ASTM A403 WPS31254 (SMO 254)
ASTM A403 WPS31254 (SMO 254) Pipe Fittings
ASTM A403 WPS31254, commonly known as SMO 254, is a super austenitic stainless steel fitting grade engineered for extreme corrosion resistance in highly aggressive environments. With a balanced composition of high molybdenum (≈6%), nitrogen, and chromium, SMO 254 offers outstanding resistance to pitting, crevice corrosion, and chloride stress-corrosion cracking.
These fittings are widely used in seawater systems, desalination plants, chemical processing, offshore equipment, and flue-gas cleaning systems, making them an ideal solution for industries requiring high strength and longevity in harsh corrosion environments.
Key Features
Extremely high pitting & crevice corrosion resistance
Superior chloride stress-corrosion cracking resistance
High strength & toughness compared to conventional stainless steel
Excellent mechanical properties at both high & low temperatures
Designed for marine, chemical & offshore applications
Excellent weldability & formability
Technical Specification Table
| Specification | Details |
|---|---|
| Standard | ASTM A403 / ASME SA403 |
| Grade | WPS31254 (SMO 254) |
| UNS | S31254 |
| WNR | 1.4547 |
| Form | Seamless / Welded / Fabricated |
| Size Range | ½” to 48” |
| Schedule | SCH 5S to XXS |
| Pressure Class | 150# to 2500# |
| Standards | ANSI / ASME / MSS-SP / DIN |
Equivalent Grades
| Standard | Grade |
|---|---|
| UNS | S31254 |
| Werkstoff Nr. | 1.4547 |
| EN | X1CrNiMoCuN20-18-7 |
| ASTM | A182 F44 / A240 254SMO |
| Trade Name | 254 SMO |
Available Sizes
Diameter: ½” NB to 48” NB
Thickness: SCH 5S, 10S, 40S, 80S, 160, XXS
Custom sizes & fabricated fittings available on request
Chemical Composition
| Element | Content (%) |
|---|---|
| C | ≤ 0.020 |
| Mn | ≤ 1.00 |
| Si | ≤ 0.80 |
| P | ≤ 0.030 |
| S | ≤ 0.010 |
| Cr | 19.5 – 20.5 |
| Ni | 17.5 – 18.5 |
| Mo | 6.0 – 6.5 |
| Cu | 0.5 – 1.0 |
| N | 0.18 – 0.22 |
| Fe | Balance |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | ≥ 650 MPa |
| Yield Strength | ≥ 300 MPa |
| Elongation | ≥ 35% |
| Hardness | ≤ 96 HRB |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.0 g/cm³ |
| Melting Range | 1320 – 1390°C |
| Thermal Conductivity | 12 W/m-K |
| Electrical Resistivity | 0.90 μΩ-m |
| Modulus of Elasticity | 195 GPa |
Types of ASTM A403 WPS31254 Fittings
ASTM A403 WPS31254 Elbow
ASTM A403 WPS31254 Tee
ASTM A403 WPS31254 Reducers
ASTM A403 WPS31254 Caps
ASTM A403 WPS31254 Cross Fittings
ASTM A403 WPS31254 Nipples
ASTM A403 WPS31254 Couplings
ASTM A403 WPS31254 Stub Ends
Corrosion Resistance
Exceptional performance in seawater & marine environments
Resistant to chloride-induced corrosion
Excellent resistance against pitting & crevice corrosion
Suitable for acidic & saline conditions
Heat Resistance
Stable mechanical properties at elevated temperatures
Recommended continuous service up to 600°C
Good oxidation resistance in moist & dry environments
Heat Treatment
Solution Annealing: 1150 – 1200°C
Rapid cooling / water quenching recommended
No post-weld heat treatment typically required
Welding
Excellent weldability using TIG / MIG / SMAW
Recommended Filler Material: AWS A5.14 ERNiCrMo-3 / ERNiCrMo-7
Avoid slow cooling to prevent intermetallic phase formation
Fabrication
Good formability & machinability
Work hardens rapidly — use rigid tooling
Suitable for bending, forming & deep-drawing
Applications
Desalination Plants & Seawater Handling Systems
Offshore Oil & Gas Platforms
Chemical & Petrochemical Industries
Heat Exchangers & Pressure Vessels
Pulp & Paper Bleaching Plants
Flue-Gas Desulfurization Systems
Marine Engineering & Shipbuilding
Pharmaceutical & Food Industry Equipment