ASTM A312 S31254 Seamless Pipe | UNS S31254 254 SMO Pipe
ASTM A 312 UNS S31254 pipe is a high-alloy super-austenitic stainless steel pipe designed for aggressive chloride-bearing and corrosive environments. With approximately 20% chromium, 18% nickel, 6% molybdenum, nitrogen and copper, S31254 provides substantially higher resistance to pitting and crevice corrosion than conventional grades such as 316L.
We supply ASTM A312 / ASME SA-312 S31254 seamless and welded stainless steel pipe in multiple outside diameters, wall thicknesses and schedules, with solution heat treatment, EN 10204 3.1 certification and project-specific inspection.
ASTM A312 S31254 Pipe Specification
| Item | Specification |
|---|---|
| Material Standard | ASTM A312 / ASME SA-312 |
| UNS | S31254 |
| Common Designation | 254 SMO |
| EN Material No. | 1.4547 |
| EN Name | X1CrNiMoCuN20-18-7 |
| Material Family | Super-Austenitic Stainless Steel |
| Pipe Type | Seamless / Welded / Heavily Cold Worked |
| Typical OD Supply | 10.3–762 mm |
| Typical WT Supply | 1–50 mm |
| Common Schedules | SCH 5S / 10S / 40S / 80S |
| Length | Random / Fixed Length |
| Heat Treatment | Solution Heat Treated |
| Surface | Pickled / Passivated when specified |
| Certification | EN 10204 3.1 / 3.2 when specified |
What Is ASTM A312 S31254?
ASTM A312 S31254 is a super-austenitic stainless steel pipe grade covered by ASTM A312 for seamless, straight-seam welded and heavily cold-worked welded austenitic stainless steel pipe.
ASTM A312 pipe is intended for high-temperature and general corrosive service.
S31254 is particularly selected where conventional 300-series stainless steel does not provide sufficient localized corrosion resistance.
The standard material designation is:
ASTM A312 UNS S31254
The corresponding ASME material designation is:
ASME SA-312 UNS S31254
Is S31254 Super Duplex Stainless Steel?
No. UNS S31254 is a super-austenitic stainless steel, not a duplex or super duplex stainless steel.
Super duplex grades such as UNS S32750 have a mixed ferritic-austenitic microstructure.
S31254 is an austenitic stainless steel with high chromium, nickel, molybdenum and nitrogen contents.
ASTM A312 S31254 Chemical Composition
| 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 | 0.18–0.22% |
| Copper, Cu | 0.50–1.00% |
The high chromium, molybdenum and nitrogen content gives S31254 strong resistance to localized chloride corrosion.
ASTM A312 S31254 Mechanical Properties
Typical minimum room-temperature mechanical requirements include:
| Property | Minimum |
|---|---|
| Tensile Strength | 650 MPa class |
| Yield Strength | 300 MPa class |
| Elongation | 35% class |
Actual test results are reported on the Material Test Certificate.
PREN and Chloride Corrosion Resistance
S31254 is widely selected because of its high resistance to pitting and crevice corrosion in chloride-containing environments.
A commonly used Pitting Resistance Equivalent Number formula is:
PREN = %Cr + 3.3 × %Mo + 16 × %N
Using the nominal composition of S31254, the PREN is typically above 40.
This high PREN contributes to significantly stronger resistance to localized chloride corrosion than conventional stainless steels such as 316L.
Material selection should also consider:
- Temperature
- Chloride concentration
- Crevice geometry
- Flow velocity
- Chlorination
- Oxidizing conditions
- Process chemistry
Is S31254 Suitable for Seawater?
UNS S31254 is widely used in demanding seawater and chloride-bearing piping systems.
Typical applications include:
- Seawater cooling systems
- Desalination plants
- Offshore process piping
- Firewater systems
- Chemical plants
- High-chloride process systems
- Flue-gas cleaning equipment
- Pulp and bleaching systems
Final material suitability depends on actual operating temperature, chlorination level, crevice conditions, flow conditions and process environment.
Heat Treatment of ASTM A312 S31254 Pipe
ASTM A312 S31254 pipe is supplied in the required heat-treated condition.
For S31254, solution heat treatment followed by sufficiently rapid cooling is important for maintaining the required austenitic structure and corrosion resistance.
Correct heat treatment helps to:
- Dissolve undesirable precipitates
- Maintain corrosion resistance
- Preserve ductility
- Reduce the risk of harmful intermetallic-phase formation
The heat-treatment cycle shall follow the applicable ASTM A312 requirements and the qualified manufacturing procedure.
ASTM A312 Seamless vs Welded S31254 Pipe
ASTM A312 covers several manufacturing routes.
| Construction | ASTM A312 |
|---|---|
| Seamless Pipe | Yes |
| Straight-Seam Welded Pipe | Yes |
| Heavily Cold-Worked Welded Pipe | Yes |
For electric-fusion-welded austenitic stainless steel pipe, ASTM A358 may also be specified.
ASTM A312 vs ASTM A358
| Item | ASTM A312 | ASTM A358 |
|---|---|---|
| Seamless Pipe | Yes | No |
| Welded Pipe | Yes | EFW |
| Manufacturing Route | Seamless / welded / heavily cold worked | Electric-fusion welded |
| Typical Selection | Process piping | Welded pipe projects |
The required specification depends on the pipe manufacturing route and project requirements.
Pipe Sizes & Schedules
Typical S31254 supply can include:
Outside Diameter: 10.3–762 mm
Wall Thickness: 1–50 mm
Length: Random or fixed length
Common schedules include:
- SCH 5S
- SCH 10S
- SCH 40S
- SCH 80S
- Project-specific wall thicknesses
Stainless steel pipe dimensions may be specified according to ASME B36.19M where applicable.
S31254 vs 316L vs 904L
| Item | S31254 | 904L | 316L |
|---|---|---|---|
| Mo | ~6% | ~4–5% | ~2–3% |
| Nitrogen | Higher | Lower | Lower |
| PREN | Above 40 | Lower | Mid-20s range |
| Chloride Pitting Resistance | Very High | High | Moderate |
| Typical Service | Aggressive chloride environments | Acid / chloride service | General corrosion service |
S31254 is often selected where 316L or 904L does not provide sufficient resistance to localized corrosion.
Inspection & Certification
ASTM A312 S31254 pipe can be supplied with:
- EN 10204 Type 3.1 MTC
- EN 10204 Type 3.2 when specified
- Heat chemical analysis
- Tensile testing
- Dimensional inspection
- Visual examination
- Hydrostatic testing or permitted NDE
- PMI when specified
- UT / ET when specified
- Surface inspection
- Intergranular corrosion testing when required
- Additional corrosion testing
- Third-party inspection
- Full heat-number traceability
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 |
For complete S31254 piping systems, ASTM A312 S31254 pipe can be supplied together with ASTM A403 WPS31254 butt-weld fittings, ASTM A182 F44 forged flanges and ASTM A240 S31254 plate according to project requirements.
Frequently Asked Questions
What is ASTM A312 UNS S31254?
ASTM A312 UNS S31254 is a super-austenitic stainless steel pipe grade containing approximately 20% Cr, 18% Ni and 6% Mo for demanding corrosive and chloride-bearing service.
Is S31254 the same as 254 SMO?
Yes. UNS S31254 is the standardized material designation, while 254 SMO is a commonly used designation for this 6% molybdenum super-austenitic stainless steel.
Is S31254 super duplex stainless steel?
No. S31254 is super-austenitic stainless steel. It is different from duplex and super duplex grades such as S31803, S32205 and S32750.
What is the PREN of S31254?
Based on its high chromium, approximately 6% molybdenum and nitrogen content, S31254 typically has a PREN above 40, giving very high resistance to localized chloride corrosion.
What fittings and flanges match S31254 pipe?
A typical material combination is:
ASTM A312 S31254 Pipe + ASTM A403 WPS31254 Fittings + ASTM A182 F44 Flanges
subject to the project piping specification.
ASTM A312 S31254 Seamless Pipe Supplier
We supply ASTM A312 / ASME SA-312 UNS S31254 seamless and welded stainless steel pipe for seawater, desalination, offshore, chemical and other aggressive chloride-service applications.
Available options include multiple OD and wall-thickness combinations, random or fixed lengths, solution heat treatment, pickled surface, PMI, NDE and EN 10204 certification.
For quotation, please specify:
Material + Construction + OD/NPS + Schedule/WT + Length + Quantity + Standard + Inspection Requirements
Example:
ASTM A312 UNS S31254 Seamless Pipe, NPS 6, SCH 40S, 6 m Length, Solution Heat Treated, EN 10204 3.1
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