These are stainless steels containing relatively high chromium (between 18 and 28%) and moderate amounts of nickel (between 4.5 and 8%). The nickel content is insufficient to generate a fully austenitic structure and the resulting combination of ferritic and austenitic structures is called duplex. Most duplex steels contain molybdenum in a range of 2.5 - 4%.

Basic properties

  • High resistance to stress corrosion cracking
  • Increased resistance to chloride ion attack
  • Higher tensile and yield strength than austenitic or ferritic steels
  • Good weldability and formability

Common uses

  • Marine applications, particularly at slightly elevated temperatures
  • Desalination plant
  • Heat exchangers
  • Petrochemical plant

Common duplex grades and their applications


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