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Seamless S32205 Duplex Steel Pipe is a widely used alloy combining high strength and excellent corrosion resistance, suitable for moderately aggressive environments. Which is Produced via hot extrusion of a steel billet, pierced, and formed through a die, ensuring no welds. Solutions annealed to achieve a balanced austenite-ferrite microstructure (50/50).
UNS S32205 duplex steel seamless pipe represents a pinnacle of metallurgical engineering, combining austenitic and ferritic phases in a balanced microstructure that delivers unmatched performance in challenging environments. This alloy, often referred to by its commercial grade SAF2205, is engineered to exceed the limitations of conventional stainless steels, offering a unique blend of high tensile strength (≥95 ksi/655 MPa) and exceptional corrosion resistance. The dual-phase structure—approximately 50% austenite and 50% ferrite—creates a synergistic effect: the ferritic phase provides robust mechanical strength, while the austenitic phase enhances ductility and resistance to chloride-induced stress corrosion cracking (SCC).
Key to its performance is the precise chemical composition: 22-23% chromium forms a protective oxide layer, 3.0-3.5% molybdenum enhances resistance to pitting and crevice corrosion, and 0.14-0.20% nitrogen stabilizes the austenitic phase while boosting tensile properties. This composition yields a Pitting Resistance Equivalent (PREN) of 34-38, making it highly effective in environments containing chlorides, sulfides, or other aggressive media.
Manufactured through a seamless extrusion process, the pipes exhibit uniform grain structure, eliminating weld lines that could compromise integrity in high-pressure applications. Post-production treatments such as pickling, annealing, and optional polishing further enhance surface quality and corrosion resistance. The result is a material that not only withstands harsh chemical exposure but also reduces lifecycle costs by minimizing maintenance and replacement needs in critical infrastructure.
ASTM A789: Defines specifications for seamless and welded ferritic-austenitic stainless steel tubing, emphasizing dimensional tolerances and mechanical property requirements for general service.
ASTM A790: Focuses on seamless, welded, and cold-worked austenitic stainless steel pipes, covering materials suitable for high-pressure and high-temperature applications.
EN 10216-5: European standard for seamless steel tubes for pressure purposes, specifying technical delivery conditions for corrosion-resistant alloys.
GB/T 21833.1-2020: Chinese standard governing duplex stainless steel pipes, addressing chemical composition and mechanical properties for industrial use.
Outer Diameter (OD): 6 mm to 720 mm (0.24" to 28.3"), accommodating everything from small-bore instrumentation tubing to large-diameter process pipes.
Wall Thickness: 1 mm to 65 mm (0.04" to 2.56"), available in standard schedules (e.g., SCH40, SCH80) or custom sizes to meet project-specific pressure ratings.
Length: Customizable up to 12 meters, with standard lengths of 6 meters for ease of transportation and installation. Special cut-to-length services are available to minimize material waste.
| Element | Role in Alloy | Specified Range | Impact on Performance |
|---|---|---|---|
| C | Enhances hardness, but controlled to ≤0.03% to prevent carbide precipitation | ≤0.03% | Excess carbon reduces corrosion resistance; low carbon ensures intergranular stability. |
| Mn | Stabilizes austenite and improves hardenability | ≤2.00% | Maintains structural balance without compromising weldability. |
| P/S | Impurities controlled for ductility | ≤0.03% (P), ≤0.02% (S) | Minimizes brittleness and ensures formability during manufacturing. |
| Si | Improves oxidation resistance | ≤1.00% | Forms a secondary protective layer at high temperatures. |
| Ni | Strengthens austenitic phase | 4.50-6.50% | Enhances toughness and resistance to chloride SCC, especially in low-temperature applications. |
| Cr | Core component of the passive corrosion layer | 22.00-23.00% | Determines general corrosion resistance; higher chromium improves pitting resistance. |
| Mo | Boosts resistance to localized corrosion | 3.00-3.50% | Enhances performance in acidic and chloride-rich environments, increasing PREN value. |
| N | Strengthens austenite and improves strength | 0.14-0.20% | Increases yield strength without sacrificing ductility, while stabilizing the microstructure. |
PREN Calculation: Cr + 3.3×Mo + 16×N ≥34, a critical metric for predicting performance in chloride-laden environments.
| Property | Value | Significance in Applications |
|---|---|---|
| Tensile Strength | ≥95 ksi (655 MPa) | Enables use in high-pressure systems, reducing wall thickness requirements. |
| Yield Strength | ≥65 ksi (450 MPa) | Ensures structural integrity under sustained loading without permanent deformation. |
| Elongation at Break | ≥25% | Provides ductility for forming, bending, and resistance to impact loads. |
| Hardness (HBW) | ≤290 | Balances wear resistance with machinability for fabrication and installation. |
| Impact Toughness | ≥40 J/cm² at 20°C | Maintains fracture resistance in low-temperature environments like LNG processing. |
Process Flow:
Hot-rolling of billets into hollow shells
Cold-drawing or extrusion for dimensional precision
Annealing to restore ductility and uniform microstructure
Pickling to remove scale and expose a clean surface
Surface Treatments:
Pickled & Annealed (standard): Removes oxidation products, ideal for general corrosion resistance.
Polished (Ra ≤0.8μm): Enhances hygienic properties for pharmaceutical/food applications.
Bright Annealed: Maintains a lustrous surface via controlled atmosphere heating, minimizing post-treatment needs.
Testing Regime:
100% Positive Material Identification (PMI) to verify chemical composition.
Non-destructive testing (UT/ET) for internal defects.
Hydrostatic pressure testing to ensure leak-tightness.
Intergranular corrosion (IGC) testing per ASTM A262 to confirm resistance to sensitization.
Mill Test Certificates (MTC): Compliant with EN 10204 3.1 and 3.2, detailing chemical analysis, mechanical properties, and heat treatment records.
Third-Party Inspection: Available from accredited bodies (e.g., Lloyd’s, DNV) for critical projects.
Traceability Marking: Each pipe is laser-marked with material grade, size, heat number, and manufacturer logo for full lifecycle traceability.
UNS S32205 seamless pipes excel in marine environments, serving as the material of choice for seawater cooling pipelines and desalination equipment in coastal power plants and desalination plants. Their high resistance to pitting in high-salinity conditions ensures long-term reliability. Additionally, in offshore platforms, these pipes are used for components and pump valves, where their high strength allows for reduced material thickness, minimizing weight while withstanding constant seawater erosion.
In the oil and gas sector, UNS S32205 pipes are critical for oil well tubing and gathering pipelines, performing exceptionally well in acidic environments rich in H₂S and CO₂, and meeting the stringent NACE MR0175 standards. They are also used in pressure vessels and heat exchangers in oil-gas processing facilities, effectively preventing chloride-induced stress corrosion and ensuring the safety and efficiency of operations.
For chemical processing, these pipes are utilized in reactors and distillation columns, providing reliable resistance to strong acids such as sulfuric and hydrochloric acid, which are common in fertilizer and pesticide production. In the pharmaceutical industry, UNS S32205 seamless pipes meet strict hygienic standards, resist disinfectants, and are easy to clean, making them ideal for pharmaceutical-grade pipes and tanks.
In power generation, especially in coastal power plants, UNS S32205 pipes are employed in Flue Gas Desulfurization (FGD) systems, withstanding sulfite corrosion in wet desulfurization processes. They are also used in wastewater treatment facilities, where they resist the corrosive effects of chloride-laden wastewater and sludge in both municipal and industrial settings.
Within the pulp and paper industry, these pipes are essential for digesters and bleaching equipment. Their ability to maintain stability in chloride-based bleaching agents prevents equipment perforation and leakage, ensuring continuous and efficient production processes.
A: S32205 offers over twice the strength of 316L (450 MPa vs. 205 MPa yield strength) and superior chloride resistance. Its PREN (34-38) far exceeds 316L’s PREN (≈24), making it ideal for high-salinity applications.
A: Service temperatures above 300°C are not recommended. Prolonged exposure may cause intermetallic phase precipitation, reducing corrosion resistance and ductility. Consider super duplex or nickel-based alloys for higher temperatures.
A: Yes. Use low-heat-input methods (e.g., TIG welding) with interpass temperatures ≤250°C. ER2209 filler wire is recommended. Post-weld heat treatment is typically unnecessary, but avoid overheating to maintain phase balance.
A: Each batch is marked with a heat number for traceability. Confirm chemical composition via PMI testing or cross-reference with Mill Test Certificates (MTC) for mechanical properties. Third-party certification is available upon request.
A: S32205 is a standard duplex steel for moderate corrosion, while S32750 is a super duplex with higher Mo/N content (PREN ≥41) for extreme conditions (e.g., deep-sea oil, concentrated acids). S32205 also offers a cost advantage.
A: Standard sizes are available within 2-4 weeks. Non-standard dimensions (OD/thickness) require 6-8 weeks, depending on production scheduling and testing. Rush orders can be arranged for urgent needs.
