1、 Introduction to duplex stainless steel
Duplex stainless steel (DSS) refers to the stainless steel with ferrite and austenite accounting for about 50% respectively, and the content of less phase generally needs to reach 30% at least. When the C content is low, the Cr content is 18% ~ 28%, and the Ni content is 3% ~ 10%. Some steels also contain alloying elements such as Mo, Cu, Nb, Ti and n.
This kind of steel has the characteristics of both austenitic and ferritic stainless steel. Compared with ferritic stainless steel, it has higher plasticity and toughness, no room temperature brittleness, significantly improved intergranular corrosion resistance and welding performance. Meanwhile, it also maintains the 475 ℃ brittleness of ferritic stainless steel, high thermal conductivity and superplasticity. Compared with austenitic stainless steel, it has high strength, and the resistance to intergranular corrosion and chloride stress corrosion is significantly improved. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel saving stainless steel.
2、 Chemical composition of duplex stainless steel
According to its chemical composition, duplex stainless steel can be divided into four types: Cr18, cr23 (excluding Mo), Cr22 and Cr25. Cr25 duplex stainless steel can be divided into ordinary and super duplex stainless steel, among which Cr22 and Cr25 are widely used.
3、 Grade of duplex stainless steel
The dual phase stainless steel used in China is mainly made in Sweden. The specific grades are: 3re60 (Cr18), saf2304 (cr23), SAF2205 (Cr22) and SAF2507 (Cr25)
4、 Welding material selection
According to the different requirements of corrosion resistance and joint toughness, select the welding rod matching the chemical composition of the base metal. For example, cr22ni9mo3 welding rod, such as E2209 welding rod, can be used for welding Cr22 dual phase stainless steel.
5、 Application field of duplex stainless steel welded pipe
Due to its special advantages, duplex stainless steel welded pipes are widely used in petrochemical equipment, seawater and wastewater treatment equipment, oil and gas pipelines, paper machinery and other industrial fields.
