S32550 Duplex Stainless Steel Pipe

1. Exceptional Pitting and Crevice Corrosion Resistance: PRE (Pitting Resistance Equivalent) ≥ 36 due to high chromium (24–27%), molybdenum (2.0–4.0%), copper (1.50–2.50%), and nitrogen (0.10–0.25%) content, providing superior resistance in seawater, chlorides, and aggressive organic acids.

2. Superior Stress Corrosion Cracking Resistance: Excellent resistance to both chloride-induced SCC and sulfide-induced SSCC, significantly outperforming 316L and standard duplex grades in high-temperature, high-chloride environments.

3. Enhanced Resistance in Reducing Acid Environments – Copper Advantage: The addition of copper (1.50–2.50%) – the highest copper content among commercial duplex grades – provides exceptional corrosion resistance in sulfuric acid, phosphoric acid, and other reducing acid media, making S32550 the preferred duplex grade for hydrometallurgical applications.

4. Excellent Erosion-Corrosion Resistance: High hardness and strength combined with copper addition provide outstanding resistance to erosion, cavitation, and wear in high-velocity seawater, slurry, and pump applications where combined mechanical and corrosive attack occurs.

5. Ultra-High Mechanical Strength: Minimum yield strength of ≥ 550 MPa (approximately 2.5 times that of 316L), allowing for significant wall thickness reduction, weight savings, and cost optimization.

6. Good Weldability: Maintains balanced ferrite/austenite ratio in the weld zone when using proper welding procedures, matching filler metals (e.g., 255 or 2594), and controlled heat input.

7. Excellent Casting and Fabrication Characteristics: Originally developed as a casting grade (CD4MCu, CD3MCuN), S32550 offers good castability and is widely used for pumps, valves, and impellers, with seamless and welded pipe forms also available.

8. High Resistance to Galling and Seizing: The duplex structure provides superior resistance to galling compared to austenitic grades, making it ideal for valve stems, pump shafts, and threaded connections.

9. International Certification: Pipes can be certified by ABS, BV, DNV, LR, GL, RINA, CCS, KR, and NK, and comply with NORSOK M-630, ISO 17781, NACE MR0175/ISO 15156, and ASTM A995 (casting equivalent) standards.

Womic Steel’s S32550 duplex pipes conform to multiple international specifications for corrosive service, high-strength applications, and pressure systems:

These standards ensure that S32550 duplex pipes meet global requirements for chemical composition, balanced dual-phase microstructure, superior mechanical properties, corrosion resistance, testing, and dimensional accuracy.

l Note: S32550 (also known as 255 duplex or F61) is distinguished from other duplex grades by its highest copper content (1.50–2.50%) . This high copper content provides:

l Superior reducing acid resistance: Exceptional performance in sulfuric acid (H₂SO₄) and phosphoric acid (H₃PO₄) environments.

l Enhanced erosion-corrosion resistance: Ideal for high-velocity seawater, pump impellers, and slurry handling.

l Improved resistance to biofouling: Copper content provides natural antifouling properties in marine environments.

l  The combination of high chromium (24–27%), molybdenum (2.0–4.0%), copper (1.50–2.50%), and nitrogen (0.10–0.25%) gives S32550 a PRE value ≥36, comparable to super duplex grades, but with unique reducing acid capabilities due to copper.

Pitting Resistance Equivalent (PRE) Calculation:
PRE = %Cr + 3.3 × %Mo + 16 × %N ≥ 36 (typically 36–40)

Impact Toughness (Charpy V-Notch, typical at -40°C):

Longitudinal: ≥ 60 J (typical)

NACE MR0175 / ISO 15156 Compliance:
S32550 is qualified for sour service applications up to the limits specified in NACE MR0175/ISO 15156 for duplex stainless steels. The high copper content provides additional resistance to hydrogen-induced cracking (HIC) in sour environments.

Heat Treatment Condition:
S32550 duplex pipes are solution annealed at 1050–1120°C followed by rapid cooling (water quenching) . This heat treatment:

(1) Restores the balanced 40–60% ferrite / 40–60% austenite microstructure.

(2) Dissolves unwanted intermetallic phases (sigma, chi) that can reduce corrosion resistance and toughness.

(3) Relieves internal stresses from forming, rolling, or welding.

(4) Ensures optimal mechanical properties and maximum corrosion resistance.

(5) Prevents copper segregation that can occur with slow cooling.

Critical Note: S32550 requires water quenching after solution annealing. Air cooling is insufficient and may result in copper segregation and intermetallic phase precipitation. Due to the high copper content, cooling rate must be rapid to maintain copper in solid solution.

Delivery Condition: Pipes are normally supplied in solution annealed and pickled condition. Bright annealing is not recommended due to the water quenching requirement.

Womic Steel adopts advanced production technology to ensure each S32550 duplex seamless pipe meets exact specifications with balanced microstructure and excellent surface quality. The high copper content requires special attention during hot working.

1. Raw Material Selection: High-quality S32550 duplex billets from certified mills (Outokumpu, Sandvik, POSCO, Baosteel) with certified chemical composition (including Cu verification at 1.50–2.50%) and ferrite/austenite balance.

2. Heating and Piercing: Billets heated to a carefully controlled temperature range (narrower window due to copper content – prevents copper segregation) and pierced using a rotary piercing mill. Temperature is continuously monitored.

3. Hot Rolling: Shells elongated and rolled to desired intermediate size with strict temperature control and controlled reduction rates to prevent hot cracking.

4. Cold Drawing / Cold Pilgering: Pipes refined to precise dimensions with improved surface finish and enhanced mechanical properties. Work hardening behavior is similar to other duplex grades.

5. Solution Annealing (Intermediate and Final) : Multiple solution annealing steps at 1050–1120°C followed by water quenching to maintain phase balance and prevent copper segregation.

6. Pickling & Passivation: Removal of oxides using specialized pickling acids optimized for copper-bearing duplex grades; thorough rinsing required to prevent copper redeposition.

7. Straightening and Dimensional Calibration: Ensures consistent roundness and wall uniformity without introducing excessive residual stress.

8. Final Inspection & Marking: Each pipe undergoes ferrite content measurement, 100% NDT, dimensional check, and is marked with grade, heat number, standard, and traceability code before packing.

This rigorous process guarantees a balanced dual-phase microstructure, smooth internal bore, high structural integrity, and exceptional corrosion resistance across all batches of Womic Steel’s S32550 Duplex Seamless Pipe.

Womic Steel utilizes state-of-the-art manufacturing technology with special procedures for copper-bearing duplex to ensure every welded pipe meets precise specifications with weld zone phase balance and excellent corrosion resistance.

1.   Raw Material Selection: High-quality S32550 duplex stainless steel strips/coils from certified suppliers with full traceability and certified Cu content (1.50–2.50%).

2.   Slitting & Uncoiling: Precision slitting to required width; edge preparation to ensure clean, burr-free edges for welding.

3.   Forming & Welding: The strip is progressively formed into a cylindrical shape. The edges are welded using advanced TIG or Plasma welding with:

(1)   Appropriate heat input control (typically 0.5–1.2 kJ/mm)

(2)   Shielding gas: Ar + N₂ (2–5% nitrogen) to prevent nitrogen loss

(3)   Matching filler metal: ER255 (S32550 specific) or ER2594 (for higher alloy matching)

(4)   Pre-weld and post-weld purge gas protection

4.   Weld Seam Treatment: External weld bead removal and optional internal bead control; weld zone carefully ground to remove surface oxides.

5.   Solution Annealing: Full heat treatment of the entire welded pipe at 1050–1120°C followed by water quenching – essential for restoring corrosion resistance, balanced microstructure, and preventing copper segregation in the weld and HAZ.

6.   Sizing & Calibration: Final precise outer diameter and roundness.

7.   Pickling & Passivation: Chemical treatment removes scale and promotes passive layer formation; specialized pickling for copper-bearing grades.

8.   Non-Destructive Testing (NDT) : Weld seam inspected using:

(1)   Eddy Current Testing (ECT)

(2)   Ultrasonic Testing (UT) – longitudinal and transverse

(3)   Optional: Radiographic Testing (RT) for critical applications

9.   Ferrite Content Measurement: Verification of base metal, weld metal, and HAZ phase balance – typically 35–65% ferrite (weld zone may be 30–60%).

10.Corrosion Testing (per project requirements): Pitting resistance test per ASTM G48 Method A as specified.

11.Final Inspection & Marking: Complete dimensional check, visual inspection, and traceable marking.

This controlled process guarantees a sound weld seam, excellent dimensional accuracy, balanced duplex microstructure, and superior corrosion resistance for every batch of Womic Steel’s S32550 Welded Pipe.

1. Outside Diameter: 6mm – 914mm (1/4″ – 36″); larger diameters available upon request

2. Wall Thickness: 0.5mm – 40mm (SCH 10S – SCH XXS)

3. Length: Up to 12m (fixed or random); longer lengths available upon request

4. Tolerances: According to ASTM A999 / EN ISO 1127

Womic Steel offers a range of surface finishes for S32550 duplex pipes, each suited to specific industrial, marine, and chemical applications.

Note: Bright annealing is not recommended for S32550 due to the water quenching requirement. Polished finishes are available upon request but are uncommon for this grade in heavy industrial service.

Each S32550 pipe surface is inspected for uniform appearance, absence of pits, surface defects, and consistent finish quality.

Every S32550 duplex stainless steel pipe undergoes comprehensive inspection in accordance with ASTM, EN, NORSOK, ISO, and NACE standards, including duplex-specific and copper-grade tests:

These extensive tests ensure that every S32550 Duplex Stainless Steel Pipe from Womic Steel meets the highest international standards for reliability, corrosion resistance (especially in reducing acids), and longevity in demanding environments.

S32550 duplex stainless steel pipe is specified for applications requiring high strength, excellent erosion-corrosion resistance, and superior performance in reducing acid environments. The high copper content makes S32550 unique among duplex grades.

Each S32550 duplex stainless steel pipe is securely packed and clearly labeled to ensure safe and efficient transport worldwide.

General packaging for local truck transport:
Bundle packing with woven fabric, iron strip bundle, plastic cap on both ends.

Hexagonal packaging:
Bundle packing with woven fabric, iron strip bundle, plastic cap on two ends.

Packaging for welded pipe in medium and large sizes:
Wrapped with woven fabric by automatic packaging for export sea-worthy transport.

Packaging for medium and large size welded pipes for export:
Wooden or steel crate packaging for export sea-worthy transport – recommended for critical surface finish requirements.

General packaging for products to be exported:
Wooden box for export sea-worthy transport.

Packaging for precision tubes and heat exchanger tubes:
Wooden box for both local truck and export sea-worthy transport.

Direct cooperation with global shipowners ensures the most competitive freight rates.

Professional loading and securing teams – S32550 pipes are handled with care to prevent surface damage.

Efficient document preparation – includes EN 10204 3.1/3.2 certificates, material test reports (MTR), and NACE compliance documentation – minimizing customs delays.

Rapid delivery time – select sizes of S32550 maintained in ready stock; custom sizes available with competitive lead times.

Continuous cargo tracking and after-sales follow-up – including pre-shipment inspection coordination and arrival notification.

Womic Steel is a trusted manufacturer and exporter specializing in duplex stainless steel pipes, including the high-copper S32550 grade. We are committed to delivering premium quality, technical expertise, and professional service for hydrometallurgical, marine, and chemical processing applications.

1. Strict quality control under ISO 9001, PED 2014/68/EU, and NORSOK M-630 compliance.

2. High-copper duplex expertise – specialized knowledge in copper-bearing duplex phase balance control, heat treatment (water quenching to prevent copper segregation), and erosion-corrosion resistance.

3. Modern production lines – cold pilger mills and automatic TIG welding lines with nitrogen shielding.

4. Complete in-house testing – including ferrite measurement, PMI with copper verification, and mechanical testing.

5. Unique reducing acid capability – S32550’s high copper content provides exceptional performance in sulfuric and phosphoric acid environments.

6. Superior erosion-corrosion resistance – ideal for high-velocity seawater, slurry, and pump applications.

7. Third-party inspection support – full coordination with SGS, BV, DNV, TUV, LR, and other approved agencies.

8. Full documentation – EN 10204 Type 3.1/3.2 certificates, material test reports (MTR), NORSOK compliance statements, NACE compliance certificates, and complete traceability.

9. Flexible customization – special diameters, wall thicknesses, lengths, beveled ends, and surface finishes.

10.Fast production cycle – efficient manufacturing for both seamless and welded S32550 pipes.

11.Reliable global shipping to all major ports worldwide.

12.Direct mill pricing – no middlemen, ensuring competitive costs for high-copper duplex products.

For inquiries, technical support, or to request a quotation for your specific clad pipe requirements, please contact us:

Website: www.womicstainless.com

E‑mail: info@womicstainless.com

Tel / WhatsApp / WeChat:

Victor: +86 15575100681

Jack: +86 18390957568

Womic Steel – Your reliable partner for high‑quality stainless steel seamless pipes, metallurgically bonded clad tubes, and custom solutions for corrosion‑resistant applications.