UNS S31254 is a fully austenitic, 6% molybdenum super duplex stainless steel, used widely in seawater cooled power plant condensers.
The first high-performance austenitic Stainless Steel designed specifically to use nitrogen for added corrosion resistance. Uses of UNS S31254 include condenser tubes, heat exchanger tubes, tube sheets and service water piping in nuclear power plants.
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Properties
Austenitic Cr-Ni-Mo stainless steel with excellent resistance to stress corrosion cracking, pitting and crevice corrosion. Resistant to intergranular corrosion in the temperature range up to 400°C (752°F). For optimum resistance, surfaces should be pickled, scale free heat treated or machined.
Application
For applications involving highly corrosive environments due to the presence of chemically aggressive media, e.g. for equipment and plants which are cooled by seawater and parts for offshore plants. In the chemical industry where resistance to the attack of pure acids as well as acids containing chloride ions (sulphuric acid in particular), of organic acids and mixed acids is required in the higher pressure and temperature ranges. The enhanced resistance to crevice corrosion permits use also for applications where incrustation must be expected, and/or where the formation of gaps cannot be avoided by design precautions.
Chemical Composition (average %)
| C | Si | Mn | Cr | Mo | Ni | N |
|---|---|---|---|---|---|---|
| max. 0,020 | 0.18 | 0.65 | 20.30 | 6.30 | 17.80 | 0.20 |
Standards
UNS S31254
Hot Forming
Forging
1150 to 1000°C (2102-1832°F)
Air cooling
Heat Treatment
Quenching:
1150 to 1200°C (2102-2192°F)
Water and air cooling
(thickness below 2mm)
Structure as quenched:
Austenite
Welding
To keep heat input low use small electrode and wire diameters and low amperage and minimise width of weaving. Maximum interpass temperature 150°C (302°F). We recommend electric arc welding with covered electrodes or inert gas welding. Heat treatment is not normally necessary after welding. However , welding without filler metal shall be followed by solution annealing at 1150 to 1200°C (2102-2192°F) and subsequent rapid cooling.
Mechanical Properties at Room Temperature
Condition: quenched
| Product | Dimension Size mm |
Hardness1) HB max. |
0.2% proof stress N/mm² |
1% proof stress N/mm² min |
Tensile strength N/mm² |
Elongation A5 % min. L Q T |
Impact strength (ISO-V) J min. L Q T |
|---|---|---|---|---|---|---|---|
| Bl | ≤ 30 | 210 | 300 | 340 | 650-800 | - - 35 - - | - - 70 - - |
| St, Sch | ≤ 200 | - - | 40 35 - - | 110 70 - - |
Bl = Sheet or plate
St = Bar , Sch = Forging,
L = Longitudinal, Q = Transverse, T = Tangential
1) Hardness values for informations, tensile strength governs.
The values for other products and dimensions shall be established by agreement.
High Temperature Properties
| Temperature | 50°C (122°F) |
100°C (212°F) |
200°C (392°F) |
300°C (572°F) |
400°C (752°F) |
|---|---|---|---|---|---|
| 0,2-Grenze 0.2% proof stress N/mm² min. |
265 | 230 | 190 | 170 | 160 |
| 1%-Dehngrenze 1% proof stress N/mm² min. |
305 | 270 | 225 | 200 | 190 |
| Zugfestigkeit Tensile strength N/mm² min. |
635 | 615 | 560 | 525 | 510 |
Physical Properties
Thermal conductivity at .................... 20°C (68°F) ............13.5 .....W/(m.K)
Specific heat at ................................ 20°C (68°F) ............500 ......J/(kg.K)
Electrical resistivity at ....................... 20°C (68°F) ............0.85 .....Ohm.mm2/m
Modulus of elasticity at .................... 20°C (68°F) ............200 x 103 N/mm2
Magnetic properties .........................................................non magnetic
| Thermal expansion between 20°C (68°F) and ...°C (°F), 10-6 m/(m.K) at |
Temperature °C / °F | 10-6 m/(m.K) | |
|---|---|---|---|
| 100°C | 212°F | 16.5 | 200°C | 392°F | 17.0 |
| 300°C | 572°F | 17.5 | |
| 400°C | 752°F | 18.0 | |
| 500°C | 932°F | 18.5 | |
As regards applications and processing steps that are not expressly mentioned in this product description/data sheet, the customer shall in each individual case be required to consult us.
