Bright Annealed ASTM A789 UNS S32750 Super Duplex Stainless Steel Seamless Tube For Desalination
UNS S32750 is a super duplex stainless steel designed for severe corrosive environments, especially those containing chlorides. Its high chromium, molybdenum, and nitrogen contents give it excellent resistance to pitting, crevice corrosion, and chloride stress corrosion cracking. ASTM A789 UNS S32750 Super Duplex Stainless Steel Seamless Tube is a seamless tubular product manufactured according to ASTM A789/A789M Specification. The material grade UNS S32750 is commonly known as 2507, SAF 2507, Duplex 2507. It is a super duplex stainless steel with a balanced ferritic-austenitic microstructure, typically about 40–60% ferrite and 40–60% austenite.
Chemical Composition, %:
| Element |
C |
Mn |
P |
S |
Si |
Cr |
Ni |
Mo |
N |
| Min. |
— |
— |
— |
— |
— |
24.0 |
6.0 |
3.0 |
0.24 |
| Max. |
0.030 |
1.20 |
0.030 |
0.020 |
0.80 |
26.0 |
8.0 |
5.0 |
0.32 |
Mechanical Properties:
| Tensile Strength, Rm (MPa) |
≥790 |
| Yield Strength, Rp0.2 (MPa) |
≥550 |
| Elongation, A (%) |
≥25 |
| Hardness, HB |
Max 310 HB |
| Hardness, HRC |
Max 32 HRC |
Surface Finishes:
1. Pickled & Annealed
The most common commercial finish. After solution annealing, tubes are descaled by acid pickling. Uniform matte metallic surface, oxide and scale removed. Suitable for general corrosion service.
2. Bright Annealed (BA)
Heat treated in a controlled inert atmosphere furnace to prevent oxidation, no subsequent pickling. Smooth, semi-bright metallic surface, no heavy acid etch marks. Widely used for instrument tubing, process lines where surface cleanliness is required.
3. Polished Finish
Fine mechanical polishing to Ra 0.8μm, 1.6μm or other custom roughness. Used for special hygienic or high-purity fluid systems, less common for heavy wall process seamless tubes.
Main Features of ASTM A789 UNS S32750 Super Duplex Seamless Tube:
High corrosion resistance
High mechanical strength
Good erosion-corrosion and abrasion resistance
Good thermal stability in moderate high temperature
Good weldability and machinability
Excellent performance in high-pressure and corrosive service
Different Applications:
- Oil & gas industry: Subsea pipelines, produced water lines, chloride-rich process piping, downhole instrument tubing
- Desalination: Seawater reverse osmosis (SWRO) piping, seawater cooling systems
- Chemical & petrochemical: Chloride-containing process media, brine systems, acid gas service
- Power industry: Flue gas desulfurization (FGD) systems, cooling water piping with high chloride
- Pulp and paper: Bleach plant piping, corrosive liquor circuits
- Marine engineering: Offshore platforms, seawater handling, ballast water systems
- Environmental engineering: Wastewater treatment with high chloride and halide contaminants
- Hydrometallurgy: Leaching circuits, acidic chloride process solutions
- Food, pharmaceutical, and high-purity systems where corrosion resistance and clean surfaces are required.
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