ASTM A789/A789M — Seamless and welded duplex stainless steel pipes
Grades
S31803, S32205, S32304, S32550, S32750, S32760, S32900, S32950
Chemical composition and mechanical properties
| Grade | Chemical composition | Mechanical properties |
|---|---|---|
| S31803 | C≤0.030, Mn≤2.00, Si≤1.00, P≤0.030, S≤0.020, N 0.08-0.20, Cr 21.00-23.00, Ni 4.50-6.50, Mo 2.50-3.50 | Rm ≥620 MPa, Rp0.2 ≥450 MPa, A≥25%, HB≤293, similar to biphase 2205. |
| S32205 | C≤0.030, Mn≤2.00, Si≤1.00, P≤0.030, S≤0.020, N 0.14-0.20, Cr 22.00-23.00, Ni 4.50-6.50, Mo 3.00-3.50 | Rm ≥655 MPa, Rp0.2 ≥485 MPa, A≥25%, HB≤293, biphase 2205 |
| S32304 | C≤0.030, Mn≤2.00, Si≤1.00, P≤0.040, S≤0.030, N 0.10-0.20, Cr 21.50-24.50, Ni 3.00-5.50, Mo 0.05-0.60, Cu 0.05-0.60 | Rm ≥600 MPa, Rp0.2 ≥400 MPa, A≥25%, HB≤293, biphase 2304 |
Application scope
ASTM A789/A789M specifications specify general-purpose seamless and weldable ferritic-austenitic duplex stainless steel tubes, delivered in a solution-annealed state to ensure phase equilibrium. The duplex structure combines high strength with excellent resistance to pitting, crevice corrosion, and stress corrosion cracking. It encompasses a range of grades from economical to super duplex, suitable for small-to-medium diameter pipelines containing chloride ions and other highly corrosive substances where high strength is required.
Typical applications
Widely used in seawater desalination plants, chemical reactors and heat exchange tubes, oil and gas extraction and gathering pipelines, as well as in high chloride ion environments such as desalination and flue gas desulfurization. Its high strength allows for thinner walls and lighter weight, and its resistance to stress corrosion cracking makes it suitable for marine and saltwater conditions. It is commonly used as heat exchanger tube bundles, process piping, and corrosion-resistant pressure pipes, serving fluid transport under harsh corrosive conditions.
