SMO 254 Round Bar (UNS S31254)
254 SMO is a 6 % molybdenum super austenitic stainless steel alloyed with nitrogen and copper. With a PREN of at least 42.5 it provides pitting and crevice corrosion resistance approaching that of nickel-base alloys in seawater and chloride bearing process streams, at a considerably lower cost. The alloy also has roughly 50 % higher yield strength than 316L and retains austenitic toughness down to cryogenic temperatures.
Nexforge Alloys supplies 254 SMO round bars in the solution annealed and quenched condition as per ASTM A276 / A479 and ASME SA479. Bars are peeled or ground and are certified with chemical analysis, mechanical properties, hardness and, on request, ASTM G48 pitting and ASTM A262 intergranular corrosion tests.
254 SMO (UNS S31254, W.Nr. 1.4547) round bars from 6 mm to 250 mm diameter, solution annealed as per ASTM A276 / A479, PREN ≥ 42.5.
SMO 254 Round Bar Specification
| Parameter | Details |
|---|---|
| Alloy Designations | 254 SMO, UNS S31254, W.Nr. 1.4547, 6Mo super austenitic |
| Standards | ASTM A276, ASTM A479, ASME SA479, ASTM A182 F44 (forged), EN 10088-3, NORSOK M-630 |
| Size Range | 6 mm to 250 mm diameter |
| Length | Random 3 to 6 metres, or cut to length |
| Condition | Solution annealed at 1150 - 1200 °C and water quenched |
| Surface Finish | Peeled, centreless ground, bright, rough turned |
| Tolerance | h9 / h10 / h11 or as per drawing |
| Testing | Chemical, tensile, hardness, ASTM G48 Method A, ASTM A262 Practice E, UT on request |
| Certification | EN 10204 3.1 mill test certificate; 3.2 on request |
Chemical Composition (% by weight)
| Element | C | Mn | Si | P | S | Cr | Ni | Mo | N | Cu | Fe |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 254 SMO (S31254) | 0.020 max | 1.00 max | 0.80 max | 0.030 max | 0.010 max | 19.5 - 20.5 | 17.5 - 18.5 | 6.00 - 6.50 | 0.18 - 0.22 | 0.50 - 1.00 | Balance |
Mechanical Properties
| Condition | Tensile Strength (min) | 0.2% Yield Strength (min) | Elongation (min) | Hardness (max) | PREN | Density |
|---|---|---|---|---|---|---|
| Solution annealed | 655 MPa (95 ksi) | 310 MPa (45 ksi) | 35 % | 223 HB | ≥ 42.5 | 8.00 g/cm³ |
Values are minimum or typical figures as per the referenced standards and are for guidance only. Please refer to the mill test certificate supplied with the material for actual values.
Key Features
- Excellent resistance to pitting and crevice corrosion in seawater and chlorides (CPT approx. 90 °C)
- High resistance to chloride stress corrosion cracking
- About 50 % higher strength than 316L, enabling thinner sections
- Good weldability and toughness at low temperatures
Applications
- Seawater cooling systems, desalination and offshore piping components
- Pump shafts, valve stems and fasteners in chemical and petrochemical plants
- Pulp and paper bleaching plant equipment
- Flue gas desulphurisation and pollution control equipment
- Food, pharmaceutical and reverse osmosis systems