (Super Duplex) |
Note: UNS S32760 is similar to UNS S32750 (Super Duplex 2507) but with the addition of tungsten (W) and copper (Cu) for improved corrosion resistance, particularly in acidic and sour service environments.
S32760 vs. S32750 Comparison
| Feature | UNS S32760 | UNS S32750 (2507) |
|---|
| Tungsten (W) | 0.50 – 1.00% | None |
| Copper (Cu) | 0.50 – 1.00% | ≤0.50% |
| PREN | ≥40 | ≥42 |
| Yield Strength (min) | ≥550 MPa | ≥550 MPa |
| Sour Service (H₂S) | Superior (with W+Cu) | Excellent |
| Acidic Environments | Superior (with Cu) | Good |
| Seawater Resistance | Excellent | Excellent |
| Erosion Resistance | Superior | Good |
Specifications & Size Range
| Parameter | Seamless Tube | Welded Tube |
|---|
| Outer Diameter (OD) | 6.0 mm – 219.1 mm | 6.0 mm – 219.1 mm |
| Wall Thickness (WT) | 0.5 mm – 15 mm | 0.5 mm – 8 mm |
| Length | 6.0 m random; custom lengths up to 12 m | 6.0 m random; custom lengths available |
| Tolerance | OD: ±0.1 mm (precision classes available) | OD: ±0.1 mm |
| Standard | ASTM A789 / ASME SA789 | ASTM A789 / ASME SA789 |
Chemical Composition (UNS S32760)
| Element | Content (%) |
|---|
| Carbon (C) | ≤0.030 |
| Chromium (Cr) | 24.0 – 26.0 |
| Nickel (Ni) | 6.0 – 8.0 |
| Molybdenum (Mo) | 3.0 – 4.0 |
| Tungsten (W) | 0.50 – 1.00 |
| Copper (Cu) | 0.50 – 1.00 |
| Manganese (Mn) | ≤1.00 |
| Silicon (Si) | ≤0.80 |
| Nitrogen (N) | 0.20 – 0.30 |
| Phosphorus (P) | ≤0.030 |
| Sulfur (S) | ≤0.010 |
| Iron (Fe) | Balance |
PREN (Pitting Resistance Equivalent Number) = %Cr + 3.3×%Mo + 16×%N ≥ 40
PREW (includes Tungsten) = %Cr + 3.3×(%Mo + 0.5×%W) + 16×%N ≥ 40
Mechanical Properties
| Property | Value |
|---|
| Tensile Strength (min) | ≥800 MPa (116 ksi) |
| Yield Strength (0.2% offset, min) | ≥550 MPa (80 ksi) |
| Elongation (min) | 25% |
| Hardness (max) | 310 HB / 32 HRC |
| Density | 7.75 – 7.80 g/cm³ |
| Modulus of Elasticity | 200 GPa (29.0 × 10⁶ psi) |
| Impact Strength (min) | 60 J at -46°C |
Corrosion Resistance Highlights
| Corrosion Type | Performance |
|---|
| Pitting / Crevice | PREN ≥40 → excellent resistance in high-chloride environments |
| Stress Corrosion Cracking (SCC) | Very high resistance in chloride and H₂S environments |
| Sour Service (H₂S) | Superior with W+Cu addition; fully NACE MR0175 / ISO 15156 compliant |
| General Corrosion | Outstanding in organic and inorganic acids |
| Seawater Resistance | Excellent; proven in long-term offshore service |
| Erosion Corrosion | Enhanced due to tungsten addition |
| Intergranular Corrosion | Low carbon content prevents sensitization |
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