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904L Stainless Steel: Definition, Composition, Properties, Processing, Applications, and More
- John
Overview of 904L Stainless Steel
904L (UNS N08904) stainless steel is a super austenitic stainless steel, mainly composed of 19-23% chromium, 23-28% nickel, 4-5% molybdenum, and 1-2% copper. It meets ASTM A240 and EN 10088-2 standards and is equivalent to 1.4539 (EN) and SUS 904L (JIS).
This grade is known for its excellent resistance to corrosion, especially in acidic environments, and high resistance to pitting and crevice corrosion. It is commonly used in chemical processing, oil and gas, and pharmaceutical industries. 904L also offers good weldability but requires filler metals.
Applications of 904L Stainless Steel
| Industry | Application |
| Chemical Processing | Heat exchangers, Tanks, Piping systems, Valves |
| Oil and Gas | Offshore platforms, Pipelines, Pumps, Wellhead equipment |
| Pharmaceutical | Mixing tanks, Sterilizers, Process reactors, Storage vessels |
| Power Generation | Flue gas scrubbers, Nuclear waste containers, Turbine blades, Cooling systems |
Advantages and Disadvantages of 904L Stainless Steel
Here are the advantages and benefits of 904L stainless steel:
- Excellent resistance to corrosion, especially in harsh environments.
- High resistance to acid attacks, including sulfuric and phosphoric acids.
- High resistance to pitting and crevice corrosion.
- Strong durability at both high and low temperatures.
- Good weldability and formability for various applications.
Here are the disadvantages and limitations of 904L stainless steel:
- Higher cost compared to other stainless steel grades.
- Difficult to machine due to its high strength and toughness.
- Requires special tools for welding and fabrication.
- Limited availability compared to more common stainless steel grades.
- Heavier weight may limit its use in some applications.
Equivalent Grades of 904L Stainless Steel
| Country/Region | Standard | Equivalent Grade |
| EU | EN 10088-1 | X1NiCrMoCu25-20-5 (1.4539) |
| USA | ASTM A240 | 904L, N08904 |
| France | NF A35-576 | Z2NCDU25-20 |
| England | BS 1449 | 904S13 |
| Sweden | SS 14 25 62 | 2562 |
| Poland | PN 67/H-86020 | 00H22N24M4TCu |
Heat & Corrosion Resistance of 904L Stainless Steel
Heat Resistance
904L stainless steel has good heat resistance, performing well up to 400°C (752°F). However, it’s not ideal for long-term use at higher temperatures. Its strength and corrosion resistance decrease beyond 400°C. While 904L is resistant to oxidation, it’s better suited for corrosion protection than extreme heat.
Corrosion Resistance
904L stainless steel offers outstanding corrosion resistance. Its high molybdenum content provides excellent protection against pitting and crevice corrosion, especially in chloride-rich environments. The addition of copper enhances its ability to resist corrosion in sulfuric acid across all concentrations, which makes it superior to many other stainless steel in this regard.
While 904L is more resistant to chloride stress corrosion cracking than other austenitic grades, it can still be vulnerable under high temperatures or in high chloride concentrations. Its low carbon content also minimizes the risk of intergranular corrosion during welding, making it ideal for applications where both corrosion resistance and weldability are critical, such as in chemical processing and seawater environments.
Processing of 904L Stainless Steel
Forming
904L stainless steel has good formability due to its austenitic structure. It can be easily shaped and formed using standard techniques such as bending, drawing, and pressing. However, its high alloy content makes it harder to work with than lower-grade stainless steel. Pre-heating is not required, but the material may require more force when forming due to its strength. After forming, annealing may be needed to relieve stress and maintain corrosion resistance.
Welding
904L stainless steel has good weldability and can be welded by common methods like TIG, MIG, and stick welding. Its low carbon content reduces the risk of intergranular corrosion. Heat input should be controlled to maintain corrosion resistance. Pre-heating is not needed, and post-weld heat treatment can improve performance in harsh environments. Use filler metals like ERNiCrMo-3 to ensure strength and corrosion resistance.
Machining
904L stainless steel has poor machinability due to its toughness and tendency to work-harden. It can gum up tools, requiring slow speeds and higher cutting forces. Sharp carbide or ceramic tools with proper lubrication are recommended to manage heat. Low cutting speeds and heavy feeds help prevent work hardening. Tool wear is significant, so frequent tool changes or regrinding may be needed. Machining 904L demands patience and precision to minimize tool wear and maintain surface quality.
Heat Treatment
904L stainless steel cannot be hardened by heat treatment. The primary heat treatment process for 904L is solution annealing, where the material is heated to around 1090-1175°C (1994-2147°F), followed by rapid cooling, usually in water, to maintain corrosion resistance and optimize mechanical properties.
Solution annealing also helps prevent sensitization by ensuring the steel cools quickly enough to avoid carbide precipitation, which can reduce corrosion resistance in welded or heated areas.
Chemical Composition of 904L Stainless Steel
Check the table below for the chemical composition of 904L stainless steel:
| Element | Carbon, C | Chromium, Cr | Copper, Cu | Iron, Fe | Manganese, Mn | Molybdenum, Mo | Nickel, Ni | Silicon, Si | Sulfur, S |
| Wt% | ≤ 0.020 % | 19 – 23 % | 1.0 – 2.0 % | 38.9 – 53 % | ≤ 2.0 % | 4.0 – 5.0 % | 23 – 28 % | ≤ 1.0 % | ≤ 0.035 % |
Properties of 904L Stainless Steel
Here are three major reasons that make 904L stainless steel unique:
- High corrosion resistance in aggressive environments like seawater and acids.
- Exceptional toughness and durability, even at low temperatures.
- Excellent weldability and formability for complex industrial applications.
Physical Properties
Check the table below for the core physical properties of 904L stainless steel:
| Property | Metric Value | Imperial Value |
| Density | 7.90 g/cc | 0.285 lb/in³ |
| CTE, Linear (20.0 – 100 °C / 68.0 – 212 °F) | 15.3 µm/m-°C | 8.50 µin/in-°F |
| Specific Heat Capacity | 0.460 J/g-°C | 0.110 BTU/lb-°F |
| Thermal Conductivity (20.0 °C / 68.0 °F) | 11.5 W/m-K | 79.8 BTU-in/hr-ft²-°F |
| Electrical Resistivity | 0.0000952 ohm-cm | 0.0000952 ohm-cm |
| Magnetic Permeability | <= 1.02 | <= 1.02 |
Mechanical Properties
Check the table below for the core mechanical properties of 904L stainless steel:
| Property | Value | Performance |
| Tensile Strength | 490 MPa (71.1 ksi) | High strength, good durability |
| Yield Strength | 220 MPa (31.9 ksi) | Decent yield strength, maintains form |
| Rockwell Hardness (HRB) | 70 – 90 HRB | Moderate hardness, resists deformation |
| Elongation at Break | 35% | High ductility, stretches without breaking |
| Young’s Modulus | 200 GPa (29.0 Msi) | Stiff material, handles high loads |
Chemical Properties
Check the table below for the core chemical properties of 904L stainless steel:
| Chemical Property | Description | Performance |
| Corrosion Resistance | Ability to resist damage caused by corrosive environments | Excellent in harsh environments, far superior to 316L |
| Oxidation Resistance | Capacity to withstand high-temperature oxidation | Very high, performs well in up to 400°C, better than standard steel |
| Chemical Stability | Stability when exposed to chemicals over time | Maintains integrity in aggressive chemical conditions |
| Acid and Alkali Resistance | Resistance to acid and alkali environments | Strong resistance to both acids and bases, handles sulfuric acid well |
| Rust Resistance | Ability to avoid rusting in various conditions | Superior to many other stainless steel, ideal for marine applications |
904L vs 316L Stainless Steel
Check the table below for a quick comparison between 904L and 316L stainless steel:
| Property | 904L | 316L |
| Type | Austenitic | Austenitic |
| Crystal Structure | Face-Centered Cubic (FCC) | Face-Centered Cubic (FCC) |
| Chemical Composition | C: ≤0.02%, Cr: 19-23%, Ni: 23-28%, Mo: 4-5%, Cu: 1-2% | C: ≤0.03%, Cr: 16-18%, Ni: 10-12%, Mo: 2-3% |
| Corrosion Resistance | Excellent in aggressive environments | Good in most environments |
| Mechanical Properties | Good overall | Balanced |
| Formability | Good | Excellent |
| Weldability | Good | Excellent |
| Machinability | Fair | Good |
| Magnetic Properties | Non-magnetic | Non-magnetic |
| Cost | High | Moderate |
| Applications | Chemical, pharmaceutical, and seawater use | Food processing, medical, marine, architecture |
Which is better, 904L or 316L?
904L is generally better than 316L in terms of corrosion resistance, especially in harsh environments like marine or chemical industries. However, 316L is more commonly used and less expensive.
What You Might Also Concern
Does 904L stainless steel rust?
904L stainless steel is highly resistant to rust and corrosion, but in extreme conditions, it can still rust over time.
Is 904L stainless steel magnetic?
No, 904L stainless steel is generally non-magnetic.
Related Reading
Is Stainless Steel Magnetic?
Is 904L stainless steel more scratch-resistant?
Yes, 904L stainless steel is more scratch-resistant compared to standard stainless steel due to its higher nickel and chromium content, but it’s not completely scratch-proof.
Is 904L stainless steel good for watches?
Yes, 904L stainless steel is excellent for watches due to its high resistance to corrosion, durability, and ability to maintain a polished finish. It is often used in high-end timepieces.
Is 904L stainless steel expensive?
Yes, 904L stainless steel is expensive compared to other stainless steel due to its high nickel and molybdenum content, which provides excellent corrosion resistance.
Summary & Furthermore
This article briefly overviews 904L and discusses the composition, properties, processing, and other important aspects of 904L stainless steel. To learn more about stainless steel or other steel types, check out our blog or contact our metal experts.
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