What is 1.4547 Stainless Steel?
Jan 26, 2026
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1.4547 stainless steel, commonly known as 254 SMo or UNS S31254, is a super austenitic stainless steel with exceptionally high molybdenum and nitrogen content. It provides outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking in chloride environments, surpassing even high-grade duplex and standard austenitic steels. This makes it ideal for demanding applications in seawater, chemical processing, and offshore industries.
This high-performance super austenitic grade is standardized under several common designations.
| Standard | Equivalent Grade |
|---|---|
| EN (Europe) | 1.4547 |
| ASTM/AISI (USA) | 254 SMo, UNS S31254 |
| Common Name | 254 SMo, S31254 |
Its high alloy content, especially molybdenum and nitrogen, is key to its corrosion resistance.
| Element | C | Si | Mn | P | S | Cr | Ni | Mo | N | Cu |
|---|---|---|---|---|---|---|---|---|---|---|
| Content (%) | ≤ 0.02 | ≤ 0.80 | ≤ 1.0 | ≤ 0.03 | ≤ 0.01 | 19.5 - 20.5 | 17.5 - 18.5 | 6.0 - 6.5 | 0.18 - 0.22 | 0.5 - 1.0 |
It combines high strength with excellent ductility and corrosion resistance.
| Property | Yield Strength (Rp0.2) | Tensile Strength (Rm) | Elongation (A) | Hardness (HB) |
|---|---|---|---|---|
| Typical Value | ≥ 300 MPa | 650 - 850 MPa | ≥ 35% | ≤ 250 |
Key Characteristics and Applications of 1.4547 / 254 SMo
Exceptional Pitting and Crevice Corrosion Resistance: With a PREN (Pitting Resistance Equivalent Number) > 42, it offers superior resistance in aggressive chloride environments, including seawater and hypochlorite solutions.
Excellent Stress Corrosion Cracking (SCC) Resistance: Performs well under tensile stress in corrosive environments where other austenitic grades may fail.
High Strength and Good Formability: Provides higher yield strength than standard austenitic grades while maintaining good ductility and weldability.
Primary Applications:
Seawater and Offshore: Heat exchangers, piping systems, pumps, and valves in desalination plants and offshore platforms.
Chemical Processing: Equipment for handling aggressive acids, chlorides, and oxidizing media.
Pollution Control: FGD (Flue Gas Desulfurization) systems and scrubbers.
Pulp and Paper Industry: Bleaching equipment and chemical recovery units.
How does 254 SMo (1.4547) compare to Duplex 2205 (1.4462) in corrosive environments?
While both offer high corrosion resistance, 254 SMo has a higher PREN and superior resistance to pitting and crevice corrosion in extremely aggressive chloride environments, especially at higher temperatures. Duplex 2205 offers higher mechanical strength and better resistance to stress corrosion cracking in certain conditions. 254 SMo is often chosen for the most severe corrosive applications where maximum pitting resistance is required.
What are the welding considerations for 254 SMo stainless steel?
Welding 254 SMo requires careful control to maintain corrosion resistance. Recommended practices include using matching or over-alloyed filler metals (such as 654 SMo), controlling heat input to avoid excessive intermetallic phase formation, and ensuring proper shielding to prevent nitrogen loss. Post-weld cleaning is essential to preserve corrosion resistance in the weld zone.
Looking for a Reliable Supplier of 1.4547 / 254 SMo Stainless Steel?
GNEE Steel supplies premium super austenitic 254 SMo (1.4547) stainless steel in plate, pipe, bar, and fitting forms for the most demanding corrosive and marine applications. We provide full material traceability and certification to ensure optimal performance. If you have any requirements, please feel free to contact us.
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