EN 1.4539 - 904L is a high alloy austenitic stainless steel with low carbon content. The grade is intended for use under severe corrosive conditions. The steel grade was originally developed to resist corrosion in dilute sulphuric acid. EN 1.4539 is fully austenitic, and is less sensitive to precipitation of ferrite and sigma phase than conventional austenitic grades with high molybdenum content. Due to the combination of relatively high contents of chromium, nickel, molybdenum and copper, EN 1.4539 has good resistance to general corrosion, particulary in dilute sulphuric acid. It is non-magnetic in the annealed condition but may become slightly magnetic as a result of cold-working or welding. Design features
⇒ Good resistance to uniform corrosion
⇒ Good resistance to pitting and crevice corrosion
⇒ Very good resistance to stress corrosion cracking
⇒ Good resistance to intercrystalline corrosion
⇒ Good formability and weldability Corrosion resistance
Uniform corrosion Uniform corrosion is characterized by a uniform corrosion of the steel surface in contact with the corrosive medium. Resistance is normally considered good if the corrosion rate is less than 0,1 mm/year. As a result of its high chromium, nickel and molybdenum contents and its alloying with copper, EN 1.4539 is passivated even in reducing environments such as dilute sulphuric acid and formic acid. Its high nickel content contributes towards its relatively low corrosion rate in the active state. Intercrystalline corrosion
EN 1.4539 has a very low carbon content. This means that there is very little risk of carbide precipitation in connection with ordinary heat treatment and welding. The risk of intercrystalline corrosion after ordinary heat treatment and welding is thereby eliminated.
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