Super austenitic 254 SMO (UNS S31254)
Super austenitic 254 SMO (UNS S31254) — 6Mo grade for seawater and aggressive chloride environments.
| UNS number | S31254 |
| Material family | Super austenitic |
| Product specifications | A182 F44, A403 WPS31254, A312 |
| Density (typical) | 8.0 g/cm³ (8000 kg/m³) |
| Weight of 6" Sch 40 pipe | 28.80 kg/m |
Specifications by product form
One alloy is ordered under different ASTM/ASME numbers depending on form: forged flanges and fittings, wrought buttweld fittings, and pipe or tube. For Super austenitic 254 SMO the usual specifications are A182 F44, A403 WPS31254, A312. Quote both the specification and the UNS number on purchase orders to avoid ambiguity.
Chemical and mechanical limits differ between these specifications — always check the edition of the standard named on your order and the mill test certificate.
Chemical composition & mechanical properties
| Property | 254 SMO (6Mo) |
|---|---|
| Family | Super austenitic |
| UNS | S31254 |
| EN / W.Nr | 1.4547 X1CrNiMoCuN20-18-7 |
| Basis spec | ASTM A240 |
| Density g/cm³ | 8.0 |
| Chemical composition, % | |
| 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 |
| N | 0.18–0.25 |
| Cu | 0.50–1.00 |
| Mechanical properties (min) | |
| Tensile strength | 655 MPa (95 ksi) |
| Yield strength (0.2%) | 310 MPa (45 ksi) |
| Elongation | 35% |
| Hardness (max) | 223 HB |
| PREN (min, from spec) | 42.2 |
Single values are maximums; ranges are min–max; "bal" = balance. Limits are typical of the basis specification for that product form — forgings, pipe and fittings specifications differ slightly. Always check the exact specification, edition and the mill test certificate.
Frequently asked questions
What is the UNS number of Super austenitic 254 SMO?
S31254.
Which ASTM specifications cover Super austenitic 254 SMO?
A182 F44, A403 WPS31254, A312.
What is the density of Super austenitic 254 SMO?
About 8.0 g/cm³ (8000 kg/m³), used for weight calculations.
Last updated 2026-11-02