Duplex seamless pipes are commonly used in oil and gas, chemical processing, marine engineering, heat exchangers, and offshore platforms.
Duplex Steel Seamless Pipe Manufacturer
We are Zhejiang Xintongda Special Steel (XTD), a China-based manufacturer of seamless duplex stainless steel pipe. Seamless duplex steel pipe is a high-strength, corrosion-resistant round product produced without a longitudinal weld. The dual-phase microstructure of roughly 50% ferrite and 50% austenite gives the pipe roughly double the yield strength of standard austenitic pipe, along with high resistance to pitting, crevice corrosion, and chloride stress corrosion cracking. We manufacture seamless duplex pipe to ASTM A790 (equivalent ASME SA-790) in the grades UNS S31803, UNS S32205, and Hyper Duplex UNS S32707. Oil and gas, offshore, chemical and petrochemical, and seawater desalination are common applications of seamless duplex steel pipe. Standard austenitic 304 or 316 would fail to withstand the chloride and pressure environment for these applications. We hold multiple international certifications, listed on our Certificate page, and we run an annual supply capacity of 25,000 tons. Stock orders ship within one week, and custom production runs are typically completed in 15 to 60 days.
As a reputable Duplex seamless steel pipe supplier, we provide pipes that meet the following specifications:
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OD Range
6-720mm
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Thickness
1-65 mm
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Length
≤ 18 m
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What is a Duplex Seamless Pipe?
Duplex steel seamless pipe is a stainless steel pipe made from a duplex alloy, which contains roughly equal parts austenite and ferrite in its microstructure. In the base grade UNS S31803, the chemistry is chromium 21 to 23%, nickel 4.5 to 6.5%, molybdenum 2.5 to 3.5%, and nitrogen 0.08 to 0.20%, with carbon capped at 0.03% to prevent sensitization and intergranular corrosion in the heat-affected zone during welding. UNS S32205 is a tighter subset of S31803 with slightly higher minimum chromium, molybdenum, and nitrogen. UNS S32707 (Hyper Duplex) sits above both, with about 27% chromium and 4.8% molybdenum, for the most aggressive chloride service. All three are manufactured as one continuous hollow section without a weld seam.
Manufacturing Process of Duplex Seamless Pipe
The duplex seamless pipe making process begins by heating a solid round steel billet until it is malleable. This hot billet is pierced to create a hollow shell and then rolled or drawn to achieve the required diameter and wall thickness. Finally, the pipe is solution annealed and water quenched to achieve the correct microstructure and strength. For the complete step-by-step manufacturing process (including mill sequence, heat-treatment cycle and inspection stages) see our production page.
Available Duplex Seamless Pipe Grades
We provide the following duplex steel grades at XTD:
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UNS S31803 Seamless Pipe
This is the original duplex grade, offering a balanced mix of high mechanical strength and excellent resistance to localised corrosion. It provides a cost-effective solution for high-pressure applications where standard stainless steels might fail.
02
UNS S32205 Seamless Pipe
This grade is a refined-composition variant of S31803 with tighter minimum ranges for chromium (22–23%), molybdenum (3.0–3.5%), and nitrogen (0.14–0.20%). This ensures more consistent corrosion resistance.
03
UNS S32707 Hyper Duplex Seamless Pipe
UNS S32707, also known as Hyper Duplex SAF 2707 HD, has about 27% chromium, 6.5% nickel, 4.8% molybdenum, and 0.40% nitrogen. The PREN of about 49 is above every standard super-duplex grade and gives near-nickel-alloy performance in warm seawater, hot chloride, and sour service. Yield strength is roughly 38% higher than S32205 (about 620 MPa vs 450 MPa minimum). Typical services include deep-water offshore risers, seawater cooling in tropical fields, and heat exchangers in aggressive brine service.
Both grades are commercially known as Duplex 2205 (Werkstoff Nr. 1.4462). Most S31803 production today also meets S32205 composition — contact us for dual-certified pipe availability.
100% Certified Testing & Documentation
- Raw Materials Certificate
- 100% Positive Material Identification (PMI)
- Heat Treatment Charts
- Third-Party Inspection Report
- Surface roughness and size measurement
- Manufacturer Test Certificate (Impact Testing, Flattening, Flare, Bend, Hardness, Intergranular Corrosion, Pitting Corrosion, Grain size, Eddy Current (ET), Ultrasonic Testing (UT), Hydrostatic Testing (HT), etc.)
- Laboratory Test Certificate from Government-Approved Lab
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Frequently Asked Questions
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Where are duplex seamless pipes commonly used?
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Which international standards do duplex seamless pipes comply with?Our duplex seamless pipes comply with ASTM A790/ASME SA-790 (seamless and welded pipe), with EN 10216-5 (European seamless tubes for pressure purposes) also available on request. The equivalent ASME Boiler & Pressure Vessel Code designation is SA-790.
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What is the lead time for bulk duplex seamless pipe export orders?The lead time for bulk duplex seamless pipe export orders at XTD is typically 15-60 days.
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Why are duplex seamless pipes preferred for critical industrial applications?Duplex seamless pipes are preferred for critical industrial applications because of their high strength, excellent corrosion resistance, and resistance to stress cracking in harsh environments.