ASTM A789 UNS S31803 Duplex Stainless Steel Pipe
ASTM A789 UNS S31803 duplex stainless steel pipes are widely used in industrial piping systems requiring a combination of high strength and excellent corrosion resistance. Manufactured according to ASTM A789 / ASME SA789 standards, these pipes are suitable for use in heat exchangers, pressure piping systems and chemical processing equipment.
UNS S31803 duplex stainless steel features a balanced microstructure of ferrite and austenite, providing improved resistance to pitting corrosion, crevice corrosion and chloride stress corrosion cracking compared with conventional austenitic stainless steels such as 304 and 316.
Due to its superior mechanical properties and corrosion resistance, ASTM A789 S31803 pipes are commonly used in oil and gas processing, petrochemical plants, offshore platforms and desalination systems.
ASTM A789 UNS S31803 Pipe Specification
| Item | Specification |
|---|---|
| Standard | ASTM A789 / ASME SA789 |
| Material | UNS S31803 |
| Type | Duplex Stainless Steel |
| Product | Seamless / Welded Pipe & Tube |
| Application | Heat Exchanger / Pressure Piping |
| Size Range | OD 6 mm – 610 mm |
| Wall Thickness | 1 mm – 50 mm |
ASTM A789 covers seamless and welded ferritic/austenitic stainless steel tubing for general corrosion resistance and high temperature service.
Chemical Composition of UNS S31803
| Element | % |
|---|---|
| Carbon | ≤ 0.03 |
| Chromium | 21 – 23 |
| Nickel | 4.5 – 6.5 |
| Molybdenum | 2.5 – 3.5 |
| Nitrogen | 0.08 – 0.20 |
The alloy composition provides strong resistance to localized corrosion and improves overall durability in aggressive environments.
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | ≥ 620 MPa |
| Yield Strength | ≥ 450 MPa |
| Elongation | ≥ 25% |
Duplex stainless steel offers higher strength compared with standard austenitic stainless steels, allowing reduced wall thickness in piping systems.
Heat Treatment
ASTM A789 UNS S31803 pipes are supplied in the solution annealed condition.
Typical heat treatment:
Rapid cooling (water quenching)
Proper heat treatment ensures optimal phase balance and corrosion resistance.
Corrosion Resistance
UNS S31803 duplex stainless steel provides excellent resistance to:
- pitting corrosion
- crevice corrosion
- chloride stress corrosion cracking
- seawater corrosion
This makes ASTM A789 duplex pipes suitable for harsh industrial and marine environments.
Manufacturing and Inspection
ASTM A789 pipes are manufactured under strict quality control processes, including:
- chemical composition analysis
- mechanical testing
- hydrostatic testing
- ultrasonic testing (UT)
- eddy current testing (ET)
Products are typically supplied with EN 10204 3.1 certification.
Typical Applications
ASTM A789 UNS S31803 duplex stainless steel pipes are widely used in:
- offshore oil and gas pipelines
- petrochemical processing plants
- desalination plants
- heat exchangers and condensers
- chemical processing systems
These pipes are suitable for environments requiring both high strength and corrosion resistance.
Equivalent Grades
| Standard | Grade |
|---|---|
| UNS | UNS S31803 |
| EN | 1.4462 |
| DIN | X2CrNiMoN22-5-3
|
ASTM A789 UNS S31803 Seamless Pipes
Related Duplex Stainless Steel Pipes
Other duplex and super duplex stainless steel pipe grades include:
