Austenitic Stainless Steel 254SMO (UNS S31254)

254SMO(UNS S31254, W.Nr. 1.4547)is an advanced super austenitic stainless steel specifically designed for highly corrosive chloride-containing environments where conventional stainless steels are inadequate.

Its high chromium, molybdenum, and nitrogen contents provide significantly improved resistance to localized corrosion compared with 316L and standard duplex stainless steels. The alloy combines excellent mechanical strength, outstanding corrosion resistance, and good fabrication characteristics, making it a preferred material for offshore platforms, seawater cooling systems, heat exchangers, desalination plants, and chemical processing equipment.

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254SMO At a Glance

Key Attribute	Value
Material	254SMO Stainless Steel
UNS Number	S31254
EN / W.Nr.	1.4547
Material Type	Super Austenitic Stainless Steel
PREN	42–44
Density	8.0 g/cm³
Main Advantage	Outstanding Chloride Corrosion Resistance
Typical Service Temperature	-196°C to 400°C
Main Industries	Marine, Offshore, Chemical, Desalination
Comparable Grade	654SMO, Alloy 625

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Features of 254SMO

• Excellent resistance to pitting corrosion
• Superior crevice corrosion resistance
• Outstanding resistance to chloride stress corrosion cracking
• High PREN (42–44)
• Excellent seawater corrosion resistance
• Good resistance to acidic environments
• High mechanical strength
• Excellent weldability
• Outstanding toughness at cryogenic temperatures
• Excellent fabrication performance

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Chemical Composition of 254SMO

Element	Content (%)
Chromium (Cr)	19.5–20.5
Nickel (Ni)	17.5–18.5
Molybdenum (Mo)	6.0–6.5
Nitrogen (N)	0.18–0.25
Copper (Cu)	0.5–1.0
Manganese (Mn)	≤1.0
Silicon (Si)	≤0.8
Carbon (C)	≤0.02
Phosphorus (P)	≤0.03
Sulfur (S)	≤0.01
Iron (Fe)	Balance

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Physical Properties of 254SMO

Property	Value
Density	8.0 g/cm³
Melting Range	1320–1390°C
Electrical Resistivity	0.85 μΩ·m
Thermal Conductivity	13.8 W/m·K
Specific Heat Capacity	500 J/kg·K
Modulus of Elasticity	195 GPa

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Mechanical Properties of 254SMO

Solution Annealed

Property	Typical Value
Tensile Strength	≥650 MPa
Yield Strength (0.2%)	≥300 MPa
Elongation	≥35%
Hardness	≤220 HB

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Corrosion Resistance

254SMO exhibits excellent resistance to aggressive chloride-containing media and acidic environments. It significantly outperforms 316L stainless steel and standard duplex grades in pitting and crevice corrosion resistance.

It is particularly suitable for:

• Seawater handling systems
• Desalination plants
• Chloride-containing process streams
• Bleaching equipment in the pulp and paper industry
• Flue gas desulfurization systems
• Offshore platforms

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High Temperature Performance

254SMO performs well from cryogenic temperatures up to approximately 400°C. Continuous service in the 600–950°C range should be avoided because intermetallic phase formation may reduce corrosion resistance and toughness.

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Available Forms

J&A Alloy supplies 254SMO in:

• Round Bar
• Flat Bar
• Plate
• Sheet
• Coil
• Pipe
• Tube
• Flanges
• Forgings
• Billets
• Wire
• Rings
• Custom Machined Parts

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Applications of 254SMO

Marine Engineering

• Seawater piping
• Offshore platforms
• Marine pumps
• Propeller shafts

Desalination

• Reverse osmosis systems
• Brine heaters
• Evaporators

Chemical Processing

• Heat exchangers
• Pressure vessels
• Acid storage tanks
• Reactor equipment

Environmental Protection

• FGD systems
• Wastewater treatment
• Pollution control equipment

Pulp & Paper

• Bleaching plants
• Chloride processing equipment

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254SMO vs Other Stainless Steels

Grade	PREN	Main Advantage
254SMO	42–44	Excellent Chloride Resistance
654SMO	>56	Maximum Corrosion Resistance
2205 Duplex	35	Higher Strength
316L	24	General Industrial Service

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Welding & Fabrication

Recommended welding methods include:

• GTAW (TIG)
• GMAW (MIG)
• SMAW
• Plasma Welding

Use matching super austenitic or nickel alloy filler metals. Post-weld heat treatment is generally not required.

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Standards & Equivalent Grades

Standard	Designation
UNS	S31254
EN / W.Nr.	1.4547
Common Name	254SMO / 6Mo
ASTM Plate	A240 UNS S31254
ASTM Bar	A479 UNS S31254
ASTM Pipe	A312 UNS S31254
NACE	MR0175 / ISO 15156

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Frequently Asked Questions

What is 254SMO stainless steel?

254SMO is a super austenitic stainless steel with approximately 6% molybdenum, developed for outstanding corrosion resistance in chloride-containing environments.

What is the UNS number of 254SMO?

UNS S31254.

Is 254SMO better than 316L?

Yes. It provides significantly better resistance to pitting, crevice corrosion and chloride stress corrosion cracking.

What is the PREN value of 254SMO?

Typically between 42 and 44.

Can 254SMO be used in seawater?

Yes. It is specifically designed for seawater and other aggressive chloride environments.

Is 254SMO magnetic?

No. In the solution-annealed condition it is essentially non-magnetic.

Can 254SMO be welded?

Yes. It has excellent weldability using conventional welding processes.

What forms are available?

Bar, rod, plate, sheet, pipe, tube, flanges, forgings, billets and machined components.

What industries use 254SMO?

Offshore oil & gas, marine engineering, desalination, chemical processing, environmental protection and pulp & paper.

What is the difference between 254SMO and 654SMO?

654SMO has a higher alloy content and superior localized corrosion resistance, while 254SMO offers an excellent balance of performance, availability and cost.

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Why Choose J&A Alloy

Professional Stainless Steel Supplier

J&A Alloy supplies super austenitic, duplex, super duplex, PH stainless steels and nickel alloys to customers worldwide.

Strict Quality Assurance

• PMI Testing
• Chemical Analysis
• Mechanical Testing
• Corrosion Testing
• Ultrasonic Inspection

International Standards

• ASTM
• ASME
• EN
• NACE
• ISO 9001
• EN 10204 3.1 / 3.2 Certification

Value-Added Processing

• Precision Cutting
• CNC Machining
• Forging
• Heat Treatment
• Custom Fabrication

Global Supply Capability

Reliable delivery and technical support for offshore, marine, chemical, energy, and industrial applications worldwide.