Duplex stainless steel is a type of stainless steel composed of approximately equal proportions of any two of the following phases: austenite, ferrite, and martensite. However, it typically refers to austenitic-ferritic duplex stainless steel. It combines the characteristics of both austenitic and ferritic stainless steels, offering excellent comprehensive mechanical properties, high strength, and high toughness; good resistance to crevice corrosion, pitting corrosion, and stress corrosion cracking; strong resistance to uniform corrosion; good weldability with low susceptibility to hot cracking; high thermal conductivity and low coefficient of linear expansion. It is widely used in applications such as catalytic tube bundles in tubular reactors for methanol production; preheater tube bundles for sulfate digestion in the pulp and paper industry; oil and gas gathering and transportation pipelines for offshore and onshore petroleum; condensers in vinyl chloride production; and heat exchanger tubes in crude oil desalination units.