Duplex stainless steel has the characteristics of both austenitic stainless steel and ferritic stainless steel because it has austenitic + ferrite duplex structure, and the content of the two phase structures is basically the same. The yield strength can reach 400Mpa ~ 550MPa, which is twice that of ordinary austenitic stainless steel. Compared with ferritic stainless steel, duplex stainless steel has high toughness, low brittle transition temperature, and significantly improved intergranular corrosion resistance and welding performance. At the same time, it retains some characteristics of ferritic stainless steel, such as 475°C brittleness, high thermal conductivity, small linear expansion coefficient, superplasticity and magnetism. Compared with austenitic stainless steel, duplex stainless steel has high strength, especially the yield strength is significantly improved, and the properties of porosity resistance, stress corrosion resistance, corrosion fatigue resistance and other properties are also significantly improved.