What is the ASTM equivalent of 254 SMO?
Nov 20, 2025
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What is 254 SMO stainless steel?
254 SMO is a high-alloy super austenitic stainless steel. Its main components include high levels of chromium (19.5-20.5%), nickel (17.5-18.5%), molybdenum (6.0-6.5%), and nitrogen. It exhibits excellent resistance to pitting corrosion, crevice corrosion, and stress corrosion cracking. 254 SMO stainless steel is stronger than ordinary stainless steel, almost twice as strong as 300 series stainless steel, combining high strength with good toughness and ductility.
What is the ASTM equivalent of 254 SMO?
The primary material equivalents for 254 SMO Stainless Steel are UNS S31254, EN 1.4547, and W.Nr. 1.4547. It is also known by other designations like AISI 6Mo and ASTM F44 (for forgings) and ASTM A351 CK3MCuN (for castings). Different industry standards provide various equivalents for specific product forms, such as ASTM A240 (sheet/plate) and ASTM A312 (pipe).
| STANDARD | WERKSTOFF NR. | UNS | AFNOR | SIS | EN |
| SMO 254 | 1.4547 | S31254 | Z1 CNDU 20.18.06Az | 2378 | X1CrNiMoCuN20-18-7 |
SMO 254 SS Chemical Composition:
| Grade | % | Ni | Cr | Mo | Cu | N | C | Mn | Si | P |
| SMO 254 | Min. | 17.5 | 19.5 | 6 | 0.5 | 0.18 | ||||
| Max. | 18.5 | 20.5 | 6.5 | 1 | 0.22 | 0.02 | 1 | 0.8 | 0.03 | 0.01 |
254 SMO Mechanical Properties
| Property | 254 SMO (UNS S31254 / F44) |
|---|---|
| Tensile Strength (MPa) | 650–750 |
| Yield Strength 0.2% (MPa) | ≥300 |
| Elongation (%) | ≥35 |
| Hardness (HB) | ≤270 |
| PREN (Pitting Resistance Equivalent Number) | ≥42 |
| Impact Toughness (J at 20°C) | Excellent |
| Service Temperature (°C) | Up to 300–350 |
254 SMO Stainless Steel Applications:
Chemical Processing Equipment
Seawater Desalination Equipment
Flue Gas Desulfurization Scrubbers
Food Processing Equipment
Heat Exchangers
Oil and Gas Production Equipment
Pulp Mill Bleaching Systems
Seawater Treatment Equipment
Tall Oil Distillation Towers and Equipment
254 SMO Grade Stainless Steel Weldability:
Welding 254 SMO grade stainless steel requires filler material; otherwise, strength properties will be poor. AWS A5.14 ERNiCrMo-3 and Alloy 625 are recommended filler metals. The electrodes used in this process must be compatible with AWS A5.11 ENiCrMo-12.
SMO 254 Heat Treatment
The heat treatment of SMO 254 includes annealing, which involves heating the material to a temperature between 1050 and 1150°C, followed by water quenching. This heat treatment process improves the material's ductility and toughness while reducing its hardness.
SMO 254 Machinability
Due to the high strength and hardness of SMO 254, machining can be challenging. However, the process can be made easier using high-speed machining and carbide tools.
What is the difference between 254SMO and al6xn?
AL-6XN possesses approximately 5-10% greater strength than 254 SMO and is also ASME approved up to 800°F, whereas 254 SMO is approved up to 700°F. AL-6XN has been assigned to P Number 45 in Section IX of the ASME Boiler & Pressure Vessel code, Group 4 and uses 625 weld filler as well.
If you have project needs for 254 SMO Grade Stainless Steel bars, please feel free to place an order. GNEE has a large inventory of popular products for your selection. They can be processed into various practical product forms, including plates, coils, tubes, bars, and wires. For detailed chemical composition and free samples, please contact our factory immediately. We offer competitive prices and excellent service.Email: sales@gneestainless.com
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