Super Duplex S32760
S32760 is a 25Cr-7Ni-3.5Mo-0.7W super duplex stainless steel that includes both tungsten and copper alongside molybdenum. This gives it a PREN above 40 and better resistance to reducing acid environments than tungsten-free super duplex grades.
1. Chemical Composition
The table below lists the elemental limits for S32760. The tungsten and copper additions are what separate this grade from other super duplex alloys.
| Grade | C | Mn | P | S | Si | Cr | Ni | Mo | N | W |
| S32760 | ≤ 0.03 | ≤ 1.0 | ≤ 0.03 | ≤ 0.01 | ≤ 1.0 | 24.0–26.0 | 6.0–8.0 | 3.0–4.0 | 0.2–0.3 | W 0.5–1.0 |
2. Mechanical Properties
These minimum mechanical values apply to S32760 in the solution-annealed condition. They cover seamless pipes and tubes intended for high-pressure service.
| Grade | Condition | Tensile Strength Min, MPa (ksi) | Yield Strength Min, MPa (ksi) | Elongation Min, % | PREN |
| S32760 | Annealed | ≥ 750 (109) | ≥ 550 (80) | ≥ 25% | ≥ 40 |
3. Equivalent Grade
This table maps S32760 to its international equivalents, so engineers can identify the correct designation when sourcing across different regional standards.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| Super Duplex Steel 32760 | S32760 | — | — | — | X2CrNiMoCuWN25-7-4 | 1.4501 | — |
4. Key Technical Advantages
- Tungsten-Boosted Corrosion Resistance: The 0.5–1.0% W works with molybdenum to strengthen pitting resistance in reducing acid environments, particularly hydrochloric and dilute sulfuric acid media where S32750 may fall short.
- Copper Addition for Reducing Media: The 0.5–1.0% Cu improves resistance to sulfuric acid and other reducing chemical environments. This extends the operating range beyond copper-free super duplex grades.
- Dual-Phase Microstructure Toughness: The balanced ferrite-austenite ratio (approximately 50:50) delivers impact toughness above requirements at sub-zero temperatures while keeping tensile and yield strength high.
- Technical Note: S32760 is commercially available as Zeron 100. Its welding consumables must be matched specifically; the tungsten and copper content requires filler metals designed for this grade. Post-weld solution annealing is recommended for critical corrosion service.
5. Common Manufacturing Standards
- ASTM A790: Covers seamless and welded ferritic/austenitic (duplex) stainless steel pipe including UNS S32760 for pressure service applications.
- ASTM A789: Covers seamless and welded ferritic/austenitic stainless steel tubing for general corrosive service, including UNS S32760, with emphasis on stress corrosion cracking resistance.
- DIN EN 10216-5: Covers seamless pressure tubes in austenitic-ferritic (duplex) stainless steels, including EN 1.4501 which is the European equivalent of S32760.
- GB/T 21833: Chinese standard for duplex stainless steel seamless pipes. S32760 is sourced against ASTM or EN specifications in most GB-aligned projects.
- NACE MR0175 / ISO 15156: S32760 is listed as a qualifying material for sour service (H2S-containing environments) subject to hardness and heat treatment requirements.
Manufacturing Standards Comparison Table:
| Standard | GB | EN/DIN | JIS | GOST |
| ASTM A790 (Pipe) | GB/T 21833 | EN 10216-5 (1.4501) | - | - |
| ASTM A789 (Tube) | GB/T 21833 | EN 10216-5 (1.4501) | - | - |
6. Primary Applications
- Offshore Topside Piping: S32760 is used for process piping and manifolds on FPSO vessels and fixed platforms where both mechanical loads and chloride/H2S exposure drive material selection.
- Chemical Injection Systems: High-pressure tubing and fittings for injecting chemicals into sour gas systems, using S32760 because it meets NACE MR0175 requirements for this service.
- Seawater Cooling Systems: Heat exchanger shells and tube bundles in once-through seawater cooling circuits where biofouling and crevice corrosion are primary concerns.
- Acid Gas Scrubbing: Absorber towers and associated piping in sulfur recovery and amine treatment units handling mixed reducing and oxidising streams.
- Pump and Valve Bodies: Castings and wrought components in chemical process pumps that need erosion-corrosion resistance in abrasive slurries alongside high strength.