Key Feature

The Super Austenitic Premium Corrosion-Resistant Bar Stock. Exceptionally high molybdenum content (6%) provides superior resistance to chloride-induced corrosion, surpassing conventional stainless steels and some nickel alloys.

The ultimate stainless steel solution for severe chloride-containing environments requiring maximum corrosion resistance in bar form.

Common Designations

UNS S31254
ASTM A276 (Stainless Steel Bars)
EN 1.4547, X1CrNiMoCuN20-18-7
Werkstoff Nr. 1.4547
Alloy 254 SMO®
F44 (Wrought product designation)

"SMO" stands for "Super Molybdenum" highlighting its key alloying element.

Chemical Composition (Typical wt.%)

C: ≤ 0.020
Cr: 19.5 - 20.5Ni: 17.5 - 18.5Mo: 6.0 - 6.5Cu: 0.50 - 1.00N: 0.18 - 0.22Mn: ≤ 1.00
Si: ≤ 0.80

High Mo (6%) + N + Cu combination provides exceptional corrosion resistance.

Mechanical Properties

Tensile Strength: ≥ 650 MPa
Yield Strength: ≥ 300 MPa
Elongation: ≥ 35%
Hardness: ≤ 223 HB
Machinability: 35% of B1112 steel
Impact Toughness: Excellent at cryogenic temperatures

Higher strength than conventional austenitic grades due to nitrogen addition.

Physical Properties

Density: 8.00 g/cm³
Melting Range: 1320 - 1390 °C
Thermal Expansion: 16.5 × 10⁻⁶/K (20-100°C)
Thermal Conductivity: 13 W/m·K (100°C)
Non-magnetic when annealed

Similar to other high-alloy austenitic grades; maintains non-magnetic properties.

Available Forms

Rounds: 6mm - 200mm diameter
Squares: 6mm - 100mm
Hexagons: 6mm - 75mm
Flats: Various sizes
Billets: For forging applications
Forgings: Custom forged components

Available in sizes suitable for critical component manufacturing.

Surface Conditions

Hot Rolled: Black bar
Cold Drawn: Bright finish
Centerless Ground: Precision ground
Polished: Mirror finishes available
Peeled/Turned: Improved surface for machining

High-quality surface finishes required for many applications.

Corrosion Resistance

Exceptional: PREN*: 42-45
Superior resistance to: chloride pitting/crevice corrosion, stress corrosion cracking, seawater corrosion, wide range of acids.
Excellent in: Seawater, bleach solutions, chlorinated water, acidic environments.

PREN 42-45 exceeds most duplex and approaches super duplex grades.

Machining Characteristics

• Difficult to machine due to high strength/work hardening
• High tool wear• Requires rigid setups and powerful equipment
• Specialized tooling recommended
• Surface finish achievable with proper techniques

One of the more challenging stainless steels to machine; requires expertise.

Welding Characteristics

Requires careful procedure controlOvermatched filler metals essential
Heat input control: 0.5-1.5 kJ/mm
Low interpass temperature: ≤ 100°C
Shielding gas: Ar + 2% N₂ recommended

Demanding but well-established welding procedures exist for critical applications.

Temperature Limits

Continuous Service: Up to 400°C (for corrosion)
Higher Temp: Up to 800°C (with property loss)
Cryogenic Service: Excellent to -196°C
Avoid: 600-900°C (sigma phase risk)

Limited high-temp corrosion service but excellent low-temp performance.

Key Standards

ASTM A276 S31254: Stainless Steel Bars
ASTM B649: Nickel Alloy Bars
EN 10088-3: Stainless Steel Bars
NORSOK M-630: Offshore materials
ASME SA276: Code Construction

Stringent quality requirements for critical applications.

Common Applications

• Seawater System Components: Pump shafts, valve stems, marine fasteners, propeller shafts
• Chemical Processing: Reactor agitator shafts, pump components, valve bodies for aggressive chemicals
• Pulp & Paper: Digester agitator shafts, bleach plant equipment, chemical recovery parts
• Pollution Control: FGD system components, scrubber parts, environmental equipment
• Oil & Gas: Sour service components, offshore seawater injection parts, topside components
• Pharmaceutical: Ultra-pure water system components, aggressive chemical process parts
• Desalination Plants: High-pressure pump shafts, RO membrane housings, valve components

Reserved for the most aggressive corrosive environments where other stainless steels fail.