Duplex stainless steel is a special type of stainless steel named for the fact that it contains about 50% ferrite and 50% austenite in its microstructure. This unique structure gives duplex stainless steel a range of excellent properties:
Chemical compositionThe main alloying elements of duplex stainless steel include chromium (Cr), nickel (Ni), molybdenum (Mo), nitrogen (N), etc. For example, the typical chemical composition of the common duplex stainless steel 2205 (UNS S31803 S32205) is: chromium content of about 22%, nickel content of about 6%, molybdenum content of about 3%, and nitrogen content of about 014%-0.22%。
Corrosion resistanceDuplex stainless steel has excellent resistance to pitting, crevice corrosion and stress corrosion cracking, especially in chloride ion environment. Its corrosion resistance is superior to that of general austenitic stainless steels and offers a more economical option in many applications than super austenitic stainless steels.
High intensityDue to the presence of both ferritic and austenitic structures, the yield strength and tensile strength of duplex stainless steels are significantly higher than those of ordinary austenitic stainless steels, which can often reach more than 500 MPa, allowing the use of thinner wall thicknesses in the design and saving material costs.
Good toughness: Although duplex stainless steels are not as tough as pure austenitic stainless steels, they still have good low-temperature impact toughness while maintaining high strength.
Welding performanceAlthough the welding of duplex stainless steels requires a certain amount of skill to avoid harmful phase precipitation in the heat-affected zone, the good performance of the welded joints can be ensured with the correct welding methods and process control.
Fields of applicationDuplex stainless steel is widely used in oil and gas, chemical industry, marine engineering, bridge construction, food processing, pharmaceutical equipment and other industries, as the preferred material for pipes, containers, valves, pumps, structural parts and other components.
Classification and development: Depending on the alloy composition and corrosion resistance requirements, duplex stainless steels are available in a variety of grades, such as standard duplex stainless steel 2205, super duplex stainless steels such as 2507 (UNS S32750), and other high-performance duplex stainless steel varieties optimized for special environments.
In conclusion, duplex stainless steel, with its comprehensive superior mechanical properties and corrosion resistance, plays an important role in modern industrial production, providing a reliable solution for structural components under complex working conditions.