#904l

UNS N08904 is a high-performance austenitic stainless steel known globally for its remarkable corrosion resistance and mechanical strength. Often specified in demanding industrial environments, this alloy is synonymous with 904L stainless steel, particularly when corrosion resistance and durability are essential. Engineers and material specialists often refer to this as 904L UNS N08904 to highlight both its grade and its unique corrosion-resistant chemistry.

In this comprehensive guide, we’ll explore the UNS N08904 material, its equivalents, chemical and mechanical characteristics, applications, and why it’s a go-to choice for aggressive industrial environments.

What Is UNS N08904?

At its core, UNS N08904 is the Unified Numbering System designation for 904L stainless steel — a super-austenitic stainless steel that incorporates high levels of nickel, chromium, molybdenum, and copper. Compared to other stainless steels, this alloy delivers superior corrosion resistance, especially against reducing acids and chloride-based environments.

The low-carbon nature of UNS N08904 also reduces the risk of sensitization during welding, meaning it maintains excellent corrosion resistance even after fabrication.

UNS N08904 Equivalent and 904L 1.4539

One key factor when specifying UNS N08904 material is understanding its international equivalents. Engineers often encounter different standards and designations globally. Fortunately, this grade is widely recognized and cross-referenced in numerous standards:

AISI/ASME: 904L

UNS: N08904

DIN/EN/Werkstoff: 1.4539 (X1NiCrMoCu25-20-5)

JIS: SUS 904L

AFNOR: Z2 NCDU 25-20

Swedish SS: 2562

These equivalents ensure that materials sourced from different regions meet the same performance criteria, making 904L UNS N08904 a truly global material.

Chemical Composition of 904L UNS N08904

The excellent corrosion resistance of 904L UNS N08904 arises from its optimized alloy chemistry. The major elements and their roles include:

Nickel (Ni): 23.0–28.0% – Enhances formability and corrosion resistance.

Chromium (Cr): 19.0–23.0% – Crucial for oxidation and general corrosion resistance.

Molybdenum (Mo): 4.0–5.0% – Improves resistance to pitting and crevice corrosion.

Copper (Cu): 1.0–2.0% – Aids resistance to reducing acids like sulfuric acid.

Carbon (C): ≤0.02% – Low carbon minimizes carbide precipitation and enhances weldability.

Manganese (Mn), Silicon (Si), Phosphorus (P), Sulfur (S): Minor elements balanced to optimize mechanical behavior and industrial usability.

This carefully balanced chemistry gives UNS N08904 material its signature performance in harsh chemical and marine environments.

Mechanical Properties of UNS N08904

Along with its corrosion resistance, 904L stainless steel delivers reliable mechanical performance. Typical properties include:

Tensile Strength: ≥ 490 MPa

Yield Strength (0.2% offset): ≥ 220 MPa

Elongation: ≥ 35%

Hardness: ≤ 90 HRB

These properties make 904L UNS N08904 suitable for structural components that must withstand both corrosive attack and mechanical loading.

Corrosion Resistance: A Major Advantage

One of the defining strengths of UNS N08904 is its superior corrosion resistance compared to standard austenitic grades such as 304L or 316L stainless steels:

Sulfuric Acids and Reducing Environments: The significant copper content improves resistance to strong reducing acids — environments in which many stainless steels fail.

Chloride Stress Corrosion Cracking: High nickel and molybdenum levels enhance resistance to chloride damage, a common issue in seawater and industrial brines.

Pitting and Crevice Corrosion: The alloy maintains excellent performance in localized corrosion zones thanks to its balanced microstructure and alloying elements.

This robustness is precisely why 904L 1.4539 is preferred in aggressive service environments where long-term reliability is essential.

Typical Applications of 904L Stainless Steel

Due to its blend of corrosion resistance and mechanical strength, UNS N08904 material is widely used across industries including:

Chemical Processing: Reactors, piping, and heat exchangers handling sulfuric and phosphoric acids.

Oil & Gas: Offshore equipment, desalination units, and robust piping systems.

Marine and Seawater Equipment: Condensers, cooling systems, and seawater piping.

Pharmaceutical and Food Processing: Hygienic process equipment with strict corrosion standards.

Power Generation: Flue gas desulfurization, cooling systems, and boiler components.

In all these sectors, 904L UNS N08904 ensures extended service life, reduced maintenance, and dependable performance.

Fabrication and Welding

Despite its high alloy content, UNS N08904 stainless steel shows good weldability and fabrication behavior. Its low carbon content prevents sensitization, making post-weld corrosion resistance reliable. It can be cold or hot formed, although higher forming forces may be required compared to lower alloyed materials.

Machining is moderate, typically requiring sharp tools and controlled speeds due to the alloy’s tough microstructure.

Conclusion

UNS N08904 represents a class of high-performance stainless steel engineered for demanding, corrosive environments. Known globally through its equivalents such as 904L UNS N08904 and 904L 1.4539, this material combines excellent corrosion resistance, sound mechanical properties, and reliable fabrication characteristics. Whether in chemical plants, marine applications, or power generation, UNS N08904 material continues to be a top choice for engineers seeking durability and performance.

904L Stainless Steel Material is a high-alloy austenitic stainless steel acknowledged for its exquisite corrosion resistance and sturdiness. This grade of stainless-steel changed into in the beginning developed to combat competitive environments, which include the ones determined in chemical processing industries. It includes higher levels of chromium, nickel, and molybdenum compared to traditional stainless-steel grades, making it especially proof against strain corrosion cracking, pitting, and crevice corrosion.

The chemical composition of 904L Stainless Steel Material includes 23-28% chromium, 19-23% nickel, four-five% molybdenum, and small quantities of copper, manganese, and silicon. This precise combination of factors affords amazing resistance to both oxidizing and lowering acids, inclusive of sulfuric acid, phosphoric acid, and acetic acid. As an end result, 904L is extensively used in industries in which exposure to harsh chemical compounds is common, together with petrochemical, pharmaceutical, and nuclear industries.

Advantages of 904L Stainless Steel

One of the primary reasons 904L Stainless Steel Material is so popular is its notable corrosion resistance in harsh environments. It outperforms many different chromes steel grades, especially when exposed to sturdy acids and chloride-wealthy atmospheres. The high nickel content prevents 904L from turning into brittle at low temperatures, while the addition of copper enhances its resistance to sulfuric and phosphoric acids.

Another advantage of 904L Stainless Steel Material is its outstanding mechanical homes. It has excessive tensile strength, proper formability, and weldability, making it appropriate for various industrial packages. The material’s potential to hold its mechanical houses even in severe temperatures, whether excessive or low, makes it relatively versatile.

The resistance to pitting and crevice corrosion also makes 904L a remarkable preference for marine applications. Saltwater environments are notoriously corrosive, and substances which can withstand this environment without degrading are essential for marine engineering, offshore oil rigs, and desalination flora.

Applications of 904L Stainless Steel

904L Stainless Steel Material is usually used in chemical processing gadget, which include warmness exchangers, garage tanks, and piping structures that cope with corrosive drinks. Its resistance to a wide variety of acids and the capability to keep its integrity in fantastically acidic environments make it a preferred desire in chemical flowers.

In the oil and fuel industry, 904L stainless steel material is often used in gadget that have to face up to high levels of sulfuric acid and hydrogen sulphide. These environments are in particular difficult for substances because of the risk of strain corrosion cracking, however 904L’s alloy composition enables it withstand those threats correctly.

Additionally, 904L has located its way into extra area of interest applications, along with the pharmaceutical and meals processing industries, where high purity requirements and corrosion resistance are essential. Its non-reactive nature with numerous compounds guarantees that no contaminants are delivered all through the manufacturing system.

Conclusion