Products Features
Outstanding resistance to uniform corrosion (core advantage)
The core advantage of N08904 lies in its excellent corrosion resistance in reducing acids. Thanks to the addition of copper (Cu), this alloy exhibits exceptional durability in non-oxidizing acids such as dilute sulfuric acid, phosphoric acid, and acetic acid. In pure sulfuric acid with concentrations ranging from 0% to 98%, it can withstand temperatures up to 40°C, with even higher tolerance at lower concentrations. This property makes it the preferred material for chemical equipment handling these highly corrosive media, such as reactors, tanks, and heat exchangers, offering corrosion resistance far superior to conventional austenitic stainless steels.
Exceptional resistance to localized corrosion
Thanks to the synergistic effects of high chromium (19-23%), high molybdenum (4-5%), and high nickel (23-28%), N08904 exhibits excellent resistance to pitting and crevice corrosion in chloride-containing media. Its Pitting Resistance Equivalent Number (PREN) is typically greater than or equal to 35, and its critical pitting temperature is approximately 30°C higher than that of 316L. This enables it to withstand environments with chloride concentrations as high as 2000 ppm or even higher, making it an ideal material choice for harsh applications such as seawater cooling systems, offshore platforms, and flue gas desulfurization (FGD) systems.
Excellent stress corrosion cracking (SCC) resistance performance
Common austenitic stainless steels (such as 304 and 316) are highly susceptible to stress corrosion cracking in chloride-rich environments at temperatures above 60°C. N08904, with a nickel content of over 24%, significantly enhances the material's resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions, and hydrogen sulfide (H₂S)-rich environments. It complies with the NACE MR0175/ISO 15156 standard and is suitable for oil and gas production environments containing hydrogen sulfide to resist sulfide stress corrosion cracking (SSCC).
Good machining and forming properties
N08904 exhibits excellent hot and cold working properties. Its austenitic structure imparts superior toughness to this type of material, even at low temperatures. The alloy can be forged, rolled, and stamped, and can also be formed through conventional machining operations such as turning, milling, and drilling. However, it is important to note that it has a pronounced tendency to work-harden. It is recommended to use carbide cutting tools along with lower cutting speeds and moderate feed rates.
Stable austenitic structure and resistance to sensitization
N08904 exhibits a fully austenitic microstructure in the solution-annealed condition. Due to its ultra-low carbon (≤0.020%) design, it minimally precipitates chromium carbides along grain boundaries after welding or short exposure to the sensitization temperature range (425-850°C). This means it retains excellent resistance to intergranular corrosion in the welded condition and typically does not require post-weld desensitization heat treatment, significantly simplifying the manufacturing process.
Technical Specifications
Chemical Composition(ASTM B673 / ASME SB-625)
|
Element |
Standard Requirements |
Notes |
|
Ni |
23.0 - 28.0% |
Stabilize the austenitic structure, improve resistance to stress corrosion and corrosion in reducing acids |
|
Cr |
19.0 - 23.0% |
Form a dense passivation film to provide basic corrosion resistance and oxidation resistance |
|
Mo |
4.0 - 5.0% |
Significantly improve resistance to pitting corrosion and crevice corrosion |
|
Cu |
1.0 - 2.0% |
Key elements that impart excellent corrosion resistance in reducing acids such as dilute sulfuric acid |
|
Fe |
Remaining quantity |
Matrix element |
|
C |
≤ 0.020% |
Ultra-low carbon content, preventing intergranular corrosion |
|
Mn |
≤ 2.0% |
|
|
Si |
≤ 1.0% |
|
|
P |
≤ 0.045% |
Impurity elements, strictly controlled |
|
S |
≤ 0.035% |
Impurity elements, strictly controlled |
|
N |
≤ 0.10% |
Physical Properties
|
Property |
Value/Range |
Test Conditions |
|
Density |
8.0 g/cm³ |
Room Temperature (20°C) |
|
Melting Point |
1360 - 1397°C |
--- |
|
Resistivity |
≈ 0.97 - 1.0 μΩ·m |
Room Temperature |
|
Thermal conductivity |
≈ 12 W/(m·K) |
Room Temperature |
|
Coefficient of thermal expansion (20-100°C) |
≈ 14.9 - 16.0 × 10⁻⁶ /K |
--- |
|
Elastic modulus (Young's modulus) |
≈ 195 GPa |
Room Temperature |
|
Magnetism |
Non-magnetic (completely austenitic in solution-annealed condition, with extremely low permeability) |
It is essentially non-magnetic under various conditions |
Mechanical Properties (Solution-annealed condition, typical value)
|
Property |
Typical Value |
Specification |
|
Tensile Strength(Rm) |
≥ 490 MPa |
ASTM B673 |
|
Strength (Rp0.2) |
≥ 220 MPa |
ASTM B673 |
|
Elongation (A) |
≥ 35% |
ASTM B673 |
|
Hardness |
≤ 90 HRB |
--- |
High-temperature performance
The maximum operating temperature of N08904 is approximately 450°C. At high temperatures, the alloy still maintains good mechanical properties and creep resistance. However, it should be noted that prolonged exposure in the temperature range of 550-900°C may lead to precipitation of carbides or σ phase, which can affect toughness and corrosion resistance. Therefore, improper heat treatment or slow cooling in this range should be avoided.
Antioxidant performance:
N08904 exhibits good oxidation resistance in normal atmospheric environments. Its oxidation rate is extremely low in air up to 400°C. However, its corrosion resistance is inferior to that of high-chromium, molybdenum-free steel grades in strongly oxidizing acids (such as concentrated nitric acid).
Organizational Stability:
N08904 can achieve a uniform austenitic microstructure through proper solution treatment (heating at 1050-1150°C followed by rapid water cooling), ensuring its excellent corrosion resistance.
Heat treatment system
The final performance of N08904 is highly dependent on the correct heat treatment regime, with common specifications as follows:
1. Solution annealing (for restoring optimal corrosion resistance):
Heat to 1050-1150°C, hold for a sufficient time (depending on the cross-sectional thickness, e.g., 35-40 minutes for tubes), and then quench rapidly in water. The purpose is to fully dissolve carbides, obtain a single austenitic structure, and restore optimal corrosion resistance.
2. Stress Relief Annealing (After Cold Working):
To eliminate cold working stress, low-temperature annealing can be performed at 300-400°C. Heat treatment or slow cooling within the sensitization temperature range of 425-850°C should be avoided to prevent precipitation of carbides or σ-phase, which would lead to reduced intergranular corrosion resistance and toughness.
Note:
Heat treatment should be performed after final mechanical machining.
Rapid water cooling after solution treatment is key to achieving optimal corrosion resistance.
Post-weld heat treatment is generally not required after welding.
Corrosion Resistance Comparison and Application Selection
|
Performance indicators |
N08904 (904L) |
Ordinary austenitic stainless steel (316L) |
Explanation |
|
Pitting Resistance Equivalent Number (PREN) |
≥ 35 |
≈ 25 |
The higher the value, the stronger the resistance to pitting corrosion |
|
Critical Pitting Temperature (CPT) |
≈ 40 - 50°C |
≈ 10 - 15°C |
Critical temperature for pitting corrosion in chloride environments |
|
Corrosion resistance in dilute sulfuric acid |
Excellent |
Difference |
The copper element is critical for use in equipment handling dilute sulfuric acid |
|
Stress Corrosion Cracking (SCC) |
Excellent (high Ni content) |
Sensitive (Chloride environment above 60°C) |
High nickel content significantly enhances resistance to stress corrosion cracking |
|
Intergranular Corrosion Sensitivity |
Not sensitive (ultra-low carbon) |
Sensitive (may be sensitized after welding) |
The ultra-low carbon design avoids sensitization issues after welding. |
|
Cost |
Higher |
Lower |
High alloy content leads to increased costs |
|
Selection suggestions |
Primarily used for strong corrosive environments: sulfuric acid/phosphoric acid treatment, seawater systems, FGD (Flue Gas Desulfurization), and harsh conditions containing chlorine/hydrogen sulfide |
Primarily used in general corrosive environments: atmosphere, water, weak acids, and food equipment |
N08904 is a high-cost-effective option for applications with extremely high requirements for corrosion resistance. |
Applicable Media
1. Sulfuric Acid: Exhibits excellent corrosion resistance in dilute sulfuric acid, making it a classic material choice for this service condition.
2. Phosphoric Acid: Performs exceptionally well in both pure phosphoric acid and impure wet-process phosphoric acid.
3. Organic Acids (e.g., Acetic Acid, Formic Acid): Demonstrates good corrosion resistance.
4. Chloride-Ion Solutions: Offers extremely strong resistance to pitting, crevice corrosion, and stress corrosion caused by chloride ions (e.g., seawater, saltwater).
5. Hydrogen Sulfide (H₂S) Environment: Complies with NACE standards and is suitable for acidic oil and gas field environments.
N08904 (904L) is specifically designed for highly corrosive environments and severe operating conditions, and is recommended for use in the following fields:
Application Fields
-
Chemical Engineering and Petrochemical Engineering
Reactors, tanks, heat exchangers, towers, pipelines, and flanges are used for handling sulfuric acid, phosphoric acid, chlorinated media, and other substances. Their excellent corrosion resistance is key to ensuring the long-term safe operation of equipment. -
Marine Engineering and Seawater Desalination
Seawater cooling systems, pump and valve components, marine platform structural parts, and corrosion-resistant sections in desalination units. Its high molybdenum and nickel content provide significantly greater reliability than conventional stainless steels in marine environments. -
Environmental Protection and Flue Gas Desulfurization (FGD) Systems
Key components such as scrubbers, flue ducts, and baffle doors. The FGD system environment is highly corrosive, and N08904 is one of the mainstream material choices in this field. -
Oil and natural gas industry
Used in acidic oil and gas field environments containing H₂S, it resists sulfide stress corrosion cracking and is suitable for downhole pipe materials, surface facilities, etc. -
Pharmaceutical and Food Industries
Pharmaceutical equipment, high-purity containers, and piping utilize their excellent corrosion resistance and non-magnetic properties to ensure product purity and process safety. -
Papermaking industry
Used in stages for handling corrosive chemicals in equipment such as bleachers and digesters.
Delivery and Customization
We offer flexible and reliable supply chain solutions to ensure you receive N08904 (904L) materials that perfectly match your project requirements.
|
Form |
 Sheet/Plate
|
 Bar/Rod
|
 Pipe / Tube
|
 Strip/Sheet Coil
|
 Wire/Wire Rod
|
|---|---|---|---|---|---|
|
Conventional Range |
Thickness: 3-60 mm |
Diameter Φ10-300mm |
Outer diameter Φ10-300mm |
Thickness: 0.5 – 3.0 mm |
Diameter Φ0.1-8mm |
|
Customization Capability |
Medium-thick plates, thin plates, fixed-length cutting, special surface treatments (pickling, polishing) |
Forged bars, hot-rolled bars, polished bars, special-shaped bars, and different heat treatment conditions |
Seamless pipes, welded pipes, fixed-length cutting, U-shaped pipes |
Precision strip materials, stamping coil materials, non-standard width |
Precision drawing, welding filler wire, special surface treatment |
Why Choose Us? - Reliable Engineering Technology. Dependable Delivery.
We are not just a supplier, but a trusted materials partner for you in China.
Vertically Integrated Production
Own 20,000㎡ facility with 10+ automated lines (8,000+ tons/year). In-house tooling & die center enables rapid customization and effective cost control - no middleman markup.
Strict Quality Control at Every Stage
Full traceability across key QC checkpoints throughout production. 100% compliant with ASTM/ASME, EN, and GB standards. Material test reports available with every shipment.
Reliable Delivery & Export Packaging
10+ years exporting to Europe, North America, Southeast Asia & Middle East with waterproof and anti-rust protection, combined with flexible shipping options ensures safe and on-time arrival.
Sample Validation Before Mass Production
We provide free samples for quality verification, allowing you to place bulk orders only after approval. We ensure consistency from sample to mass production by accurate dimensional measurement and transparent manufacturing.
FAQ
Q: What are the core advantages of N08904 compared to ordinary stainless steels (such as 316L)?
Q: What is the optimal heat treatment process for N08904?
Q: Is N08904 easy to machine?
Q: What is the maximum operating temperature for N08904?
Q: Does N08904 have magnetic properties?
Q: What is the main difference between N08904 and PERMALLOY (1J79)?
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