Structure and type of duplex stainless steel

Duplex stainless steel has the characteristics of austenitic stainless steel and ferritic stainless steel because of its austenitic + ferritic biphase structure, and the content of the two phase structures is basically equivalent. 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 higher toughness, lower brittleness transition temperature, higher intergranular corrosion resistance and higher weldability. At the same time, it retains some characteristics of ferritic stainless steel, such as 475℃ brittleness, high thermal conductivity, small linear expansion coefficient, superplasticity and magnetism. Compared with austenitic stainless steel, the strength of duplex stainless steel is high, especially the yield strength is significantly improved, and the performance of pitting corrosion resistance, stress corrosion resistance, corrosion fatigue resistance is also significantly improved.
Duplex stainless steel according to its chemical composition classification, can be divided into Cr18 type, Cr23 (without Mo) type, Cr22 type and Cr25 type four categories. For Cr25 type duplex stainless steel can be divided into ordinary type and super duplex stainless steel, of which Cr22 type and Cr25 type are more used. The biphase stainless steel used in China is mostly produced in Sweden, and the specific grades are: 3RE60 (Cr18), SAF2304 (Cr23), SAF2205 (Cr22), SAF2507 (Cr25).