Stainless Steel – Grade 904L (UNS N08904) Chemical formula Fe, <of 0.02% C, 19-23% Cr, 23-28% Ni, 4-5% Mo, <2.0% Mn, <1.0% Si , <0.045% P <0.035% S, 1.0-2.0% Cu
904L is a low carbon high alloy austenitic stainless steel is not stable. The addition of copper to this grade gives it greatly improved resistance to acids significantly reduced, especially sulfuric acid. It is also resistant to chloride attack – both pitting / crevice corrosion and stress corrosion cracking.
This layer is non-magnetic in all conditions and has excellent weldability and formability. Austenitic structure also gives these grades excellent toughness, even down to freezing temperatures.
904L no content are important components of nickel and molybdenum high cost. Many of the applications in which this class has done previously can also be made with lower costs in 2205 duplex stainless steel (S31803 or S32205), so it is used less common than before.
Important attributes of stainless steel 901
These properties are specified for flat rolled products (plate, sheet and coil) in ASTM B625. Similar nature but not necessarily identical specified for other products such as pipe, tube and bar in the corresponding specifications.
Although originally developed for its resistance to sulfuric acid it also has a very high resistance to a wide range of environments. A PRE of 35 indicates that the material has good resistance to warm sea water and other high chloride environments. High nickel content results in a better resistance to stress corrosion cracking than the standard austenitic grades. Council adds resistance to sulfuric acid and other reduction, particularly in the very aggressive “mid concentration” range.
In most environments 904L stainless steel with corrosion performance intermediate between the standard austenitic grades 316L and high alloy 6% molybdenum and similar “super austenitic” grades.
In aggressive nitric acid 904L has less resistance than grade molybdenum – 304L and 310L free like.
Good resistance to oxidation, but like other high grade alloys lose structural stability (precipitation of brittle phases such as sigma) at high temperatures. 904L should not be used above 400 ° C.
Treatment Solutions (annealing) – Heat from 1090 to 1175 ° C and cool rapidly. This class can not be hardened by heat treatment.
904L can be successfully welded by all standard methods. Care should be taken, such as strengthening layers completely austenitic, so is susceptible to hot cracking, especially in the limited weldments. No pre-heat should be used and in most cases the weld heat treatment is not necessary all. AS 1554.6 pre qualified class bar 904L and 904L welding electrodes.
904L is a high purity, low sulfur grade, and as such will not machine well. Even so the layers can be processed using standard techniques.
Bending to a small radius is easily done. In most cases this is performed cold. Next Incubate usually not necessary, although it should be considered if the fabrication is used in an environment where corrosive conditions serious stress cracking is predicted.
Applications of Stainless Steel 901
Typical applications include:
• Processing plant for sulfuric, phosphoric and acetic acid
• pulp and paper processing
• The composition of the gas plant scrub
• seawater cooling equipment
• Components Refinery
• Wires in electrostatic