UNS S31254|1.4547|254SMO Seamless Stainless Steel Tube

XinZhe is a leading Chinese manufacturer and supplier of High-Performance 254SMO Seamless Tubes, delivering precision-engineered alloy solutions from our advanced production hub in Wenzhou. Our UNS S31254 tubing is designed to handle the most aggressive chloride-rich environments, providing a reliable and durable choice for offshore oil & gas, chemical processing, and desalination projects.

We leverage decades of metallurgical expertise to provide export-grade seamless pipes in a wide range of schedules and customized dimensions tailored to project-specific requirements. Backed by full traceability (MTRs) and international certifications, XinZhe ensures the reliability of every order through stringent Non-Destructive Testing (NDT) and Third-Party Inspection (TPI) approvals. Discover the superior performance of our 6-moly stainless steel solutions. Request a quote today to benefit from our factory-direct pricing and comprehensive technical support.

PREN = %Cr + 3.3 x%Mo + 16x%N ≥ 42.5

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What Is a Seamless 254SMO Stainless Steel Tube?

254SMO (UNS S31254) is a super austenitic stainless steel with 20% chromium, 18% nickel, 6% molybdenum and 0.2% nitrogen, giving a PREN above 42. It delivers exceptional resistance to pitting, crevice corrosion and chloride stress-corrosion cracking in seawater and high-chloride process streams, at a lower cost than nickel-based alloys.

254SMO (UNS S31254) is a high-alloy 6-molybdenum super austenitic stainless steel specifically engineered for extreme corrosion environments. Due to its elevated chromium, molybdenum, and nitrogen content, this alloy offers exceptional resistance to pitting corrosion, crevice corrosion, and chloride-induced stress corrosion cracking (SCC).

254SMO seamless stainless steel tubing is widely used in marine engineering, offshore platforms, chemical processing plants, and desalination systems, where conventional stainless steels such as 316L cannot provide sufficient corrosion resistance.

Manufactured according to international standards such as ASTM A213, ASTM A312, and EN 10216-5, seamless UNS S31254 tubes deliver superior mechanical strength, uniform microstructure, and high pressure resistance.

Key Features and Technical Advantages

• Outstanding Corrosion Resistance High molybdenum (6–6.5%) and nitrogen content significantly improve resistance to chloride-induced pitting and crevice corrosion.

• Excellent Mechanical Strength 254SMO provides nearly twice the yield strength of standard 300-series stainless steels, allowing thinner wall thickness and reduced structural weight.

• Superior Performance in Chloride Environments The alloy performs exceptionally well in seawater, brine solutions, and high-salinity industrial media.

• Outstanding Corrosion Resistance

High molybdenum (6–6.5%) and nitrogen content significantly improve resistance to chloride-induced pitting and crevice corrosion.

• Excellent Mechanical Strength

254SMO provides nearly twice the yield strength of standard 300-series stainless steels, allowing thinner wall thickness and reduced structural weight.

• Superior Performance in Chloride Environments

The alloy performs exceptionally well in seawater, brine solutions, and high-salinity industrial media.

• Cost-Effective Alternative to Nickel Alloys

Compared with nickel-based alloys and titanium, 254SMO provides comparable corrosion resistance at a more competitive cost.

• Sustainable and Recyclable Material

Like all stainless steels, 254SMO is 100% recyclable, supporting sustainable manufacturing and ESG compliance.

Chromium (Cr)

Chromium forms a stable passive oxide layer that protects the steel surface from corrosion.

Nickel (Ni)

Nickel stabilizes the austenitic structure and enhances resistance to chloride stress corrosion cracking.

Molybdenum (Mo)

Molybdenum is critical for improving resistance to pitting and crevice corrosion, particularly in chloride-rich environments.

Product Specifications and Data

C	Cr	Ni	Mo	N	Cu	S	P	Si	Mn	Fe
≤0.020	19.50-20.50	17.50-18.50	6.00-6.50	0.18-0.25	0.50-1.00	≤0.010	≤0.030	≤0.80	≤1.00	Bal

Tensile Strength, min.		Yield Strength, min.		Elongation, min.	Hardness, max.
ksi	Mpa	ksi	Mpa	%	Brinell HBW	Rockwell
95	655	45	310	35	223	96 HRBW

Modulus Elasticity	Thermal Conductivity	Specific Heat	Density	Melting Range	M.P
10⁶psi	Btu/hft°F	Btu/lb°F	g/cm³	°C	-
29	7.5	0.12	8.1	1320-1390	1.003

Standard	OD(D)	Tolerance（MM)		Thickness(S)	Tolerance(MM)	Length	Tolerance
	MM	Common	High	MM			MM
EN 10216-5 HFD	30≤D≤219.1（D2)	±1.0% or ±0.5mm, whicever is the greater(取较大者)		T1, T≤4	±15% or ±0.6mm, whicever is the greater(取较大者)	L≤6M	+5/0
				T2	±12.5% or ±0.4mm, whicever is the greater(取较大者)
	219.1≤D≤610 (D1)	±1.5% or ±0.75mm, whicever is the greater (取较大者)		T≤0.05D	+22.5%/-15%	6≤12	+10/0
				T1, 0.05D≤0.09D	±15% or ±0.6mm, whicever is the greater(取较大者)
				T2, T>0.09D	±12.5% or ±0.4mm, whicever is the greater(取较大者)	L>12	+by agreement/0
EN 10216-5 CFD	D3(D≤219.1)	±0.75% or ±0.3mm, whicever is the greater(取较大者)		T3	±10% or ±0.2mm, whicever is the greater(取较大者)
	D4(D≤219.1)	±0.5% or ±0.mm, whicever is the greater(取较大者)		T4	±7.5% or ±0.15mm, whicever is the greater(取较大者)
ASTM A213 HFD	D≤100	+0.4/-0.8		D<100,S≤2.4	+40%/0	HFD, all size	+5.0/0
		+0.4/-1.2		D<100,2.4≤3.8	+35%/0
		+0.4/-1.6		D<100,3.8≤4.6	+33%/0
				D<100,S>4.6	+28%/0
	100≤200	+0.4/-1.2		D>100, 2.4≤3.8	+35%/0
	200≤225	+0.4/-1.6		D>100,3.8≤4.6	+33%/0
				D>100,S>4.6	+28%/0
ASTM A213 CFD	D<25	±0.10		D≤38.1	+20%/0	CFD, D<50.8	+3.0/0
	25≤D≤40	±0.15
	40	±0.20
	50≤D<65	±0.25
	65≤D<75	±0.30		D>38.1	+22%/0	CFD, D≥50.8	+5.0/0
	75≤D≤100	±0.38
	100≤200	+0.38/-0.64
	200≤225	+0.38/-1.14
ASTM A269	D≤13	±0.13		D≤13	±15%	D<38	+3.2/0
	13	±0.13		13	±10%
	38≤D<89	±0.25				D>38	+4.8/0
	89≤D<140	±0.38
	140≤D<203	±0.76
	203≤D<305	±1.01
	305≤D<356	±1.26
ASTM A270	D<25	±0.13		For weld pipe all size	±12.5%		+3.0/0
	25-50	±0.20
	50-75	±0.25
	75-100	±0.38		For CD SMLS pipe D≤38.1	+20%/0
	100-140	±0.38					+5.0/0
	140-200	±0.75		For CD SMLS pipe D>38.1	+22%/0
	200-300	±1.25

Dimensional Standards and Tolerances

254SMO seamless tubes are supplied to the dimensional tolerances of ASTM A213 / A1016 or EN 10216-5 as specified.

254SMO seamless stainless steel tubing is produced under strict dimensional tolerances defined by international standards such as:

EN 10216-5
ASTM A213
ASTM A269
ASTM A270

These standards define acceptable tolerances for:

Outside Diameter (OD)
Wall Thickness (WT)
Length

Strict dimensional control ensures precise installation and compatibility with industrial piping systems.

Common Industrial Applications

Marine and Offshore Engineering

Seawater cooling and firewater systems
Offshore platform pipework
Desalination plant piping

Oil and Gas Industry

Process and utility piping
High-chloride service lines
Heat exchanger tubing

Chemical Processing Industry

Reactors and heat exchangers
Halide-containing process streams
Acid handling equipment

Pulp and Paper Industry

Bleach plant equipment
Digester and liquor lines
Heat exchangers

Power Generation

FGD scrubber internals
Condenser and heat exchanger tubing
Water treatment piping

Quality Assurance and Manufacturing Process

Certification

All 254SMO (UNS S31254) tubes are supplied to ASTM A213 / ASME SA213 and ASTM A312 / ASME SA312 with EN 10204 3.1 mill test certificates. Third-party inspection (SGS, BV, TUV, Lloyd's), PMI reports and full heat-number traceability can be provided on request.

Non-Destructive Testing (NDT)

Hydrostatic or eddy-current testing is performed on 100% of tubes. Ultrasonic testing (UT) and dye-penetrant inspection (PT) are available for critical service, with records retained for each production lot.

Material Verification

Positive Material Identification (PMI) and spectrometric analysis confirm that the chemical composition matches the ordered grade and that the ferrite/austenite balance is within the specified range.

Mechanical Testing

Tensile, yield, elongation and hardness tests are carried out per heat. Impact testing can be supplied at the project design temperature for subsea and low-temperature service.

Dimensional Inspection

Outside diameter, wall thickness, ovality and straightness are measured against ASTM A1016 / A1016M or ASTM A789 tolerances. Length, square-cut ends and end-finish conditions are verified before packing.

254SMO (S31254) vs TP316L / TP904L – Technical Comparison

254SMO is a super austenitic grade positioned above 316L and alongside 904L. The comparison maps out the three-step progression in chloride resistance.

Chemical Composition and PREN

TP316L: 16–18% Cr, 10–14% Ni, 2–3% Mo — PREN about 25
254SMO (S31254): 20% Cr, 18% Ni, 6% Mo, 0.2% N — PREN above 42
TP904L (N08904): 20% Cr, 25% Ni, 4.5% Mo, 1.5% Cu — PREN about 35

Chloride Resistance

254SMO's 6% molybdenum and 0.2% nitrogen give it a critical pitting temperature well above the other two, which is why it is the standard choice for seawater and high-chloride process streams. TP904L offers good resistance but is more often chosen for acid service.

Acid Resistance

TP904L's 25% nickel and copper addition give it an advantage in sulphuric and phosphoric acid service, where its austenitic stability and copper content resist both oxidising and moderately reducing conditions. 254SMO performs well in many acids too, but its strength is chloride service.

Selection Guide

Choose 254SMO for seawater, brine and high-chloride process duty where pitting and crevice resistance govern
Choose TP904L for sulphuric and phosphoric acid service and for mixed acid/chloride duty
Choose TP316L for general corrosion service where chlorides are low

Frequently Asked Questions

What is 254SMO tube?

254SMO (UNS S31254) is a super austenitic stainless steel tube with 20% chromium, 18% nickel, 6% molybdenum and 0.2% nitrogen, giving a PREN above 42. It delivers exceptional resistance to pitting, crevice corrosion and chloride stress-corrosion cracking.

What is the difference between 254SMO and 316L?

254SMO contains roughly twice the molybdenum of 316L plus a deliberate nitrogen addition, raising its PREN from about 25 to above 42. This gives it a much higher critical pitting temperature, making it suitable for seawater and high-chloride process streams where 316L would pit.

What standard covers 254SMO tube?

254SMO seamless tube is supplied to ASTM A213 / ASME SA213 and ASTM A312 / ASME SA312, with EN 10216-5 as the European equivalent.

What is 254SMO tube used for?

254SMO is used for seawater cooling and firewater systems, offshore platform pipework, reverse-osmosis and desalination piping, pulp and paper bleach plants and flue-gas desulphurisation equipment.

Ready to Request a Quotation?

Send your Seamless 254SMO Stainless Steel Tube enquiry with grade, application, size (OD and wall thickness or schedule), quantity, length, end finish and inspection requirements including any PREN or corrosion test data required.

Request a 254SMO Tube Quotation

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