904l Super Austenitic Stainless Steel Forgings Corrosion Resistance

Product Specification

Forging 904L stainless steel forgings forging rod forgings square forgings manufacturing

904L (N08904, 14539) super austenitic stainless steel contains 14.0-18.0% chromium, 24.0-26.0% nickel, and 4.5% molybdenum. 904L super austenitic stainless steel is a low-carbon, high-nickel, molybdenum austenitic stainless acid-resistant steel, which is a proprietary material introduced from H.S. Company of France. It has good activation-passivation transformation ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid, good pitting resistance in neutral chloride ion media, and good crevice corrosion resistance and stress corrosion resistance. It is suitable for various concentrations of sulfuric acid below 70°C, and has good corrosion resistance in acetic acid of any concentration and any temperature under normal pressure, and mixed acid of formic acid and acetic acid.

Super austenitic stainless steel 904L (00Cr20Ni25Mo4.5Cu; UNS: N08904; EN: 1.4539) is a high-alloy austenitic stainless steel with low carbon content. It has good corrosion resistance in dilute sulfuric acid and is designed for harsh corrosive environments. It has a high chromium content and sufficient nickel content. The addition of copper makes it highly resistant to acid, especially chloride crevice corrosion and stress corrosion cracking. It is not easy to have pitting and cracks. The pitting resistance is slightly better than other steel grades. It has good machinability and weldability and can be used for pressure vessels.

Metallographic structure of 904L stainless steel:
904L is a completely austenitic structure. Compared with austenitic stainless steel with a high molybdenum content, 904L is insensitive to the precipitation of ferrite and α phase.
Physical and mechanical properties:
Density: 8.0g/cm3. Tensile strength: σb≥520Mpa. Elongation: δ≥35%. Corrosion resistance of 904L stainless steel:
Since the carbon content of 904L is very low (maximum 0.020%), no carbide will precipitate under general heat treatment and welding. This eliminates the risk of intergranular corrosion after general heat treatment and welding. Due to the high chromium, nickel and molybdenum content and the addition of copper, 904L can be passivated even in a reducing environment such as sulfuric acid and formic acid. The high nickel content makes it 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 influence on corrosion resistance. Among all kinds of phosphoric acid, 904L has better corrosion resistance than ordinary stainless steel. In strongly oxidizing nitric acid, 904L has lower corrosion resistance than high-alloyed steels without molybdenum. In hydrochloric acid, the use of 904L is limited to lower concentrations of 1-2%. In this concentration range. 904L has better corrosion resistance than conventional stainless steel. 904L steel has high resistance to pitting corrosion. Its resistance to crevice corrosion in chloride solutions is also very good. The high nickel content of 904L reduces the corrosion rate in pits and crevices. Ordinary austenitic stainless steels may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 degrees Celsius. This sensitization can be reduced by increasing the nickel content of stainless steel. Due to the high nickel content, 904L has high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.