Duplex stainless steel Filter element for Filtration
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Duplex stainless steel (DSS) refers to stainless steel in which ferrite and austenite account for about 50% respectively. Generally, the content of less phase also needs to reach 30% at least. When the content of C is low, the content of Cr is 18% ~ 28%, and the content of Ni is 3% ~ 10%. Some steels also contain Mo, Cu, Nb, Ti, N and other alloy elements.
This kind of steel has the characteristics of both austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, significantly improved intergranular corrosion resistance and welding performance. At the same time, it also maintains the 475 ℃ brittleness, high thermal conductivity and Superplasticity of ferritic stainless steel. Compared with austenitic stainless steel, it has high strength and significantly improved resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel saving stainless steel.
Due to the characteristics of two-phase structure, by correctly controlling chemical composition and heat treatment process, duplex stainless steel has the advantages of both ferritic stainless steel and austenitic stainless steel. It combines the excellent toughness and weldability of austenitic stainless steel with the high strength and resistance of ferritic stainless steel
Combined with chloride stress corrosion properties, it is these superior properties that make duplex stainless steel develop rapidly as a weldable structural material. Since the 1980s, it has become a kind of steel juxtaposed with martensitic, austenitic and ferritic stainless steel.
Duplex stainless steel has the characteristics of both austenitic stainless steel and ferritic stainless steel because it has austenitic + ferritic duplex structure and the content of the two phases 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 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 brittleness at 475 ℃, high thermal conductivity, low coefficient of linear expansion, superplasticity and magnetism. Compared with austenitic stainless steel, duplex stainless steel has higher strength, especially the yield strength is significantly improved, and the properties of pitting corrosion resistance, stress corrosion resistance and corrosion fatigue resistance are also significantly improved.
According to their chemical composition, duplex stainless steel can be divided into 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. Most duplex stainless steels used in China are made in Sweden, and the specific brands are: 3re60 (Cr18), saf2304 (cr23), SAF2205 (Cr22) and SAF2507 (Cr25).