ASME SA789 UNS S32750 Super Duplex Stainless Steel Seamless Tube
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What is ASME SA789 UNS S32750 Super Duplex Stainless Steel Seamless
Tube?
ASME SA789 UNS S32750 Super Duplex Stainless Steel Seamless Tube is
a specification for seamless tubes made from UNS S32750, a super
duplex stainless steel. This material is known for its exceptional
combination of high strength, excellent corrosion resistance, and
good toughness, making it suitable for demanding applications in
harsh environments. The ASME SA789 standard specifies the
requirements for seamless and welded stainless steel tubes used in
general service and corrosive environments.
Key Features of UNS S32750 Super Duplex Stainless Steel
- High Strength: UNS S32750 has a higher yield strength compared to standard
duplex and austenitic stainless steels, making it suitable for
high-pressure applications.
- Excellent Corrosion Resistance:It offers superior resistance to pitting, crevice corrosion, and
stress corrosion cracking (SCC), especially in chloride-rich
environments like seawater.
- Balanced Microstructure: The material has a dual-phase microstructure (approximately 50%
austenite and 50% ferrite), which contributes to its strength and
corrosion resistance.
- Good Weldability and Fabricability:UNS S32750 can be welded and fabricated using standard techniques,
though proper procedures must be followed to maintain its
properties.
- Resistance to Acids and Chemicals: It performs well in environments with acids, alkalis, and other
corrosive chemicals.
ASME SA789 Specification:
The ASME SA789 standard covers the requirements for seamless and
welded stainless steel tubes used in general service and corrosive
environments. Key aspects of the specification include:
- Material Composition:
UNS S32750 has a specific chemical composition, including high
levels of chromium (Cr), molybdenum (Mo), and nitrogen (N):
Chromium (Cr): 24–26%
Molybdenum (Mo): 3–4%
Nickel (Ni): 6–8%
Nitrogen (N): 0.24–0.32%
-Mechanical Properties:
Tensile Strength: ≥ 800 MPa (116 ksi)
Yield Strength: ≥ 550 MPa (80 ksi)
Elongation: ≥ 15%
- Dimensional Tolerances:
The standard specifies tolerances for outer diameter, wall
thickness, and length of the tubes.
-Testing Requirements:
Tubes must undergo hydrostatic testing or non-destructive testing
(NDT) to ensure integrity.
Additional tests, such as pitting resistance testing (ASTM G48),
may be required to verify corrosion resistance.
-Heat Treatment:
Tubes are typically supplied in the solution-annealed condition to
optimize corrosion resistance and mechanical properties.
What's the application of A789 UNS S32750 seamless tubes?
A789 UNS S32750 seamless tubes are made from a super duplex
stainless steel known for its high strength and excellent corrosion
resistance. These properties make them suitable for a variety of
demanding applications, particularly in industries where materials
are exposed to harsh environments. Here are some common
applications:
1. Oil and Gas Industry
Offshore and Onshore Pipelines: UNS S32750 tubes are used in the transportation of oil and gas,
especially in environments with high chloride content, such as
seawater.
Downhole and Subsea Equipment: These tubes are used in components like umbilicals, risers, and
flowlines due to their resistance to pitting, crevice corrosion,
and stress corrosion cracking.
2. Chemical and Petrochemical Industry
Heat Exchangers and Condensers: The high corrosion resistance of UNS S32750 makes it ideal for
heat exchangers and condensers that handle aggressive chemicals.
Process Piping: These tubes are used in piping systems that transport corrosive
chemicals, acids, and solvents.
3. Desalination Plants
Seawater Desalination: UNS S32750 tubes are used in desalination plants for components
like heat exchangers and piping systems due to their resistance to
chloride-induced corrosion.
4. Power Generation
Nuclear and Fossil Fuel Power Plants: These tubes are used in heat exchangers, condensers, and
feedwater systems where high strength and corrosion resistance are
required.
Flue Gas Desulfurization (FGD) Systems: UNS S32750 tubes are used in FGD systems to handle corrosive
gases and liquids.
5. Marine and Shipbuilding
Seawater Cooling Systems: The tubes are used in seawater cooling systems and other marine
applications due to their excellent resistance to seawater
corrosion.
Propulsion Systems: UNS S32750 is used in components like shafts, propellers, and
pumps in marine environments.
6. Pulp and Paper Industry
Bleaching Equipment: The tubes are used in bleaching equipment and other areas where
exposure to corrosive chemicals is common.
7. Pharmaceutical Industry
High-Purity Systems: UNS S32750 tubes are used in high-purity systems where corrosion
resistance and cleanliness are critical.
8. Food and Beverage Industry
Sanitary Processing Equipment: The tubes are used in sanitary processing equipment where
resistance to corrosion and ease of cleaning are important.
9. Water Treatment
Wastewater Treatment Plants: UNS S32750 tubes are used in wastewater treatment plants for
components like pumps, valves, and piping systems.
10. Aerospace and Defense
High-Strength Components: The high strength and corrosion resistance of UNS S32750 make it
suitable for certain aerospace and defense applications where these
properties are required.
