254SMO Super Austenitic Stainless Steel (UNS S31254)
254SMO is an austenitic stainless steel with 6% molybdenum content. Because of its high molybdenum concentration, 254SMO has very strong resistance to pitting and crevice corrosion, as well as good resistance to uniform corrosion, especially in acids containing halides; thus, this stainless steel was created for use in halide-containing conditions such as saltwater. 254SMO is also particularly resistant to localized corrosion in aerated seawater. It is an alternative to Ni-based alloys and titanium alloys due to the presence of gaps, low-velocity scouring conditions, strong resistance to pitting (PI 40), and good stress corrosion resistance. Second, in terms of high-temperature resistance or corrosion resistance, 304 stainless steel has superior high-temperature resistance or corrosion resistance.
Because of its high nitrogen concentration, 254SMO has better mechanical strength than other austenitic stainless steels. Furthermore, 254SMO possesses great ductility, impact strength, and weldability. Because of its high molybdenum concentration, 254SMO has a faster annealing oxidation rate, resulting in a rougher surface than conventional stainless steel after pickling. However, this has no influence on the steel's corrosion resistance. Because 254SMO is a highly alloyed material, the manufacturing process is fairly complicated, and it is often necessary to rely on traditional techniques to create this specific stainless steel, such as infusion, forging, calendering, and so on.
Chemical Composition (%) of 254SMO Super Austenitic Stainless Steel (UNS S31254)
| CHEMICAL COMPOSITION (%) | |||||||||
| C, max | Mn, max | P, max | S, max | Si, max | Cr | Ni | Mo | Cu | N |
| 0.02 | 1.00 | 0.03 | 0.01 | 0.80 | 19.50-20.50 | 17.50-18.50 | 6.00-6.50 | 0.50-1.00 | 0.18-0.22 |
Mechanical Properties of 254SMO Super Austenitic Stainless Steel (UNS S31254)
| MECHANICAL PROPERTIES | |||
| Tensile Strength, MPa, min | Yield Strength, MPa, min | Elongation (%), min | Hardness, max |
| 655 | 310 | 35 | 223 HB |
Physical Properties of 254SMO Super Austenitic Stainless Steel (UNS S31254)
| PHYSICAL PROPERTIES | ||||||
| Density | Melting Point | Modulus of Elasticity | Poisson's ratio | Coefficient of Thermal Expansion | Thermal Conductivity | Electrical Resistivity |
| 8.24 g/cm³ | 1320-1390℃ | 200 GPa | 0.30 | 16.5 µm/m°C | 13 W/m·K | 0.85 Ωmm²/m |
Corrosion Resistance of 254SMO Super Austenitic Stainless Steel (UNS S31254)
In pure sulfuric acid, 254SMO is far more corrosion-resistant than 316, the common type of stainless steel. However, at high concentrations, the corrosion resistance of 254SMO is slightly lower than that of 904L (NO8904) type stainless steel. 254SMO has the best corrosion resistance of all the sulfuric acids containing chloride ions. Because of the likelihood of localized and uniform corrosion, 316 common types of stainless steel cannot be used in hydrochloric acid; however, 254SMO can be used at normal temperatures in diluted hydrochloric acid. There is no need to be concerned about pitting corrosion in the following boundary line regions: Attempts must be made, however, to avoid the occurrence of crevices. Ordinary stainless steel has a relatively restricted corrosion resistance range in fluorosilicic acid (H2SiF4) and hydrofluoric acid (HF), whereas 254SMO can be used in a very wide range of concentrations and temperatures.
Heat Treatment of 254SMO Super Austenitic Stainless Steel (UNS S31254)
254SMO is solution annealed at a temperature of no less than 1150 ℃ (2100 ℉). After solution annealing, it should be quenched rapidly with air or water cooling.
Standard Specifications of 254SMO Super Austenitic Stainless Steel (UNS S31254)
| ASTM A182/ASME SA182 | Standard Specification for Forged or Rolled Alloy-Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service |
| ASTM A240/ASME SA240 | Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General |
| ASTM A276 | Standard Specification for Stainless Steel Bars and Shapes |
| ASTM A312/ASME SA312 | Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes |
Features of 254SMO Super Austenitic Stainless Steel (UNS S31254)
- Non-magnetic
- Excellent resistance to pitting corrosion and crevice corrosion
- Excellent resistance to intergranular corrosion
- High cost-effectiveness
- Excellent resistance to uniform corrosion
- Outstanding resistance to localized corrosion
- Excellent resistance to stress corrosion
- Extremely high-temperature resistance
- High ductility
- Good weldability
- Excellent impact toughness
- Excellent processability
Applications of 254SMO Super Austenitic Stainless Steel (UNS S31254)
254SMO super austenitic stainless steel is widely used in chemical industry, petrochemical industry, energy, paper making, marine, and other industries.
- Paper bleaching equipment
- Flue gas desulfurization equipment
- Seawater desalination treatment equipment
- Heat exchangers
- Chemical chemical machinery
- Sea tide power generation
- Wastewater treatment equipment
Equivalent Grades of 254SMO Super Austenitic Stainless Steel (UNS S31254)
| ASTM | UNS | WERKSTOFF NR. | GB | EN |
| 254SMO | S31254 | 1.4547 | 00Cr20Ni18Mo6CuN | X1CrNiMoCuN20-18-7 |
