904L stainless steel
2025-05-26
Basic Overview of 904L Stainless Steel
1. Material definition
904L is a high-alloy austenitic stainless steel with extremely low carbon content (UNS N08904, national standard grade: 015Cr21Ni26Mo5Cu2), belonging to the category of super stainless steel. Its chemical composition characteristics are:
High nickel (Ni 23-25%), high molybdenum (Mo 4.5-5.5%), copper (Cu 1.0-2.0%), carbon content ≤0.02%, and has extremely strong corrosion resistance.
Compared with common stainless steels (such as 304, 316L) : The higher content of alloying elements makes it perform outstandingly in highly corrosive environments, especially resistant to non-oxidizing acids such as sulfuric acid, phosphoric acid, formic acid, and acetic acid.
2. Physical properties
Density: 8.0 g/cm³
Melting point: 1300-1390℃
Tensile strength: ≥490 MPa
Elongation: ≥35%
Corrosion resistance: Its corrosion resistance in dilute sulfuric acid far exceeds that of 316L, approaching that of high-alloy nickel-based alloys (such as Hastelloy), but at a lower cost.
Core Features and Advantages
1. Super corrosion resistance
Non-oxidizing acids: They are not easily corroded in environments such as sulfuric acid, phosphoric acid, and hydrochloric acid, and are widely used in chemical, pharmaceutical, and pickling equipment.
Stress corrosion cracking (SCC) resistance: The high nickel content makes it less prone to stress corrosion in a chloride environment, which is superior to that of ordinary austenitic stainless steel.
2. Stable high-temperature performance
It can be used for a long time within the range of -196℃ to 250℃ and is suitable for high-temperature scenarios such as heat exchangers and pressure vessels.
3. Good processing and weldability
Although it is slightly more difficult to process than 304 stainless steel, it can still be formed through conventional processes. During welding, attention should be paid to controlling the heat input to avoid intergranular corrosion. '
Typical Application Fields
1. Chemical industry
The chemical industry is one of the most important application fields of 904L stainless steel. In chemical production, many devices need to be in long-term contact with strong acids, strong alkalis or other corrosive chemicals. Due to its excellent corrosion resistance, 904L stainless steel has become an ideal choice. For example:
Acidic environment equipment: 904L can effectively resist the corrosion of strong acids such as sulfuric acid and phosphoric acid, and is thus often used in the manufacture of storage tanks, pipelines, heat exchangers and other equipment.
Chemical reactors: Reactors operating in highly corrosive media require high strength and high corrosion resistance. The 904L can meet these demands.
2. Marine Engineering
There is a large amount of salt and moisture in the Marine environment, which poses extremely high requirements for the corrosion resistance of materials. 904L stainless steel has been widely used in Marine engineering due to its excellent resistance to pitting and crevice corrosion. For example:
Seawater desalination equipment: In an environment with a high concentration of brine, 904L can effectively resist the erosion of chloride ions.
- Shipbuilding: It is used to manufacture key components in ships, such as propeller shafts, seawater cooling systems, etc.
- Offshore platforms: including structural components in oil drilling platforms and offshore wind power generation equipment.
3. Pharmaceutical industry
The pharmaceutical industry has very strict requirements for equipment materials. They not only need to be corrosion-resistant but also meet food-grade hygiene standards. The applications of 904L stainless steel in the pharmaceutical industry include:
- Reaction vessels and agitators: Used for processing high-purity chemicals and pharmaceutical raw materials.
- Pipeline system: It is used for transporting high-purity liquids to ensure no pollution during the pharmaceutical production process.
- Storage container: Suitable for storing corrosive liquids or high-purity raw materials.
4. The oil and gas industry
In the oil and gas industry, equipment often comes into contact with corrosive media such as sulfides and chlorides. 904L stainless steel is widely used in the following scenarios due to its resistance to stress corrosion cracking:
- Oil pipeline: Used for transporting sulfur-containing crude oil or natural gas.
- Refining equipment: such as heat exchangers, pressure vessels, etc.
Submarine pipelines: Capable of withstanding corrosive media in deep-sea environments.
5. Environmental protection industry
In the field of environmental protection, especially in wastewater treatment and flue gas desulfurization systems, 904L stainless steel also has significant applications. For example:
Wastewater treatment equipment: It is used to treat wastewater containing strong acids, strong alkalis or other corrosive substances.
Flue gas desulfurization equipment: In coal-fired power plants, desulfurization towers need to resist the invasion of high temperatures, high humidity and corrosive gases. 904L is an ideal choice.
6. High-end consumer goods sector
In addition to the industrial field, 904L stainless steel is also widely used in the manufacturing of high-end consumer goods, especially in the luxury goods sector. For example:
- Watch manufacturing: Some high-end watch brands use 904L stainless steel to make watch cases and bracelets, as this material is not only aesthetically pleasing but also can maintain its luster for a long time.
Jewelry: 904L has excellent antioxidant properties and is not prone to discoloration, thus it is used to make high-end jewelry.
7. Food processing industry
The food processing industry has extremely high requirements for the hygiene and corrosion resistance of materials. 904L stainless steel has become an important choice for food processing equipment due to its non-toxic, harmless and easy-to-clean properties. For example:
Dairy processing equipment: such as milk tanks, mixing tanks, etc.
- Beer brewing equipment: such as fermentation tanks and storage tanks.
Food delivery pipelines: Ensure the safety and purity of food during the processing.
Market Status Quo and Development Trends
1.Supply and demand situation
On the supply side, major global producers include ThyssenKrupp, ArcelorMittal, Baowu Special Steel, etc. Domestic enterprises such as Taiyuan Iron & Steel and Zhangpu have gradually increased their production capacity in recent years.
Demand side: The demand in emerging markets (such as chemicals in Southeast Asia and infrastructure in Africa) has grown significantly, driving 904L stainless steel from "high-end niche" to "medium-scale application".
2. Price trend
Cost-driven: Significantly affected by the price fluctuations of alloying elements such as nickel and molybdenum, the current domestic price of 904L stainless steel plates is approximately 80,000 to 120,000 yuan per ton (2025), while that of coil plates is slightly lower (75,000 to 110,000 yuan per ton).
The competitive landscape: Imported brands (such as Outokumpu) are relatively expensive, and the trend of domestic substitution is obvious, with a prominent advantage in terms of cost performance.
3. Technological Development direction
Low-carbonization: Further reduce the carbon content (such as ≤0.015%) to enhance welding performance and corrosion resistance.
Composite production: Bimetallic plates are produced by compounding with carbon steel, reducing costs while maintaining corrosion resistance, and are suitable for non-critical corrosive surfaces.
Precautions for Purchase and Use
Identification of authenticity
The contents of Ni, Mo and Cu are detected through spectral analysis to avoid inferior counterfeits (such as those passed off as low-nickel alloys).
Require the supplier to provide the material report (such as the EN 10204 3.1 certificate).
Processing suggestions
When performing cutting operations, lubricants containing sulfur or chlorine are used, and the cutting tools need to be wear-resistant (such as hard alloy).
Welding is recommended to use ER385 (904L dedicated) welding wire. No heat treatment is required after welding, but the sensitization temperature (427-816℃) should be avoided.
Maintenance and upkeep
Avoid long-term retention of chloride ions (such as seawater and salt spray), and rinse the surface with clean water regularly.
If local corrosion occurs, it can be repaired with stainless steel pickling and passivation paste.
