ASTM A790 UNS S31803 Seamless Pipe – Duplex Stainless Steel
ASTM A790 UNS S31803 Seamless Pipe is a duplex ferritic-austenitic stainless steel pipe designed for general corrosive service where high mechanical strength and resistance to chloride stress corrosion cracking, pitting and crevice corrosion are required.
UNS S31803 belongs to the Duplex 2205 material family and is commonly cross-referenced with EN 1.4462 / X2CrNiMoN22-5-3.
ASTM A790 S31803 seamless pipes are widely used in oil & gas, offshore, chemical processing, heat exchangers, water treatment and other chloride-containing industrial piping systems.
ASTM A790 UNS S31803 Specification
| Item | Specification |
|---|---|
| Product | Seamless Duplex Stainless Steel Pipe |
| Standard | ASTM A790/A790M |
| Grade | UNS S31803 |
| Material Family | Duplex 2205 |
| EN Cross-Reference | 1.4462 / X2CrNiMoN22-5-3 |
| Manufacturing | Seamless |
| Typical Seamless Range | NPS 1/2–24, subject to mill availability |
| Wall Thickness | SCH 10S / 40S / 80S and heavier-wall options where applicable |
| Delivery Condition | Solution Heat Treated and Rapidly Cooled |
| Certification | EN 10204 3.1 when specified |
| Additional Testing | PMI, Ferrite, ASTM A923, ASTM G48, Impact Test or TPI when specified |
What Is ASTM A790 UNS S31803?
ASTM A790/A790M covers seamless and straight-seam welded ferritic-austenitic stainless steel pipe for general corrosive service, with particular emphasis on resistance to stress corrosion cracking.
UNS S31803 has a duplex microstructure consisting of both ferritic and austenitic phases.
This combination provides:
- High mechanical strength
- Good chloride stress corrosion cracking resistance
- Good pitting and crevice corrosion resistance
- Good weldability
- Higher yield strength than conventional 300-series austenitic stainless steels
Its corrosion resistance and high strength make S31803 suitable for many demanding industrial piping applications.
UNS S31803 vs S32205
S31803 and S32205 both belong to the Duplex 2205 family, but they are not identical UNS grades.
| Item | UNS S31803 | UNS S32205 |
|---|---|---|
| Chromium | 21.0–23.0% | 22.0–23.0% |
| Nickel | 4.5–6.5% | 4.5–6.5% |
| Molybdenum | 2.5–3.5% | 3.0–3.5% |
| Nitrogen | 0.08–0.20% | 0.14–0.20% |
| Tensile Strength | 620 MPa min. | 655 MPa min. |
| Yield Strength | 450 MPa min. | 450 MPa min. |
| Elongation | 25% min. | 25% min. |
S32205 has tighter minimum chromium, molybdenum and nitrogen requirements.
Many modern Duplex 2205 heats can satisfy both S31803 and S32205 chemistry requirements and may be supplied with dual certification where the actual heat and product requirements comply with both grades.
Dual certification should always be confirmed from the Material Test Certificate (MTC).
ASTM A790 S31803 Chemical Composition
| Element | Requirement |
|---|---|
| Carbon, C | ≤ 0.030% |
| Manganese, Mn | ≤ 2.00% |
| Silicon, Si | ≤ 1.00% |
| Phosphorus, P | ≤ 0.030% |
| Sulfur, S | ≤ 0.020% |
| Chromium, Cr | 21.0–23.0% |
| Nickel, Ni | 4.5–6.5% |
| Molybdenum, Mo | 2.5–3.5% |
| Nitrogen, N | 0.08–0.20% |
Actual heat chemistry should be verified against the MTC supplied with the pipe.
Mechanical Properties
Typical ASTM A790 minimum requirements for UNS S31803 include:
| Property | Requirement |
|---|---|
| Tensile Strength | ≥ 620 MPa |
| Yield Strength | ≥ 450 MPa |
| Elongation | ≥ 25% |
| Hardness | ≤ 290 HBW / 30 HRC |
The relatively high yield strength of duplex stainless steel is one of its main advantages compared with conventional austenitic stainless steels.
Heat Treatment
ASTM A790 UNS S31803 pipe is supplied in a heat-treated condition.
For S31803, the specified solution heat-treatment range is approximately:
1020–1100°C, followed by rapid cooling in water or by other suitable means.
Proper solution treatment and rapid cooling are important for obtaining the required duplex microstructure and avoiding detrimental intermetallic phases.
ASTM A790 vs ASTM A789
ASTM A790 and ASTM A789 cover different tubular products.
| Standard | Product |
|---|---|
| ASTM A790/A790M | Seamless and welded duplex stainless steel pipe |
| ASTM A789/A789M | Seamless and welded duplex stainless steel tubing for general service |
For piping systems specified by NPS and Schedule, ASTM A790 is normally the relevant product specification.
ASTM A789 should not be used interchangeably with A790 simply because the material grade is the same.
Testing and Inspection
ASTM A790 includes material and product verification requirements applicable to the ordered pipe.
Typical standard verification includes:
- Chemical analysis
- Tensile testing
- Hardness testing
- Flattening testing where applicable
- Hydrostatic and/or nondestructive electric testing according to the specification
- Dimensional inspection
- Material traceability
Additional project requirements may include:
- Positive Material Identification – PMI
- Ferrite measurement
- ASTM A923 testing
- ASTM G48 corrosion testing
- Charpy impact testing
- Additional UT / ET
- EN 10204 3.1 / 3.2 certification
- Third-party inspection
These additional tests should be specified in the RFQ and should not automatically be considered mandatory ASTM A790 requirements.
Seamless vs Welded Duplex Pipe
Both seamless and straight-seam welded pipe can be supplied to ASTM A790 when they meet the applicable specification requirements.
| Feature | Seamless Pipe | Welded Pipe |
|---|---|---|
| Manufacturing | Produced without a longitudinal weld seam | Formed and longitudinally welded |
| Weld Seam | None | Present |
| Typical Size Positioning | Common in small and medium diameters | Often advantageous for larger diameters |
| Cost | Generally higher | Often more economical |
| Inspection Focus | Base material and pipe integrity | Base material, weld and pipe integrity |
| Pressure Capability | Determined by dimensions, allowable stress and design code | Determined by dimensions, allowable stress and design code |
| Selection | Project specification | Project specification |
A seamless pipe should not automatically be described as having a higher pressure rating or better corrosion resistance than a compliant welded pipe.
The final selection depends on the piping design code, NPS, wall thickness, operating pressure, temperature, service environment and project specification.
Corrosion Resistance
UNS S31803 provides good resistance to:
- Chloride stress corrosion cracking
- Pitting corrosion
- Crevice corrosion
- General corrosion in many process environments
- Erosion-corrosion under suitable conditions
It generally provides better chloride-related corrosion resistance than conventional 304 and 316 stainless steels.
However, suitability for aggressive seawater, high-temperature chloride environments or severe sour service should be evaluated against the actual process conditions.
For more severe chloride environments, Super Duplex UNS S32750 or S32760 may be specified.
Applications
ASTM A790 UNS S31803 Seamless Pipes are commonly used in:
- Oil & gas processing
- Offshore platforms
- Chemical and petrochemical plants
- Heat exchangers
- Water treatment systems
- Desalination equipment
- Pulp and paper processing
- Marine piping
- Process piping containing chlorides
- Industrial pressure piping
How to Order ASTM A790 S31803 Seamless Pipe
A complete RFQ should normally include:
Standard + Grade + Seamless/Welded + NPS/OD + Schedule/WT + Length + Quantity + Certification + Additional Testing
Example:
PIPE, SMLS, ASTM A790 UNS S31803, NPS 6, SCH 40S, 6 M LENGTH, EN 10204 3.1, QTY: 120 M
For critical projects, also specify any requirements for PMI, ferrite content, ASTM A923, ASTM G48, impact testing, NACE compliance or third-party inspection.
Frequently Asked Questions
What is ASTM A790 UNS S31803?
ASTM A790 UNS S31803 is a duplex ferritic-austenitic stainless steel pipe grade for general corrosive service, offering high strength and good resistance to chloride stress corrosion cracking.
Is UNS S31803 the same as Duplex 2205?
S31803 belongs to the Duplex 2205 family. However, the term 2205 can also refer to UNS S32205, so the exact UNS grade should be stated in procurement documents.
What is the difference between S31803 and S32205?
S32205 has tighter minimum chromium, molybdenum and nitrogen requirements and a higher minimum tensile strength under ASTM A790.
They are related 2205 grades but should not automatically be treated as identical.
What is the difference between ASTM A789 and A790?
ASTM A790 covers pipe, while ASTM A789 covers tubing for general service.
The correct standard should be selected according to the required product form and project specification.
Related Products
ASTM A790 UNS S32205 Duplex 2205 Pipe
Duplex stainless steel pipe with tighter Cr, Mo and N chemistry controls.
ASTM A790 UNS S32750 Super Duplex Pipe
Super Duplex 2507 pipe for more severe chloride and seawater applications.
ASTM A789 S31803 Duplex Stainless Steel Tube
Seamless and welded duplex tubing for general service.
ASTM A182 F51 Duplex Flange
Forged UNS S31803 flange for duplex piping systems.
ASTM A815 S31803 Duplex Pipe Fittings
Wrought duplex stainless steel elbows, tees and reducers.
ASTM A240 S31803 / S32205 Duplex Plate
Duplex 2205 stainless steel plate for industrial fabrication.
ASTM A790 UNS S31803 Seamless Pipe Manufacturer, Supplier & Exporter
We manufacture, supply and export ASTM A790 UNS S31803 Duplex Stainless Steel Seamless Pipes for oil & gas, offshore, chemical, marine and industrial piping projects.
Typical supply includes seamless pipe from NPS 1/2 to NPS 24, with common Schedule and heavy-wall options subject to size and mill availability.
Project-specific requirements such as EN 10204 3.1 certification, PMI, ferrite measurement, ASTM A923, ASTM G48, NDT and third-party inspection can be supported when specified.
Send us your NPS/OD, Schedule or wall thickness, length, quantity, material grade and inspection requirements for technical review and quotation.
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