904L stainless steel is a low carbon high nickel, high molybdenum austenitic stainless steel. Excellent corrosion resistance. It has good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid. It has good pitting corrosion resistance in neutral chloride-containing media and has good resistance Crevice corrosion and stress corrosion resistance. It is suitable for various concentrations of sulfuric acid below 70°C, and has good corrosion resistance in acetic acid at any concentration and at any temperature and mixed acid of formic acid and acetic acid under normal pressure.

Processing Performance of 904L

904L has good workability and weldability.

● Workability: The maximum heating temperature during hot forging can reach 1180 degrees Celsius, and the minimum stop forging temperature is not less than 900 degrees Celsius. The hot forming of this steel can be carried out at 1000-1150 degrees Celsius. The heat treatment process of the steel is 1100–1150 degrees Celsius, and it is quickly cooled after heating.

● Weldability: Although this steel can be welded by a general welding process, the most appropriate welding method is manual arc welding and argon tungsten arc welding. When manual arc welding is used to weld plates no larger than 6 mm, the electrode diameter is no more than 2.5 mm; when the plate thickness is greater than 6 mm, the electrode diameter is less than 3.2 mm.

When heat treatment is required after welding, it can be heated at 1075-1125 degrees Celsius and then quickly cooled for treatment. When using tungsten argon arc welding, the filler metal can use the same material electrode, and the weld must be pickled and passivated after welding.

Microstructure

904L is a completely austenitic structure. Compared with general austenitic stainless steel with high molybdenum content, 904L is not sensitive to the precipitation of ferrite and α phase.

Corrosion Resistance of 904L Stainless Steel

Because the carbon content of 904L is very low (maximum 0.020%), there will be no carbide precipitation in the case of general heat treatment and welding. This eliminates the risk of intergranular corrosion that occurs after general heat treatment and welding. Due to the high content of chromium, nickel and molybdenum and the addition of copper, 904L can be passivated even in reducing environments such as sulfuric acid and formic acid.