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What You Should Know About 254 SMO

Views: 2     Author: Shirley     Publish Time: 2025-06-11      Origin: Site

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What is 254 SMO?

254 SMO (UNS S31254) is a super austenitic stainless steel with enhanced content of chromium, molybdenum and nitrogen. This special alloying makes 254 SMO resistant to pitting, crevice corrosion and stress corrosion cracking to an extent of 254. The alloy was initially developed for use in seawater and other chloride-containing environments, where conventional stainless steels would quickly succumb to corrosion. Significant additions of Mo, Ni and Cu gives Stainless Steel 254 SMO a good resistance to pitting and crevice corrosion, especially in environments containing halide ions e.g. chloride, bromide and fluoride solutions. Alloy 254 SMO product is therefore widely used in applications in brackish water, seawater, pulp mill bleach plants and other chloride process streams, where it can be a cost-effective alternative to more expensive nickel and titanium alloys in such environments.


Stainless steel grade 254 SMO is created with twice the strength of the stainless steel 300 series and a combination of impact toughness, resistance to chloride stress corrosion, cracking, pitting, and crevice corrosion. These pipes and tubes are available in a wide range of sizes, standards, thicknesses, and requirements. The grade 254 SMO offers outstanding anti-biofouling qualities that are particularly noticeable in seawater. These are extremely resistant to pitting and crevice cracking, as well as to ordinary corrosion. In terms of impact loads, these bears stress corrosion cracking. SMO 254 grade has a lot of power. Because of their weldability, they may be welded with any sort of filler material and can even be regulated at low temperatures.


Chemical Composition of Alloy 254 SMO

The unique chemical composition of Alloy 254 SMO includes chromium (19.5-20.5%), nickel (17.5-18.5%), molybdenum (6.0-6.5%), and nitrogen (0.18-0.20%). This blend enhances its resistance to various forms of corrosion and contributes to its overall strength.Alloy 254 SMO, also known as UNS S31254 or 6Mo, is a high-performance stainless steel designed to withstand extremely corrosive environments. Its carefully balanced chemical composition enhances both its corrosion resistance and mechanical properties, making it ideal for use in challenging conditions.

Major Elements

Chromium (19.5-20.5%): Enhances general corrosion resistance by forming a protective passive layer.

Nickel (17.5-18.5%): Improves ductility and overall corrosion resistance.

Molybdenum (6.0-6.5%): Increases resistance to pitting and crevice corrosion, particularly in chloride-rich environments.

Nitrogen (0.18-0.22%): Boosts resistance to corrosion in specific areas and strengthens the alloy.

Copper (0.50-1.00%): Adds extra protection against corrosion in environments containing chlorides and enhances durability.

Minor Elements

Minor elements like carbon, manganese, silicon, phosphorus, and sulfur are carefully controlled to maintain the alloy’s mechanical properties and corrosion resistance. For example, low carbon content reduces the risk of carbide precipitation during heating, while manganese and silicon improve weldability and strength.


Specifications of Stainless Steel 254 SMO Products

254SMO – UNS S31254

Product

Norm ASTM

Seamless Tubes

A-269 A-312

Welded Tubes

A-249 A-269 A-312 A-358 A-409

Plates

A-240 A-480

Bars

A-276 A-479

Flanges

A-403 A-473

Fittings

A-182 F44 A-403


General Properties of Stainless Steel 254SMO

Mechanical Strength

Alloy 254 SMO exhibits remarkable tensile strength, with a minimum of 95 ksi (655 MPa) for plates and 100 ksi (690 MPa) for sheets and strips. This ensures the alloy can withstand significant stress without deformation. Additionally, its yield strength is impressive, with a minimum of 45 ksi (310 MPa), meaning it can endure substantial loads before undergoing permanent deformation. This combination of tensile and yield strength makes Alloy 254 SMO ideal for structural applications and components subjected to high mechanical stresses.


Hot Working

Hot working should be carried out in the temperature range 1000-1200C. Higher temperatures will reduce the workability. Fairly heavy scaling occurs at tempertaures exceeding 1150C.

To ensure dissolution of possible precipitations of secondary phases from the hot forming, the subsequent heat treatment should take place at minimum 1150C.


Cold Working

254 SMO possesses very good cold formability. Bending, pressing and other forming operations which are used in fabrication can be carried out without difficulty. Practical experience obtained from the pressing of heat exchanger plates has been very favourable. The steel work hardens rapidly.


Welding

254 SMO possesses good weldability. When delivered, sheets and plates have a homogeneous composition. Remelting of the parent metal, such as during welding without filler metal, may cause microscale variations in composition for elements such as chromium, nickel and particularly molybdenum. This phenomenon occurs in all highly alloyed stainless steels. These variations may reduce the pitting resistance of the weld. GTA and plasma arc welding without filler metal should therefore be avoided.


Common Uses of 254 SMO

Chemical Processing

In the chemical processing industry, 254 SMO is often used for equipment that comes into contact with highly corrosive substances. This includes reactors, heat exchangers, and piping systems. Its ability to resist the corrosive effects of various chemicals ensures long-term reliability and safety.


Oil and Gas Industry

The oil and gas industry relies heavily on 254 SMO for components such as pipes, valves, and fittings. The alloy’s strength and corrosion resistance are essential for handling the demanding conditions of offshore drilling and production.


Desalination Plants

Desalination plants, which convert seawater into freshwater, use 254 SMO for critical components like evaporators and condensers. The alloy’s resistance to seawater corrosion makes it ideal for these applications, ensuring longevity and efficiency.


Marine and Offshore Engineering

Given its development for seawater environments, it’s no surprise that 254 SMO is widely used in marine and offshore engineering. This includes applications like seawater cooling systems, shipbuilding, and coastal structures.


Food and Beverage Industry

In the food and beverage industry, 254 SMO is used in equipment that must maintain high levels of hygiene and corrosion resistance. This includes components in food processing machinery, dairy equipment, and brewery systems.

JN Alloy is a distributor and product manufacturer of stainless steel, duplex steel, and nickel alloy.
Tel: +86 19339900211
Add: Stainless steel Market 289, Xinwu District , Wuxi, China
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