What is ASTM A240 UNS S31254 stainless steel plate?

What is UNS S31254 stainless steel plate?

UNS S31254 stainless steel plate is a super austenitic stainless steel (also known as 254 SMO or 6Mo) characterized by its high molybdenum, nitrogen, and nickel content. This high alloy composition provides superior strength and outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking, making it ideal for use in high-chloride environments like seawater, brackish water, and chemical processing. It is often supplied as plates and sheets for applications in the oil and gas, marine, and pulp industries.

 

What is uns S31254 material equivalent to?

Standard	Grade
Common Name	254 SMO
UNS Number	S31254
DIN	1.4547
EN	X1CrNiMoCuN20-18-7
ISO	X1CrNiMoCuN20-18-7
JIS	SUS312L
W. Nr.	1.4547

 

UNS S31254, EN 1.4547, 254SMO, 6Mo, F44, X1CrNiMoCuN20-18-7-4 Stainless Steel Plate

Standard: ASTM A240/A240M, ASTM A480/480M
Grade: UNS S31254, EN 1.4547, 254SMO, X1CrNiMoCuN20-18-7-4

Density: 7.8 x 10³ Kg/m³
Width: 1000mm, 1200mm, 1220mm, 1500mm, 1800mm, 2000mm, 2200mm
Length: 2438mm, 3000mm, 6000mm, 8000mm, 12000mm
Thickness: 0.3 - 50mm
Manufacturing Process: Hot Rolled/Cold Rolled
Surface finish: No.1, 2B

 

Chemical Composition

Weight%	C	S	Mn	S	P	Cr	Ni	Mo	N	Cu
Min.						19,50	17,50	6,00	0,18	0,50
Max.	0,020	0,80	1,00	0,010	0,030	20,50	18,50	6,50	0,25	1,00

 

Mechanical Property

Yield strength Rp0.2, Mpa	Tensile strength Rm, Mpa	Elongation [%]	Hardness [HB]	Impact, Sharp-V, -46℃ [J]	before
≥ 310	655 – 850	≥ 35	≤ 310	≥ 45	≥ 40

 

Forming

UNS S31254 (254 SMO) has good formability and can be formed using conventional cold and hot forming techniques. However, due to its higher strength, more powerful equipment may be needed for cold forming. Post-forming annealing is recommended to restore the material's properties, especially after severe cold work.

 

Heat Treatment

Solution annealing of S31254 stainless steel plate at temperatures between 1150°C and 1200°C (2102°F–2192°F) followed by rapid cooling, typically water quenching, restores the alloy's corrosion resistance and mechanical properties. This process is essential after forming or welding to maintain the austenitic structure and prevent the formation of adverse phases.

 

What is the difference between uns S31254 and ss316?

254 SMO stainless steel, also known as UNS S31254 or 6% molybdenum stainless steel, contains 6% molybdenum, 20% chromium, 18% nickel, and 0.20% nitrogen. 316 stainless steel, also known as UNS S31600 or marine grade stainless steel, contains 16-18% chromium, 10-14% nickel, and 2-3% molybdenum.

 

Applications of ASTM A240 UNS S31254 Stainless Steel Plate

Seawater treatment equipment and desalination plants,
Chemical processing and the oil & gas industry,
Pulp and paper mill bleaching departments,
As well as tall oil distillation towers and related equipment.

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254 SMO stainless steel plate Price per ton

The price of 254 SMO (UNS S31254 / 6Mo) stainless steel plate typically ranges from $2,500 to $6,700 per ton (USD), depending heavily on the plate thickness, finish type, and order volume. Premium finishes or specialized cut sizes can push retail or smaller-lot pricing even higher on a per-ton basis.

 

ASTM A240 UNS S31254 stainless steel plate supplier

UNS S31254 stainless steel plates are processed using advanced production equipment to ensure the precision and consistency of each plate. Our factory utilizes efficient tools such as laser cutting machines, CNC punching machines, and polishing equipment, capable of processing a wide range of stainless steel plate thicknesses from 0.3mm to 8mm, ensuring that products meet international standards such as ASTM A240. Before shipment, each batch undergoes rigorous quality inspections, including surface finish, thickness tolerance, and dimensional accuracy, to ensure that the product meets customer requirements.

 

Quality Inspection 

ASTM A240 UNS S31254 (254 SMO) stainless steel plates undergo multi-stage inspections, including PMI (Positive Material Identification)/chemical composition verification, as well as tensile strength, yield strength, elongation, and hardness testing. Additionally, dimensional and surface quality checks are performed on every batch. For applications in high-chloride environments, ASTM G48 Method A pitting corrosion testing can also be arranged. An EN 10204 3.1 Material Test Certificate (MTC) is provided with every shipment to ensure heat number traceability and quality verification.

 

Standard Packaging

For packaging and shipping, all stainless steel plates are moisture-proofed and securely packaged in wooden crates, pallets, or bubble wrap. Delivery times are typically 7-15 days, ensuring timely delivery to customers.

FAQ 

What is the difference between S31254 and 316L?

S31254 has twice the molybdenum content of 316L (6% vs. 2%) and a higher nitrogen content; its yield strength is nearly 50% higher than that of 316L. While 316L often fails due to pitting corrosion in seawater, S31254 is specifically designed for environments where 316L is unsuitable.

 

Are UNS S31254 and 254 SMO the same?

Yes. 254 SMO is the trade name originally used by Outokumpu, while UNS S31254 is the Unified Numbering System (UNS) designation used in ASTM standards. Both refer to the same material specification.

 

What is the PREN value of S31254, and why is it important?

Value: PREN = Cr + 3.3Mo + 16N ≈ 42–45.
Importance: A PREN value exceeding 40 is the industry benchmark for "super" stainless steels. This indicates that the material can resist localized pitting corrosion in warm seawater and other highly corrosive chloride-rich environments.

 

Can UNS S31254 be welded?

Yes, it has good weldability. However, due to its high alloy content, it is crucial to use "over-alloyed" filler metals (such as Alloy 625 or Alloy C276). If welding is performed without filler metal or with matching-composition filler metal, the weld zone may lose its corrosion resistance.

 

Is S31254 susceptible to stress corrosion cracking (SCC)?

Although its resistance to stress corrosion cracking (SCC) is far superior to that of 304 or 316 stainless steel, it is not completely immune. In chloride environments characterized by extremely high stress and high temperatures, duplex stainless steels (such as S32205) or nickel-based alloys (such as Alloy 625) may be more suitable choices; however, S31254 still performs exceptionally well under most industrial conditions involving stress corrosion cracking (SCC).

 

What is the maximum service temperature for S31254?

For pressure vessel applications (ASTM A240/ASME SA240), the rated maximum service temperature is typically 400°C (750°F). Exceeding this temperature poses a risk of "sigma phase" precipitation, which can cause the metal to become brittle.