ASTM A789 UNS S31803 Duplex Stainless Steel Tubes
What is the ASTM A789 standard?
ASTM A789 is the standard specification for seamless ferritic/austenitic stainless steel tubing intended for general corrosion-resistant service. Products covered by this standard are commonly referred to as duplex stainless steel tubing and are designed for applications requiring high strength and excellent resistance to stress corrosion cracking (SCC), particularly in chloride-containing environments.
ASTM A789 UNS S31803 Tube Supplier,Manufacturer,Exporter,Stockist
As a professional stainless steel manufacturer with over 18 years of export experience, GNEE provides ASTM A789 UNS S31803 duplex stainless steel tube solutions to more than 80 countries and regions worldwide. We supply seamless tubes, U-tubes for heat exchangers, coiled tubes (coil tubes), and custom-length tubes, covering applications such as heat exchangers, condensers, instrumentation tubes, and fluid transportation.
Our ASTM A789 UNS S31803 duplex stainless steel tubes feature a dual-phase microstructure consisting of approximately 50% austenite and 50% ferrite, combining high strength with excellent corrosion resistance. With a yield strength of ≥ 450 MPa and a tensile strength of ≥ 620 MPa, roughly double that of 304/316L austenitic stainless steels these tubes allow for reduced wall thickness, lower equipment weight, and minimized material costs while fully ensuring pressure-bearing capacity.
UNS S31803 stainless steel heat exchanger tubes offer a high Pitting Resistance Equivalent Number (PREN ≥ 35), effectively resisting chloride pitting, crevice corrosion, and stress corrosion cracking (SCC). Regarding service temperatures, S31803 duplex stainless steel is recommended for long-term continuous operation within the range of -50°C to 300°C. It can withstand higher temperatures for short intervals; however, prolonged exposure above 300°C may lead to the precipitation of detrimental intermetallic phases, which impairs impact toughness and corrosion resistance. Therefore, for high-temperature working conditions, materials such as 310S or nickel-based alloys are generally recommended.
Our UNS S31803 seamless tubes are manufactured in accordance with international standards, including ASTM A789, ASME SA789, and EN 10216-5. We support a wide range of specifications with outside diameters (OD) from 6 to 114 mm and wall thicknesses from 0.5 to 15 mm. Available processing techniques include pickling, solution annealing, and a Bright Annealed surface finish.
ASTM A789 UNS S31803 Tube Specification
Chemical Composition of ASTM A789 UNS S31803 Tubes
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N | |
| 2205 (UNS S31803) | Min Max | - 0.030 | - 2.00 | - 1.00 | - 0.030 | - 0.020 | 21.0 - 23.0 | 2.5 - 3.5 | 4.5 - 6.5 | 0.08 - 0.20 |
| 2205 (UNS S32205) | Min Max | - 0.030 | - 2.00 | - 1.00 | - 0.030 | - 0.020 | 22.0 - 23.0 | 3.0 - 3.5 | 4.5 - 6.5 | 0.14 - 0.20 |
Mechanical Properties of ASTM A789 UNS S31803 Duplex Stainless Steel Tubes
| Grade | Standard | Heat Treating Temp. : min | Tensile Strength Min. MPa |
Yield Strength Min. MPa |
Elongation min. % |
| S31803 | A789 | 1020–1100°C | 620 | 450 | 25 |
| S32205 | A789 | 1020–1100°C | 655 | 450 | 25 |
Physical Properties OF ASTM A789 UNS S31803 Duplex Stainless Steel tubes
| Grade | Density (g/cm³) |
Elastic Modulus (GPa) |
Mean Co-eff of Thermal Expansion (μm/m/°C) |
Thermal Conductivity (W/m.K) |
Specific Heat 0-100°C ( J/kg.K) |
Electrical Resistivity (nΩ.m) |
|||
| 0-100°C | 0-315°C | 0-538°C | at 100°C | at 500°C | |||||
| UNS S32205 / 2205 | 7.8 | 190 | 13.7 | 14.2 | N/A | 19 | N/A | 418 | 850 |
ASTM A789 stainless steel pipe Tolerances
| STANDARD | OD(D) | TOLERANCE(MM) | THICKNESS(S) | TOLERANCE | LENGTH | TOLERANCE |
| MM | COMMON HIGH | MM | MM | MM | ||
| A789 | D<12.7 | ±0.13 | S(ave):±15% | S(Min):+30%/0 | OD<38.1 | +3.0/0 |
| 12.7≤D<38.1 | ±0.13 | |||||
| 38.1≤D<88.9 | ±0.25 | S(ave):±10% | S(Min):+20%/0 | OD≥38.1 | +5.00/0 | |
| 88.9≤D≤139.7 | ±0.38 | |||||
| 139.7≤D≤203.2 | ±0.76 |
ASTM A789 UNS S31803 Tube Pressure Rating
| Tube O.D. (In.) |
Wall Thickness (in.) | |||||||
|---|---|---|---|---|---|---|---|---|
| Working Pressure (Psig) | ||||||||
| .120 | .095 | .028 | .065 | .035 | .083 | .049 | .109 | |
| 5/16 | 7300 | 3700 | 5400 | |||||
| 1/8 | 7900 | 10100 | ||||||
| 3/8 | 6100 | 3100 | 4400 | |||||
| 3/4 | 4600 | 3000 | 4000 | 2200 | ||||
| 1/4 | 3700 | 9500 | 4800 | 7000 | ||||
| 1 | 4300 | 3400 | 2200 | 2900 | 3900 | |||
| 1/2 | 4400 | 2300 | 3200 | |||||
ASTM A789 S31803 vs S32205
UNS S32205 is an upgraded, premium-composition version of UNS S31803; both are standard "Duplex 2205" stainless steels. S32205 requires tighter controls and higher minimums for chromium, molybdenum, and nitrogen. Because of this, S32205 always meets the requirements for S31803, but the reverse is not true.
What is the difference between UNS S31803 and SS316?
UNS S31803 is a duplex stainless steel containing ~22% chromium, whereas SS316 is an austenitic stainless steel with ~18% chromium. S31803 offers roughly twice the yield strength and superior pitting corrosion resistance, making it ideal for harsh marine and chemical environments, while SS316 remains easier to fabricate.
What is the difference between ASTM A789 and ASTM A790?
ASTM A789 covers small-diameter tubing intended for heat exchangers, instrumentation lines, and general industrial applications; specifications are typically defined by outside diameter (OD) and average or minimum wall thickness, and the material is commonly used in pressure vessels such as heat exchangers and condensers.
ASTM A790 applies to large-diameter piping. It generally covers large-diameter industrial piping used for fluid transport; specifications are defined by Nominal Pipe Size (NPS) and wall thickness schedule (e.g., Sch 40S), and the material is widely used in industrial fluid transport pipelines.
Applications of ASTM A789 UNS S31803 Duplex Tubes
Chemical Production: Used in shell-and-tube heat exchangers, condensers, and air coolers for reactor effluents.
Oil, Gas, and Petrochemicals: Used in topside instrumentation systems for offshore platforms, subsea umbilical systems, and sour gas service (e.g., handling hydrogen sulfide/H₂S).
Seawater Desalination: Commonly used in multi-stage flash (MSF) and reverse osmosis (RO) desalination plants.
Power Generation and Pulp & Paper: Used in cooling water systems, scrubber towers within flue-gas desulfurization (FGD) units, and pulp bleaching facilities in paper manufacturing.
ASTM A789 UNS S31803 Tube Price (For reference only)
If you are purchasing in bulk (over 2 tons), the price is usually calculated by weight:
Seamless ASTM A789 S31803: $7,500 - $9,500 USD / Metric Ton
Welded ASTM A789 S31803: $6,500 - $8,000 USD / Metric Ton
If you can provide the exact dimensions (Outer Diameter and Wall Thickness), the total quantity in meters/feet, and whether you need seamless or welded types, I can help you get a more precise quote.
Quality Control
All products are available with EN 10204 3.1 Material Test Certificates (MTC) and support PMI testing, chemical composition analysis, hydrostatic testing, eddy current testing, and ultrasonic testing, as well as third-party inspections by agencies such as SGS, BV, and TÜV, ensuring dimensional accuracy, material authenticity, and batch traceability.
High-quality packaging
The wooden frames are constructed entirely from ISPM 15 heat-treated lumber and bear quarantine markings to ensure smooth customs clearance;
The units are fully sealed in 0.12mm thick PE film, with calcium chloride desiccant included as needed, ensuring no corrosion during 720-hour salt spray transit;
Frame lengths are customizable from 3 to 12 meters, accommodating 2 to 8 heat exchanger tubes per frame and compatible with wall thicknesses ranging from 0.8 to 12mm;
Tube ends are sealed with PE plastic caps to prevent the ingress of silt and moisture;
Shipping marks, material details, specifications, and heat numbers can be printed on the exterior of the frames, ensuring full traceability and compliance with acceptance standards for overseas engineering projects.
