ASTM A789 / ASME SA789
ASTM A789 – Standard Specification for Seamless and Welded Ferritic/Austenitic (Duplex) Stainless Steel Tubing
ASTM A789 is a widely used specification covering seamless and welded duplex stainless steel tubing. These tubes are known for their excellent corrosion resistance, high strength, and superior stress-corrosion cracking resistance, making them ideal for demanding environments such as oil & gas, chemical processing, power generation, and seawater systems.
Key Features
High tensile and yield strength
Excellent resistance to pitting, crevice corrosion, and chloride stress-corrosion cracking
Good weldability and formability
Suitable for high-pressure & high-temperature applications
Excellent performance in seawater and chloride-rich environments
Common Types of Tubing
Seamless Duplex Tubes
Welded Duplex Tubes
Heat Exchanger Tubes
Instrument Tubing
U-bend Tubes
Limitations
Not suitable for applications above 315–330°C, as duplex microstructure may degrade.
May not perform well in severe reducing acid environments (e.g., strong sulfuric acid).
Requires controlled heat treatment and welding to avoid phase imbalance or embrittlement.
Cold forming is more challenging compared to austenitic stainless steels due to higher strength.
Not recommended where extremely high corrosion resistance like nickel alloys is required.
Applications
- Oil & Gas pipelines
- Heat exchangers & condensers
- Chemical and petrochemical plants
- Desalination plants
- Marine engineering
- Power plants
- Pulp & paper industry