Key Feature

The Super Austenitic Premium Corrosion-Resistant Pipe. 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.

Common Designations

UNS S31254
ASTM A312 TP S31254 (Seamless/Welded)
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
Impact Toughness: Excellent at cryogenic temps

Higher strength than conventional austenitic grades due to nitrogen addition.

Corrosion Resistance

Exceptional: PREN*: 42-45
Superior resistance to: chloride pitting/crevice corrosion, stress corrosion cracking, seawater corrosion, wide range of acids.

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

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.

Pressure Ratings

Schedule 10S/40S: Standard
Schedule 80S/160: Heavy wall
ASME B31.3 compliant
Higher allowable stresses than 316L

Nitrogen strengthening allows for potential weight reduction in piping systems.

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.

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.

Key Standards

ASTM A312 S31254: Seamless & Welded Pipe
ASTM A358 S31254: EFW Pipe
ASTM B674: Welded Pipe
NORSOK M-630: Offshore materials
EN 10216-5: Seamless Pressure Tubes

Stringent quality requirements for critical applications.

Common Applications

• Seawater Systems: Offshore platforms, desalination plants, seawater cooling
• Chemical Processing: Highly corrosive chemical transport, acid piping, reactors
• Pulp & Paper: Bleach plant piping, digesters, aggressive chemical recovery
• Pollution Control: FGD systems, scrubbers, wastewater treatment
• Oil & Gas: Sour service, offshore seawater injection, topside piping
• Pharmaceutical: Aggressive process piping, CIP systems
• Marine: Shipboard piping, seawater systems, ballast piping

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