Types of austenitic stainless steel

Ferritic stainless steel uses ferritic stainless steel. The chromium content is 1 1%~30%, and it has a body-centered cubic crystal structure. This kind of steel generally does not contain nickel, and sometimes contains a small amount of elements such as molybdenum, titanium and niobium. This kind of steel has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance and excellent stress corrosion resistance, and is mostly used to manufacture parts resistant to atmospheric, steam, water and oxidative acid corrosion. This kind of steel has some disadvantages, such as poor plasticity, obviously reduced plasticity after welding and corrosion resistance, which limits its application. The application of refining technology outside the furnace (AOD or VOD) can greatly reduce the interstitial elements such as carbon and nitrogen, so this kind of steel is widely used. Austenite-ferrite duplex stainless steel is a stainless steel with about half austenite and half ferrite structure. In the case of low C content, Cr content is 18%~28%, and Ni content is 3%~ 10%. Some steels also contain alloying elements, such as molybdenum, copper, silicon, niobium, titanium and nitrogen. This steel has the characteristics of both austenitic and ferritic stainless steel. Compared with ferritic steel, it has higher plasticity and toughness, no brittleness at room temperature, significantly improved intergranular corrosion resistance and weldability, and maintained the brittleness, high thermal conductivity and superplasticity of ferritic stainless steel at 475℃. Compared with austenitic stainless steel, it has high strength and obviously improved intergranular corrosion resistance and chloride stress corrosion resistance. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-saving stainless steel. Martensite stainless steel is a kind of stainless steel whose mechanical properties can be adjusted by heat treatment. Generally speaking, it is a hardenable stainless steel. Typical brands are Cr 13, such as 2cr 13, 3cr 13, 4cr 13 and so on. After quenching, the hardness is high, and different tempering temperatures have different combinations of strength and toughness, which are mainly used for steam turbine blades, tableware and surgical instruments. According to different chemical compositions, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium-nickel steel. According to the different microstructure and strengthening mechanism, it can also be divided into martensite stainless steel, martensite and semi-austenite (or semi-martensite) precipitation hardening stainless steel and martensite aging stainless steel. For product inspection, understanding the source and organizational performance of products is the best means of nondestructive testing, and it is also the innovation of nondestructive testing practitioners.