S32950 Seamless Super Duplex Steel Tube

UNS S32950 | 1.4655 | ASTM A789

S32950 Seamless Super Duplex Steel Tube (S32950 / 1.4655) 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.

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What Is a Seamless Super Duplex S32950 Tube?

UNSS32950 is a super duplex stainless steel with a balanced austenite-ferrite structure and elevated chromium (26–29%) plus nitrogen. The high alloy content raises the PREN well above the duplex range, delivering markedly better resistance to pitting, crevice corrosion and chloride stress-corrosion cracking than standard 2205 duplex.

SeamlessSuper Duplex Steel UNS S32950 Tube is a high-performance stainless steel tubing solution produced from a solid billet without welding seams. This seamless construction ensures maximum structural integrity, leak resistance, and pressure reliability in demanding environments.

UNS S32950 is a Super Duplex Stainless Steel grade featuring a balanced austenite–ferrite (50:50) microstructure, combining:

With elevated chromium (26–29%) and nitrogen content, S32950 offers significantly improved performance compared to:

S32950 Key Features and Technical Advantages

S32950 is specifically designed to maintain its strength and shape in high-stress, corrosive environments.

These physical properties highlight the material's ability to perform reliably under a wide range of conditions.

Feature	Description
1. Superior Corrosion Resistance	High PREN value (≥ 40 typical) Pitting corrosion Crevice corrosion Chloride-rich environments
2. High Strength & Weight Reduction	Yield strength ≈ 2× higher than 316L stainless steel Reduced wall thickness Lower system weight Cost-efficient engineering design
3. Excellent SCC Resistance	Ferritic phase provides natural resistance to chloride-induced SCC Ensures long service life in aggressive environments
4. Thermal & Structural Stability	In cryogenic conditions Under moderately high temperatures
Standards & Compliance	ASTM A789 / ASME SA789 ASTM A790 / ASME SA790 ASTM A1016 NACE MR0175 (if required for sour service)

S32950 Product Specifications and Data

To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for Super Duplex Steel S32950.

The composition of S32950 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
≥795 MPa	≥550 MPa	≥25%	≤290 HBW

Density	Melting Point	Thermal Expansion	Thermal Conductivity	Modulus of Elasticity	Electrical Resistivity
7.8 g/cm3	1400−1440 ∘C approx.	13.0 μm/m⋅∘C (20−100∘C)	15 W/m⋅K (20∘C)	200 GPa	0.80×10−6 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

S32950 Dimensional Standards and Tolerances

S32950 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.

S32950 Common Industrial Applications

Industry	Typical Applications
Offshore Oil and Gas	Flowlines and manifolds Sour and high-chloride service High-pressure process tubing
Desalination and Water Treatment	RO membrane high-pressure piping Brine and reject handling Evaporator tubing
Chemical and Petrochemical	Heat exchangers and reactors Chloride-bearing process streams Acid service piping
Marine Engineering	Seawater systems Propulsion and cooling pipework Port and harbour infrastructure

S32950 Quality Assurance and Production Process

Process Step	Description
Certification	All Super Duplex S32950 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.

S32950 vs S32750 (2507) – Technical Comparison

S32950 and S32750 both sit in the super duplex family, but their chromium and molybdenum balances differ, which shifts where each performs best.

Chemical Composition

S32950: 26–29% Cr, ~1.5% Mo, ~0.3% N — notably higher chromium, lower molybdenum
S32750: ~25% Cr, ~4% Mo, ~0.3% N — lower chromium, higher molybdenum
Both are balanced duplex with high PREN

Corrosion Resistance

S32950's higher chromium favours resistance in oxidising and nitric-acid-bearing environments, while S32750's higher molybdenum favours resistance to pitting and crevice attack in chloride-bearing media. Both resist chloride stress-corrosion cracking well.

Mechanical Strength

Both grades deliver roughly twice the yield strength of standard austenitic stainless steels, allowing thinner walls and lighter structures, with good toughness maintained to sub-zero temperatures.

Selection Guide

Choose S32950 where oxidising acid resistance and high chromium content matter most
Choose S32750 where maximum pitting and crevice resistance in chloride service is the priority
Confirm the actual service chemistry before selecting between them

Frequently Asked Questions About S32950 Seamless Super Duplex Steel Tubes

What is S32950 super duplex tube?

UNS S32950 is a super duplex stainless steel tube with a balanced austenite-ferrite structure and elevated chromium (26–29%) plus nitrogen. The high alloy content raises the PREN well above the standard duplex range.

How does S32950 compare with S32750?

S32950 carries higher chromium and lower molybdenum than S32750. Its higher chromium favours resistance in oxidising and nitric-acid-bearing environments, while S32750's higher molybdenum favours pitting and crevice resistance in chloride-bearing media.

What is S32950 tube used for?

S32950 serves in offshore oil and gas flowlines and manifolds, desalination and water treatment piping, chemical and petrochemical process lines, and marine engineering where high strength and chloride resistance are both required.

What standard covers S32950 tube?

S32950 seamless tube is supplied to ASTM A789 / ASME SA789 and ASTM A790 / ASME SA790, with dimensional tolerances per ASTM A1016 / A1016M.

Request a S32950 Tube Quotation

Send your Seamless Super Duplex S32950 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 S32950 Tube Quotation