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Utilizing 26 high-precision cold rolling mills and 6 cold drawing machines, we ensure dimensional accuracy and superior mechanical properties.
ASTM A789 S31803 Seamless Duplex Tube
Duplex Ferritic-Austenitic | UNS S31803 | 2x Austenitic Yield Strength
ASTM A789/A790 | PREN ≥35 | NACE AvailableRelated Products
Introduction
ASTM A789 S31803 Seamless Duplex Tube is built from a duplex microstructure — roughly equal parts ferrite and austenite — that delivers a fundamentally different property balance than any single-phase austenitic grade discussed elsewhere in this range. The ferritic phase contributes high yield strength and resistance to chloride stress corrosion cracking, a failure mode that limits standard 300-series austenitic grades in hot chloride service, while the austenitic phase retains the toughness and weldability that make duplex steels practical to fabricate. With chromium at 21-23%, nickel at 4.5-6.5%, molybdenum at 2.5-3.5%, and nitrogen added for strength and phase balance, S31803 delivers a pitting resistance equivalent number comfortably above standard 316L while using less nickel per unit of corrosion performance.
The most immediately practical benefit of this duplex structure is mechanical: minimum yield strength of roughly 450 MPa is more than double that of standard austenitic tube, which allows thinner wall sections to carry the same pressure rating — directly reducing both material weight and cost per meter of installed pipe in high-pressure applications. This strength advantage does come with a narrower practical service temperature window than austenitic grades; duplex alloys are generally limited to continuous service below about 300°C to avoid intermetallic phase precipitation (475°C embrittlement and sigma phase formation), so this grade is not a drop-in high-temperature substitute for the austenitic tubes described elsewhere in this range.
S31803 duplex tube is specified extensively in offshore and onshore oil and gas gathering systems, desalination plant piping, pulp and paper digesters, and chemical process piping handling moderately aggressive chloride-bearing fluids at ambient to moderate temperature. Welding requires close control of heat input and interpass temperature to maintain the correct ferrite-austenite phase balance in the heat-affected zone, and post-weld inspection commonly includes ferrite content measurement in addition to standard radiographic or dye penetrant testing.
Specifications
| Material Grade | 2205 Duplex (UNS S31803/S32205) |
| Standard | ASTM A789 (welded) / A790 (seamless) |
| Outer Diameter | 12.7mm - 273mm |
| Wall Thickness | 1.2mm - 20mm |
| Length | Up to 12000mm |
| Finish | Solution Annealed, Pickled |
Chemical Composition
| C | Cr | Ni | Mo | N |
| ≤.03 | 21-23 | 4.5-6.5 | 2.5-3.5 | .08-.20 |
Duplex High Strength
Mechanical Strength
Comprehensive Info
| MOQ | 500kg |
| Lead Time | 30 - 45 Days |
| Testing | Ferrite Content & Hydro-test |
| Max Continuous Temp | ~300°C |
Key Applications
Oil & Gas Gathering Onshore and offshore process piping
Desalination High-pressure RO and thermal desalination lines
Pulp & Paper Digester and bleach plant process piping
Advantages
2x Yield Strength
Allows thinner walls at equivalent pressure rating.
Chloride SCC Resistant
Ferritic phase resists cracking that limits austenitic grades.
Weight & Cost Savings
Thinner wall sections reduce material cost per meter.
Balanced PREN
Strong pitting resistance without full super-duplex cost.
About Jiangsu Jend Tube Co.,Ltd.
As China ASTM A789 S31803 Seamless Duplex Tube Manufacturers and Wholesale ASTM A789 S31803 Seamless Duplex Tube Factory, Established in 2011 and is a manufacturing enterprise with a complete manufacturing cycle from raw material selection to finished product delivery. The company currently has more than 100 employees, covers an area of 30015 square meters, and has a registered capital of 48 million yuan, annual production capacity of 3800 tons.
The company has passed ISO9001:2015 quality certification, domestic pressure vessel TS certification, and foreign pressure vessel PED certification. With rich experience and mature technology, we have been expanding our market internationally. At present, our products are exported to more than 50 countries and regions including Europe, America, Southeast Asia, and the Middle East.
The company adheres to different production norms and standards such as the American standard (ASTM), the European standard (EN), the German standard (DIN), the Japanese standard (JIS), the Russian standard (GOST), and the Chinese standard (GB).
Our company specializes in and customizes various specifications of Martensite TP410 (0Cr13, 1Cr13), Ferrite TP405 (1Cr13Al), TP430 (1Cr17), TP444 (0Cr18Mo2), TP439, TP409 (0Cr11Ti), It is also proficient in manufacturing Austenitic seamless stainless steel pipes of series such as TP304(L/H), TP316(L/H/Ti), TP310S, TP317, TP321(H) and TP347(H). Duplex such as S31803, S2205, S32750, S32304, and Nickel-based alloys Monel400, Monel600, Monel800, GH3030, 904L, Inconel 625, etc.
The company mainly produces seamless steel pipes with the following specifications: outer diameter: 3.18mm to 406.4mm, wall thickness: 0.3mm to 20mm, and the longest length is 25000mm. Additionally, it can customize seamless steel pipes with special materials and specifications according to customer requirements. The company attaches great importance to scientific innovation. The staff of the company vigorously develop technological research and development.
Jiangsu Jend Tube Co.,Ltd. will continuously accumulate professional knowledge and capabilities, striving to become a leader in the domestic market and even the world market. Strive to be the most reassuring pipe manufacturing enterprise for customers.
Precision Manufacturing and Process Optimization
We rely on precision equipment and optimized production technologies to achieve outstanding mechanical performance and consistent product quality.
Cold Rolling and Cold Drawing
Solution Heat Treatment
Natural gas solution treatment furnaces and BA solution treatment furnaces optimize the material's grain structure, enhancing corrosion resistance.
Precision Straightening and Polishing
10 straightening machines and 8 finishing polishing machines guarantee product surface smoothness and dimensional accuracy.
Automated Inspection and Quality Assurance
Real-time monitoring systems ensure the stable quality of every batch of products.
Usage Tips
Heat Input Control
Maintain controlled heat input and interpass temperature during welding to preserve the correct ferrite-austenite balance in the HAZ.
Temperature Limit
Avoid continuous service above roughly 300°C to prevent sigma phase and 475°C embrittlement from degrading toughness.
Services
Ferrite Content Testing
Verification of phase balance per heat and after welding.
Bevel & End Prep
Weld-ready ends for high-pressure tie-ins.
Certified Documentation
Full mechanical and PREN-relevant chemical certification.
Logistics
30% T/T Deposit / L/C at sight. VCI-wrapped with end caps, packed in reinforced wooden crates suited to offshore project logistics.
Standards
ASTM A789/A790
NACE MR0175 (on request)
PED 2014/68/EU
ISO 9001
Frequently Asked Questions
What does 'duplex' mean in this grade?
Duplex refers to a microstructure that is roughly half ferrite and half austenite, combining the strength of ferritic steel with the toughness and weldability of austenitic steel.
How much stronger is S31803 than standard 316L?
Minimum yield strength is roughly 450 MPa, more than double the approximately 170-205 MPa typical of standard austenitic 300-series grades.
What is the maximum service temperature for this grade?
Continuous service is generally limited to about 300°C to avoid sigma phase and 475°C embrittlement that reduce toughness at higher sustained temperatures.
Is special welding procedure required?
Yes, controlled heat input and interpass temperature are needed to maintain the correct ferrite-austenite ratio in the weld and heat-affected zone.
What industries commonly specify this tube?
Oil and gas gathering systems, desalination plants, and pulp and paper digesters are among the most common applications.
Is ferrite content testing standard?
Yes, ferrite content measurement is commonly performed on both base material and welds to confirm phase balance meets specification.
Ready to Order S31803 Duplex Tube?
Send your design pressure and service temperature for a duplex wall-thickness comparison against standard austenitic tube.
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