ASTM A789 ASME SA 789 UNS S32750 Stainless Steel Pipe Tube
SAF 2507, also designated as UNS S32750, is a super duplex stainless steel widely used in demanding industrial environments requiring high strength and excellent corrosion resistance. Pipes and tubes manufactured according to ASTM A789 / ASME SA789 are commonly supplied for use in heat exchangers, pressure piping systems and offshore applications.
Super duplex stainless steel SAF 2507 combines a balanced microstructure of ferrite and austenite, providing significantly improved resistance to pitting corrosion, crevice corrosion and stress corrosion cracking compared with conventional stainless steels such as 304 or 316.
Due to its excellent mechanical properties and corrosion resistance, UNS S32750 pipes and tubes are widely used in oil and gas processing, offshore platforms, petrochemical plants, desalination systems and chemical processing equipment.
Chemical Composition
The chemical composition of UNS S32750 is carefully controlled to achieve its super duplex structure and corrosion resistance.
| Element | C | Cr | Ni | Mo | N |
|---|---|---|---|---|---|
| % | ≤0.03 | 24–26 | 6–8 | 3–5 | 0.24–0.32 |
High chromium, molybdenum and nitrogen content provide excellent resistance to localized corrosion.
Mechanical Properties
UNS S32750 super duplex stainless steel provides significantly higher strength than conventional austenitic stainless steels.
| Property | Value |
|---|---|
| Tensile Strength | ≥ 800 MPa |
| Yield Strength | ≥ 550 MPa |
| Elongation | ≥ 15% |
| Hardness | ≤ 310 HB |
The high strength allows thinner wall thicknesses in piping systems while maintaining structural integrity.
Manufacturing Standards
SAF 2507 pipes and tubes are commonly manufactured according to the following standards:
| Standard | Description |
|---|---|
| ASTM A789 | Seamless and welded ferritic/austenitic stainless steel tubing |
| ASME SA789 | Pressure piping specification equivalent to ASTM A789 |
| ASTM A790 | Seamless and welded duplex stainless steel pipe |
| ASME SA790 | ASME equivalent of ASTM A790 |
These standards define requirements for chemical composition, mechanical properties, heat treatment and testing procedures.
Heat Treatment
UNS S32750 pipes and tubes must be supplied in the solution annealed condition to achieve the proper duplex microstructure.
Typical heat treatment:
Rapid water quenching
Proper heat treatment ensures optimal corrosion resistance and mechanical performance.
Testing Requirements
Pipes and tubes manufactured according to ASTM A789 / ASME SA789 are subject to several inspection and testing procedures.
Typical tests include:
Chemical Analysis
Verification of chemical composition to ensure compliance with UNS S32750 requirements.
Tensile Test
Mechanical testing to confirm tensile strength, yield strength and elongation.
Hardness Test
Hardness testing ensures that the material remains within the acceptable limits for duplex stainless steels.
Hydrostatic Test
Hydrostatic pressure testing verifies the integrity of the pipe under internal pressure.
Non-Destructive Testing
Non-destructive testing methods may include:
-
Ultrasonic testing (UT)
-
Eddy current testing (ET)
These inspections detect internal or surface defects.
Corrosion Resistance
SAF 2507 super duplex stainless steel provides outstanding corrosion resistance due to its high chromium, molybdenum and nitrogen content.
The material exhibits excellent resistance to:
-
pitting corrosion
-
crevice corrosion
-
chloride stress corrosion cracking
-
seawater corrosion
The PREN (Pitting Resistance Equivalent Number) of SAF 2507 is typically above 40, indicating very high corrosion resistance.
Typical Size Range
Super duplex stainless steel pipes and tubes are typically supplied in the following size ranges:
Wall Thickness: 1 mm – 50 mm
Pipe Length: 6 m – 12 m
Dimensions may vary depending on production standards and project requirements.
Applications
SAF 2507 UNS S32750 pipes and tubes are widely used in:
-
offshore oil and gas pipelines
-
subsea piping systems
-
desalination plants
-
chemical processing equipment
-
heat exchangers and pressure vessels
The material is particularly suitable for environments containing chlorides or seawater.
ASTM A789 vs ASTM A790
ASTM A789 and ASTM A790 are two widely used specifications covering duplex and super duplex stainless steel pipes and tubes. Although both standards apply to ferritic–austenitic stainless steels, they are intended for different types of products and applications.
The main difference between these two standards is that ASTM A789 applies to tubing, while ASTM A790 covers pipe used in pressure service.
Specification Comparison
| Standard | Product Type | Typical Applications |
|---|---|---|
| ASTM A789 / ASME SA789 | Stainless steel tubing | Heat exchangers, condensers, instrumentation tubing |
| ASTM A790 / ASME SA790 | Stainless steel pipe | Pressure piping, offshore pipelines, chemical processing |
Equivalent Grades
| Standard | Grade |
|---|---|
| UNS | S32750 |
| EN | 1.4410 |
| SAF | SAF 2507 |
ASTM A789 ASME SA789 UNS S32750 Super Duplex Stainless Steel Pipe and Tube
SAF 2507 UNS S32750 super duplex stainless steel pipes and tubes provide a combination of high mechanical strength and exceptional corrosion resistance. Manufactured according to ASTM A789 / ASME SA789 standards, these materials are widely used in critical industrial applications where reliability and long-term performance are required.
