Super austenitic stainless steel: 254SMO (UNS S31254,F44,1.4547)

254SMO (UNS S31254, f44, 1.4547) super austenitic stainless steel overview:

254SMO (UNS S31254, f44, 1.4547) is a super austenitic stainless steel. Because of its high molybdenum content, it has high resistance to spot corrosion and crevice corrosion. This brand of stainless steel is developed for use in halogenated environments such as seawater. 254SMO also has good corrosion resistance. Especially in the acid containing halide, the steel is superior to ordinary stainless steel. Its C content is less than 0.03%, so it is called pure austenitic stainless steel (< 0.01% is also called super austenitic stainless steel).
Super stainless steel is a kind of special stainless steel. First of all, it is different from ordinary stainless steel in chemical composition. It refers to a kind of high alloy stainless steel with high nickel, high chromium and high molybdenum. Among them, 254SMO containing 6% Mo is more famous. This kind of steel has very good local corrosion resistance. It has good pitting resistance (PI ≥ 40) and better stress corrosion resistance under the conditions of sea water, inflation, gap and low-speed scouring. It is a substitute material for Ni based alloy and titanium alloy. Secondly, in terms of high temperature or corrosion resistance, it has better high temperature or corrosion resistance, which is irreplaceable for 304 stainless steel. In addition, the microstructure of special stainless steel is a stable austenite microstructure.

Because 254SMO (s31254, f44, 1.4547) is a kind of special stainless steel with high alloy, its manufacturing process is quite complex. Generally, people can only rely on traditional processes to manufacture this special stainless steel, such as pouring, forging, rolling, or seamless steel pipes can be made by center punching, cold rolling or cold drawing.

astm a403 254smo 90d elbow - Super austenitic stainless steel: 254SMO (UNS S31254,F44,1.4547)

Chemical composition of 254SMO (s31254, f44, 1.4547) super austenitic stainless steel:

Element Wrought Castings
Carbon ≤0.020 ≤0.025
Chromium 19.5-20.5 19.5-20.5
Nickel 17.5-18.5 17.5-19.5
Molybdenum 6.0-6.5 6.0-7.0
Nitrogen 0.18-0.22 0.180-0.240
Copper 0.50-1.00 0.50-1.00
Sulfur ≤0.010 ≤0.010
Phosphorus ≤0.030 ≤0.045
Silicon ≤0.80 ≤1.00
Manganese ≤1.00 ≤1.20
Iron Balance Balance

Mechanical Properties of 254 SMO

astm a182 f44 s31254 wn flanges - Super austenitic stainless steel: 254SMO (UNS S31254,F44,1.4547)

254SMO WNRF flanges 300# 3″ SCH80, ASTM A182 F44(S31254).

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

*The values are furnished on the basis of 254SMO plates.

Physical Properties of 254 SMO

Modulus Elasticity Thermal Conductivity Specific Heat Density Melting Range M.P
106psi Btu/hft°F Btu/lb°F g/cm3 °C
29 7.5 0.120 8.1 1320-1390 1.003

*All values are measured at room temperature.

Corrosion resistance of 254SMO (s31254, f44, 1.4547) super austenitic stainless steel:

254SMO (s31254, f44, 1.4547) stainless steel is a kind of super austenitic stainless steel with high corrosion resistance. It is developed for the environment of halide and acid, and widely used in high concentration chloride ion medium, seawater and other harsh working conditions. 254SMO is much better than other stainless steel in various industrial occasions of acid medium, especially in the acid containing halide. In some cases, it can be compared with Hastelloy alloy and titanium. Low carbon content and high molybdenum content make it have better resistance to spot corrosion and crevice corrosion, excellent resistance to intergranular corrosion. It is a high cost-effective stainless steel, widely used in chemical industry, desulfurization and environmental protection at home and abroad.

  • A large number of field experiments and extensive use experience show that even at a slightly higher temperature, 254SMO has a very high resistance to crevice corrosion in seawater, and only a few kinds of stainless steel have this performance.
  • 254SMO’s corrosion resistance in acid solutions and oxidizing halide solutions, such as those required for bleaching production in the paper industry, is comparable to that of the most corrosion-resistant nickel base and titanium alloys.
  • Because 254SMO has high nitrogen content, its mechanical strength is higher than other kinds of austenitic stainless steel. In addition, 254SMO has high ductility, impact strength and good weldability.
  • The high molybdenum content of 254SMO can make it have a higher oxidation speed during annealing, so it has a rougher surface than the ordinary stainless steel after pickling. However, it has no adverse effect on the corrosion resistance of the steel.

Welding material 254SMO (s31254, f44, 1.4547) super austenitic stainless steel supporting:

Welding wire: ERNiCrMo-3, welding rod: enicrmo-3.

Applications of 254SMO (s31254, f44, 1.4547) super austenitic stainless steel:

  • Ocean: marine structure of sea environment, desalination, mariculture, heat exchange of sea water, etc.
  • Environmental protection: flue gas desulfurization device of thermal power generation, waste water treatment, etc.
  • Energy field: atomic power generation, comprehensive utilization of coal, tidal power generation, etc.
  • Petrochemical Industry: oil refining, chemical equipment, etc.
  • Food field: salt making, soy sauce brewing, etc.
  • High concentration chloride environment: papermaking industry, various bleaching devices

Metallographic structure of 254SMO:

254SMO is face centered cubic lattice structure. In order to obtain austenite structure, 254SMO is annealed at 1150-1200 ℃. In some cases, there may be traces of metal intermediate phases (χ and α phases) in the center of the material. But in general, they have no adverse effect on impact strength and corrosion resistance. When placed in the range of 600-1000 ℃, these phases may precipitate on the grain boundary.

Product Forms and Relative Standards

a ball valve with astm a182 f44 body - Super austenitic stainless steel: 254SMO (UNS S31254,F44,1.4547)

A floating ball valve with ASTM A182 F44 body, Maersk Oil, Kazakhstan.

Product Form Standard
Plate, Sheet, Strip ASTM A240,A480
Bar, Billet ASTM A276, A479
Seamless and Welded Pipe ASTM A312, A358, A409, A813, A814
Seamless and Welded Tube ASTM A249, A269, A270
Fittings, Forgings ASTM A182, A403, A473
Bolting, Nuts ASTM A193, A194
Casting ASTM A351, A743, A744

*254SMO is designated differently in different product forms: for wrought pipe fittings, it is ASTM A403 WPS31254; for forgings, it is ASTM A182 F44; for castings, it should be CK3MCuN or UNS J93254.

Source: China 254SMO Flanges Manufacturer – Yaang Pipe Industry (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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