Development of Duplex Stainless Steel Products

 Duplex stainless steel in the organization of the ferrite phase and austenite phase 50%, generally less content of at least also need to reach 30%. The development of duplex stainless steels began in the 1930s when the problem of intergranular corrosion of high carbon austenitic stainless steels was addressed. So far, duplex stainless steel has been developed to the 3rd generation:
1, the first generation: the United States in the 1940s developed the 329 stainless steel as the representative, is widely used in nitric acid plant heat exchanger pipe. In the mid-1960s, Sweden developed 3RE60 duplex steel (00Cr18Ni5Mo3N) designed to improve resistance to chloride corrosion, but is generally used for casting and forging because of its high carbon content.
2, the second generation: since the 1970s, with the secondary refining technology (AOD), vacuum refining technology (VOD) and the continuous development of continuous casting technology, ultra-low carbon (w (C) ≤ 0.03%) steel Production easier to achieve, 00Cr22Ni5Mo3N is the second generation of representatives of duplex stainless steel. The steel in the 20th century, 70 years by the successful development of Sweden, material grade SAF 2205, the corresponding US brand UNS S31803.
3, the third generation: the late 20th century, 80, the third generation of duplex stainless steel development success, the main brands have SAF2507 and so on. (W (C) = 0.01% ~ 0.02%, w (Mo) = 4.0%, w (N) = 0.3%), which has excellent pitting corrosion resistance, and its resistance to ultra-low carbon Pitting equivalent PREN greater than 40.

 
The 21st century, duplex stainless steel mainly in two directions: First, nickel, such as S32101, S32003 steel, the steel has good corrosion resistance, but also has lower production costs, can replace 304,316 stainless steel. Second, more resistant to corrosion, such as 2507,2906 super duplex stainless steel, with good resistance to pitting corrosion, stress corrosion resistance, can replace 904L austenitic stainless steel, nickel-based alloys.