Duplex steel
The austenitic-ferritic, also called duplex, have a mixed structure of austenite and ferrite. This is a chrome steel hybrid: the content of chromium is 18 to 26% and nickel 4.5 to 6.5%, an amount insufficient to determine fully austenitic microcrystalline structure (so that it remains part of ferritic) . Almost all its variants contain between 2.5 and 3% molybdenum. There are also forms of Duplex, called "poor" that do not contain molybdenum and nickel levels were lower by 4.5%.
The basic properties are:
microcrystalline structure known as the special duplex, austenitic and ferritic, which gives more resistance to stress corrosion cracking;
greater degree of passivation for the highest chromium content (and the presence of molybdenum) and therefore better resistance to pitting corrosion (pitting) than 18-8 stainless;
good weldability and forgeability;
high tensile strength and yield strength.
The most common uses are: heat exchangers, material handling equipment, tanks and tanks for liquids with high concentration of chlorine, sea water chillers, desalination plants for food and brine-rich groundwater and aggressive.
