Grade 904L stainless steel is a non-stabilized austenitic stainless steel with low carbon content. This high alloy stainless steel is added with copper to improve its resistance to strong reducing acids, such as sulphuric acid. The steel is also resistant to stress corrosion cracking and crevice corrosion. Grade 904L is non-magnetic, and offers excellent formability, toughness and weldability.
Grade 904L contains high amounts of expensive ingredients, such as molybdenum and nickel. Today, most of the applications that employ grade 904L are replaced by low-cost duplex stainless steel 2205.
|Grade||Tensile Strength (MPa) min||Yield Strength 0.2% Proof (MPa) min||Elongation (% in 50mm) min||Hardness|
|Rockwell B (HR B)||Brinell (HB)|
|904L.||490||220||36||70-90 typical||70-90 typical|
|Grade||Density(kg/m3)||Elastic Modulus(GPa)||Mean Co-eff of Thermal Expansion||Thermal Conductivity(W/m.K)||Specific Heat 0-100oC(J/kg.K)||Elec Resistivity|
|0-100ÃÆâÃâÂ°C||0-315ÃÆâÃâÂ°C||0-538ÃÆâÃâÂ°C||At 20ÃÆâÃâÂ°C||At 500ÃÆâÃâÂ°C|
|Grade||UNS No||Old British||Euronorm||Swedish SS||Japanese JIS|
Grade 904L stainless steels have excellent resistance to warm seawater and chloride attack. The high resistance of grade 904L against stress corrosion cracking is due to the presence of high amounts of nickel in its composition. Moreover, the addition of copper to these grades develops resistance to sulphuric acid and other reducing agents in both aggressive and mild conditions.
The corrosion resistance of grade 904L is intermediate between super austenitic grades, with 6% molybdenum content, and standard 316L austenitic grades. Grade 904L is less resistant to nitric acid than grades 304L and 310L, which are free of molybdenum. This steel grade needs to be solution treated following cold working, to achieve maximum stress corrosion cracking resistance under critical environments.
Grade 904L stainless steels offer good oxidation resistance. However, the structural stability of this grade collapses at high temperatures, particularly above 400ÃÆâÃâÂ°C.
Grade 904L stainless steels can be solution heat-treated at 1090 to 1175ÃÆâÃâÂ°C, following by rapid cooling. Thermal treatment is suitable for hardening these grades.
Welding of grade 904L stainless steels can be performed using all conventional methods. This grade does not require pre-heat and post-weld heat treatments. Grade 904L can be subjected to hot cracking in constrained weldment. Grade 904L electrodes and rods are used for welding grade 904L steels according to AS 1554.6.
Grade 904L stainless steels are high purity steels with low sulphur content. They can be machined using any standard methods. These grades can be readily bent to a small radius under cold conditions. Although subsequent annealing is not required in most cases, it should be carried out when the fabrication is performed under severe stress corrosion cracking conditions.