Home > Seamless Tube > Duplex & Super Duplex Seamless Tubes
Inox Steel India supplies premium Duplex and Super Duplex Stainless Steel Seamless Tubes, engineered for applications where conventional stainless steel fails due to chloride stress corrosion cracking, pitting, crevice corrosion or high-pressure seawater environments. Manufactured according to ASTM A789 / A790, these tubes combine high mechanical strength with exceptional corrosion resistance, making them ideal for the toughest industrial conditions.
Duplex (S31803/S32205) and Super Duplex (S32750/S32760) materials feature a balanced ferritic–austenitic microstructure, offering up to 2× the strength of 300-series stainless steels with significantly higher resistance to chlorides and corrosive media. This makes them the preferred choice for critical components in offshore platforms, desalination plants, subsea systems, chemical processing loops, refinery units and marine pipelines.
✔ Duplex & Super Duplex Grades Supplied
These grades offer high pitting resistance (PREN 28–45+), low thermal expansion, strong fatigue resistance and excellent weldability—making them ideal for high-pressure and offshore environments.
Our Duplex & Super Duplex seamless tubes are produced using hot finished & cold drawn processes, followed by controlled solution annealing to ensure consistent ferrite-austenite balance, enhanced mechanical strength and stable corrosion performance in harsh media including chlorides, sulfides, seawater, high-pressure brines and acidic process streams.
Inox Steel India supplies these tubes to leading EPC contractors, oil & gas companies, desalination plants, marine engineering firms, chemical plants and OEM equipment manufacturers across India, GCC, Europe, Africa and Southeast Asia.
| Parameter | Duplex & Super Duplex Seamless Tubes |
|---|---|
| Applicable Standards | ASTM A789 (Seamless & Welded Tubes) • ASTM A790 (Seamless Pipe) • EN 10216-5 • ISO / NORSOK MDS |
| Grades Available | Duplex: S31803 / S32205 • Super Duplex: S32750 (2507) / S32760 |
| Material Structure | Ferritic–Austenitic (50/50 Duplex Microstructure) |
| Manufacturing Process | Hot Finished Seamless (HFS) • Cold Drawn Seamless (CDS) • Solution Annealed |
| Size Range (OD) | 6 mm to 168 mm OD |
| Thickness Range | 0.8 mm to 12.7 mm |
| Length Options | 6m • 12m • Cut-to-Length • U-bent Tubes |
| Mechanical Properties | Tensile Strength: 620–800 MPa • Yield Strength: 450–550 MPa • Elongation: 25–30% |
| Temperature Capability | Service Range: –50°C to +300°C (higher for Super Duplex) |
| Heat Treatment | Solution Annealed (mandatory for corrosion stability) |
| Surface Finish | Annealed & Pickled • Bright Annealed • Clean ID Finish |
| Dimensional Tolerances | Tight tolerances as per ASTM A789/A790 |
| End Finish | PE • BE • Deburred |
| Corrosion Resistance | Excellent resistance to chlorides, pitting, crevice corrosion, erosion & high-pressure seawater |
| Pitting Resistance (PREN) | Duplex: 28–35 • Super Duplex: 40–45+ |
| Mandatory Testing | Hydro-Test • Eddy Current • Tensile • Hardness • Impact Test (Sub-zero optional) |
| Special Testing | ASTM G48 Pitting Test • Ferrite Content (35–65%) • PMI • NDT / UT • Microstructure Analysis |
| Documentation Provided | MTC EN 10204 3.1 • Chemical/Mechanical Test Reports • NDT Reports • Ferrite Test Report |
| Key Grade Benefits | S31803/S32205: Balanced strength + corrosion resistance • S32750/S32760: High strength + excellent chloride resistance |
| Typical Applications | Offshore Platforms • Desalination • Heat Exchangers • Chemical Processing • Oil & Gas • Marine Pipelines • High-Pressure Systems |
Duplex and Super Duplex stainless steels are specifically designed for environments requiring high mechanical strength, excellent stress corrosion cracking resistance, and extreme chloride resistance. Their high PREN values (28–45+) make them ideal for aggressive marine, seawater, chemical, and oil & gas environments.
🔹 1. Offshore & Subsea Oil & Gas Systems
High pressure and high chloride environments demand duplex microstructure.
Applications:
Best Grades: S32750 / S32760
🔹 2. Desalination & Marine Engineering
Super Duplex withstands warm seawater, chlorides, and brine at high pressure.
Used For:
Recommended: S32750 (2507) / S32760
🔹 3. Chemical & Petrochemical Plants
Duplex grades perform well against sulfides, chlorides, acids and mixed media.
Applications:
Preferred: S31803 / S32205 / Super Duplex for higher corrosion
🔹 4. Refinery & Power Plant Systems
Thermal cycling + pressure stability = Duplex requirement.
Applications:
Best Grades: S32205 / S32750
🔹 5. High-Strength Structural & Mechanical Tubing
Duplex offers up to 2× strength of SS 316, making it ideal for load-bearing systems.
Applications:
Recommended: S31803 / S32205
| Application | Recommended Grade | Why |
|---|---|---|
| General chemical processing | Duplex S31803/S32205 | Balanced strength + corrosion resistance |
| High chloride / seawater systems | Super Duplex S32750 | High PREN (40+) for pitting resistance |
| Subsea oil & gas | S32760 | Higher strength + superior pitting/crevice resistance |
| Heat exchangers (chloride-rich) | S32205 / S32750 | Thermal stability + SCC resistance |
| Acidic & mixed corrosive environments | S32760 | Best corrosion resistance in the family |
| Tube Type | OD Range | WT Range | Typical Use |
|---|---|---|---|
| Duplex S31803/S32205 | 6 – 114 mm | 0.8 – 10 mm | Chemical, refinery, heat exchangers |
| Super Duplex S32750/S32760 | 6 – 89 mm | 1 – 12 mm | Offshore, subsea, desalination |
| U-Bent Super Duplex Tubes | Custom | Custom | Heat exchangers & desalination units |
(Fully customized OD/WT available.)
| Grade | Price Range (₹/kg) | Notes |
|---|---|---|
| Duplex S31803/S32205 | ₹750 – ₹1,050 | Moderate chloride resistance |
| Super Duplex S32750 | ₹900 – ₹1,350 | High-strength offshore alloy |
| Super Duplex S32760 | ₹1,000 – ₹1,450 | Premium grade with maximum PREN |
| U-bent tubes | Add 10–20% | Heat exchangers & desalination |
Prices vary by OD, WT, NORSOK/MDS requirement & origin.
Duplex & Super Duplex tubes undergo specific testing to ensure correct microstructure and corrosion performance.
Mandatory Tests
Special Duplex Test Requirements
Documentation Supplied
Inox Steel India is a trusted supplier of Duplex & Super Duplex Seamless Tubes for severe-service environments where conventional stainless steel fails. Our tubes meet strict ASTM A789/A790 requirements and are manufactured with precise ferrite–austenite balance to ensure maximum corrosion resistance and long-term durability.
✔ What Makes Our Duplex & Super Duplex Tubes Superior
We are preferred by EPC contractors, desalination companies, offshore engineering firms, and oil & gas operators globally.
| Industry | Applications |
|---|---|
| Offshore Oil & Gas | Subsea lines, manifolds, control systems |
| Desalination Plants (MSF/MED/RO) | Brine heaters, pressure lines, evaporators |
| Marine & Shipbuilding | Cooling systems, piping, heat exchangers |
| Chemical Processing | Reactors, heat exchangers, corrosive loops |
| Refineries & Petrochemical | Furnace tubes, condensers, FGD systems |
| Power Plants | Heat recovery, seawater cooling, condensers |
Duplex and Super Duplex alloys are known for their exceptional reliability in chloride-rich and corrosive environments.
We export Duplex & Super Duplex seamless tubes to 40+ countries with premium packing suitable for marine & chemical-grade shipping.
Export Packaging Includes:
Major Export Markets:
UAE • Saudi Arabia • Qatar • Oman • Kuwait
Europe • Turkey • Singapore • Malaysia
South Africa • Nigeria • Egypt
USA (project-specific approvals)
We support engineers & procurement teams with:
✔ Grade selection for chloride & corrosive environments
✔ NORSOK / ASTM / ASME compliance guidance
✔ Heat exchanger & seawater system recommendations
✔ TPI coordination (SGS, BV, Lloyds, TÜV)
✔ Project-based pricing and fast dispatch
Request datasheets, ferrite test reports, and MTC samples.
52-A, Mulji Thackersi Bldg, Islampura Street, Shop No. 10, Near Alankar Cinema, Mumbai – 400 004
steel@inoxsteelindia.in
+91 9930796690
Duplex has moderate chloride resistance; Super Duplex has very high PREN (40+) for aggressive marine & chemical environments.
Correct ferrite range (35–65%) ensures corrosion resistance, weldability and mechanical strength.
Yes — S32750 and S32760 are among the best materials for warm seawater and high-pressure marine pipelines.
Yes, U-bent Duplex & Super Duplex tubes are supplied with controlled bending and solution annealing.
MTC 3.1, PMI, G48 test report, ferrite % report, microstructure report, NDT documents.
Inox Steel India supplies Duplex & Super Duplex Seamless Tubes in S31803, S32205, S32750 and S32760 as per ASTM A789/A790. Ideal for offshore, desalination, chemical processing and marine applications. High strength, excellent chloride resistance with full MTC 3.1.
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