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Super Duplex Stainless Steel Pipe

OD Range :

12.7 – 508 mm(Common sizes: 21.3, 26.9, 33.7, 48.3, 60.3, 76.1, 89, 114.3, 168.3, 219.1, 273, 323.9, 355.6, 406.4, 457, 508 mm)

WT Range :

1.2 – 25 mm

Length :

5.8 – 12 m

Tolerance :

Outer diameter ±1% / Wall thickness ±10% / Length ±50 mm

Material :

UNS S32750 / S32760，Super Duplex

Standard :

ASTM A789 / A790, ASME SA789 / SA790, EN 10216-5, GB/T 2513-2008

Surface :

Polishing, acid pickling and passivation, sandblasting, heat treatment followed by a bright or matte finish.

Application :

Petrochemicals, seawater treatment, shipbuilding, chemical industry, petrochemical pipelines, pipelines in highly corrosive environments.

I. Overview of Super Duplex Stainless Steel Pipes

Super Duplex stainless steel pipes are high-performance duplex stainless steel pipes that combine the advantages of both austenitic and ferritic stainless steels, possessing both extremely high strength and excellent corrosion resistance.
This pipe material is particularly suitable for the transportation of seawater, acid and alkaline solutions, and chemical media, and is resistant to pitting corrosion, crevice corrosion, and stress corrosion cracking.
Super Duplex stainless steel pipes are widely used in petrochemicals, seawater desalination, shipbuilding, the chemical industry, and pipelines in highly corrosive environments, making them an ideal choice for high-end industrial pipelines and special application pipelines.

II. Chemical Composition and Mechanical Properties of Super Duplex Stainless Steel Tubes

i. Chemical Composition Table (%)

Steel grade	C	Cr	Ni	Mo	N	Mn
S32750	≤0.03	24–26	6–8	3–5	0.24–0.32	≤1.2
S32760	≤0.03	25–26	7–9	3–5	0.24–0.32	≤1.2

ii. Mechanical Properties Table

Steel Grade	Yield Strength ReH (MPa)	Tensile Strength Rm (MPa)	Elongation A (%)	Hardness HB
S32750	≥ 550	800–900	≥ 25	250–280
S32760	≥ 600	850–1000	≥ 25	280–310

III. Common Steel Grades and Differences of Super Duplex Stainless Steel Pipes

i. Common Steel Grades

Steel Grade	UNS Number	Abbreviation	Features
S32750	UNS S32750	25Cr-7Ni-3Mo	Standard Super Duplex steel, good corrosion resistance, high strength, suitable for seawater and chemical pipelines
S32760	UNS S32760	25Cr-7Ni-4Mo	High nickel, high chromium, high molybdenum duplex steel, superior resistance to chloride stress corrosion, suitable for harsh environments
S32906	UNS S32906	Lean Duplex	Low nickel, low molybdenum super duplex steel, lower cost, suitable for general chemical and seawater applications
S32520	UNS S32520	Lean Duplex	Lower alloy content, slightly lower corrosion resistance, suitable for moderate corrosion environments, more economical

ii. Main Differences Between Steel Grades

Corrosion Resistance
S32760 > S32750 > S32906/S32520
S32760 has a higher molybdenum content and is most resistant to chloride corrosion and stress corrosion cracking.
Mechanical Strength
S32760 has slightly higher strength, followed by S32750, while Lean Duplex steel has slightly lower strength.
High strength is suitable for high-pressure, high-temperature pipeline applications.
Alloy Cost
High-nickel, high-molybdenum steel (S32760) has the highest cost.
Lean Duplex steel (S32906/S32520) has a lower cost and is more economical.
Application Environment
S32760: High-chloride, highly corrosive environments, such as offshore oil and gas platforms and seawater desalination.
S32750: General seawater and chemical pipelines.
Lean Duplex: Medium to low corrosive environments, chemical plants, freshwater transportation.
Applicable Standards
ASTM A789 / A790, ASME SA789 / SA790, EN 10216-5, GB/T 2513
Different steel grades have corresponding chemical composition and mechanical property requirements in the standards.

IV. Applications of Super Duplex Stainless Steel Pipes

Oil and Gas Industry
Offshore oil and gas platforms, subsea pipelines
High-pressure oil and gas transmission pipelines
Resistant to chloride stress corrosion cracking and seawater corrosion
Chemical and Petrochemical Industry
Pipelines for conveying acidic, alkaline liquids, brine, and corrosive chemicals
Reactor and heat exchanger connecting pipes
Piping systems in high-temperature, highly corrosive environments
Seawater Desalination and Water Treatment
Seawater intake pipelines, desalination plant pipelines
Cooling water circulation pipelines
Resistant to seawater corrosion, extending service life
Shipbuilding and Marine Engineering
Ship deck pipelines, internal piping systems
Offshore platforms, floating device pipelines
High strength and excellent corrosion resistance
Energy and Power Generation Industry
Thermal power and nuclear power plant cooling water pipelines
High-temperature and high-pressure steam pipelines
Suitable for harsh operating conditions, improving safety
Other High-Corrosion Environments
Chemical plants, seaport facilities
Industrial wastewater transmission pipelines
Scenarios requiring both high strength and corrosion resistance

V. Super Duplex Stainless Steel Pipe Selection Guide

Selecting the Steel Grade Based on the Working Medium
S32750: Suitable for seawater, desalinated water, and general chemical liquid transportation.
S32760: Suitable for more demanding chemical media and high-concentration chloride environments.
Note: For conditions with high chloride content or a risk of stress corrosion cracking, S32760 is the preferred choice.
Selecting Wall Thickness Based on Working Pressure and Temperature
High-pressure pipelines: Choose thicker-walled pipes to increase the safety factor.
High-temperature conditions: Pay attention to thermal expansion and strength changes, and select a steel grade and wall thickness that meet the temperature requirements.
It is recommended to refer to the ASTM A789 / ASME SA789 standard wall thickness table for selection.
Determining Flow Rate and Installation Method Based on Pipe Diameter
Larger outer diameter results in lower pressure loss per unit flow rate.
When selecting the appropriate pipe diameter, consider flow rate, pressure, installation space, and the number of elbows.
Surface Treatment and Corrosion Protection Requirements
Seawater and highly corrosive environments: Acid pickling and passivation or polished surface to improve corrosion resistance.
Chemical and high-temperature steam pipelines: Sandblasted or bright surface can be chosen for easier cleaning and maintenance.
Standards and Certification Requirements
Confirm that the pipe material complies with ASTM A789 / A790, ASME SA789 / SA790, EN 10216-5, GB/T 2513, etc.
For critical engineering pipelines, prioritize products with certifications and test reports.
Construction and Maintenance Considerations
Welding can be performed using TIG, MIG, butt welding, etc., and passivation treatment is required after welding.
When bending pipes, control the cold bending or hot bending radius to avoid local stress concentration leading to cracking.

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Super Duplex Stainless Steel Pipe Specifications and Dimensions Table

Inch	Outer Diameter (mm)	Wall Thickness (mm)	Theoretical Weight (kg/m)	Tolerance
1/2″	21.3	1.2, 1.5, 2.0, 2.5, 3.0, 3.25, 4.0, 4.5, 5.0, 5.56, 6.0	1.68 – 5.34	OD ±1% / Wall ±10% / Length ±50 mm
3/4″	26.9	1.5, 2.0, 2.5, 3.0, 3.25, 4.0, 4.5, 5.0, 5.56, 6.0, 6.35	2.21 – 6.92	OD ±1% / Wall ±10% / Length ±50 mm
1″	33.7	2.0, 2.5, 3.0, 3.25, 4.0, 4.5, 5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0	2.89 – 9.84	OD ±1% / Wall ±10% / Length ±50 mm
1 1/4″	42.4	2.5, 3.0, 3.25, 4.0, 4.5, 5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0, 9.0	4.03 – 14.6	OD ±1% / Wall ±10% / Length ±50 mm
1 1/2″	48.3	2.5, 3.0, 3.25, 4.0, 4.5, 5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0, 9.0, 10.0	4.61 – 17.4	OD ±1% / Wall ±10% / Length ±50 mm
2″	60.3	2.5, 3.0, 3.25, 4.0, 4.5, 5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0	5.83 – 22.1	OD ±1% / Wall ±10% / Length ±50 mm
2 1/2″	76.1	3.0, 3.25, 4.0, 4.5, 5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0	7.38 – 31.7	OD ±1% / Wall ±10% / Length ±50 mm
3″	88.9	3.25, 4.0, 4.5, 5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0	8.57 – 42.9	OD ±1% / Wall ±10% / Length ±50 mm
4″	114.3	3.25, 4.0, 4.5, 5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0, 18.0	11.1 – 61.5	OD ±1% / Wall ±10% / Length ±50 mm
6″	168.3	4.0, 4.5, 5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0, 18.0, 20.0	17.6 – 106	OD ±1% / Wall ±10% / Length ±50 mm
8″	219.1	5.0, 5.56, 6.0, 6.35, 7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0, 18.0, 20.0, 22.0	26.2 – 161	OD ±1% / Wall ±10% / Length ±50 mm
10″	273	6.0, 6.35, 7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0, 18.0, 20.0, 22.0, 25.0	36.5 – 236	OD ±1% / Wall ±10% / Length ±50 mm
12″	323.9	6.35, 7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0, 18.0, 20.0, 22.0, 25.0, 28.0	47.7 – 307	OD ±1% / Wall ±10% / Length ±50 mm
14″	355.6	7.0, 7.11, 8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0, 18.0, 20.0, 22.0, 25.0, 28.0, 30.0	53.9 – 377	OD ±1% / Wall ±10% / Length ±50 mm
16″	406.4	8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0, 18.0, 20.0, 22.0, 25.0, 28.0, 30.0, 32.0	67.4 – 484	OD ±1% / Wall ±10% / Length ±50 mm
18″	457	8.0, 9.0, 10.0, 11.0, 12.0, 14.0, 16.0, 18.0, 20.0, 22.0, 25.0, 28.0, 30.0, 32.0	81.7 – 603	OD ±1% / Wall ±10% / Length ±50 mm
20″	508	10.0, 11.0, 12.0, 14.0, 16.0, 18.0, 20.0, 22.0, 25.0, 28.0, 30.0, 32.0, 35.0	102 – 758	OD ±1% / Wall ±10% / Length ±50 mm

Super duplex stainless steel pipe standards

Standard Type	Standard Number	Scope / Description
International Standard	ASTM A789 / A790	Austenitic-ferritic (duplex) stainless steel seamless and welded pipes; specifies chemical composition, mechanical properties, dimensions, tolerances, and heat treatment; suitable for highly corrosive piping
International Standard	ASME SA789 / SA790	Equivalent to ASTM A789 / A790; applicable to ASME piping systems and boiler pressure piping
European Standard	EN 10216-5	Steel seamless pipes for pressure purposes made of austenitic-ferritic stainless steel; specifies chemical composition, mechanical properties, and dimensional tolerances
Chinese National Standard	GB/T 2513-2008	Austenitic-ferritic stainless steel pipes; suitable for chemical, seawater, petroleum, and other corrosive environments; specifies chemical composition, mechanical properties, dimensions, and tolerances
International Standard	ISO 17781	Austenitic-ferritic (duplex) stainless steel pipes; suitable for pressure applications and corrosion-resistant environments

Super Duplex Stainless Steel Pipe Production Process

Steel billet preparation → Heating and hot rolling → Cold/hot rolling and finishing → Welding → Solution treatment → Pickling and passivation → Size cutting and inspection → Packaging and shipment

Step	Brief Description
Billet Preparation	Select high-quality duplex stainless steel billets and check chemical composition
Heating & Hot Rolling	Heat billets to high temperature and roll into pipe billets, forming initial outer diameter and wall thickness
Cold/Hot Finishing	Adjust dimensional accuracy and improve surface quality
Welding	TIG/MIG welding for pipes (if welded); post-weld heat treatment and passivation
Solution Treatment	High-temperature heating followed by rapid water quenching to optimize austenite/ferrite ratio, improving strength and corrosion resistance
Pickling & Passivation	Remove oxide scale and impurities, forming a dense passive layer
Cutting & Inspection	Cut to customer-specified lengths; inspect dimensions, wall thickness, mechanical properties, and chemical composition
Packaging & Dispatch	Protective packaging; include material certificate and inspection report, ready for shipment

Testing Standards for Super Duplex Stainless Steel Pipes

Inspection Item	Purpose / Description
Chemical Composition Test	Verify that elements such as C, Cr, Ni, Mo, N meet the steel grade requirements (S32750 / S32760), ensuring corrosion resistance and mechanical properties
Yield Strength & Tensile Strength	Measure maximum stress and yield point under tension to ensure pipe strength meets design pressure requirements
Elongation	Measure material elongation after fracture, reflecting pipe ductility and toughness, preventing brittle failure
Hardness Test	Brinell or Rockwell hardness test to confirm strength and wear resistance, ensuring processing and service performance
Non-Destructive Testing (UT / PT / MT)	Ultrasonic, magnetic particle, or dye penetrant testing of welds and pipe body to ensure no internal cracks, porosity, or inclusions
Dimensional & Tolerance Check	Verify outer diameter, wall thickness, and length comply with standard tolerances, ensuring proper installation and flow requirements
Surface Quality Inspection	Check for oxide scale, scratches, dents, or corrosion spots to ensure corrosion resistance and aesthetic quality
Bend & Flattening Test	Verify that pipes do not crack during on-site bending or flattening, ensuring construction safety
Chloride Pitting / Crevice Corrosion Test (Optional)	Simulate seawater or corrosive environments to verify pipe resistance to chloride corrosion, especially for marine and chemical projects

Super Duplex Stainless Steel Pipe Selection FAQ

Q1: What types of media are suitable for super duplex stainless steel pipes?

A:
Suitable for seawater, desalinated water, chloride environments, highly corrosive chemical liquids, petrochemical media, and high-temperature steam pipelines. The S32760 grade is suitable for harsh environments with high chloride concentrations or high risk of stress corrosion cracking.

Q2: How to select the pipe wall thickness based on working pressure and temperature?

A:
Thick-walled pipes should be selected for high-pressure pipelines to ensure a safety factor; for high-temperature pipelines, the mechanical properties and thermal expansion characteristics of the steel grade should be considered. It is recommended to refer to the standard wall thickness table in ASTM A789 / ASME SA789 for selection.

Q3: What are the differences between S32750 and S32760?

A:
S32760 has slightly higher nickel and molybdenum content, offering better corrosion resistance and resistance to chloride stress corrosion cracking, making it suitable for harsh environments; S32750 is suitable for general seawater and chemical media, and is slightly less expensive.

Q4: What surface treatment options are available for the tubing?

Answer:
Options include pickling and passivation, polishing, matte finish, or sandblasting. For seawater and highly corrosive environments, pickling and passivation or polishing are recommended to improve corrosion resistance and service life.

Q5: What are the welding properties of the tubing? What welding methods can be used?

Answer:
TIG, MIG, or butt welding can be used. Post-weld heat treatment and passivation are recommended to ensure weld strength and corrosion resistance. The austenite/ferrite ratio should be controlled during welding to prevent stress corrosion cracking.

Q6: What standards and certifications should be considered when purchasing tubing?

Answer:
Confirm compliance with ASTM A789/A790, ASME SA789/SA790, EN 10216-5, or GB/T 2513 standards. For critical applications, it is best to choose products with material certificates, mechanical property reports, and chemical composition test reports.