Duplex & super duplex / UNS S31254
254 SMO® is a 6% molybdenum super-austenitic stainless steel (not a duplex grade) with outstanding resistance to pitting and crevice corrosion in seawater and chloride-bearing process streams.
- UNS S31254
- W.Nr. 1.4547
- Spec ASTM A240
- Density 8 g/cm³
Also known as / equivalents
| System | Designation |
|---|---|
| UNS | S31254 |
| W.Nr. | 1.4547 |
| EN | X1CrNiMoCuN20-18-7 |
| Also known as | F44, S31254, 1.4547, 6Mo |
Chemical composition
| Element | Min % | Max % |
|---|---|---|
| C | — | 0.020 |
| Mn | — | 1.00 |
| P | — | 0.030 |
| S | — | 0.010 |
| Si | — | 0.80 |
| Cr | 19.5 | 20.5 |
| Ni | 17.5 | 18.5 |
| Mo | 6.0 | 6.5 |
| Cu | 0.50 | 1.00 |
| N | 0.18 | 0.25 |
| Fe | Bal. | — |
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength (min) | 650 MPa (94.3 ksi) |
| Yield strength, 0.2% offset (min) | 300 MPa (43.5 ksi) |
| Elongation in 50 mm (min) | 35 % |
| Hardness | 223 HB max |
Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 8 g/cm³ | 0.289 lb/in³ |
| Magnetic response | Non-magnetic | — |
Available forms & specifications
| Form | Specification | Size range |
|---|---|---|
| Sheets, plates & coils | ASTM A240 / ASME SA240 | 0.3 mm – 6 mm |
| Seamless & welded pipe | ASTM A790 / A928 | 1/8" – 24" NB |
| Tubes | ASTM A789 | 1/8" – 24" NB |
| Bars & rods | ASTM A276, A479 | 3 mm – 500 mm |
| Flanges & forgings | ASTM A182 / ASME SA182 (F51, F53, F55, F60, F61, F44) | 1/2" – 48" NB (larger on request) |
| Buttweld fittings | ASTM A815 | 1/2" – 48" NB |
Corrosion & temperature resistance
Duplex grades combine high strength with resistance to chloride pitting, crevice corrosion and stress-corrosion cracking; super duplex grades (PREN ≥ 40) are used for seawater and aggressive brines. Service is normally limited to about 250–300 °C because of embrittlement at higher temperatures.
Applications
254 SMO®: Seawater cooling, bleach plants, desalination. Offshore and subsea piping, desalination, chemical tankers, pulp bleaching, heat exchangers and pressure vessels where weight saving matters.
Frequently asked questions
What is the UNS number of 254 SMO®?
254 SMO® is designated UNS S31254 (W.Nr. 1.4547, EN X1CrNiMoCuN20-18-7).
What is 254 SMO® used for?
Super-austenitic 6Mo. Typical uses: seawater cooling, bleach plants, desalination.
Is 254 SMO® magnetic?
Non-magnetic.
In which forms can I buy 254 SMO® from Rajkamal Metals?
Coils & Strips, Sheets & Plates, Pipes & Tubes, Round Bars & Rods, Structural Sections, Flanges, Buttweld Fittings, Socket Weld & Threaded Fittings, Fasteners, Ferrule / Instrumentation Fittings, Dish Ends, Custom Orders. Sizes as per standard; other sizes on request.
Do you supply a Mill Test Certificate with 254 SMO®?
Yes. Actual values are given in the Mill Test Certificate (EN 10204 3.1) supplied with each order.
Last updated: 30 October 2026. Grade names identify the supply range; designations are not engineering equivalents. Availability, make, origin and documentation are confirmed at quotation.
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