In the world of advanced engineering materials, Stainless Steel 904L Sheet stands out as a high-alloy austenitic stainless steel that delivers exceptional corrosion resistance, especially in aggressive environments involving strong reducing acids like sulphuric acid. Whether you’re working in chemical processing, power generation, marine, or oil & gas industries, this grade offers long-term reliability, excellent weldability, and superior mechanical properties.
In this blog, we delve deep into the technical specifications, chemical composition, mechanical properties, corrosion resistance, fabrication characteristics, and industrial applications of Stainless Steel 904L Sheet.
What is Stainless Steel 904L?
Stainless Steel 904L is a low carbon, high alloy austenitic stainless steel primarily designed for corrosion resistance in harsh environments. Originally developed for resistance to sulphuric acid, 904L contains high levels of chromium, nickel, molybdenum, and copper, giving it superior performance over standard 300 series stainless steels like 304 and 316.
This grade conforms to specifications such as ASTM B625, ASTM A240, and EN 10088-2.
Chemical Composition of Stainless Steel 904L Sheet
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.02 |
| Chromium (Cr) | 19.0 – 23.0 |
| Nickel (Ni) | 23.0 – 28.0 |
| Molybdenum (Mo) | 4.0 – 5.0 |
| Copper (Cu) | 1.0 – 2.0 |
| Manganese (Mn) | ≤ 2.0 |
| Silicon (Si) | ≤ 1.0 |
| Iron (Fe) | Balance |
Note: The high nickel and molybdenum content are key to its stress corrosion and pitting resistance.
Mechanical Properties of Stainless Steel 904L Sheet
| Property | Value |
|---|---|
| Tensile Strength | 490 MPa (min) |
| Yield Strength (0.2% offset) | 220 MPa (min) |
| Elongation | ≥ 35% |
| Hardness (Brinell) | ≤ 220 HB |
| Modulus of Elasticity | ~195 GPa |
These properties make it suitable for high-load structural components exposed to corrosive media.
Corrosion Resistance of Stainless Steel 904L Sheet
One of the biggest advantages of 904L stainless steel sheet is its excellent corrosion resistance. Here’s how it performs in different environments:
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Sulphuric Acid Resistance: Outstanding due to the presence of high copper content.
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Pitting and Crevice Corrosion: High resistance in chloride environments due to the molybdenum content.
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Stress Corrosion Cracking: Performs better than 316L or 317L in high chloride environments.
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Intergranular Corrosion: Excellent resistance even after welding, thanks to its low carbon content (L-grade).
Fabrication and Welding Characteristics
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Weldability: Stainless Steel 904L Sheet is readily weldable using conventional fusion methods like GTAW (TIG), GMAW (MIG), and SMAW (stick).
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Formability: Excellent due to its high ductility. Can be cold-formed or deep drawn.
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Machinability: Slightly tougher to machine than 304 or 316 due to higher alloy content; however, carbide tooling improves results.
Important Note: Post-weld pickling and passivation are recommended to restore maximum corrosion resistance.
Applications of Stainless Steel 904L Sheet
Due to its high resistance to chemical attack, SS 904L sheets are used across demanding sectors, including:
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Chemical Processing Equipment: Reactors, heat exchangers, piping systems.
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Marine Applications: Desalination plants, offshore platforms.
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Oil & Gas Industry: Flue gas scrubbers, acid processing systems.
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Pharmaceutical Industry: Storage tanks, clean-in-place systems.
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Pulp and Paper Industry: Digesters, bleach washers, evaporators.
Available Sizes and Tolerances
Thickness Range: 0.5 mm to 50 mm
Width: Up to 2000 mm
Length: Up to 6000 mm or as per custom cut
Surface Finishes: 2B, BA, No. 4, Mirror Finish, HRAP
All sheets are supplied with full mill test certificates (MTC) in compliance with EN 10204 3.1/3.2 standards.
Equivalent Grades of Stainless Steel 904L
| Standard | Grade |
|---|---|
| ASTM | 904L (UNS N08904) |
| EN/DIN | 1.4539 |
| BS | 904S13 |
| AFNOR | Z2NCDU25-20 |
Why Choose Stainless Steel 904L Sheet?
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Exceptional resistance to reducing acids like H₂SO₄
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High pitting resistance equivalent number (PREN > 34)
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Non-magnetic even after cold working
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Long service life in corrosive environments
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Excellent weldability and formability
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Complies with NACE MR0175 for sour service applications
Final Thoughts
If your industry demands a high-performance material that can withstand corrosive chemicals, elevated temperatures, and mechanical stress, Stainless Steel 904L Sheet is the right choice. Its unique composition and superior properties make it invaluable across critical sectors.
Always source from trusted suppliers who provide material traceability, test certifications, and precision cutting for your specifications.