To weld a duplex steel pipe, control heat input to maintain ferrite–austenite balance, use suitable processes such as GTAW (TIG) or GMAW (MIG), apply matching filler metal (ER2209), and keep interpass temperature below 150°C to prevent phase imbalance.
Duplex Stainless Steel Pipe Manufacturer
At Xintongda Special Steel (XTD), we are a leading manufacturer in China of duplex stainless steel pipes. We have around 4 decades of experience, and our products are ISO9001, ISO14001, and ISO45001 certified. Duplex stainless steel (DSS) pipe, also referred to as austenitic-ferritic stainless steel pipe, is a tubular product made from iron-chromium-nickel-molybdenum-nitrogen alloy. We manufacture our duplex pipes in accordance with ASTM A790 standards. At Xintongda, we provide two main grade options of DSS pipes: S32205 and S31803. Here, we keep a balanced focus between quality, consistency, and timely delivery. As a duplex pipe supplier, we offer pipes in various sizes, thicknesses, and lengths.
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OD Range
6-720 mm
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Thickness Range
1-65 mm
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Length
≤ 18 m
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What is Duplex Pipe?
Duplex pipe is a stainless steel tubular product alloyed with approximately 22% chromium, 5% nickel, 3% molybdenum, and nitrogen, along with other controlled elements. It has a hybrid microstructure combination of ferritic (magnetic) and austenitic (corrosion-resistant), which makes the SS duplex material strong, tough, ductile, and more resistant to pitting corrosion, crevice corrosion, and stress corrosion cracking (SCC) than conventional austenitic stainless steels.
Features and Benefits of Duplex SS Pipe
There are 4 main characteristics that make Duplex SS Pipe stand out. They are:
- High Corrosion Resistance: The higher amounts of chromium, molybdenum, and nitrogen give this DSS pipe excellent resistance to pitting, crevice corrosion, and SCC.
- High Toughness and Ductility: The duplex pipe has such good toughness and ductility that it can retain its properties from sub-zero temperatures (down to -50°C) up to approximately 280–300°C.
- Improved Strength: It has significantly higher tensile and yield strength than many other austenitic stainless steels.
- Ease of Fabrication: The DSS pipe has high weldability and formability due to its dual-phase microstructure.
Duplex Pipe Specification
At XTD, we provide our duplex steel pipes of various diameters, thicknesses, and lengths. We also offer customised solutions to our clients. Let us have a look at some product specifications:
Standard
ASTM A790
Outside Diameters
6-720 mm
Length
≤ 18 m
Thickness Range
1-65 mm
Surface Finish
Bright, Annealing, Polished, Mirror, Brushed
Form
Round, Square, Rectangular, Hydraulic etc
End
Plain End, Beveled End, Threaded
Testing
PMI, Radiography, Mechanical, Chemical
Types & Shapes Of Duplex Steel Pipe
We at XTD specialise in manufacturing high-quality seamless pipes, and our production capacity is 25,000 tons annually. Here are types and shapes of duplex steel pipes:
Duplex Steel Seamless Pipe
Duplex Steel Round Pipe
Duplex Steel Square Pipe
Duplex Steel Rectangular Pipe
Duplex Stainless Steel Pipe Grades
The duplex steel grades used in pipe systems combine austenitic and ferritic structures that help increase the strength and corrosion resistance. Each grade has its own strengths and uses.
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UNS S31803 Pipe
The UNS S31803 grade pipe uses a combination of a hybrid microstructure, austenitic and ferritic (approximately 40-50% ferrite in the annealed condition), to resist corrosion and increase strength. This grade has 21–23% chromium, 4.5–6.5% nickel, 2.5–3.5% molybdenum, 0.08–0.20% nitrogen, with manganese (2% max), silicon (1% max), and carbon (0.03% max). This pipe can resist pitting, crevice corrosion, seawater, and chloride stress corrosion cracking very well.
02
UNS S32205 Pipe
The UNS S32205 pipe, also known as 2205, combines high mechanical strength with excellent corrosion resistance. This grade pipe has 22–23% chromium, 4.5–6.5% nickel, 3.0–3.5% molybdenum, and 0.14–0.20% nitrogen. S32205 is a tighter composition range within S31803, with higher minimum nitrogen, chromium, and molybdenum to guarantee superior corrosion resistance, particularly in the weld heat-affected zone.
Industrial Applications of Duplex Pipe
Our DSS pipes are used in industrial applications exposed to harsh acids & chemicals, seawater, high temperatures, and many other environments.
Chemical Processing
Used in reactors, heat exchangers, storage tanks, and transport pipelines for handling dilute sulfuric acid, organic acids, and mildly corrosive chloride-bearing chemical solutions.
Petrochemical Equipment
Primarily used for heat exchangers, distillation, process piping, desalination plants, seawater cooling systems, condensers, etc.
Oil and Gas
Since it can resist chloride easily, the duplex steel pipe is used extensively in offshore platforms, risers, and onshore transportation.
Food production
Used for hot water systems in breweries and dairies, processing lines in sugar production, transporting the products in the beverage industry, and large tanks in storage and transportation.
Marine applications
This alloy provides exceptional seawater corrosion resistance and, hence, is used for pipelines and risers in the offshore industry, exhaust systems and pumps in shipbuilding, and equipment handling in desalination plants.
Water Treatment and Desalination
Used in seawater reverse osmosis (SWRO) systems for the membranes, intake/outlet lines for handling raw and corrosive seawater, pumps & valves for fabricating components, and energy recovery systems.
100% Certified Testing & Documentation
- EN 10204 3.1 and EN 10204 3.2 Material Test Certificates (MTC)
- 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 Govt. Approved Lab
If you want to know more product details, please contact us!
Frequently Asked Questions
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How to Weld Duplex Pipe?
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Why are duplex steel pipes better than standard stainless steel pipes?Duplex steel pipes are better than conventional stainless steel pipes (e.g., 304/316 austenitic grades) because of the hybrid microstructure combination of ferritic and austenitic structures. This dual-phase microstructure gives them enhanced strength and superior corrosion resistance.