-Martensitic stainless steel , austenitic Stainless Steel and duplex stainless steel
-1.Austenitic Stainless Steel：
It contains more than 18% of chromium, also contains about 8% of nickel. And a small amount of molybdenum, titanium, nitrogen and other elements. Which has good overall performance of corrosion resistant variety of media. And its normal grades are: 1Cr18Ni9、0Cr19Ni9 and others. 0Cr19Ni9 contains C<0.08%. It contains amount of Ni and Cr. The steel was austenitic state at room temperature. Such steel has good ductility, toughness, weld ability and corrosion resistance. As a result which has good corrosion resistance in both oxidizing and reducing media.
Consequently we use the steel to make equipments anti nitric acid. Such as anti corrosion containers and equipment lining, transport pipelines. And also some parts of anti nitric acid corrosion. Austenitic stainless steel commonly treated by solution treatment. The heatment process is heating to the upcoming 1050 ~ 1150 ℃. Then cooled to obtain single- phase austenite.
-2. Duplex stainless steel: It has the advantages of both austenitic and ferritic stainless steel. And also has super plasticity. Austenitic and ferritic stainless steel is of about half. In the case of containing a low C, Cr content of 18% ~ 28%, Ni content of 3% to 10%. Some steel further contains Mo, Cu, Si, Nb, Ti, N and other alloying elements. It has both austenitic l and ferritic stainless steel features. Compared with ferrite it has higher ductility and toughness. No brittle at room temperature. Consequently it significantly improves resistance to intergranular corrosion and welding properties. Meanwhile it maintains 475 ℃ brittleness of ferritic stainless steel. And also has high thermal conductivity, with super plastic characteristics.
Compared with the austenitic stainless steel it has high strength. And similarly has significantly improvement in anti corrosion. They are resistance to intergranular corrosion and chloride stress corrosion. As a result duplex stainless steel has excellent resistance to pitting corrosion. And also it is a nickel saving stainless steel.
-3. Martensitic stainless steel: Martensitic stainless steel has high strength. But ductility and weld ability are poor. Martensitic stainless steel normal grades are: 420、430、410、409 and others. Due to higher carbon contents Martensitic stainless steel has a high strength, hardness and wear resistance. But somewhat less corrosion resistance. Martensitic stainless steel are normally used for some parts which require higher mechanical performance and general corrosion requirements. Such as springs, turbine blades, valves of hydraulic machines. Such steel is all after heat treatment like quenching, tempering.