Product Description
Duplex F50 is a 26% chromium duplex stainless steel with nitrogen strengthening, providing higher strength than standard duplex grades while maintaining good corrosion resistance . The alloy offers PREN values of approximately 34-36, making it suitable for chloride-containing environments where standard austenitic stainless steels such as 316L would be inadequate. The nitrogen content (0.15-0.35%) provides enhanced strengthening and improved toughness compared to non-nitrogen duplex grades, making F50 a reliable choice for moderate chloride service where cost-effectiveness is a priority.
Key characteristics include:
High strength – yield strength ≥ 450 MPa (65 ksi)
Good corrosion resistance – PREN 34-36
Nitrogen-strengthened for improved toughness and ductility
Excellent resistance to chloride stress corrosion cracking
Good weldability with proper procedures and filler metals
Cost-effective alternative to higher-alloyed duplex grades
Wide operating temperature range from -50°C to 300°C
Chemical Composition
| Element | Content (%) | Role |
| Chromium (Cr) | 26.0 – 29.0 | Provides oxidation and corrosion resistance; forms protective Cr₂O₃ oxide film |
| Nickel (Ni) | 3.5 – 5.2 | Austenite stabilizer; provides resistance to reducing acids and SCC |
| Molybdenum (Mo) | 1.0 – 2.5 | Enhances resistance to pitting and crevice corrosion in chlorides |
| Nitrogen (N) | 0.15 – 0.35 | Austenite stabilizer; provides solid-solution strengthening and improves toughness |
| Carbon (C) | ≤ 0.030 | Controlled to prevent intergranular corrosion and maintain weldability |
| Manganese (Mn) | ≤ 2.00 | Deoxidizer; improves hot workability |
| Silicon (Si) | ≤ 0.60 | Deoxidizer; improves oxidation resistance |
| Phosphorus (P) | ≤ 0.035 | Impurity; tightly controlled for toughness |
| Sulfur (S) | ≤ 0.010 | Impurity; tightly controlled for hot workability and corrosion resistance |
| Iron (Fe) | Balance | Base element |
Room Temperature Properties (Solution Annealed)
| Property | ASTM Requirement | Typical Achieved |
| Tensile Strength | ≥ 620 MPa (90 ksi) | 650 – 750 MPa |
| Yield Strength (0.2% Offset) | ≥ 450 MPa (65 ksi) | 470 – 520 MPa |
| Elongation | ≥ 25% | 28 – 35% |
| Hardness | ≤ 290 HB | 240 – 280 HB |
| Density | 7.80 g/cm³ | |
| Melting Range | 1420 – 1460°C | |
| Thermal Conductivity at 20°C | 15.0 W/m·K | |
| Coefficient of Thermal Expansion (20-100°C) | 13.0 × 10⁻⁶/°C | |
| Elastic Modulus | 195 GPa | |
| PREN | 34 – 36 |
Impact Properties (Typical)
| Temperature | Impact Energy (Longitudinal) |
| Room Temperature | ≥ 80 J |
| -40°C | ≥ 45 J |
| -50°C | ≥ 27 J |
Key Advantages of Duplex F50
High Strength – Duplex F50 offers yield strength of 450 MPa (65 ksi), approximately twice that of 316L stainless steel (220 MPa). This high strength allows designers to specify significantly thinner wall sections, reducing overall weight and material costs in structural and pressure-containing applications. The nitrogen addition provides enhanced solid-solution strengthening without compromising ductility.
Good Corrosion Resistance – With PREN values of 34-36, Duplex F50 provides good resistance to pitting and crevice corrosion in moderate chloride environments. The high chromium content (26-29%) ensures a stable passive film, while molybdenum (1.0-2.5%) enhances resistance to localized corrosion. This makes F50 suitable for seawater piping, chemical processing, and marine applications where 316L is inadequate but Super Duplex grades may be over-specified.
Nitrogen Strengthening – The nitrogen content (0.15-0.35%) provides multiple benefits: enhanced solid-solution strengthening for higher yield strength; improved toughness and ductility; increased resistance to pitting corrosion; and stabilization of the austenite phase for better weldability. Nitrogen is an essential element in modern duplex stainless steel design.
Excellent Chloride Stress Corrosion Cracking Resistance – The ferritic-austenitic microstructure provides outstanding resistance to chloride stress corrosion cracking (SCC), a common failure mode for 304 and 316 stainless steels in marine and chemical environments. The mixed microstructure prevents the propagation of cracks that would rapidly fail austenitic stainless steels.
Good Weldability – Duplex F50 can be welded using standard techniques including GTAW (TIG), GMAW (MIG), SMAW (stick), and SAW (submerged arc). Matching filler metal (typically ER2209 or similar) is recommended. Proper heat input control (typically 0.5-2.5 kJ/mm) and interpass temperature management (≤ 150°C) are essential to maintain the correct ferrite-austenite balance (typically 40-60% ferrite) in the weld zone and heat-affected zone.
Cost-Effective Alternative – Duplex F50 offers a favorable balance of performance and price, providing corrosion resistance approaching Duplex 2205 at a lower cost. This makes it an attractive option for applications where the higher performance of 2205 is not required, or where cost constraints are significant.
Good Fabricability – The alloy can be readily formed, machined, and fabricated using standard techniques. It has good hot and cold workability, though its high strength requires more powerful equipment for forming and shearing compared to austenitic grades.
Duplex F50 vs Duplex 2205 vs 316L Stainless Steel
| Property | Duplex F50 | Duplex 2205 (F60) | 316L |
| Chromium | 26.0 – 29.0% | 22.0 – 23.0% | 16.0 – 18.0% |
| Nickel | 3.5 – 5.2% | 4.5 – 6.5% | 10.0 – 14.0% |
| Molybdenum | 1.0 – 2.5% | 3.0 – 3.5% | 2.0 – 3.0% |
| Nitrogen | 0.15 – 0.35% | 0.14 – 0.20% | ≤ 0.10% |
| PREN | 34 – 36 | ≥ 36 | ~25 |
| Yield Strength | ≥ 450 MPa | ≥ 450 MPa | ≥ 220 MPa |
| Tensile Strength | ≥ 620 MPa | ≥ 620 MPa | ≥ 485 MPa |
| SCC Resistance | Excellent | Excellent | Poor in chlorides |
| Pitting Resistance | Good | Excellent | Moderate |
| Seawater Service | Good | Excellent | Limited |
| Cost | Lower | Moderate | Lowest |
Available Product Forms from Womic Steel
Seamless Pipe & Seamless Tube
Outside Diameter: 6mm – 300mm (1/4" – 12")
Wall Thickness: 1mm – 30mm (Schedule 5S to XXS)
Length: Up to 12m (Single Random, Double Random, Cut Length)
End Finish: Plain End, Beveled End, Threaded
Standards: ASTM A790, ASTM A789, ASME SA-790
Applications: Heat exchanger tubes, process piping, seawater systems, instrumentation lines, structural tubing
Keywords: Duplex F50 seamless pipe, UNS S32950 tube, F50 pipe, 1.4484 seamless tube, nitrogen-strengthened duplex pipe
Welded Pipe
Outside Diameter: 50mm – 1200mm (2" – 48")
Wall Thickness: 1.0mm – 25mm
Standards: ASTM A790, ASTM A928, ASME SA-790
Applications: Large-diameter process piping, seawater intake systems, structural applications, cooling water lines
Keywords: Duplex F50 welded pipe, F50 ERW pipe, S32950 welded tube, large diameter duplex pipe
Steel Bar (Round, Square, Flat, Hex)
Diameter: 6mm – 400mm
Surface: Hot rolled, Bright (cold drawn), Ground, Turned, Peeled
Standards: ASTM A276, ASTM A479, ASME SA-479
Applications: Valve stems, fasteners, shafts, pumps, machining stock, fittings, flanges, structural supports
Keywords: Duplex F50 round bar, F50 bar stock, S32950 bar, duplex stainless steel bar
Steel Plate & Sheet
Thickness: 1mm – 80mm
Width: Up to 2500mm
Length: Up to 6000mm
Surface: Hot rolled, Cold rolled, Pickled, 2B finish, Polished
Standards: ASTM A240, ASME SA-240
Applications: Vessel shells, heat exchanger plates, structural components, flange blanks, pressure vessel plates, tank linings
Keywords: Duplex F50 plate, F50 sheet, S32950 plate, duplex stainless steel plate
Steel Coil & Strip
Thickness: 0.5mm – 6.0mm
Width: 10mm – 1500mm
Weight: Up to 2,000kg per coil
Standards: ASTM A240
Applications: Formed components, bellows, expansion joints, stampings, thin-walled tubing
Keywords: Duplex F50 coil, F50 strip, S32950 coil, duplex stainless steel strip
Flanges & Pipe Fittings
Types: Weld Neck (WN), Slip-On (SO), Blind (BL), Socket Weld (SW), Threaded (THD), Lap Joint (LJ)
Sizes: 1/2" – 48" (DN15 – DN1200)
Pressure Rating: Class 150 – Class 2500 (PN20 – PN420)
Standards: ASTM A182, ASME SA-182, ASME B16.5, ASME B16.47, MSS SP-44
Fittings: Elbows (90°, 45°), Tees, Reducers, Caps, Stub Ends, Couplings
Keywords: Duplex F50 flanges, F50 weld neck flange, S32950 pipe fittings, duplex stainless steel flanges
Forgings
Types: Rings, disks, shafts, valve bodies, pump parts, blocks, custom geometries
Weight: Up to 4,000kg per piece
Standards: ASTM A182, ASME SA-182
Applications: High-strength structural components, valve bodies, flanges, custom engineered parts, pump impellers
Keywords: Duplex F50 forging, F50 ring, S32950 forged block, duplex stainless steel forging
Duplex F50 Valves
Types: Ball valves, Gate valves, Globe valves, Check valves, Plug valves
Sizes: 1/2" – 24" (DN15 – DN600)
Pressure Rating: Class 150 – Class 2500
Temperature Range: -50°C to +300°C
Design Standards: API 608, API 6D, BS 6364, ASME B16.34
Seating: Stellite hardfaced, RPTFE, PEEK, PCTFE (cryogenic)
Actuation: Manual (lever, gear), Pneumatic (spring-return, double-acting), Electric (on-off, modulating)
Applications: Seawater isolation, chemical process control, oil and gas manifolds, desalination plants, cooling water systems
Keywords: Duplex F50 ball valve, F50 gate valve, S32950 stainless steel valve, duplex stainless steel valve
Standards & Specifications
| Product Form | ASTM Standard | ASME Standard |
| Seamless Pipe/Tube | ASTM A790, ASTM A789 | ASME SA-790 |
| Welded Pipe | ASTM A790, ASTM A928 | ASME SA-790 |
| Bar/Rod | ASTM A276, ASTM A479 | ASME SA-479 |
| Plate/Sheet/Strip | ASTM A240 | ASME SA-240 |
| Forgings | ASTM A182 | ASME SA-182 |
| Fittings | ASTM A182 | ASME SA-182 |
| UNS Designation | S32950 | |
| W.Nr. | 1.4484 | |
| F No. | F50 |
Applications of Duplex F50
Chemical Processing – Duplex F50 is used in heat exchangers, pressure vessels, tanks, piping systems, pumps, and valves in chemical plants where moderate corrosion resistance and high strength are required. The alloy's resistance to both oxidizing and reducing chemicals makes it suitable for a wide range of chemical services where 316L is inadequate but Super Duplex is over-specified.
Marine Engineering – The alloy is used in seawater piping systems, ballast water systems, cooling water systems, and offshore platform equipment in moderate chloride environments. Its resistance to pitting and crevice corrosion in seawater makes it suitable for many marine applications where the more expensive 2205 may not be justified.
Oil and Gas – Duplex F50 is used in pipelines, manifolds, process equipment, separators, and wellhead components in moderate chloride environments. Its high strength and SCC resistance make it suitable for oil and gas processing equipment where weight reduction and corrosion resistance are important.
Structural Applications – The high strength of Duplex F50 makes it suitable for structural applications in marine and offshore environments, including platform walkways, handrails, supports, and other structural components requiring corrosion resistance.
Desalination Plants – The alloy is used in seawater intake systems, brine handling equipment, and evaporator tubes in desalination plants where moderate corrosion resistance and high strength are required.
Pulp and Paper – Duplex F50 is used in digesters, bleaching equipment, and chemical recovery systems in pulp and paper mills where corrosion resistance and strength are required.
Frequently Asked Questions
Q: What is the difference between Duplex F50 and Duplex 2205?
A: Duplex F50 has higher chromium content (26-29% vs 22-23%) but lower molybdenum content (1.0-2.5% vs 3.0-3.5%). This results in similar PREN values (34-36 vs ≥36) but at a lower cost. Duplex 2205 offers slightly better pitting resistance due to higher molybdenum, while F50 offers higher chromium for improved oxidation resistance. F50 is more economical and is often selected for applications where the cost premium of 2205 is not justified.
Q: Is Duplex F50 suitable for seawater service?
A: Yes, for moderate seawater service. The PREN of 34-36 provides good resistance to pitting in seawater, making it suitable for many marine applications. For high-temperature seawater, stagnant seawater, or more severe chloride conditions, Super Duplex 2507 (PREN ≥ 40) may be required.
Q: Is Duplex F50 readily weldable?
A: Yes. Duplex F50 is weldable using GTAW (TIG), GMAW (MIG), SMAW (stick), and SAW (submerged arc) processes. Filler metal selection should match the base material chemistry. Proper heat input control (0.5-2.5 kJ/mm) and interpass temperature management (≤150°C) are essential to maintain the correct ferrite-austenite balance and corrosion resistance in the weld zone.
Q: What is the maximum service temperature for Duplex F50?
A: The recommended maximum service temperature is 300°C (572°F). Above this temperature, the alloy is susceptible to embrittlement due to sigma phase precipitation. The minimum service temperature is approximately -50°C.
Q: What is the PREN value of Duplex F50?
A: The PREN (Pitting Resistance Equivalent Number) of Duplex F50 is approximately 34-36, calculated using the formula: PREN = %Cr + 3.3×%Mo + 16×%N.
Q: What is the Chinese equivalent of Duplex F50?
A: The Chinese equivalent is 022Cr26Ni5Mo2N (GB/T 20878). It is also commonly referenced by its UNS designation S32950 and F number F50.
Q: What product forms are available for Duplex F50?
A: Womic Steel supplies Duplex F50 in seamless pipe, welded pipe, steel bar, steel plate, steel coil, strip, flanges, pipe fittings, forgings, and valves. Complete product specifications and size ranges are listed in the product availability section.
Contact Womic Steel
Website: www.womicsteel.com
E-mail: sales@womicsteel.com
Tel / WhatsApp / WeChat:
Victor: +86 15575100681
Jack: +86 18390957568
Womic Steel – Your reliable partner for Duplex F50 (UNS S32950) seamless pipe, welded pipe, steel bar, steel plate, steel coil, flanges, fittings, forgings, and valves for chemical processing, marine engineering, oil and gas, and structural applications worldwide. Full traceability, classification society certification, and EN 10204 Type 3.1/3.2 documentation available.
Related Products
-
ASTM A789/A790 2205 Duplex Stainless Steel Seam...
-
Duplex F50 (UNS S32950) – Nitrogen-Strengthened...
-
ASTM A312 TP347/347H Seamless Stainless Steel Pipe
-
Duplex 31803 (UNS S31803 / F51) – Standard Dupl...
-
ASTM A312 TP321/321H Seamless Stainless Steel Pipe
-
ASTM A312 TP317L Seamless Stainless Steel Pipe
-
ASTM A312 TP316Ti Seamless Stainless Steel Pipe
-
Duplex 2205 (UNS S32205 / S31803 / F60) – The I...
-
ASTM A312 TP316LN Seamless Stainless Steel Pipe