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Duplex stainless steel (DSS) is a stainless steel with a duplex structure in which the ferrite phase and the austenite phase each account for about half of the solid solution structure. Due to its unique microstructure characteristics, through the correct control of chemical composition and heat treatment process, the excellent toughness of austenitic stainless steel is combined with the high strength and chloride stress corrosion resistance of ferritic stainless steel. Stainless steel combines the advantages of two phases and is used more and more widely around the world. At present, the output of duplex stainless steel in the world is 150,000 to 400,000 tons, although it only accounts for 1% to 3% of the total output of stainless steel, but the average annual growth rate has been rapid in the past 10 years, which has increased by 6 times from 2005 to 2008. It is widely used in oil and gas, chemical industry, fresh water purification, paper and pulp, food and light industry, as well as structural parts such as construction and buildings.
The current development of duplex stainless steel has gone through three generations: the first generation of DSS is represented by 3RE60 steel developed in Sweden in the mid-1960s. This steel can be used as a chloride ion stress corrosion resistant environment, but has the problem of welding heat affected zone; The second generation of DSS was developed after the 1970s, combined with the development of AOD and VOD refining technologies, and has the characteristics of ultra-low carbon and nitrogen content. The third generation of DSS is the ultra-low carbon, high molybdenum, high nitrogen content super duplex stainless steel (SuperDSS, SDSS) developed in the late 1980s. Its representative grades include SAF2507, UR52N+, ZERON100, etc.
Since the development of the third generation of super duplex stainless steels, they have cost advantages compared with super austenitic stainless steels and nickel-based alloys with similar properties, while combining excellent mechanical properties and high corrosion resistance. , so the application in industries such as oil and gas fields, petrochemical and chemical processing is growing rapidly. However, in areas with more severe corrosive environments, such as long-term service conditions in hot sea water, and in marine and deep-sea areas with higher requirements for the comprehensive performance of corrosion resistance/mechanical properties, such as wellheads with improved oil and gas recovery methods The corrosion resistance and mechanical properties of duplex stainless steel still cannot fully meet the requirements for use in control systems, deep-sea submarine pipelines and pipeline cables and other working conditions. In addition, from the perspective of cost control, by reducing the thickness of the design, the end user can reduce the cost, which puts forward a demand for higher-strength materials.
Therefore, with the continuous improvement of people's requirements and the development of duplex stainless steel in recent years, a new generation of duplex stainless steel material with higher strength and better corrosion resistance - super duplex stainless steel came into being and has been developed and applied. For more professional information, please continue to pay attention to our welded stainless steel pipe manufacturers.