Stainless Steel 904L/ UB6 (1.4539)
Stainless Steel 904L/ UB6 (1.4539)
Stainless Steel 904L, or UB6 or 1.4539, is a high-alloy austenitic stainless steel with exceptional corrosion resistance and durability in extreme environments. Originally developed for resistance to sulfuric acid, 904L is now widely utilized in various industries where superior resistance to highly aggressive chemical conditions is required. Its high nickel and molybdenum content makes it a standout material for demanding applications.
Worldwide equivalent equivalent grade table 904L
| Standard | Grade | Material Number |
|---|---|---|
| EN (Europe) | X1NiCrMoCu25-20-5 | 1.4539 |
| UNS (USA) | N08904 | – |
| AFNOR (France) | Z2NCDU25-20 | – |
| DIN (Germany) | X1NiCrMoCu25-20-5 | 1.4539 |
| JIS (Japan) | SUS 890L | – |
| GOST (Russia) | 02ChN28M2D | – |
| BS (UK) | 904S13 | – |
Stainless Steel 904L Chemical Compositions
| Element | % Present (in product form) |
|---|---|
| Carbon (C) | 0.02 |
| Silicon (Si) | 0.70 |
| Manganese (Mn) | 2.00 |
| Phosphorous (P) | 0.03 |
| Sulfur (S) | 0.01 |
| Chromium (Cr) | 19.00 – 21.00 |
| Nickel (Ni) | 24.00 – 26.00 |
| Nitrogen (N) | 0.15 |
| Molybdenum (Mo) | 4.00 – 5.00 |
| Copper (Cu) | 1.20 – 2.00 |
| Iron (Fe) | Balance |
Stainless Steel 904L Mechanical Properties
Mechanical Properties Values
Tensile Strength (at RT) 490-670 Mpa
Yield Strength (0.2% offset) 220-310 Mpa
Elongation (at RT) 35-40%
Hardness (Brinell) 150 max
Impact Strength Good
Stainless Steel 904L Physical Properties
| Physical Properties | Values |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Range | 1300 to 1390°C (2372 to 2534°F) |
| Thermal Conductivity | 11.5 W/(m·K) |
| Specific Heat Capacity | 20°C: 500 J/(kg·K) |
| Eectrical Resistivity | 20°C: 0.95 μΩ·m |
Possible Alternative Grades
For specific applications, the following grades may serve as alternatives to Stainless Steel 904L:
- Stainless Steel 316L: Suitable for moderate corrosion environments but lacks the copper and high molybdenum content of 904L.
- Alloy 20 (UNS N08020): Offers similar resistance to sulfuric acid with enhanced resistance to chloride stress corrosion cracking.
- Super Duplex 2507: Provides higher strength and excellent resistance to chloride-induced stress corrosion cracking, making it ideal for offshore applications.
- Hastelloy C276: An excellent choice for highly aggressive chemical environments, though at a higher cost.
Corrosion Resistance
Stainless Steel 904L’s exceptional corrosion resistance stems from its alloy composition:
- Sulfuric Acid: Performs exceptionally well in diluted sulfuric acid concentrations across a wide temperature range.
- Chloride Stress Corrosion Cracking: Its high nickel content minimizes the risk of chloride-induced cracking.
- Pitting and Crevice Corrosion: The high molybdenum and chromium content provide superior resistance in chloride-rich environments, including seawater and brackish water.
- Intergranular Corrosion: Low carbon content reduces the risk of carbide precipitation, ensuring protection against intergranular corrosion.
Stainless Steel 904L Products
Stainless Steel 904L Pipe
Stainless Steel 904L Sheet & Plates
Stainless Steel 904l Flanges
Stainless Steel 904l Bars and Rods
Stainless Steel 904l Perforated Sheet
Stainless Steel 904l Pipe Fittings
Heat Resistance
904L stainless steel exhibits excellent performance at high temperatures:
- It maintains its mechanical properties and corrosion resistance up to 400°C (752°F).
- Prolonged exposure to elevated temperatures may lead to slight embrittlement but does not significantly affect its overall performance.
- Not suitable for high-temperature structural applications beyond the specified range.
Heat Treatment
Heat treatment for 904L includes solution annealing:
- Solution Annealing:
- Temperature: 1090–1170°C (1994–2138°F).
- Rapid cooling is achieved through water quenching to retain its austenitic structure.
- Stress Relieving:
- Generally not required due to its low susceptibility to thermal stress-induced cracking.
- Heat treatment does not harden this grade as it is non-magnetic and remains fully austenitic.
Welding
904L offers excellent weldability with various techniques:
- Common Welding Methods: TIG, MIG, and manual arc welding are all suitable for 904L.
- Filler Material: 904L-compatible filler material, such as AWS A5.9 ER385 or E385, should be used to maintain corrosion resistance.
- Post-Weld Treatment: Typically not required, but solution annealing can be performed for stress relief in critical applications.
- Challenges: Attention to interpass temperature and control of heat input ensures superior weld quality and minimizes distortion.
Fabrication
Stainless Steel 904L can be readily fabricated using standard techniques:
- Machining: Requires sharp tools and slow speeds due to its high strength and work-hardening properties.
- Forming: Can be cold-formed with ease but may require intermediate annealing for complex shapes.
- Cutting: Plasma, laser, and waterjet cutting are effective methods for precision.
- Polishing: Offers excellent surface finish, especially for aesthetic and hygienic applications.
Applications
The versatility and high-performance characteristics of Stainless Steel 904L make it suitable for a wide range of industries and applications:
Chemical Processing:
- Ideal for sulfuric acid production plants, phosphoric acid plants, and chemical reactors due to its resistance to acidic environments.
Pharmaceutical Industry:
- Used in the manufacture of equipment that requires hygienic and corrosion-resistant materials.
Petrochemical Industry:
- Applicable in heat exchangers, storage tanks, and piping systems for handling corrosive liquids.
Marine Industry:
- Extensively used in seawater cooling systems, marine hardware, and desalination plants due to its chloride resistance.
Environmental Systems:
- Suitable for flue gas desulfurization systems in power plants.
Oil and Gas:
- Found in offshore platforms, wellhead components, and pipelines where exposure to saltwater is common.
Food and Beverage Industry:
- Utilized in manufacturing equipment that must resist corrosion and maintain hygiene.
Conclusion
Stainless Steel 904L / UB6 (1.4539) is a premium-grade material that excels in demanding environments requiring unparalleled corrosion resistance and durability. Its unique properties make it a preferred choice across various industries, from chemical processing to marine applications. Whether it’s resisting the harshest acidic conditions or ensuring structural integrity in chloride-rich environments, 904L remains a reliable and cost-effective solution for critical applications. Choosing 904L means investing in longevity, performance, and quality.