Stainless steel often according to the organization state is divided into: martensitic steel, ferritic steel, austenitic steel, austenitic - ferrite (two-phase) stainless steel and precipitation hardening stainless steel. In addition, according to the composition is divided into: chrome stainless steel, chrome nickel stainless steel and chromium manganese nitrogen stainless steel. The following are the same as the ones,
1, ferritic stainless steel: chromium 12% to 30%. Its corrosion resistance, toughness and weldability with the increase in chromium content increased resistance to chloride stress corrosion resistance is better than other types of stainless steel. Belongs to this category are Crl7, Cr17Mo2Ti, Cr25, Cr25Mo3Ti, Cr28 and so on. Ferritic stainless steel because of high chromium content, corrosion resistance and oxidation resistance are better, but the mechanical properties and process performance is poor, and more for the resistance of acid structure and for the use of anti-oxidation steel. This kind of steel can resist the corrosion of atmospheric, nitric acid and brine solution, and has high temperature oxidation resistance, thermal expansion coefficient is small, for nitric acid and food factory equipment, can also be made in high temperature work parts, such as gas turbine parts The
2, austenitic stainless steel: chromium greater than 18%, also contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Comprehensive performance is good, can withstand a variety of media corrosion. Austenitic stainless steel commonly used grades are 1Cr18Ni9,0Cr19Ni9 and so on. 0Cr19Ni9 steel Wc <0.08%, steel marked "0". This kind of steel contains a lot of Ni and Cr, so that steel at room temperature was austenitic state. This type of steel has good plasticity, toughness, weldability and corrosion resistance. It is good for corrosion resistance in oxidizing and reducing media. It is used to make acid resistant equipment such as corrosion resistant containers and equipment lining, Nitric acid equipment parts and so on. Austenitic stainless steel is generally treated with solution, that is, the steel heated to 1050 ~ 1150 ℃, and then water-cooled, in order to obtain single-phase austenite.
3, austenitic - ferrite duplex stainless steel: both austenitic and ferritic stainless steel advantages, and has a superplasticity. Austenitic and ferrite organizations account for about half of the stainless steel. In the case of low C, Cr content of 18% to 28%, Ni content of 3% to 10%. Some steel also contains Mo, Cu, Si, Nb, Ti, N and other alloying elements. The steel has the characteristics of austenitic and ferritic stainless steel, compared with the ferrite, plasticity, higher toughness, no room temperature brittleness, resistance to intergranular corrosion and welding performance are significantly improved, while also maintaining iron Qualified stainless steel 475 ℃ brittleness and high thermal conductivity, with superplasticity and so on. Compared with the austenitic stainless steel, high strength and resistance to intergranular corrosion and resistance to chloride stress corrosion has improved significantly. Duplex stainless steel has excellent resistance to pitting corrosion resistance, but also a section of nickel stainless steel.
4, martensitic stainless steel: high strength, but poor plasticity and weldability. Martensitic stainless steel commonly used grades are 1Cr13, 3Cr13, etc., because of high carbon content, it has a high strength, hardness and wear resistance, but slightly less corrosion resistance, for high mechanical properties, corrosion resistance Requirements of some general parts, such as springs, steam turbine blades, water pressure valves and so on. This type of steel is used after quenching and tempering.
5, precipitation hardening stainless steel: the matrix is austenitic or martensite, precipitation hardening stainless steel commonly used grades are 04Cr13Ni8Mo2Al and so on. Which can be hardened (also known as aging hardening) treatment to make it hard (strong) of stainless steel.