Home > Welded Pipes > Duplex & Super Duplex Welded Pipes
Inox Steel India is a leading manufacturer and global supplier of Duplex and Super Duplex Welded Pipes in grades UNS S31803, S32205 (Duplex 2205) and UNS S32750 (Super Duplex 2507), produced as per ASTM A790 and ASTM A928 standards.
These high-strength, corrosion-resistant welded pipes are engineered for extreme service environments involving high-pressure, high-chloride, seawater, brine, acids, and critical offshore conditions.
Duplex & Super Duplex Welded Pipes combine ferritic and austenitic microstructures, offering twice the strength of conventional stainless steels, superior pitting resistance, and exceptional resistance to chloride stress corrosion cracking (SCC). With PREN values exceeding 35 (Duplex) and 40+ (Super Duplex), these pipes are ideal for aggressive and corrosive environments.
Inox Steel India manufactures welded duplex & super duplex pipes using GTAW root + SAW/ERW multi-pass welding, followed by solution annealing and pickling to ensure uniform corrosion resistance and mechanical properties equal to or better than the base metal.
Our products are supplied to offshore platforms, desalination plants, chemical processing units, and marine engineering companies worldwide.
Duplex (22% Cr) and Super Duplex (25% Cr) stainless steels are advanced alloys designed to deliver:
These welded pipes are used when stainless steel (304/316) is not adequate for corrosive or high-pressure conditions.
ASTM A928 governs the welded pipe manufacturing, NDT, weld class requirements, and solution annealing conditions necessary to maintain duplex phase balance.
Types of Duplex & Super Duplex Welded Pipes We Manufacture
1️⃣ Raw Material Verification
Plates/coils undergo PMI to confirm duplex/super duplex chemistry (Cr, Mo, N levels).
2️⃣ Plate Edge Preparation
Bevelled edges ensure optimal weld penetration.
3️⃣ Forming / Rolling
Plates are rolled into cylindrical shape maintaining duplex phase balance.
4️⃣ Root Welding – GTAW (TIG)
High-quality, controlled root pass for defect-free internal weld.
5️⃣ Multi-Pass Welding – SAW/ERW
Sequential weld passes achieve full fusion & mechanical strength.
6️⃣ Solution Annealing
Critical step to restore duplex ferrite-austenite balance.
7️⃣ Pickling & Passivation
Removes heat tint, restores corrosion resistance & passive layer.
8️⃣ Mandatory NDT – As per ASTM A928
Includes UT, RT (depending on class), DP, weld inspection & dimensions.
9️⃣ Hydrostatic Testing
Confirms pipe integrity under pressure.
🔟 Final Inspection & Marking
Heat number, grade, OD/WT, ASTM standard, and duplex phase condition.
Offshore & Subsea Engineering
Risers, umbilicals, subsea piping, and high-pressure flowlines.
Desalination Plants
Seawater intake, brine discharge & evaporator piping.
Chemical Processing Industries
Duplex & Super Duplex pipes used for reactors, mixers, acid transfer & chloride-rich processes.
Oil & Gas (Onshore & Offshore)
Used in separators, injection lines, gas cleaning systems & umbilical tubing.
Heat Exchangers & Pressure Vessels
Corrosion-resistant tubes for thermal cycles & high-pressure equipment.
Marine & Shipbuilding
Ballast water systems, cooling water pipelines & exhaust scrubbers.
Pulp & Paper Industry
Highly corrosive bleaching environments require duplex performance.
Duplex (2205 / UNS S31803 / S32205) and Super Duplex (2507 / UNS S32750) welded pipes are designed for high-pressure, high-strength, and highly corrosive service conditions. Their ferritic–austenitic dual-phase structure offers twice the yield strength of austenitic stainless steels and exceptional resistance to chloride-induced pitting, crevice corrosion, and Stress Corrosion Cracking (SCC).
Manufactured according to ASTM A790 (general duplex pipes) and ASTM A928 (welded duplex pipes), Inox Steel India ensures each pipe undergoes strict welding, solution annealing, pickling, and NDT requirements that protect duplex phase balance and corrosion resistance.
These pipes are crucial for offshore platforms, desalination plants, chemical processing, pulp & paper mills, and marine engineering applications.
| Parameter / Property | Duplex 2205 (UNS S31803 / S32205) | Super Duplex 2507 (UNS S32750) | Standard Requirements (ASTM A790 / A928) |
|---|---|---|---|
| Material Type | Duplex Stainless Steel | Super Duplex Stainless Steel | Duplex/Super Duplex Welded Pipes |
| Manufacturing Standard | ASTM A790 / A928 | ASTM A790 / A928 | ASTM A790 (seamless/welded) / A928 (welded only) |
| Key Alloy Composition | 22% Cr, 5–6% Ni, 3% Mo, N | 25% Cr, 7% Ni, 4% Mo, N | As per ASTM chemical limits |
| Corrosion Resistance | Excellent (pitting resistance ~35–38 PREN) | Exceptional (PREN > 40) | Mandatory corrosion performance |
| Strength Level | High Strength (2× austenitic SS) | Very High Strength | As per grade mechanical table |
| Temperature Resistance | Up to 280–315°C | Up to 280°C | As per ASTM allowable limits |
| Chloride Stress Corrosion Cracking | Highly Resistant | Extremely Resistant | Must pass ASTM tests |
| Weld Type | GTAW root + SAW/ERW | GTAW root + SAW/ERW | Weld integrity per ASTM A928 Class 1 / 2 / 3 |
| Heat Treatment | Solution Annealed | Solution Annealed | Mandatory solution annealing |
| Mechanical Strength (TS) | 620–800 MPa | 750–900 MPa | As per grade |
| Yield Strength (YS) | 450+ MPa | 550+ MPa | As ASTM specified |
| Density | 7.80 g/cm³ | 7.85 g/cm³ | — |
| Corrosion Tests | ASTM G48 Method A | ASTM G48 Method A | Mandatory pitting test |
| NDT Requirements | UT, RT, DP | UT, RT, DP | ASTM A928 requires RT/UT |
| OD Range | ½” – 24″ | ½” – 24″ | Welded sizes as per A928 capability |
| Wall Thickness | SCH 10 – SCH 80 / Custom | SCH 10 – SCH 80 / Custom | As specified |
| Typical Applications | Offshore, desalination, heat exchangers | Subsea, chemical injection, seawater systems | Corrosion + pressure service |
| Surface Finish | Pickled & Passivated | Pickled & Passivated | Required |
| Testing Documentation | PMI, MTC 3.1 / 3.2 | PMI, MTC 3.1 / 3.2 | ASTM-compliant |
| HSN Code | 7304.41 / 7304.51 | 7304.41 / 7304.51 | Duplex/Super Duplex SS pipes |
✔ Duplex Stainless Steel — UNS S31803 / S32205 (2205)
✔ Super Duplex Stainless Steel — UNS S32750 (2507)
✔ Applicable Standards
✔ For high-pressure seawater piping / desalination lines
Use Super Duplex S32750 (2507)
Exceptional chloride resistance + very high strength.
✔ For offshore platforms & risers
Use Duplex 2205 (S31803/S32205)
Strong + highly resistant to SCC and pitting.
✔ For heat exchangers & pressure vessels
Use Duplex 2205
Good weldability + corrosion resistance.
✔ For subsea umbilicals and injector lines
Use Super Duplex 2507
Superior mechanical strength under deepwater pressure.
✔ For bleaching & chemical processing plants
Use Duplex 2205
Resists corrosive solutions and chloride-rich environments.
| Application | Recommended Grade | Reason |
|---|---|---|
| Seawater intake & discharge lines | Super Duplex S32750 | Best chloride corrosion resistance |
| Offshore risers & subsea pipelines | Duplex S31803 / S32205 | High strength + SCC resistance |
| Chemical reactors & scrubbers | Duplex 2205 | Corrosion + stress handling |
| High-pressure heat exchangers | 2205 / 2507 | Strength + thermal performance |
| Desalination RO plants | Super Duplex 2507 | Pitting & crevice corrosion resistance |
| Pulp & paper bleaching lines | Duplex 2205 | Resistant to corrosive chemicals |
| Parameter | Capability |
|---|---|
| Outside Diameter (OD) | ½” – 24” |
| Wall Thickness | SCH 10 – SCH 80 / Custom |
| Length | 6 m / 12 m |
| Weld Type | GTAW root + SAW/ERW multi-pass |
| Heat Treatment | Solution Annealed |
| Ends | Bevelled / Plain |
| Surface Finish | Pickled & Passivated |
| Duplex / Super Duplex Grade | Price (INR/kg) | Price (USD/kg) |
|---|---|---|
| Duplex 2205 (S31803/S32205) | ₹ 650 – ₹ 950 | $ 8 – $ 12 |
| Super Duplex 2507 (S32750) | ₹ 850 – ₹ 1,400 | $ 11 – $ 18 |
| Welded Duplex Pipe (ASTM A928) | ₹ 700 – ₹ 1,200 | $ 9 – $ 15 |
| Welded Super Duplex Pipe | ₹ 900 – ₹ 1,600 | $ 12 – $ 20 |
Prices vary based on OD, thickness, NDT class, ASTM A928 requirement, heat treatment, and project documentation.
7304.41 / 7304.51 — Duplex & Super Duplex Stainless Steel Pipes
✔ Mandatory NDT – As per ASTM A928
✔ Mechanical Testing
✔ Mechanical Tests
✔ Corrosion Testing
✔ PMI (Positive Material Identification)
Ensures correct Cr–Mo–N composition.
✔ Hydrostatic Testing
All welded duplex pipes undergo hydro test.
✔ Documentation
✔ Documentation
Inox Steel India exports Duplex & Super Duplex Welded Pipes to:
Middle East:
Africa:
Europe:
Americas:
Asia Pacific:
Used in offshore, desalination, chemical, pulp & paper, and oil & gas industries.
Duplex and Super Duplex welded pipes demand high welding precision, correct ferrite–austenite balance, and strict corrosion testing to perform under extreme chloride and pressure conditions. Inox Steel India is one of the leading manufacturers with deep expertise in duplex metallurgy and ASTM A928 welding standards.
What makes our Duplex & Super Duplex Welded Pipes superior:
Our duplex welded pipes are trusted in some of the world’s harshest operating environments.
Offshore Oil & Gas Platforms
High-strength, corrosion-resistant pipes for risers, manifolds, separators & subsea lines.
Desalination & Marine Water Systems
Super Duplex 2507 used for seawater intake/outfall, brine disposal & evaporator piping
Chemical & Petrochemical Plants
Duplex 2205 used in reactors, tanks, mixers, high-acid & chloride-rich processes.
Pulp & Paper Industry
Resistant to corrosive bleaching chemicals and chloride solutions.
Heat Exchangers & Pressure Vessels
Duplex & Super Duplex used for high-pressure, heat cycling equipment.
Firefighting, Cooling & Utility Systems
High-strength duplex pipes offer extended durability and corrosion life.
Duplex & Super Duplex Welded Pipes require corrosion-safe and export-grade protection.
✔ Standard Export Packaging Includes:
✔ For Marine & Offshore Exports:
✔ Ports of Dispatch:
JNPT • Mundra • Hazira • Chennai
✔ Global Destinations:
Gulf (GCC), Europe, USA, South Korea, Southeast Asia, Africa
Looking for Duplex or Super Duplex Welded Pipes for seawater, chemical, offshore, or high-pressure applications?
52-A, Mulji Thackersi Bldg, Islampura Street, Shop No. 10, Near Alankar Cinema, Mumbai – 400 004
steel@inoxsteelindia.in
+91 9930796690
ASTM A928 — mandatory weld testing & solution annealing.
Yes — Super Duplex 2507 is one of the best alloys for seawater & brine.
Yes — Ferrite scope testing is included in the documentation.
Yes — RT/UT is performed as per ASTM A928 Class requirement.
Yes — Inox Steel India exports to 45+ countries with complete documentation.
We provide full technical support, NDT documentation, ferrite test reports, and export packing.