UNS S31803|1.4462|2205 Seamless Duplex Steel Pipe
Our S31803 duplex pipes offer a strategic combination of high yield strength—nearly double that of conventional 300-series stainless steels—and outstanding resistance to chloride-induced stress corrosion cracking (SCC) and pitting. While UNS S31803 is the foundational duplex grade, XinZhe ensures every pipe meets the most rigorous industrial requirements through hydrostatic and ultrasonic testing. Through advanced cold-drawing and precision solution annealing, we guarantee optimal phase balance and a high-integrity surface finish for long-term reliability in petrochemical, marine, and energy infrastructure.
"Our S31803 pipes are often dual-certified to meet S32205 standards, ensuring a Pitting Resistance Equivalent Number (PREN) ≥ 35 for superior performance."
What Is Seamless Duplex Steel UNS S31803 Pipe?
Seamless Duplex Stainless Steel UNS S31803 Pipe is a high-performance, corrosion-resistant piping product manufactured from a solid billet through a seamless hot-forming process. Unlike welded pipes, it contains no weld seams, ensuring superior structural integrity, uniform mechanical properties, and enhanced reliability in high-pressure, high-temperature and corrosive service.
Duplex stainless steel derives its name from its dual-phase microstructure of approximately 50% austenite and 50% ferrite — combining the toughness and pitting resistance of austenitic grades with the high yield strength and SCC resistance of ferritic grades.
UNS S31803, commonly known as Duplex 2205 base grade, is standardized under ASTM A790 / ASTM A789 for seamless duplex stainless steel pipes and tubes. All pipes are manufactured in accordance with ASTM A790 / ASTM A999 standards with strict control of composition, mechanical properties and dimensional tolerances.
Key Advantages of Seamless Duplex Stainless Steel Pipes
Superior Corrosion Resistance
exceptional resistance to chloride-induced stress corrosion cracking, pitting and crevice corrosion — significantly outperforming conventional austenitic grades such as 304 and 316.
High Mechanical Strength
nearly twice the yield strength of standard austenitic stainless steels, allowing thinner wall designs while maintaining structural performance — reducing system weight and material cost.
Excellent Pressure and Temperature Performance
the seamless process eliminates weld defects, suiting high-pressure pipelines, offshore platforms and cyclic thermal service.
Optimized Cost Efficiency
higher strength-to-weight ratio and reduced nickel content provide lower lifecycle cost compared with high-alloy stainless steels and nickel alloys.
Technical Specifications of Duplex Stainless Steel UNS S31803
Chemical Composition
Composition of UNS S31803 and related duplex grades, mass %. Confirm the ordered standard edition and heat analysis on the material test certificate.
| 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 | … |
Typical Mechanical Properties
Room-temperature requirements for UNS S31803 seamless pipe, per the ordered specification.
| Tensile Strength | Yield Strength | Elongation | Hardness |
|---|---|---|---|
| ≥ 620 MPa | ≥ 450 MPa | ≥ 25% | ≤ 293 HBW |
Typical Physical Properties
These physical properties highlight the material’s ability to perform reliably under a wide range of conditions.
| Density | Melting Point | Thermal Expansion | Thermal Conductivity |
|---|---|---|---|
| 7.82 g/cm³ | 1385–1440 ℃ | 13.0 µm/m·℃ | 14.6 W/m·K |
Size Tolerance Chart
The standard of stainless steel seamless pipe size tolerance (ASTM A790 / ASME SA790, per ASTM A999 references):
| NPS Designator (Inches) | Over | Under |
|---|---|---|
| 1/8 to 1 1/2, incl. | +1/64 in. (0.015 in.) | −1/32 in. (0.031 in.) |
| Over 1 1/2 to 4, incl. | +1/32 in. (0.031 in.) | −1/32 in. (0.031 in.) |
| Over 4 to 8, incl. | +1/16 in. (0.062 in.) | −1/32 in. (0.031 in.) |
| Over 8 to 18, incl. | +3/32 in. (0.093 in.) | −1/32 in. (0.031 in.) |
| Over 18 to 26, incl. | +1/8 in. (0.125 in.) | −1/32 in. (0.031 in.) |
| Over 26 to 34, incl. | +5/32 in. (0.156 in.) | −1/32 in. (0.031 in.) |
| Over 34 to 48, incl. | +3/16 in. (0.187 in.) | −1/32 in. (0.031 in.) |
Wall Thickness (WT) Tolerance — minimum wall at any point shall not be more than 12.5% under the nominal wall; maximum over-nominal variation depends on size and the t/D ratio:
| NPS Designator (Inches) | t/D Ratio | Permissible Variation (Over Nominal WT) |
|---|---|---|
| 1/8 to 2, incl. | All ratios | +20.0% |
| 3 to 18, incl. | t/D ≤ 5% | +22.5% |
| t/D >5% | +15.0% | |
| 20 and larger (Seamless) | t/D ≤ 5% | +22.5% |
| t/D >5% | +15.0% | |
| 20 and larger (Welded) | All ratios | +17.5% |
Length Tolerance: for pipe ordered to a specific cut length, the standard tolerance is +1/8 in. (3.2 mm), −0. Pipe is typically supplied in Single Random Lengths (17 to 24 ft) or Double Random Lengths (38 to 40 ft), unless otherwise specified.
Disclaimer: these tolerances reflect common ASTM A790 requirements (primarily via its reference to ASTM A999). The current edition of the applicable specification governs acceptance.
Industrial Applications of UNS S31803 Seamless Pipes
Thanks to excellent corrosion resistance and high mechanical strength, Duplex S31803 seamless pipes are widely used in demanding industries.
Oil and Gas Industry
- Offshore platforms
- Subsea pipelines
- Manifolds, risers, and flowlines
Chemical Processing Industry
- Heat exchangers
- Pressure vessels
- Chloride-rich processing equipment
Marine and Desalination Systems
- Seawater piping systems
- Reverse osmosis (RO) desalination plants
- Cooling water pipelines
Pulp and Paper Industry
- Digesters
- Bleaching systems
- Chemical storage tanks
Quality Assurance and Certified Testing
Every seamless duplex stainless steel pipe undergoes comprehensive inspection and testing to ensure compliance with international quality standards, including EN 10204 3.1 / 3.2 certification:
Non-Destructive Testing (NDT)
Ultrasonic Testing (UT), Eddy Current Testing (ET) and hydrostatic pressure testing.
Corrosion Resistance Testing
intergranular corrosion testing and pitting corrosion testing according to ASTM G48.
Material Verification
100% Positive Material Identification (PMI).
Mechanical Testing
impact testing, flattening and flare tests, and hardness testing.
Frequently Asked Questions About UNS S31803 Pipe
Is UNS S31803 the same as Duplex 2205?
UNS S31803 is the original Duplex 2205 composition. The later UNS S32205 tightens the minimum chromium, molybdenum and nitrogen limits; S31803 alone does not certify compliance with S32205.
What standards apply to UNS S31803 seamless pipe?
Seamless pipe is supplied to ASTM A790 / ASME SA790; tube is covered by ASTM A789. Dimensional tolerances follow ASTM A999 references.
What mechanical properties does S31803 pipe provide?
Minimum tensile strength 620 MPa, minimum yield strength 450 MPa, minimum elongation 25% and maximum hardness 293 HBW at room temperature, per the ordered specification.
Where is UNS S31803 seamless pipe commonly used?
Oil and gas platforms and subsea lines, chemical processing equipment, marine and desalination systems, and pulp and paper plant equipment.
What inspection and certification are available?
EN 10204 3.1 or 3.2 certificates, PMI, UT or ET non-destructive testing, hydrostatic testing and ASTM G48 corrosion testing can be agreed before ordering.
Ready to Request a Quotation?
Send your S31803 pipe enquiry with grade, ASTM A790 or ASME SA790 and edition, OD × wall thickness or NPS/schedule, length, quantity, end finish, delivery destination and inspection documents — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
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