+The ferrite dual phase structure has similar contents of both phases, thus possessing the characteristics of both austenitic stainless steel and ferritic stainless steel. The yield strength can reach 400Mpa~550MPa，It is twice that of ordinary austenitic stainless steel. Compared with ferritic stainless steel, duplex stainless steel has higher toughness, lower brittle transition temperature, significantly improved intergranular corrosion resistance and welding performance; At the same time, it retains some characteristics of ferritic stainless steel, such as 475 ℃ brittleness, high thermal conductivity, low coefficient of linear expansion, superplasticity, and magnetism. Compared with austenitic stainless steel, duplex stainless steel has higher strength, especially significantly improved yield strength, and significant improvements in properties such as pitting corrosion resistance, stress corrosion resistance, and corrosion fatigue resistance.
Cr18 type, Cr23 (excluding Mo) type, Cr22 type, and Cr25 type. For Cr25 duplex stainless steel, it can be divided into ordinary type and super duplex stainless steel, among which Cr22 type and Cr25 type are more commonly used. The duplex stainless steel used in China is mostly produced in Sweden, with specific grades including 3RE60 (Cr18 type), SAF2304 (Cr23 type), SAF2205 (Cr22 type), and SAF2507 (Cr25 type).