ASTM A403 WPS31254 elbows are super-austenitic stainless steel butt-weld fittings manufactured from UNS S31254, commonly identified in industry as 254 SMO. The grade contains approximately 20% chromium, 18% nickel, 6% molybdenum, copper and nitrogen, providing very high resistance to pitting, crevice corrosion and stress-corrosion cracking in many aggressive chloride-containing environments.

We manufacture and supply ASTM A403 / ASME SA-403 WPS31254 elbows, tees, reducers and caps in seamless and welded construction to ASME B16.9, with EN 10204 3.1 certification and project-specific NDE when required.

ASTM A403 WPS31254 Quick Specification

Item	Specification
Material Standard	ASTM A403 / ASME SA-403
Grade	WPS31254
UNS	S31254
Common Industry Name	254 SMO
EN Number	1.4547
Material Family	Super-Austenitic Stainless Steel
Dimensional Standard	ASME B16.9
Products	Elbow / Tee / Reducer / Cap
Construction	Seamless / Welded
Classes	WP-S / WP-W / WP-WX / WP-WU as applicable
Standard Size Range	NPS 1/2–48
Ends	Butt-Weld Ends
Certification	EN 10204 3.1 / 3.2 when specified

What Is ASTM A403 WPS31254?

ASTM A403 WPS31254 is the wrought pipe-fitting grade corresponding to UNS S31254 super-austenitic stainless steel.

ASTM A403 covers wrought austenitic stainless steel fittings intended for pressure piping applications.

WPS31254 may be used for factory-made butt-weld fittings such as:

• 90° elbows
• 45° elbows
• 180° returns
• Equal tees
• Reducing tees
• Concentric reducers
• Eccentric reducers
• Caps

The material designation should be written as:

ASTM A403 WPS31254 / UNS S31254

For ASME material specifications, the corresponding designation is:

ASME SA-403 WPS31254

What Is 254 SMO / UNS S31254?

UNS S31254 is a high-alloy super-austenitic stainless steel developed for aggressive chloride-containing environments.

It is not a duplex stainless steel.

UNS S31254 combines high levels of chromium, nickel and molybdenum with nitrogen and copper to provide resistance to:

• Pitting corrosion
• Crevice corrosion
• General corrosion
• Stress-corrosion cracking
• Seawater and high-chloride environments under suitable design conditions

Its alloy design gives it substantially higher localized corrosion resistance than conventional stainless steels such as 316L.

254 SMO Chemical Composition

Typical ASTM A403 WPS31254 chemistry includes:

Element	UNS S31254
Carbon, C	0.020% max
Manganese, Mn	1.00% max
Silicon, Si	0.80% max
Phosphorus, P	0.030% max
Sulfur, S	0.010% max
Chromium, Cr	19.50–20.50%
Nickel, Ni	17.50–18.50%
Molybdenum, Mo	6.00–6.50%
Nitrogen, N	0.18–0.25%
Copper, Cu	0.50–1.00%

The key corrosion-resistant alloying system is therefore approximately:

20Cr + 18Ni + 6Mo + N + Cu

Actual heat chemistry should be confirmed by the supplied Material Test Certificate.

ASTM A403 WPS31254 Mechanical Properties

Typical specified minimum room-temperature mechanical properties include:

Property	Minimum
Tensile Strength	650 MPa / 94 ksi
Yield Strength	300 MPa / 44 ksi
Elongation	35%

Actual production values may exceed these minimums and should be verified from the supplied MTC.

The main engineering advantage of S31254 is not only strength, but its combination of high alloy content and strong localized corrosion resistance.

PREN and Chloride Corrosion Resistance

The Pitting Resistance Equivalent Number (PREN) is commonly used as one indicator of resistance to localized chloride corrosion.

A widely used formula is:

PREN = %Cr + 3.3 × %Mo + 16 × %N

Because UNS S31254 contains approximately:

• 20% Cr
• 6% Mo
• 0.2% N

its PREN is typically above 40.

This gives S31254 significantly better resistance to pitting and crevice corrosion than conventional grades such as 316L in many chloride-containing environments.

PREN should not be used as the only material-selection criterion. Actual performance also depends on:

• Temperature
• Chloride concentration
• Crevice geometry
• Flow condition
• Oxidizing potential
• Process chemistry

Is 254 SMO Suitable for Seawater?

UNS S31254 is widely selected for demanding seawater and chloride-bearing applications because of its high resistance to localized corrosion.

Typical applications include:

• Seawater cooling systems
• Offshore piping
• Firewater systems
• Desalination equipment
• Chemical-processing systems
• Bleaching systems
• Flue-gas cleaning systems

However, suitability must still be evaluated against the actual seawater temperature, chlorination level, flow condition, crevice design and operating environment.

It should not be described as universally immune to seawater corrosion under every condition.

Heat Treatment of WPS31254 Fittings

Proper heat treatment is critical for high-molybdenum super-austenitic stainless steel fittings.

WPS31254 fittings are solution heat treated followed by rapid cooling in accordance with the applicable material requirements.

The objectives are to:

• Restore the required austenitic structure
• Maintain corrosion resistance
• Dissolve undesirable precipitates
• Minimize harmful intermetallic phases

Because S31254 has high chromium and molybdenum content, prolonged exposure in certain intermediate-temperature ranges can promote detrimental phases and reduce toughness and corrosion performance.

Heat treatment should therefore follow a controlled and documented procedure rather than a generic stainless-steel heat-treatment cycle.

Seamless vs Welded ASTM A403 WPS31254 Fittings

ASTM A403 identifies fitting classes according to construction and weld examination.

Class	General Meaning
WP-S	Seamless construction
WP-W	Welded construction with applicable examination requirements
WP-WX	All welds radiographically examined
WP-WU	All welds ultrasonically examined

For critical chemical, offshore or chloride-service projects, WP-S or WP-WX construction may be specified depending on the piping class and project requirements.

The required fitting class should be clearly stated in the purchase order.

ASME B16.9 254 SMO Butt-Weld Fittings

Current ASME B16.9 covers factory-made wrought butt-welding fittings from NPS 1/2 through NPS 48.

The standard addresses requirements including:

• Overall dimensions
• Tolerances
• Ratings
• Testing
• Marking

Short-radius elbows and returns historically associated with ASME B16.28 are now incorporated into the current ASME B16.9 framework.

Therefore, the main dimensional standard on a current product page should be:

ASME B16.9

rather than presenting B16.28 as a separate primary standard.

Available 254 SMO Pipe Fittings

Our typical ASTM A403 WPS31254 product range includes:

45° Elbow
90° Long-Radius Elbow
90° Short-Radius Elbow
180° Return
Equal Tee
Reducing Tee
Concentric Reducer
Eccentric Reducer
Butt-Weld Cap

Typical wall-thickness options can include:

SCH 10S / 40S / 80S and project-specific wall thicknesses, depending on fitting size and construction route.

ASME B16.9 covers NPS 1/2–48, but actual commercial availability in S31254 should be confirmed according to fitting type, wall thickness, quantity and production method.

254 SMO vs 904L

S31254 and 904L are both highly corrosion-resistant austenitic stainless steels, but S31254 is more highly alloyed for localized chloride-corrosion resistance.

Item	S31254 / 254 SMO	904L / N08904
Structure	Super Austenitic	Austenitic
Cr	~20%	~19–23%
Ni	~18%	~23–28%
Mo	~6%	~4–5%
Nitrogen	Higher	Lower
PREN	Above 40	Lower
Main Strength	Aggressive chloride resistance	Acid and general corrosion resistance

S31254 is often selected where pitting and crevice-corrosion resistance in chloride-containing service is more demanding than conventional 904L performance.

The final material choice should still be based on actual process chemistry and design conditions.

UNS S31254 / EN 1.4547 Designations

The material is commonly identified as:

System	Designation
UNS	S31254
EN Material No.	1.4547
EN Name	X1CrNiMoCuN20-18-7
Common Industry Name	254 SMO

These are corresponding material designations in different standards systems.

They should not automatically be treated as interchangeable product specifications without verifying the applicable material standard, product form and project requirements.

Related S31254 Piping Products

A complete S31254 piping system can include:

Component	Typical Specification
Pipe	ASTM A312 UNS S31254
Butt-Weld Fitting	ASTM A403 WPS31254
Forged Flange	ASTM A182 F44
Plate / Sheet	ASTM A240 UNS S31254

 

Inspection & Certification

ASTM A403 WPS31254 fittings can be supplied with:

• EN 10204 Type 3.1 MTC
• EN 10204 Type 3.2 when specified
• Heat chemical analysis
• Mechanical-test results
• Heat-treatment records
• PMI
• Dimensional inspection
• Visual examination
• PT
• RT for WP-WX construction
• UT for WP-WU construction
• Third-party inspection
• Full heat-number traceability

Additional corrosion testing or project-specific examination can be evaluated when required.

Frequently Asked Questions

What is ASTM A403 WPS31254?

ASTM A403 WPS31254 is the wrought butt-weld fitting grade corresponding to UNS S31254 super-austenitic stainless steel, commonly identified in industry as 254 SMO.

Is 254 SMO the same as UNS S31254?

Yes. UNS S31254 is the standard material designation, while 254 SMO is a commonly used industry name for this high-alloy super-austenitic stainless steel.

Is 254 SMO a duplex stainless steel?

No. UNS S31254 is super-austenitic stainless steel, not duplex stainless steel.

Duplex grades such as S31803, S32205 or S32750 have a mixed ferritic-austenitic microstructure.

What is the difference between WP-S and WP-WX S31254 fittings?

WP-S indicates seamless construction, while WP-WX indicates welded construction with all welds radiographically examined.

The required class depends on the project specification and service conditions.

Why is S31254 used in chloride service?

Its high Cr, Mo and N content produces a PREN typically above 40, giving strong resistance to pitting and crevice corrosion in many aggressive chloride-containing environments.

ASTM A403 WPS31254 Fitting Manufacturer

We manufacture and supply ASTM A403 / ASME SA-403 WPS31254 UNS S31254 butt-weld fittings for seawater, offshore, chemical, desalination and high-chloride process systems.

Available products include:

45° / 90° / 180° elbows, tees, reducers and caps in seamless or welded construction, with WP-S, WP-WX and project-specific inspection options.

For quotation, please specify:

Material + Class + Fitting Type + NPS + Schedule/WT + Standard + Quantity + Inspection Requirements

Example:

ASTM A403 WPS31254-WX, 90° LR Elbow, NPS 6, SCH 40S, ASME B16.9, EN 10204 3.1