904L is an
austenitic stainless steel. Though notably softer than
316L, its molybdenum addition gives it superior resistance to localized attack (pitting and crevice corrosion) by chlorides and greater resistance reducing acids and in particular its copper addition gives it useful corrosion resistance to all concentrations of sulphuric acid. Its high alloying content also gives it greater resistance to chloride
stress corrosion cracking, but it is still susceptible. Its low carbon content makes it resistant to sensitization by welding and which prevents
intergranular corrosion
In materials science, intergranular corrosion (IGC), also known as intergranular attack (IGA), is a form of corrosion where the boundaries of crystallites of the material are more susceptible to corrosion than their insides. (''Cf.'' transgranu ...
.
It has applications in piping systems, pollution control equipment, heat exchangers, and bleaching systems.
Omega SA
Omega SA is a Swiss luxury watchmaker based in Biel/Bienne, Switzerland. Founded by Louis Brandt in La Chaux-de-Fonds in 1848, the company formerly operated as ''La Generale Watch Co.'' until incorporating the name ''Omega'' in 1903, becoming ...
experimented with 904L or 'Uranus Steel' with the PloProf dive watches in 1971-72. The inspiration came from French deep sea diving company COMEX, who used this steel in their diving bells due to superior corrosion resistance in salt water.
In 1985
Rolex
Rolex SA () is a British-founded Swiss watch designer and manufacturer based in Geneva, Switzerland. Founded in 1905 as ''Wilsdorf and Davis'' by Hans Wilsdorf and Alfred Davis in London, the company registered ''Rolex'' as the brand name of ...
began to utilize 904L grade steel in its watches.
Watch manufacturers chose to use this variety of steel because it takes a higher polish than other grades of steel and provides greater corrosion resistance.
Composition
*
Nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
, 23–28%
*
Chromium, 19–23%
*
Carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
, 0.02% maximum
*
Copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
, 1–2%
*
Molybdenum, 4–5%
*
Manganese
Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
, 2% maximum
*
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...
, 1.0% maximum
*
Iron
Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
, (balance)
Other names
*UNS N08904
*EN 1.4539
*SUS 904L
*SS2562
See also
*
SAF 2205
References
{{SAE International
Stainless steel