In today’s industries, where severe pressure, aggressive environments, and strength and structural integrity are day-to-day occurrences, Super Duplex Stainless Steel is a major material. With exceptional corrosion resistance, mechanical strength, and ease of maintenance, super duplex stainless steel is the first choice in a variety of industrial applications such as offshore platforms, chemical and petrochemical plants, desalination plants, and high-pressure piping systems.
If you’re sourcing super duplex stainless steel sheets, plates, super duplex flanges or you want super duplex pipe, you have found the right article that will explore its properties, its uses and guidelines to buy super duplex products.
What Is Super Duplex Stainless Steel?
Super Duplex Stainless Steel is a high-alloy material that has approximately 50% austenite and 50% ferrite in its microstructure, which enhances its performance characteristics. A duplex structure provides a good level of corrosion resistance to chloride pitting and crevice corrosion in corrosive environments.
Common Designations:
- UNS S32750
- UNS S32760
- EN 1.4410
- ASTM A240 (for plates/sheets)
- ASTM A182 (for flanges)
Its popularity is founded upon better performance than both austenitic materials (such as 316L) and super duplex materials in critical operations.
Super Duplex Chemical Composition (UNS S32750/S32760)
| Element | Typical Range (%) |
| Chromium (Cr) | 24 – 26 |
| Nickel (Ni) | 6 – 8 |
| Molybdenum (Mo) | 3 – 5 |
| Nitrogen (N) | 0.24 – 0.32 |
| Manganese (Mn) | ≤ 1.2 |
| Carbon (C) | ≤ 0.030 |
| Iron (Fe) | Balance |
In super duplex materials, the combination of high levels of chromium, molybdenum, and nitrogen provides the material with a highly pitting resistance equivalent number (PREN), which is often over 40.
Mechanical Properties of Super Duplex Steel
| Property | Value |
| Density | 7.8 g/cm³ |
| Tensile Strength | 770–850 MPa |
| Yield Strength | ≥ 550 MPa |
| Elongation | ≥ 15% |
| Hardness | ≤ 32 HRC |
| Impact Toughness | Excellent (even at -50°C) |
These aspects make super duplex materials well suited for high resistant conditions and for full corrosion forces.
Where Is Super Duplex Stainless Steel Used?
| Industry | Applications |
| Oil & Gas | Subsea pipelines, heat exchangers, separators |
| Petrochemical | Pressure vessels, scrubbers, heat exchangers |
| Desalination | Evaporator tubes, brine heaters |
| Marine | Propeller shafts, hull reinforcements |
| Pulp & Paper | Digesters, bleach washers |
| Power Plants | Superheaters, water treatment lines |
Super duplex materials are widely used in aggressive environments due to their superb resistance to corrosion and high strength.
Common Product Forms of Super Duplex Steel
| Form | Standard/Spec | Application |
| Super Duplex Stainless Steel Sheets and Plates | ASTM A240 | Structural panels, tanks, pressure vessels |
| Super Duplex Flanges | ASTM A182 F53/F55 | Piping connections in high-pressure systems |
| Super Duplex Pipes | ASTM A790 / A928 | Oil & gas piping, marine exhaust |
| Super Duplex Fittings | ASTM A815 | Pipe couplings, reducers, elbows |
| Super Duplex Round Bars | ASTM A479 | Shafts, valve stems, fasteners |
These materials are frequently certified with NACE MR0175, PED, and ISO 9001 for use worldwide.
Super Duplex Grades Overview
| Grade | UNS Number | PREN | Common Use |
| S32750 | UNS S32750 | >41 | Oil & gas pipelines |
| S32760 | UNS S32760 | >42 | Desalination & marine |
| S39274 | UNS S39274 | >45 | Aggressive sour service |
| F53 | ASTM A182 | >40 | High-pressure flanges |
| F55 | ASTM A182 | >42 | Offshore and chemical plants |
Super duplex materials have a PREN (pitting resistance equivalent number) of over 40, which means that they have outstanding corrosion resistance when exposed to seawater.
Why should you specify super duplex for your use?
1. Strength and Durability:
It can provide yield strengths that are up to double that of austenitic stainless steels, such as 304 or 316. When creating pressure vessels and piping, this strength allows for thinner walls.
2. Corrosion Resistance:
Super duplex has superior resistance to stress corrosion cracking due to chlorides, as well as pitting and general corrosion.
3. Cost-Effective Over the Life Cycle:
Super duplex materials can be more expensive than 316L material upfront, but their service life, maintenance (time and cost), and downtime are lower in comparison to austenitic stainless steels, resulting in a lower total cost of ownership.
4. Easy to Maintain:
Super duplex pipes and fittings do not need to be heavily maintained as a result of their resistance to scaling, corrosion, and erosion.
Super Duplex vs Other Stainless Steels
| Property | 316L | Duplex 2205 | Super Duplex S32750 |
| Yield Strength (MPa) | 290 | 450 | 550–600 |
| PREN | ~24 | ~35 | >41 |
| Chloride SCC Resistance | Moderate | Good | Excellent |
| Cost | Low | Medium | High (but value-rich) |
| Lifespan in Aggressive Environments | Short | Medium | Long |
Installation & Maintenance Recommendations
- When welding super duplex, make sure to use matching filler materials such as ER2594 or ENiCrMo-3.
- Avoid keeping the temperature above 250°C for an extended period to avoid embrittlement.
- A post-weld heat treatment is not generally necessary and can save you the time and cost of fabrication.
- After installation, use pickling and passivation for surface protection.
In Need of Super Duplex Stainless Steel Products?
Are you looking for super duplex stainless steel sheets, plates, flanges, or pipe that are certification-compliant?
Connect with certified suppliers based in India that supply:
- Materials conforming to ASTM and ASME standards
- Custom fabrication and cut-to-length capabilities
- Packaging and logistics support are ready for export
- Third-party inspection approvals
Improve your company’s industrial base with materials developed for extreme environments and longevity.
Conclusion
Super duplex stainless steel is not just another alloy it is a workhorse of the industrial world that was developed for extreme environments where strength, corrosion properties, and overall value were essential. From super duplex flanges for a petrochemical pipeline, to easily maintained super duplex pipe for a desalination plant, the reliability of the material pays off in both performance and longevity.
Always select a reputable certified super duplex stainless steel supplier for your compliance project.