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