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Due to its excellent properties such as superior corrosion resistance, high strength, and ease of processing, duplex stainless steel is replacing austenitic stainless steel in various fields, offering great market prospects. The annual global production of duplex stainless steel accounts for only about 1% of the total stainless steel production. Since 1990, the annual growth rate of duplex stainless steel has been close to 17%, with annual production increasing from 24,000 tons in 1990 to 110,000 tons in 1999. Its products consist of hot-rolled sheets (accounting for 71% of total production), which are used to manufacture containers for welded pipes (representing 6% of the applications for duplex stainless steel) ； Cold-rolled sheets account for 14%, while seamless pipes account for 8%. The lower-grade duplex stainless steel (type 2304) among modern duplex stainless steels is a low-alloyed duplex stainless steel. It possesses good mechanical and physical properties, excellent resistance to stress corrosion cracking and other forms of corrosion, as well as good weldability; it can replace standard austenitic stainless steels 304/306 ； Standard duplex stainless steel (type 2205) is a moderately alloyed duplex stainless steel. Due to its excellent corrosion resistance, it is suitable for manufacturing equipment used in chloride and hydrogen sulfide environments; it is particularly appropriate for heat exchangers that use water containing chloride ions or brackish water as a cooling medium, as well as for equipment used with diluted sulfuric acid solutions and for storing and transporting organic acids. At the same time, 2205 duplex stainless steel, thanks to its high strength, serves as an ideal alternative to austenitic stainless steel in structural applications with heavy loads. Thanks to the excellent mechanical properties and corrosion resistance of 2005 duplex stainless steel, it helps to reduce the life-cycle cost of equipment. Therefore, in many applications, 2205 stainless steel is an economical choice. Currently, it is the main member of the duplex stainless steel series, accounting for 80% of the world’s total production of duplex stainless steel ； Super duplex stainless steel (type 2507) is widely used in harsh corrosive environments, accounting for approximately 13% of the market share. Dual-phase stainless steel is widely used in various fields thanks to its unique advantages: Pulp and paper industry: The pulp and paper industry was the first manufacturing sector to utilize dual-phase stainless steel. Sulfuric acid and sulfurous acid cooking pots made of 304 and 316 austenitic stainless steels often end up being scrapped due to stress corrosion cracking, sometimes with a service life of only two months. At the same time, when the cooking pot is made of low-carbon steel, its wall thickness is as high as 43 mm, which results in a very high total weight for the pot. By using duplex stainless steel, corrosion resistance is achieved, strength is high, and the wall thickness can be significantly reduced. Since 1998, there has been an increasing use of containers made of duplex stainless steel in pulp and paper mills abroad, resulting in an **extended service life and excellent performance. Chemical processing industry: The chemical processing industry covers a very wide range of areas, and its operating conditions are relatively complex. Tanks for storing industrial wet phosphoric acid are usually made of 316L or 317L austenitic stainless steel, but with thick walls. Using duplex stainless steel 2205 provides almost twice the strength of 316L and 317L, and it allows for thinner wall thicknesses, thereby reducing the size and cost of storage tanks. At the same time, in industrial sulfuric acid environments, especially in the presence of chloride ions, 2205 exhibits better resistance to local corrosion than austenitic stainless steels. Food and beverage industry: Production in the food and beverage industry is generally carried out in hot solutions containing chloride ions. Duplex stainless steel has unique advantages in terms of resistance to stress corrosion cracking. Therefore, different duplex stainless steels can be selected depending on the application environment, but they also have an advantage over austenitic stainless steels in terms of total cost. Among them, SAF2304 is the cheapest. Currently, duplex stainless steel is used in the equipment of some sugar mills and breweries abroad. Transportation industry: Thanks to its high strength and excellent corrosion resistance, duplex stainless steel offers significant advantages when used in the construction of chemical carriers. It reduces the weight of the ship and lowers fuel consumption; in this regard, 22% chromium duplex stainless steel is the most commonly used. It can also meet the corrosion resistance requirements of the materials needed for the cargo carried. Construction industry: In coastal areas, the air is filled with gases evaporated from seawater (marine atmosphere). The chloride ion concentration in this marine atmosphere is much higher than that in inland air; therefore, a material resistant to seawater is required. And duplex stainless steel possesses this advantage in terms of corrosion resistance; at the same time, its high strength also helps to reduce weight. Currently, many offshore oil platforms use duplex stainless steel to manufacture explosion-proof walls. Some bridges and buildings abroad also use duplex stainless steel. Petrochemical industry: The corrosive conditions in the petrochemical and chemical industries are characterized by high reaction temperatures, and the media often contain high or moderate concentrations of chlorides, which can easily induce stress corrosion cracking in stainless steel. Therefore, in this field, not only duplex stainless steel is needed, but also super duplex stainless steel is required even more. The refining industry is one of the fields that makes extensive use of duplex stainless steel, which is primarily applied in units such as atmospheric and vacuum distillation, catalytic cracking, and hydrodesulfurization; it is used both domestically and internationally. Furthermore, duplex stainless steel is being used increasingly in the production of acidic gases and oils, mainly for manufacturing pipe linings, onshore and offshore pipeline systems, as well as heat exchangers. In addition, duplex stainless steel has also been successfully applied in wastewater treatment heat exchangers, hot water pipes, and water heaters. To date, China has developed 5 types of duplex stainless steels, all of which belong to the second generation of such steels. Only the 0Cr18Ni5Mo3Si2 steel has been adopted internationally and is produced on a large scale; the others are manufactured according to factory standards in limited quantities. Given the development level of duplex stainless steels in our country, as well as the production conditions and technical capabilities of relevant specialized steel mills, some domestically produced duplex stainless steels can serve as substitutes for imported ones. For example, in the technical upgrades, new constructions, and expansions of large and medium-sized fertilizer plants, domestic duplex stainless steels can be used to replace imported 316L and 329 steels, thereby enabling an upgrade and localization of the materials used in ammonium ammonium pump casings. Taigang and Pugang are the main domestic manufacturers of duplex stainless steel. The 2205 duplex stainless steel used in the Three Gorges Project is produced by companies such as Taiyuan Iron and Steel. However, the duplex stainless steel market still relies heavily on imported products from abroad. In industries where duplex stainless steel is most widely used, such as the chemical industry, the equipment is mostly imported, and thus the duplex stainless steel used in that equipment is also introduced from abroad. At present, China is able to produce thinner grades of duplex stainless steel that are required for certain specialized equipment, while thicker grades of this material still need to be imported