Reliable Steel is well known for the high-quality Duplex pipes that we source and stock for our discerning clients around the world. We can provide a different grades of duplex pipes, such as A/SA 789 tube, A/SA 790 pipes.
Email us Whatsapp us Call us
Duplex stainless steel is a very useful metal that is used the world over. It gets its name from the fact that it consists of two different grades of metal.
Essentially, Duplex is a Fe-Ni-Cr alloy that has a two-phase ferritic-austenitic stainless-steel microstructure when it is at room temperature.
Duplex steels are characterised by high chromium (19–28%) and molybdenum (up to 5%) and lower nickel contents than austenitic stainless steels. The most used duplex stainless steels are the 2205 (22% Chromium, 5% Nickel) and the 2507 (25% Chromium, 7% Nickel); 2507 is known as “super duplex” due to its higher resistance to corrosion.
The advantage of combining ferritic and austenitic grades is that the resultant metal has a metallurgical structure that consists of two phases and therefore benefits from the properties of both microstructures.
ASTM A789 and ASTM A790 are the standard specifications for duplex stainless steel tubing and pipes, respectively, known for their excellent strength and corrosion resistance.
| Feature | ASTM A789 / ASME SA789 | ASTM A790 / ASME SA790 |
|---|---|---|
| Product Type | Tubing (smaller sizes, typically used for heat exchangers, boilers, etc.) | Pipes (larger sizes, generally used for fluid/gas transport and structural applications) |
| Dimensions | Based on outside diameter (OD) and wall thickness, often in Birmingham Wire Gauge (BWG) | Based on Nominal Pipe Size (NPS) and schedule numbers (e.g., Sch 40, Sch 80) as per ASME B36.10M and B36.19M |
| Manufacturing | Seamless or welded (automatic welding without filler metal) | Seamless or welded (automatic welding without filler metal) |
| Heat Treatment | Mandates a final solution annealing and rapid cooling/water quenching | Mandates a final solution annealing and rapid cooling/water quenching |
| Testing | Hydrostatic or non-destructive electric testing (Eddy Current, UT) | Hydrostatic or non-destructive electric testing (Eddy Current, UT) |
Duplex stainless steel pipes and tubes are used in demanding industries due to their high durability, strength, and resistance to corrosion and stress corrosion cracking.