Contact us now!

+91 9930796690

Home > Seamless Tube > Duplex & Super Duplex Seamless Tubes

Duplex & Super Duplex Seamless Tubes – High-Strength Corrosion-Resistant Tubing for Offshore, Desalination, Oil & Gas and Marine Applications

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.

Table of Contents

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

  • Duplex S31803 / S32205 – General chloride-resistant duplex grade
  • Super Duplex S32750 (2507) – High PREN value for severe marine exposure
  • Super Duplex S32760 – Superior resistance to pitting, crevice corrosion & erosion

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.

Master Technical Datasheet

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

Applications of Duplex & Super Duplex Seamless Tubes

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:

  • Subsea flowlines
  • Injection tubing
  • Manifold systems
  • Hydraulic control & umbilical tubing
  • Offshore topside piping

Best Grades: S32750 / S32760

🔹 2. Desalination & Marine Engineering

Super Duplex withstands warm seawater, chlorides, and brine at high pressure.

Used For:

  • MSF / MED desalination units
  • Brine heaters
  • High-pressure seawater lines
  • Evaporators & cooling systems

Recommended: S32750 (2507) / S32760

🔹 3. Chemical & Petrochemical Plants

Duplex grades perform well against sulfides, chlorides, acids and mixed media.

Applications:

  • Chemical reactors
  • Heat exchanger tubes
  • Acid processing loops
  • High-pressure piping

Preferred: S31803 / S32205 / Super Duplex for higher corrosion

🔹 4. Refinery & Power Plant Systems

Thermal cycling + pressure stability = Duplex requirement.

Applications:

  • Heat exchangers
  • Condensers
  • Furnace tubes
  • Flue gas desulfurization (FGD) units

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:

  • Offshore structural supports
  • Marine mechanical systems
  • Pressure vessel components

Recommended: S31803 / S32205

Material Selection Guide for Duplex & Super Duplex Tubes

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

Common Size Range Used (Indicative)

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.)

Indicative Pricing for Duplex & Super Duplex Seamless Tubes (India Market)

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.

Testing & Quality Compliance

Duplex & Super Duplex tubes undergo specific testing to ensure correct microstructure and corrosion performance.

Mandatory Tests

  • Hydrostatic Test
  • Eddy Current Test
  • Tensile & Hardness Tests
  • Flattening & Flaring

Special Duplex Test Requirements

  • ASTM G48 Pitting Test
  • Ferrite Content Measurement (35–65%)
  • Microstructure Examination
  • Impact Test (Charpy)
  • Intergranular Corrosion Test (IGC)
  • Ultrasonic Testing (UT)

Documentation Supplied

  • MTC EN 10204 3.1
  • Chemical & Mechanical Properties
  • Ferrite Test Report
  • NDT Reports
  • Heat Treatment Chart

Why Choose Inox Steel India for Duplex & Super Duplex Seamless Tubes

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

  1. Solution-annealed for stable ferrite–austenite structure (35–65% ferrite)
  2. Extremely high pitting resistance (PREN 28–45+)
  3. Excellent SCC (Stress Corrosion Cracking) resistance in chloride-rich media
  4. Up to 2× the strength of SS 316/317L
  5. High resistance to seawater, brine, sulfides, and acidic environments
  6. Available in U-bent, cut-length & custom fabrication
  7. Fully tested as per ASTM + NORSOK standards
  8. 100% traceability with MTC 3.1, NDT, and ferrite % reports

We are preferred by EPC contractors, desalination companies, offshore engineering firms, and oil & gas operators globally.

Industries & Applications We Serve

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.

Export Packaging & Global Supply

We export Duplex & Super Duplex seamless tubes to 40+ countries with premium packing suitable for marine & chemical-grade shipping.

Export Packaging Includes:

  • Heavy-duty hexagonal bundles with steel straps
  • HDPE wrapping for moisture-proofing
  • End caps for protection
  • Anti-corrosion oil (if required)
  • Wooden crates for U-bent tubes
  • Color-coded marking for grade & heat number

Major Export Markets:

UAE • Saudi Arabia • Qatar • Oman • Kuwait
Europe • Turkey • Singapore • Malaysia
South Africa • Nigeria • Egypt
USA (project-specific approvals)

Talk to Our Technical Team

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.

Inox Steel India

52-A, Mulji Thackersi Bldg, Islampura Street, Shop No. 10, Near Alankar Cinema, Mumbai – 400 004

Email

steel@inoxsteelindia.in

Phone

+91 9930796690

Frequently Asked Questions (FAQs)

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.