ASTM A182 F44 254 SMO Flange | UNS S31254
ASTM A182 F44 flanges are forged super-austenitic stainless steel flanges manufactured from UNS S31254, also designated EN 1.4547. With approximately 20% chromium, 18% nickel, 6% molybdenum, nitrogen and copper, F44 provides very high resistance to pitting, crevice corrosion and stress-corrosion cracking in many aggressive chloride-containing environments.
We manufacture and supply ASTM A182 / ASME SA-182 F44 weld neck, blind, slip-on and other forged flanges to ASME B16.5 and ASME B16.47, with RF, FF and RTJ facing as applicable and EN 10204 3.1 certification.
ASTM A182 F44 Flange Quick Specification
| Item | Specification |
|---|---|
| Material Standard | ASTM A182 / ASME SA-182 |
| Grade | F44 |
| UNS | S31254 |
| Common Designation | 254 SMO / 6Mo |
| EN Material No. | 1.4547 |
| EN Name | X1CrNiMoCuN20-18-7 |
| Material Family | Super-Austenitic Stainless Steel |
| Flange Standard | ASME B16.5 / ASME B16.47 |
| Flange Types | WN / Blind / Slip-On / SW / Threaded |
| Facing | RF / FF / RTJ as applicable |
| Certification | EN 10204 3.1 / 3.2 when specified |
What Is ASTM A182 F44?
ASTM A182 F44 is a forged super-austenitic stainless steel grade corresponding to UNS S31254.
ASTM A182 covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, valves and related pressure-system components.
F44 is selected where conventional austenitic stainless steels do not provide sufficient resistance to aggressive chloride-containing environments.
The principal material designations are:
| System | Designation |
|---|---|
| ASTM | A182 F44 |
| ASME | SA-182 F44 |
| UNS | S31254 |
| EN Material No. | 1.4547 |
| EN Name | X1CrNiMoCuN20-18-7 |
F44 is an austenitic stainless steel, not a duplex or super duplex grade.
ASTM A182 F44 Chemical Composition
| Element | ASTM A182 F44 / 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% |
| Copper, Cu | 0.50–1.00% |
| Nitrogen, N | 0.18–0.25% |
The combination of approximately 20% Cr, 18% Ni and 6% Mo with nitrogen and copper gives F44 its characteristic resistance to localized corrosion.
Actual heat chemistry is reported on the Material Test Certificate.
ASTM A182 F44 Mechanical Properties
Typical minimum room-temperature tensile requirements are:
| Property | Requirement |
|---|---|
| Tensile Strength, min. | 650 MPa / 94 ksi |
| Yield Strength, min. | 300 MPa / 44 ksi |
| Elongation, min. | 35% |
| Reduction of Area, min. | 50% |
Actual mechanical test results are reported on the supplied MTC.
PREN and Chloride Corrosion Resistance
One of the main advantages of UNS S31254 is its high resistance to localized corrosion in chloride-bearing environments.
A commonly used Pitting Resistance Equivalent Number formula is:
PREN = %Cr + 3.3 × %Mo + 16 × %N
Based on the nominal composition of F44 / S31254, its PREN is typically above 40.
The high chromium, molybdenum and nitrogen contents provide strong resistance to:
- Pitting corrosion
- Crevice corrosion
- General corrosion
- Stress-corrosion cracking
- Many aggressive chloride-bearing environments
PREN is an important comparative indicator, but actual material suitability also depends on temperature, chloride concentration, chlorination, crevice conditions, flow conditions and process chemistry.
Heat Treatment of ASTM A182 F44
ASTM A182 F44 forgings require controlled solution heat treatment followed by rapid cooling.
A typical ASTM F44 heat-treatment requirement includes:
Solution treatment at not less than approximately 1150°C / 2100°F followed by liquid quenching.
Rapid cooling is important for maintaining the required austenitic structure and reducing the formation of harmful intermetallic phases.
Correct heat treatment helps maintain:
- Corrosion resistance
- Ductility
- Mechanical properties
- Stable austenitic microstructure
Heat-treatment records can be supplied when required by the purchase specification.
ASTM A182 F44 Weld Neck Flange
The weld neck flange (WNRF) is one of the most commonly specified F44 flange types for critical piping systems.
Its long tapered hub is butt-welded directly to the pipe, providing:
- Gradual stress transition
- Full-penetration welded connection
- Good performance under pressure and thermal cycling
- Strong connection for corrosive process piping
- RF or RTJ sealing surfaces as applicable
For weld neck flanges, the bore and weld end can be machined according to the specified pipe wall thickness or schedule.
Available F44 Flange Types
| Flange Type | Typical Availability |
|---|---|
| Weld Neck / WNRF | Yes |
| Blind Flange | Yes |
| Slip-On Flange | Yes |
| Socket Weld Flange | Yes |
| Threaded Flange | Yes |
| Lap Joint Flange | When specified |
| Reducing Flange | When specified |
Available facing configurations include:
Raised Face (RF)
Flat Face (FF)
Ring Type Joint (RTJ)
The exact flange type and facing should be selected according to the applicable piping design and gasket system.
ASME B16.5 F44 Flange Sizes & Classes
ASME B16.5 flange size ranges vary by pressure class.
| Pressure Class | Standard Size Range |
|---|---|
| Class 150 | NPS 1/2–24 |
| Class 300 | NPS 1/2–24 |
| Class 400 | NPS 1/2–24 |
| Class 600 | NPS 1/2–24 |
| Class 900 | NPS 1/2–24 |
| Class 1500 | NPS 1/2–24 |
| Class 2500 | NPS 1/2–12 |
For larger diameters, ASME B16.47 covers steel flanges from NPS 26 through NPS 60 with Class 75, 150, 300, 400, 600 and 900 ratings.
Large-diameter F44 flanges can therefore be manufactured according to ASME B16.47 or project-specific dimensional requirements where applicable.
F44 Flange Applications
ASTM A182 F44 flanges are commonly selected for demanding process systems such as:
- Seawater piping
- Desalination plants
- Offshore platforms
- Firewater systems
- Chemical-processing plants
- High-chloride process piping
- Flue-gas treatment systems
- Pulp and bleaching equipment
- Heat-exchanger piping
- Process equipment connections
F44 offers particularly strong resistance to localized corrosion where conventional 300-series stainless steels may be inadequate.
For seawater service, final suitability should still consider temperature, chlorination, flow conditions and crevice geometry.
ASTM A182 F44 vs F51
F44 and F51 are both corrosion-resistant flange grades but belong to different stainless steel families.
| Item | ASTM A182 F44 | ASTM A182 F51 |
|---|---|---|
| UNS | S31254 | S31803 |
| Structure | Super Austenitic | Duplex |
| Cr | ~20% | 21–23% |
| Mo | 6.0–6.5% | 2.5–3.5% |
| Ni | ~18% | ~4.5–6.5% |
| PREN | Above 40 | Typically low-to-mid 30s |
| Main Feature | High localized corrosion resistance | High strength + chloride resistance |
F44 should therefore not be confused with duplex F51.
The appropriate material depends on mechanical requirements, corrosion environment, temperature and project specification.
Related S31254 Piping Products
A complete UNS 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 |
ASTM A182 F44 flanges can be supplied together with ASTM A312 S31254 pipe and ASTM A403 WPS31254 butt-weld fittings for complete high-alloy piping systems.
Inspection & Certification
ASTM A182 F44 flanges 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
- Hardness testing when specified
- PT when required
- UT when specified
- Additional corrosion testing
- Third-party inspection
- Full heat-number traceability
Inspection requirements can be specified according to the material specification, flange standard and project ITP.
Frequently Asked Questions
What is ASTM A182 F44?
ASTM A182 F44 is a forged super-austenitic stainless steel grade corresponding to UNS S31254 and EN 1.4547. It contains approximately 6% molybdenum and is used for highly corrosive chloride-bearing applications.
Is ASTM A182 F44 the same as UNS S31254?
Yes. F44 is the ASTM A182 forging grade corresponding to UNS S31254.
For pipe, fittings and plate, the same UNS material is specified under different ASTM product standards.
Is F44 a duplex stainless steel?
No. F44 / S31254 is super-austenitic stainless steel.
ASTM A182 F51, F60, F53 and F55 belong to duplex or super duplex stainless steel families.
What is the PREN of ASTM A182 F44?
Based on its high chromium, approximately 6% molybdenum and nitrogen content, F44 typically has a PREN above 40, providing very high resistance to pitting and crevice corrosion.
What pipe and fittings are used with F44 flanges?
A typical matching material system includes:
ASTM A312 S31254 Pipe + ASTM A403 WPS31254 Butt-Weld Fittings + ASTM A182 F44 Flanges
according to the project piping specification.
ASTM A182 F44 Flange Manufacturer
We manufacture and supply ASTM A182 / ASME SA-182 F44 UNS S31254 forged flanges for seawater, desalination, offshore, chemical and other aggressive chloride-service piping systems.
Available products include weld neck, blind, slip-on, socket weld, threaded, RF and RTJ flanges, with PMI, NDE, heat-treatment documentation and EN 10204 certification when required.
For quotation, please specify:
Material + Flange Type + NPS + Pressure Class + Facing + Bore/Wall Thickness + Quantity + Standard + Inspection Requirements
Example:
ASTM A182 F44, WNRF, NPS 8, Class 600, RF, ASME B16.5, EN 10204 3.1
