Development History of Dual Phase Steel

 　　The development of dual phase steel originated in the 1930s. In 1936, a steel grade called Uranus50 obtained the first dual phase steel patent in France, and to this day, dual phase steel has developed into three generations of CV548.

　　The first generation of dual phase steel is represented by Sweden's 3RE60 and the United States' AISI329. 3RE60 is a dual phase steel developed specifically to improve its resistance to chloride stress corrosion cracking. AISI329 dual phase steel is widely used in heat exchanger pipelines in nitric acid plants. The first generation dual phase steel has good performance characteristics, but has limitations in the welded state. The Heat-affected zone of the weld has low toughness due to excessive ferrite, and its corrosion resistance is significantly lower than that of the base metal. These limitations limit the application of the first generation dual phase steel to specific applications in non welded states.

　　The invention of argon oxygen decarburization, a stainless steel refining process in 1968, made it possible to produce a series of new stainless steel grades. One of the many advancements brought about by AOD is the addition of alloying element nitrogen. Adding nitrogen to dual phase steel can make the toughness and corrosion resistance of Heat-affected zone in welding state close to the properties of base metal, and nitrogen also reduces the formation rate of harmful intermetallic phase. Nitrogen containing dual phase steel is called the second generation dual phase steel. 2205 dual phase steel is the representative steel of the second generation of dual phase steel and is widely used in offshore oil platform, chemical industry, papermaking and other fields.

　　The super duplex steel developed in the late 1980s belongs to the third generation of duplex steel, with representative grades such as 2507 duplex steel, UR52N, Zeron100, etc. This type of steel is characterized by low carbon content, high molybdenum and nitrogen content. This type of steel has excellent resistance to pitting corrosion. The pitting equivalent is greater than 40.

　　From the current research and production level, Europe and America are at a leading level in the research and development, production, and user recognition of dual phase steel. Their representative companies include Outokumpu and Sandvik from Sweden, as well as American manufacturers. In Asia, Japan and South Korea are the main producers of dual phase steel.

　　The research on dual phase steel in China began in the mid-1970s, and the Beijing Iron and Steel Research Institute was the first to start this research work. The developed 00Cr18Ni5Mo3Si2 has been included in the national standard. At present, Taigang and Baosteel are capable of supplying commercial materials in China. Taigang began developing 2205 dual phase steel in the late 1990s and launched its products in the market in 2005. Baosteel also began developing Cr22 dual phase steel in 2006. It is worth noting that some large domestic private enterprises are also at the forefront of research and promotion in the field of dual phase steel, such as Jiuli Group and Wujin Steel Pipe.

　　In recent years, with the continuous rise and significant fluctuations of Ni prices, dual phase steel has shown a trend of dual development. Firstly, fully leverage the advantages of dual phase steel resource conservation and develop economical dual phase steel such as 2101. Its development direction is to replace the traditional 300 series austenitic stainless steel, and its design concept replaces precious metals such as Ni and Mo with Mn and N elements. Secondly. It is to fully utilize the high strength and good corrosion resistance characteristics of dual phase steel, and develop super dual phase steel represented by 2507 to partially replace super austenitic stainless steels such as 904L and 254SMo.

　　In China, the main production of duplex steel is 2205, and the production of economical duplex stainless steel and super duplex stainless steel 2507 is constantly increasing. The production of super duplex stainless steel is in a state of continuous trial and application. The application field is also constantly expanding, while further consolidating its application in the petrochemical industry, it has also expanded its application in fields such as oil and gas transportation, chemical ship manufacturing, nuclear power, equipment manufacturing, construction, and continuously exploring the international market. From the development of dual phase steel both domestically and internationally, it can be seen that 2507 dual phase steel is a resource saving high-performance stainless steel product, and its production and application are in line with the future development direction of stainless steel.

　　Dual phase steel is also a high-tech and high value-added product. Its development and production not only reflect the technical level of stainless steel production enterprises, but also create more economic benefits for enterprises. It can be foreseen that the proportion of dual phase steel usage will further expand in the future.