Duplex stainless steel development

Time: 2018-07-14
Since France obtained its first patent in 1935, the development of duplex stainless steel experienced three generations.The first generation of duplex stainless steel is represented by 329 steel developed in the United States in the 1940s. The first-generation duplex stainless steels contains high chromium and molybdenum and has good resistance to localized corrosion. The 3RE60 steel developed by Sweden in the mid-1960s is already an ultra-low carbon duplex stainless steel.
Since the 1970s, the development of secondary refining technology and the discovery of the important role of nitrogen in maintaining phase equilibrium and improving corrosion resistance have become important milestones for duplex stainless steels. At that time, ultra-low carbon type N-containing second-phase duplex stainless steel was developed, representing 2205 steel grades.On this basis, by further increasing the alloy content and PREN value the third-generation duplex stainless steel, super duplex stainless steel, was developed in the late 1980s. The PREN value of the third-generation duplex stainless steel is greater than 40, representing the brands SAF2507, UR52N+, ZERON100 and so on. This type of steel has a higher content of alloying elements such as chromium, nickel, molybdenum, and nitrogen. They better balance the ratio between ferrite and austenite, giving them better corrosion resistance and higher strength.
After entering the 21st century, special super duplex stainless steel and economical duplex stainless steel have become two important development directions for duplex stainless steel. Special super duplex stainless steels contain higher alloying elements for higher strength and better corrosion resistance. The economical duplex stainless steel has the characteristics of low nickel content and no molybdenum or only a small amount of molybdenum. The lower cost makes economical duplex stainless steel a strong competitor for 304, 316 austenitic stainless steels and even 2205 duplex stainless steels. At the same time, it has also become an important development direction and growth point of duplex stainless steel.