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ASTM A789 Duplex Stainless Steel Tubing – Seamless & Welded 2205/2507
Xi'an Dongmeng Group Co., Ltd. is a professional manufacturer and exporter of industrial metal products, supplying ASTM A789 duplex stainless steel tubing for international distributors, engineering contractors, equipment manufacturers, and industrial fabrication projects.
Our ASTM A789 tubing solutions cover duplex and super duplex stainless steel grades, including UNS S31803, S32205, S32750, and S32760. Seamless and welded tube options can be evaluated for heat exchangers, chemical processing equipment, offshore systems, desalination facilities, and other corrosion-sensitive industrial applications.
Duplex stainless steel combines high mechanical strength with improved resistance to chloride-induced stress corrosion cracking compared with conventional austenitic grades.
We support project-based procurement through material selection assistance, dimensional review, manufacturing coordination, quality inspection, and export delivery.
Request a quotation, submit your technical drawing, or contact us for material specifications and inspection documentation.
What Is ASTM A789 Duplex Stainless Steel Tubing?
ASTM A789/A789M is the standard specification covering seamless and welded ferritic-austenitic stainless steel tubing for general corrosion-resistant service.
Duplex stainless steels contain both ferrite and austenite phases. Their combination of chromium, nickel, molybdenum, and nitrogen provides an attractive balance of strength, toughness, and corrosion resistance.
Compared with conventional 304L and 316L stainless steels, properly selected duplex grades generally offer higher yield strength and improved resistance to chloride-induced stress corrosion cracking.
ASTM A789 covers tubing manufactured with either average wall thickness or specified minimum wall thickness. The purchaser must identify the applicable dimensional basis and standard edition.
The specification does not establish universal suitability for every pressure, temperature, or corrosive environment.
Final material selection should consider operating temperature, chloride concentration, pH, oxidizing conditions, pressure, fabrication requirements, and applicable engineering design codes.
ASTM A789 Duplex Stainless Steel Tubing Specifications
| Parameter | Specification |
|---|---|
| Product | Duplex Stainless Steel Tubing |
| ASTM Standard | ASTM A789/A789M |
| ASME Specification | SA-789/SA-789M, where applicable |
| Material Family | Duplex / Super Duplex Stainless Steel |
| Main Grades | S31803, S32205, S32750, S32760 |
| Manufacturing | Seamless / Welded |
| Tube Geometry | Primarily Round Tubing |
| Outside Diameter | Specified in mm or inches |
| Wall Thickness | Average Wall / Minimum Wall |
| Tube Length | Random / Fixed / Cut-to-Length |
| Delivery Condition | Solution Heat Treated |
| Surface | Annealed & Pickled / Other Approved Finish |
| End Preparation | Square Cut / Deburred / Project-Specific |
| Testing | ASTM-Specified Mechanical and Integrity Testing |
| Documentation | Inspection Report / Material Test Certificate |
| Optional Processing | Precision Cutting / Bending / Surface Treatment |
| Supply Basis | Project Specification and Confirmed Availability |
Note: Dimensions, special processing, and supply quantities are subject to manufacturing capability and order confirmation. ASTM A789 does not establish a universal commercial stock range.
ASTM A789 Duplex Stainless Steel Tubing Sizes
ASTM A789 tubing can be ordered using metric or imperial outside diameters.
Common engineering enquiries involve small- and medium-diameter tubing for heat exchangers, process equipment, and instrumentation-related applications.
Reference Tube Size Chart
| Outside Diameter (mm) | Outside Diameter (inch) | Example Wall Thickness (mm) |
|---|---|---|
| 6.35 | 1/4 | 0.89 / 1.24 |
| 9.53 | 3/8 | 0.89 / 1.24 / 1.65 |
| 12.70 | 1/2 | 0.89 / 1.24 / 1.65 |
| 15.88 | 5/8 | 1.24 / 1.65 / 2.11 |
| 19.05 | 3/4 | 1.24 / 1.65 / 2.11 |
| 25.40 | 1 | 1.65 / 2.11 / 2.77 |
| 31.75 | 1-1/4 | 1.65 / 2.11 / 2.77 |
| 38.10 | 1-1/2 | 1.65 / 2.11 / 2.77 |
| 50.80 | 2 | 1.65 / 2.11 / 3.05 |
The dimensions above are representative purchasing combinations, not a statement of stock availability or an ASTM-required size series.
Actual tube dimensions must be confirmed against the selected grade, manufacturing route, wall basis, tolerances, and production capability.
Tube Dimensional Requirements
For accurate engineering procurement, specify:
Outside diameter and permissible OD deviation.
Average or minimum wall thickness.
Required inside diameter, where applicable.
Fixed length and cutting tolerance.
Straightness and ovality requirements.
Surface condition and allowable defects.
Internal cleanliness requirements.
Tube-end preparation.
Average Wall vs Minimum Wall Tubing
Average-wall tubing is ordered with a nominal wall thickness and the permissible wall variation specified by the applicable standard.
Minimum-wall tubing must satisfy the required minimum thickness at the relevant inspection locations.
These two ordering methods are not interchangeable.
For heat exchangers and pressure-retaining equipment, the correct wall-thickness basis should be established during mechanical design.
ASTM A789 Available Duplex Stainless Steel Grades
UNS S31803 – Duplex Stainless Steel
UNS S31803 is a conventional 22% chromium duplex stainless steel grade.
It provides higher strength than many common austenitic stainless steels and improved resistance to chloride-induced stress corrosion cracking.
Typical applications include:
Industrial heat exchangers
Chemical processing equipment
Pulp and paper equipment
Process cooling systems
General corrosion-resistant tubing
UNS S32205 – Duplex 2205 Stainless Steel
UNS S32205 is a widely specified duplex stainless steel grade with tighter chromium, molybdenum, and nitrogen requirements than S31803.
It is frequently selected for industrial applications requiring a combination of mechanical strength and resistance to localized corrosion.
Typical applications include:
Heat exchanger tubing
Offshore process equipment
Chemical processing facilities
Brackish-water equipment
Industrial cooling systems
S31803 and S32205 may be supplied as dual-certified material only when the actual heat and finished product satisfy both specifications.
UNS S32750 – Super Duplex 2507
UNS S32750 is a high-alloy super duplex stainless steel containing approximately 25% chromium, together with elevated molybdenum and nitrogen levels.
It provides greater localized corrosion resistance than standard duplex 2205 in many chloride-containing environments.
Typical applications include:
Offshore equipment
Desalination systems
High-chloride industrial cooling
Chemical processing equipment
Corrosion-critical heat exchangers
Material selection must still consider crevice geometry, fluid temperature, chlorination, and operating conditions.
UNS S32760 – Super Duplex Stainless Steel
UNS S32760 is a super duplex stainless steel grade containing chromium, nickel, molybdenum, nitrogen, copper, and tungsten.
It is commonly evaluated for demanding industrial environments involving chlorides and corrosive process fluids.
Typical applications include:
Offshore processing systems
Seawater-related equipment
Chemical plant components
Industrial heat exchangers
High-integrity corrosion-resistant systems
S32760 should not be treated as an automatic substitute for S32750 without checking the material specification and engineering requirements.
ASTM A789 Chemical Composition
The following table summarizes the principal chemical composition ranges published for common grades in ASTM A789/A789M-24.
| NS Grade | C Max | Cr | Ni | Mo | N |
|---|---|---|---|---|---|
| S31803 | 0.030 | 21.0–23.0 | 4.5–6.5 | 2.5–3.5 | 0.08–0.20 |
| S32205 | 0.030 | 22.0–23.0 | 4.5–6.5 | 3.0–3.5 | 0.14–0.20 |
| S32750 | 0.030 | 24.0–26.0 | 6.0–8.0 | 3.0–5.0 | 0.24–0.32 |
| S32760 | 0.030 | 24.0–26.0 | 6.0–8.0 | 3.0–4.0 | 0.20–0.30 |
Additional alloying requirements:
S32750: Copper maximum 0.50%.
S32760: Copper 0.50–1.00% and tungsten 0.50–1.00%.
Other chemical limits, including manganese, phosphorus, sulfur, and silicon, must also comply with the specified grade.
Technical note: This table is a reference to the 2024 edition. Purchase orders specifying ASTM A789/A789M-26 must be checked against the complete 2026 standard before final certification.
ASTM A789 Mechanical Properties
The following values provide engineering reference data for the principal duplex and super duplex grades.
| UNS Grade | Tensile Strength Min. (MPa) | Yield Strength Min. (MPa) | Elongation Min. | Hardness Max. (HB) |
|---|---|---|---|---|
| S31803 | 620 | 450 | 25% | 290 |
| S32205 | 655 | 485 | 25% | 290 |
| S32750 | 800 | 550 | 15% | 310 |
| S32760 | 750 | 550 | 25% | 300 |
These reference values are based on earlier published ASTM A789 requirements and are not substitutes for the complete applicable edition.
Mechanical-property applicability and test conditions depend on tube dimensions and the governing specification.
For pressure equipment, actual design allowable stresses must be obtained from the applicable engineering code rather than calculated directly from minimum tensile strength.
ASTM A789 Heat Treatment Requirements
Duplex stainless steel tubing must receive appropriate solution heat treatment to develop the required microstructure and mechanical properties.
Proper heat treatment helps reduce the risk of undesirable intermetallic phases and preserves corrosion resistance.
Reference Solution Treatment Temperatures
| Grade | Temperature Range |
|---|---|
| S31803 | 1020–1100°C |
| S32205 | 1020–1100°C |
| S32750 | 1025–1125°C |
| S32760 | 1070–1140°C |
These temperatures are reference ranges from ASTM A789/A789M-24.
The final thermal cycle, cooling method, and acceptance criteria must follow the applicable standard edition.
Important: Duplex stainless steels are susceptible to microstructural degradation during prolonged exposure to certain elevated temperatures. They should not be marketed as universally suitable for high-temperature service.
Seamless vs Welded ASTM A789 Duplex Tubing
Both seamless and welded manufacturing routes are covered by ASTM A789.
| Feature | Seamless Tubing | Welded Tubing |
|---|---|---|
| Manufacturing | Piercing and tube-forming processes | Strip forming and autogenous welding |
| Weld Seam | None | Longitudinal weld seam |
| Heat Treatment | Required | Required |
| Common Applications | Heat exchangers and industrial equipment | Heat exchangers and industrial equipment |
| Inspection | Applicable ASTM requirements | Applicable ASTM requirements |
| Selection Basis | Design, dimensions, availability and integrity requirements | Design, dimensions, availability and integrity requirements |
Seamless Duplex Stainless Steel Tubing
Seamless tubes are manufactured without a longitudinal weld joint.
They are often considered for applications with demanding dimensional, fabrication, or integrity requirements.
However, seamless construction alone does not establish a higher allowable operating pressure.
Welded Duplex Stainless Steel Tubing
Welded A789 tubing is produced using a welding process without added filler metal.
The welded product must meet the applicable heat-treatment, mechanical, dimensional, and integrity-testing requirements.
Welded tubing can be an economical engineering option when its production method and inspection requirements are accepted by the project specification.
Corrosion Resistance of ASTM A789 Duplex Tubing
Resistance to Pitting Corrosion
Chromium, molybdenum, and nitrogen contribute to resistance against localized corrosion.
The Pitting Resistance Equivalent Number (PREN) is commonly used as an initial screening parameter:
PREN = %Cr + 3.3 × %Mo + 16 × %N
A higher PREN generally indicates improved resistance to chloride pitting under comparable conditions.
However, PREN is not a complete predictor of service performance.
Resistance to Crevice Corrosion
Crevice corrosion can develop beneath deposits, gaskets, tube supports, and other restricted-flow areas.
Super duplex grades generally offer improved localized corrosion resistance compared with standard duplex grades.
Nevertheless, material selection must consider seawater chlorination, temperature, deposits, and crevice geometry.
Chloride Stress Corrosion Cracking
Duplex stainless steels generally provide better resistance to chloride-induced stress corrosion cracking than conventional 304L and 316L grades.
This advantage is particularly relevant in chloride-containing industrial environments.
However, no duplex grade should be considered completely immune to stress corrosion cracking.
Chemical Processing Environments
Duplex tubing may be appropriate for selected chemical processing conditions.
Suitability depends on the actual chemical composition, concentration, temperature, aeration, and contamination of the process medium.
Chemical compatibility should be established through engineering data, relevant operating experience, or corrosion testing.
ASTM A789 Tubing Applications
1. Heat Exchanger Tubing
ASTM A789 duplex tubes can be used in shell-and-tube heat exchangers where mechanical strength and chloride corrosion resistance are important.
Selection considerations include:
Tube outside diameter and wall thickness
Tube-sheet connection method
Fluid composition and operating temperature
Tube expansion or welding requirements
Vibration and fatigue considerations
Inspection and cleanliness requirements
2. Offshore Oil & Gas Equipment
Duplex stainless steel tubing is used in selected offshore process equipment exposed to demanding corrosive conditions.
Important evaluation factors include chloride exposure, design pressure, temperature, and applicable project material specifications.
Sour-service applications require separate verification against the relevant ISO 15156/NACE MR0175 requirements and project-specific restrictions.
3. Desalination and Water Treatment
Duplex and super duplex grades are considered for selected desalination and industrial water-treatment components.
Super duplex stainless steels may offer advantages in aggressive chloride-containing environments.
However, chlorinated seawater and crevice conditions can remain highly challenging, even for super duplex alloys.
4. Chemical Processing Equipment
ASTM A789 tubing can be specified for selected chemical processing applications involving corrosion-resistant heat-transfer surfaces and industrial equipment.
The final alloy selection should be supported by chemical compatibility data and design requirements.
5. Industrial Cooling Systems
Duplex stainless steel tubing is used in selected cooling systems involving brackish water, contaminated water, or process fluids.
Engineering evaluation should include localized corrosion risk, fluid velocity, deposits, and operating temperature.
ASTM A789 vs ASTM A790
ASTM A789 and ASTM A790 cover related duplex stainless steel materials but different tubular product specifications.
| Comparison | ASTM A789 | ASTM A790 |
|---|---|---|
| Product | Stainless Steel Tubing | Stainless Steel Pipe |
| Material Family | Duplex / Super Duplex | Duplex / Super Duplex |
| Manufacturing | Seamless / Welded | Seamless / Welded |
| Common Size Designation | OD × Wall Thickness | NPS / Schedule or OD × Wall |
| Typical Application | Heat Exchangers and Industrial Tubing | Industrial Process Piping |
| Ordering Focus | Tube Dimensions and Wall Basis | Pipe Dimensions and Piping Requirements |
| Relevant General Requirements | ASTM A1016/A1016M | ASTM A999/A999M |
A789 and A790 are not automatically interchangeable.
The material specification should match the intended product form, engineering drawings, fabrication method, and governing design code.
For process piping applications, see our ASTM A790 Duplex Stainless Steel Pipe product range.
ASTM A789 Tubing Inspection & Quality Assurance
Material inspection is an essential part of industrial duplex stainless steel tubing procurement.
Depending on the applicable standard edition, product condition, and purchase order, the inspection program may include the following activities.
Chemical Composition Verification
Heat analysis and applicable product analysis verify compliance with the specified chemical requirements.
Positive Material Identification (PMI) may be arranged for additional alloy verification.
Mechanical Testing
Applicable mechanical testing includes tensile and hardness testing.
The relevant product specification also establishes forming-related tests for seamless and welded tube products.
Tube Integrity Testing
ASTM A789 requires the applicable hydrostatic or nondestructive electric testing route.
Additional inspection, such as ultrasonic testing, may be arranged where technically appropriate and specified in the purchase order.
Dimensional Inspection
Dimensional inspection verifies:
Outside diameter
Wall thickness
Length
Straightness
Surface condition
Additional agreed dimensional requirements
Additional Project Inspection
Depending on the project specification, additional testing may include:
Ferrite content measurement
Metallographic examination
Corrosion testing to an agreed method
Surface roughness inspection
Third-party inspection
Special nondestructive examination
These additional tests should not be confused with the minimum requirements of ASTM A789.
Material Test Certificates
Material test reports can be prepared in accordance with the purchase order.
EN 10204 Type 3.1 inspection certificates may be supplied where the manufacturer has agreed to the relevant certification requirements.
Third-party inspection and Type 3.2 documentation may be evaluated separately when required.
Surface Finish & Custom Processing
ASTM A789 duplex tubing is commonly supplied in a solution heat-treated condition with appropriate surface treatment.
Depending on manufacturing capability and application, available processing options may include:
Annealed & Pickled: Surface treatment to remove heat-treatment scale and improve surface cleanliness.
Bright Surface Finish: Subject to an approved manufacturing and heat-treatment process.
Precision Cutting: Fixed-length cutting according to approved dimensional requirements.
Tube Bending: Project-specific bending subject to grade, radius, wall thickness, and process qualification.
End Preparation: Square-cut ends, deburring, and specified end preparation.
Surface Cleaning: Additional cleaning and protection for selected industrial applications.
All processing requirements should be confirmed before production.
Packaging & International Shipping
ASTM A789 duplex stainless steel tubing requires suitable protection during handling, storage, and transportation.
Packaging arrangements may include:
Protected tube bundles
End caps where appropriate
Wooden or plywood cases
Moisture-resistant protective materials
Identification labels
Heat-number traceability
Export shipping marks
Special packaging can be discussed for precision tubing, polished tubing, and project-specific deliveries.
Shipment arrangements depend on tube length, order quantity, destination, and agreed Incoterms.
Why Choose Xi'an Dongmeng Group Co., Ltd.?
Industrial Material Supply
We support international procurement requirements for stainless steel tubing and related metal products.
Multiple Duplex Stainless Steel Grades
Our supply coordination covers standard duplex and super duplex materials for different industrial applications.
Technical Procurement Support
We assist customers in reviewing material grades, tube dimensions, production methods, and inspection requirements.
Quality Documentation
We coordinate material identification, inspection records, and agreed certification requirements.
Customized Project Supply
Special dimensions, fixed lengths, processing, and packaging requirements can be reviewed against customer drawings and manufacturing feasibility.
International Export Support
We support international enquiries, commercial documentation, export packaging, and shipment coordination.
Frequently Asked Questions
1. What is ASTM A789 duplex stainless steel tubing?
ASTM A789 is a specification for seamless and welded ferritic-austenitic stainless steel tubing intended for general corrosion-resistant service, particularly where resistance to stress corrosion cracking is important.
2. What grades are commonly specified under ASTM A789?
Common grades include UNS S31803, S32205, S32750, and S32760. The correct grade depends on operating conditions and material requirements.
3. What is the difference between S31803 and S32205?
S32205 has tighter chromium, molybdenum, and nitrogen composition limits. Dual certification is possible only when the finished material meets both specifications.
4. Is ASTM A789 tubing available in seamless and welded forms?
Yes. Both manufacturing methods are covered. Product selection should consider the engineering specification, dimensional requirements, and inspection acceptance criteria.
5. Is ASTM A789 the same as ASTM A790?
No. A789 covers tubing, while A790 covers pipe. Their dimensional and general-requirement systems differ.
6. What is the difference between duplex 2205 and super duplex 2507?
Duplex 2205 provides a combination of high strength and good chloride corrosion resistance. Super duplex 2507 generally offers greater resistance to localized corrosion because of its higher alloy content.
7. Can ASTM A789 tubing be used in seawater systems?
Some duplex and super duplex grades are used in seawater-related applications. Actual suitability depends on temperature, chlorination, fluid chemistry, crevice conditions, and engineering design.
8. What inspections are required for ASTM A789 tubing?
The applicable specification includes chemical, mechanical, and tube-integrity requirements. Hydrostatic or nondestructive electric testing is required as specified. Additional inspection may be ordered separately.
9. Is ASTM A789 suitable for high-pressure service?
Duplex stainless steels provide relatively high strength, but allowable pressure must be determined by engineering calculation under the applicable design code using the actual material, dimensions, temperature, and other relevant factors.
10. Can ASTM A789 tubing be bent?
Tube bending may be possible, depending on grade, wall thickness, bend radius, and manufacturing process. Project-specific forming and inspection requirements should be confirmed before ordering.
11. Can ASTM A789 tubing be supplied with an EN 10204 3.1 certificate?
EN 10204 Type 3.1 certification can be specified in the purchase order, subject to agreement with the manufacturer and the applicable inspection and documentation requirements.
12. What information is required for an ASTM A789 tubing quotation?
Customers should provide the material grade, specification edition, seamless or welded construction, outside diameter, wall thickness, length, quantity, required inspections, certification requirements, and delivery destination.
Request a Quote – ASTM A789 Duplex Stainless Steel Tubing
Looking for ASTM A789 seamless or welded duplex stainless steel tubing for your next industrial project?
Xi'an Dongmeng Group Co., Ltd. supports global customers with material procurement, dimensional review, inspection coordination, and export delivery.
For an accurate quotation, please provide:
Material Grade: S31803 / S32205 / S32750 / S32760
Product Standard: ASTM A789/A789M or ASME SA-789/SA-789M, with the required edition
Manufacturing Method: Seamless / Welded
Tube Dimensions: OD × Wall Thickness × Length
Wall Basis: Average Wall / Minimum Wall
Required Quantity: Pieces / Meters / Total Weight
Inspection Requirements: Standard Testing / Additional NDT / PMI / Third-Party Inspection
Documentation: MTC / EN 10204 3.1 / Project-Specific Documents
Delivery Destination: Country / Port / Project Location
Office Information
Xi'an Dongmeng Group Co., Ltd.
Phone / WhatsApp: +86 157 6921 4734
Email: office@dongmjd.com
Office Address: Room 4107, Runfeng Building, Sanqiao New Street, Weiyang District, Xi'an City, Shaanxi Province, China
Contact us to request a quotation, technical specification review, or material documentation for your ASTM A789 duplex stainless steel tubing project.
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