Chemical composition
Nominal: mid-range where both limits are given, the cap where only a maximum is, balance takes the remainder. Exact specified ranges below.
| Element | Name | Content % | |
|---|---|---|---|
| Main elements6 elements | |||
| Fe | Iron | Bal. | |
| Cr | Chromium | 19.5 – 20.5% | |
| Ni | Nickel | 17.5 – 18.5% | |
| Mo | Molybdenum | 6 – 6.5% | |
| Cu | Copper | 0.5 – 1% | |
| N | Nitrogen | 0.18 – 0.25% | |
| Element | Name | Content % | |
|---|---|---|---|
| Minor & residual5 elements | |||
| C | Carbon | ≤ 0.02% | |
| Mn | Manganese | ≤ 1% | |
| Si | Silicon | ≤ 0.8% | |
| P | Phosphorus | ≤ 0.03% | |
| S | Sulphur | ≤ 0.01% | |
Mechanical minima by form
Guaranteed values differ by form, size and delivery condition; quotations confirm the specification, form, size and condition.
| Form | Condition | Rm MPa | Rp0.2 MPa | A ≥ % | Other requirements and notes |
|---|---|---|---|---|---|
| Bar and forgings | |||||
| Bar and shapes | Condition A; solution treated at not less than 1150 °C, water quenched or otherwise rapidly cooled | ≥ 650 (94 ksi) | ≥ 300 (44 ksi) | ≥ 35 | |
| Forgings and flanges (F44) | Solution treated at not less than 1149 °C and liquid quenched below 260 °C | ≥ 650 (94 ksi) | ≥ 305 (44 ksi) | ≥ 35 | |
| Pressure-retaining forgings (1.4547, reference section ≤160 mm) | +AT: solution treated at 1020–1120 °C, water cooled | 650 – 850 | ≥ 300 | ≥ 40 | |
| Bars (EN 10088-3, ≤160 mm) | +AT (solution annealed) | 650 – 850 | ≥ 300 | ≥ 35 | Also specified: Hardness ≤ 260 HBW Rp1.0 ≥ 340 MPa; KV ≥ 100 J longitudinal; 160–250 mm: transverse A ≥ 30 %, KV ≥ 60 J. |
| Plate, sheet and strip | |||||
| Plate | Solution annealed | ≥ 655 (95 ksi) | ≥ 310 (45 ksi) | ≥ 35 | |
| Sheet and strip | Solution annealed | ≥ 690 (100 ksi) | ≥ 310 (45 ksi) | ≥ 35 | |
| Cold-rolled strip (EN 10088-2, ≤8 mm) | +AT (solution annealed) | 650 – 850 | ≥ 320 | ≥ 35 | Rp1.0 ≥ 350 MPa. |
| Hot-rolled plate (EN 10088-2, ≤75 mm) | +AT (solution annealed) | 650 – 850 | ≥ 300 | ≥ 40 | Rp1.0 ≥ 340 MPa; hot-rolled strip (≤13.5 mm): A ≥ 35 %. KV ≥ 100/60 J (long./transv., over 10 mm). |
| Tube and pipe | |||||
| Seamless and welded pressure tubes (EN 10216-5 / EN 10217-7, wall ≤60 mm) | +AT (solution annealed) | 650 – 850 | ≥ 300 | ≥ 35 | Rp1.0 ≥ 340 MPa; transverse A ≥ 30 %; KV ≥ 100/60 J (long./transv.). |
| Fittings and flanges | |||||
| Factory-made fittings | Solution treated at not less than 1149 °C, rapidly cooled in water or otherwise; all welding must be completed before the final heat treatment | 650 – 820 | ≥ 305 (44 ksi) | ≥ 28 | |
| Fittings (wrought austenitic stainless, butt-weld / socket) | Solution annealed 2100 °F [1149 °C], water quenched or otherwise rapidly cooled | 650 – 820 | ≥ 305 (44 ksi) | ≥ 28 | Elongation: ≥28% longitudinal, ≥20% transverse. A single temperature is a minimum. All fittings are supplied heat-treated. |
Where this grade is recommended
Matched in 3 service conditions; ranks and scores computed from the condition-scoring matrix.
| Service condition | Industry | Temperature | Rank | Score |
|---|---|---|---|---|
| Seawater piping & HX | Marine & Offshore | 40 – 90 °C | 2 / 11 | 92 |
| Flue-gas desulphurisation | Environmental & FGD | 80 – 180 °C | 6 / 11 | 88 |
| Desalination & RO | Marine & Offshore | 45 – 110 °C | 7 / 12 | 88 |
Designations & equivalents
| W.Nr. (Germany) | 1.4547 |
| EN designation | X1CrNiMoCuN20-18-7 |
| Trade name(s) | 254 SMO / 1.4547 |
| ASTM / AISI | A240 / A276 / A403 / A479 / A484 |
Cross-references are common near-equivalents for search and shortlisting; substitution across standards requires clause-by-clause verification. All grades in one cross-reference table →
Applicable standards
12 specifications. Name the standard and its edition on the order.
Guaranteed values and required tests differ between specifications — see Mechanical minima by form for the figures per form.
Frequently asked questions
What is 254 SMO · UNS S31254?
254 SMO · UNS S31254 — Super-austenitic stainless. 6Mo super-austenitic workhorse — seawater, bleach and FGD, interchangeable with 926
What is the maximum service temperature of S31254?
Typically about 400 °C; the practical limit depends on media, stress and design life — acceptance per the governing standard.
What is the tensile strength of S31254?
The specified minimum tensile strength is 655 MPa for the main product form. Minima for other forms and sizes are listed under "Mechanical minima by form" on this page.
Which standards cover S31254?
ASTM A240/A240M, ASTM A480/A480M, ASTM A276/A276M, ASTM A479/A479M, ASTM A484/A484M, ASTM A403/A403M, ASTM A182/A182M, EN 10088-2 (sheet, plate, strip), EN 10222-5 (forgings for pressure purposes), EN 10088-3 (bar, rod, wire, sections), EN 10216-5 (seamless pressure tubes), EN 10217-7 (welded pressure tubes)
Where is S31254 typically used?
Seawater piping & HX (Marine & Offshore); Flue-gas desulphurisation (Environmental & FGD); Desalination & RO (Marine & Offshore)
In which forms is S31254 available?
Tube, plate, strip, bar, forgings, wire and other forms — sizes and delivery condition confirmed per order, with EN 10204 3.1 / 3.2 certification.
Same series
Download PDF datasheet
This grade’s datasheet as an A4 PDF — for filing, printing or forwarding to colleagues.
Download PDF datasheetSupply & enquiry
Tube & pipeφ1 – 219 × 0.25 – 25 mm
Plate4.76 – 80 mm
Barφ8 – 300 mm
Wire & filler metalsφ0.01 – 8 mmFor this grade we can supply, against your service conditions:
- Tube, plate, strip, bar, forgings, wire and more — with size range and lead time
- Chemistry and mechanical test report (EN 10204 3.1 / 3.2)
- Like-for-like alternatives and selection advice
- Applicable standards and inspection scope
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