S32550 Seamless Super Duplex Steel Tube

UNS S32550 | 1.4507 | ASTM A789

S32550 Seamless Super Duplex Steel Tube (S32550 / 1.4507) is manufactured to ASTM A789 from super duplex steel billet, cold-drawn to the required outside diameter and wall thickness. Supplied from our Wenzhou mill with EN 10204 3.1 mill test certificate, PMI and dimensional inspection on request.

Quantity:

Contact Now

What Is a Seamless Super Duplex UNS S32550 Tube?

UNSS32550, commonly known as Ferralium 255, is a high-alloy super duplex stainless steel engineered for extremely aggressive, high-chloride environments. With roughly 25% chromium plus molybdenum, nitrogen and copper, it achieves a Pitting Resistance Equivalent Number (PREN) above 40 — enough to resist pitting, crevice attack and chloride stress-corrosion cracking in seawater and sour service alike.

S32550 Key Features and Technical Advantages

UNS S32550, commonly known as Ferralium 255, is a high-alloy super duplex stainless steel engineered for extremely aggressive and high-chloride environments.

With a high chromium content (~25%) and alloying elements such as molybdenum (Mo), nitrogen (N), and copper (Cu), S32550 achieves a Pitting Resistance Equivalent Number (PREN) > 40, delivering exceptional resistance to localized corrosion.

ASTM A789 S32550 seamless tubes are produced from solid billets using cold drawing or hot finishing processes, ensuring:

Feature	Description
1. Exceptional Corrosion Resistance	Pitting corrosion Crevice corrosion Chloride-induced Stress Corrosion Cracking (SCC)
2. Superior Mechanical Strength	DuplexS31803 / S32205 Austenitic grades such as 316L
3. Enhanced Erosion-Corrosion Resistance	High-velocity seawater Abrasive slurries
4. Excellent Impact Toughness	Maintains ductility at sub-zero temperatures Ideal for offshore, deepwater, and Arctic environments
5. Cost-Effective Alternative to Nickel Alloys	Comparable corrosion performance in many environments Lower material and fabrication cost vs Ni-based alloys

S32550 Product Specifications and Data

ASTM A789 / ASME SA789
ASTM A1016
EN 10216-5
NORSOK / offshore specifications available upon request

To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for Super Duplex UNS S32550.

The composition of UNS S32550 is carefully balanced to achieve its superior corrosion resistance and high strength.

Grade	C	Mn	P	S	Si	Ni	Cr	Mo	N	Cu	Others
31803	≤0.03	≤2.00	≤0.03	≤0.02	≤1.00	4.50-6.50	21.00-23.00	2.50-3.50	0.08-0.20	…	…
32205	≤0.03	≤2.00	≤0.03	≤0.02	≤1.00	4.50-6.50	22.00-23.00	3.00-3.50	0.14-0.20	…	…
31500	≤0.03	1.20-2.00	≤0.03	≤0.03	1.40-2.00	4.3-5.2	18.00-19.00	2.50-3.00	0.05-0.10	…	…
32550	≤0.04	≤1.50	≤0.04	≤0.03	≤1.00	4.50-6.50	24.00-27.00	2.90-3.90	0.10-0.25	1.50-2.50	…
32750	≤0.03	≤1.20	≤0.035	≤0.02	≤0.80	6.00-8.00	24.00-26.00	3.00-5.00	0.24-0.32	≤0.50	…
32760	≤0.03	≤1.00	≤0.030	≤0.01	≤1.00	6.00-8.00	24.00-26.00	3.00-4.00	0.20-0.30	0.50-1.00	W 0.50 -1.00
32950	≤0.03	≤2.00	≤0.035	≤0.01	≤0.60	3.50-5.20	26.00-29.00	1.00-2.50	0.15-0.35	…	…
32906	≤0.03	0.80-1.50	≤0.030	≤0.03	≤0.50	5.80-7.50	28.00-30.00	1.50-2.60	0.30-0.40	≤0.80	…

Tensile Strength	Yield Strength	Elongation	Hardness
≥850 MPa	≥580 MPa	≥25%	≤320 HBW

Density	Melting Point	Thermal Expansion	Thermal Conductivity	Modulus of Elasticity	Electrical Resistivity
7.8 g/cm³	1420 - 1460 °C approx.	13.5 µm/m·°C (20-100°C)	15.0 W/m·K (20°C)	200 GPa	0.82 x 10⁻⁶ Ω·m (20°C)

Specified Outside Diameter (OD) (Inches)	Permissible Variations in OD (± Inches)
1⁄2 to 1	±0.005
Over 1 to 1-1⁄2	±0.008
Over 1-1⁄2 to 2	±0.010
Over 2 to 2-1⁄2	±0.012
Over 2-1⁄2 to 3-1⁄2	±0.014
Over 3-1⁄2 to 5	±0.020

Specified Outside Diameter (OD) (Inches)	Specified Wall Thickness (WT) (Inches)	Permissible Variation (± Inches)
1⁄2 to 1 (Inclusive)	0.025 to 0.065(Inclusive)	±0.010
	Over 0.065to 0.134 (Inclusive)	±0.012
Over 1 to 1-1⁄2 (Inclusive)	0.025 to 0.065 (Inclusive)	±0.010
	Over 0.065 to 0.134 (Inclusive)	±0.012
Over 1-1⁄2 to 2 (Inclusive)	0.025 to 0.049 (Inclusive)	±0.011
	Over 0.049 to 0.083 (Inclusive)	±0.012
	Over 0.083 to 0.148 (Inclusive)	±0.014
Over 2 to 2-1⁄2 (Inclusive)	0.032 to 0.065 (Inclusive)	±0.013
	Over 0.065 to 0.109 (Inclusive)	±0.015
	Over 0.109 to 0.165 (Inclusive)	±0.017
Over 2-1⁄2 to 3-1⁄2 (Inclusive)	0.032 to 0.165 (Inclusive)	±0.020
	Over 0.165 to 0.220 (Inclusive)	±0.025
Over 3-1⁄2 to 5 (Inclusive)	0.083 to 0.165 (Inclusive)	±0.025
	Over 0.165 to 0.220 (Inclusive)	±0.030

S32550 Dimensional Standards and Tolerances

S32550 super duplex seamless tubes are supplied to the dimensional tolerances of ASTM A789 / A1016 unless a tighter project specification applies.

For Specific Cut Lengths, the standard tolerance is +1⁄8 in. [3 mm], -0 in. [0 mm].

Important Note: The values presented here are based on the common tables in the ASTM A789 standard. The full specification, particularly the referenced ASTM A1016/A1016M (General Requirements for Ferritic Alloy Steel, Austenitic Alloy Steel, and Stainless Steel Tubes), contains other essential requirements like straightness and details for tubes with ODs outside of this range. Always consult the latest official standard for design and procurement.

S32550 Common Industrial Applications

Industry	Typical Applications
Offshore Oil and Gas	Subsea manifolds and flowlines Riser and umbilical tubing High-pressure process piping
Marine Engineering	Seawater cooling systems Propulsion and ballast piping Firewater and deluge systems
Desalination Systems	Reverse osmosis (RO) high-pressure piping Brine handling and reject lines Multi-stage flash evaporator tubing
Environmental and Pollution Control	Flue gas desulphurisation (FGD) systems Wastewater and effluent handling Scrubber and absorber internals

S32550 Quality Assurance and Production Process

Process Step	Description
Certification	All Super Duplex S32550 tubes are supplied to ASTM A789 / ASME SA789 and ASTM A790 / ASME SA790 with EN 10204 3.1 mill test certificates. Third-party inspection (SGS, BV, TUV, Lloyd's), PMI reports and full heat-number traceability can be provided on request.
Non-Destructive Testing (NDT)	Hydrostatic or eddy-current testing is performed on 100% of tubes. Ultrasonic testing (UT) and dye-penetrant inspection (PT) are available for critical service, with records retained for each production lot.
Material Verification	Positive Material Identification (PMI) and spectrometric analysis confirm that the chemical composition matches the ordered grade and that the ferrite/austenite balance is within the specified range.
Mechanical Testing	Tensile, yield, elongation and hardness tests are carried out per heat. Impact testing can be supplied at the project design temperature for subsea and low-temperature service.
Dimensional Inspection	Outside diameter, wall thickness, ovality and straightness are measured against ASTM A1016 / A1016M or ASTM A789 tolerances. Length, square-cut ends and end-finish conditions are verified before packing.

S32550 (Ferralium 255) vs S32750 (2507) – Technical Comparison

S32550 and S32750 are both super duplex grades with PREN above 40, but they differ in chemistry and in how that chemistry is used.

Chemical Composition

S32550 (Ferralium 255): ~25% Cr, ~3% Mo, ~2% Cu, with nitrogen — the copper addition is the distinguishing feature
S32750 (2507): ~25% Cr, ~4% Mo, ~0.3% N, no deliberate copper
Both achieve a balanced austenite-ferrite microstructure

Corrosion Resistance

Both resist pitting, crevice corrosion and chloride stress-corrosion cracking in seawater. The copper addition in S32550 specifically improves resistance to erosion-corrosion in high-velocity seawater and abrasive slurries, which is why it is often selected for pump and valve components and for lines carrying solids.

Mechanical Strength

S32550 offers a yield strength of at least 580 MPa, comparable to or slightly above S32750, and both allow significant weight reduction against austenitic grades. Toughness at sub-zero temperature is good in both.

Selection Guide

Choose S32550 where erosion-corrosion resistance in high-velocity or abrasive seawater service is the design driver
Choose S32750 where maximum pitting and crevice resistance with the broadest established service record is preferred
Both are cost-effective alternatives to nickel alloys in many chloride-bearing duties

Frequently Asked Questions About S32550 Seamless Super Duplex Steel Tubes

What is UNS S32550 super duplex tube?

UNS S32550, commonly known as Ferralium 255, is a high-alloy super duplex stainless steel tube with a balanced austenite-ferrite structure. Its approximately 25% chromium plus molybdenum, nitrogen and copper deliver a PREN above 40, giving exceptional resistance to pitting, crevice corrosion and chloride stress-corrosion cracking.

What is the difference between S32550 and S32750?

Both are super duplex grades with PREN above 40. S32550 contains copper, which specifically improves resistance to erosion-corrosion in high-velocity seawater and abrasive slurries. S32750 (2507) carries more molybdenum and no copper, favouring maximum pitting and crevice resistance.

What standard covers S32550 tube?

S32550 seamless tube is normally supplied to ASTM A789 / ASME SA789 for general seamless tubing, with ASTM A790 / ASME SA790 covering pipe dimensions. Dimensional tolerances follow ASTM A1016 / A1016M.

What is S32550 tube used for?

S32550 is used for subsea manifolds and flowlines, seawater cooling systems, reverse-osmosis high-pressure piping, and flue-gas desulphurisation equipment — anywhere high-chloride service combines with mechanical load.

Request a S32550 Tube Quotation

Send your Seamless Super Duplex UNS S32550 Tube enquiry with grade, application, size (OD and wall thickness or schedule), quantity, length, end finish and inspection requirements including any ferrite content limits or third-party witnessing.

Request an S32550 Tube Quotation