904L

Our company’s scope of supply includes

Non-standard forgings, round rods, steel plates/steel belts, flange pipe fittings, seamless pipes, capillaries, etc. Welcome to inquire!

1. Introduction to 904L materials

      904L super austenitic stainless steel is a low-carbon high-nickel, molybdenum austenitic stainless acid-resistant steel, and is a proprietary material for the introduction of French H.S company. It has good activation-passivation transformation ability, excellent corrosion resistance, excellent corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid, and good pitting resistance in neutral chloride-containing media, and good anti-cavity corrosion and stress corrosion resistance. It is suitable for sulfuric acid at various concentrations below 70°C. It is also very corrosion-resistant in acid at any concentration or temperature under normal pressure, and the mixture of formic acid and acetic acid.

2. 904L chemical composition

3. 904L physical properties

Mechanical properties:

Minimum value of mechanical properties of alloys at room temperature:

3. 904L corrosion resistance

      Since the carbon content of 904L is very low (maximum 0.020%), there will be no carbide precipitation under general heat treatment and welding. This eliminates the risk of intergranular corrosion that occurs after general heat treatment and welding. Due to the high chromium nickel-molybdenum content and the addition of copper elements, 904L can be passivated even in a reducing environment, such as sulfuric acid and formic acid. The high nickel content also causes it to have a lower corrosion rate in the active state;

      In pure sulfuric acid in the concentration range of 0~98%, the operating temperature of 904L can be as high as 40 degrees Celsius. In pure phosphoric acid in the concentration range of 0~85%, its corrosion resistance is very good;

      In industrial phosphoric acid produced by wet process, impurities have a strong impact on corrosion resistance. Of all the various phosphoric acids, 904L is better than ordinary stainless steel. Among the strong oxidative nitric acid, 904L has lower corrosion resistance compared with highly alloyed steel grades without molybdenum;

      In hydrochloric acid, the use of 904L is limited to a lower concentration of 1-2%. In this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel. 904L steel has a high resistance to pit corrosion;

      Its anti-cavity corrosion ability is also very good in chloride solutions. The high nickel content of 904L reduces the corrosion rate in the pits and gaps. Common austenitic stainless steels may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 degrees Celsius, and this sensitization can be reduced by increasing the nickel content of the stainless steel. Due to the high nickel content, 904L has high resistance to stress corrosion and fracture in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.

4. 904L application fields

• Petroleum and petrochemical equipment, such as reactors in petrochemical equipment, etc.
• Sulfuric acid storage and transportation equipment, such as heat exchangers, etc.
• The main use parts of the flue gas desulfurization device of the power plant include: the tower body, flue, gear door panel, inner parts, spray system, etc. of the absorption tower.
• Scrubbers and fans in organic acid treatment systems.
• Seawater treatment devices, seawater heat exchangers, papermaking industry equipment, sulfuric acid and nitric acid equipment, acid production, pharmaceutical industry and other chemical equipment, pressure vessels, and food equipment.
• Pharmaceutical factory: centrifuge, reactor, etc.
• Plant food: soy sauce cans, cooking wine, salt cans, equipment and dressings.
• The highly corrosive medium of dilute sulfuric acid is a matching steel type.