Stainless steel is often classified according to the state of the organization: martensitic steel, ferritic steel, austenitic steel, austenitic-ferritic (duplex) stainless steel and precipitation hardened stainless steel. In addition, it can be divided into: chromium stainless steel, chrome nickel stainless steel and chromium manganese nitrogen stainless steel.
Stainless steel 1, ferritic stainless steel: 12% to 30% chromium. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and its resistance to chloride stress corrosion is better than other types of stainless steel. Among these, there are Crl7, Cr17Mo2Ti, Cr25, Cr25Mo3Ti, Cr28 and the like. Because of its high chromium content, ferritic stainless steel has better corrosion resistance and oxidation resistance, but its mechanical properties and process performance are poor. It is mostly used for acid-resistant structures with little stress and used as anti-oxidation steel.
This kind of steel can resist the corrosion of atmospheric, nitric acid and saline solution, and has the characteristics of high temperature oxidation resistance and small thermal expansion coefficient. It can be used in nitric acid and food factory equipment, and can also manufacture parts working at high temperature, such as gas turbine parts. .
Title2, austenitic stainless steel:
The title contains more than 18% chromium and contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Good overall performance, resistant to a variety of media corrosion. Commonly used grades for austenitic stainless steels are 1Cr18Ni9, 0Cr19Ni9, and the like. 0Cr19Ni9 steel has Wc<0.08%, and the steel number is marked as “0”. This type of steel contains a large amount of Ni and Cr, making the steel austenitic at room temperature. This type of steel has good plasticity, toughness, weldability, corrosion resistance and non-magnetic or weak magnetic properties. It has good corrosion resistance in both oxidizing and reducing media. It is used to make acid-resistant equipment such as corrosion-resistant containers and equipment. Lining, conveying pipes, equipment parts resistant to nitric acid, etc., can also be used as the main material of stainless steel watches and clocks. Austenitic stainless steels are generally treated by solution treatment, that is, the steel is heated to 1050 to 1150 ° C, and then water-cooled or air-cooled to obtain a single-phase austenite structure.
3. Austenitic - ferritic duplex stainless steel:
The title combines the advantages of austenitic and ferritic stainless steels and is superplastic. Austenitic and ferrite structures each account for about half of the stainless steel. In the case of a lower C content, the Cr content is between 18% and 28%, and the Ni content is between 3% and 10%. Some steels also contain alloying elements such as Mo, Cu, Si, Nb, Ti, and N. This type of steel combines the characteristics of austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity, toughness, no room temperature brittleness, resistance to intergranular corrosion and weldability, and iron retention. The 475 ° C brittleness and high thermal conductivity of the stainless steel are characterized by superplasticity. Compared with austenitic stainless steel, it has high strength and resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel has excellent pitting resistance and is also a nickel-saving stainless steel.
4. Martensitic stainless steel:
The title is high in strength but poor in plasticity and weldability. The commonly used grades of martensitic stainless steels are 1Cr13, 3Cr13, etc., because of the high carbon content, they have high strength, hardness and wear resistance, but the corrosion resistance is slightly poor, which is used for high mechanical properties and corrosion resistance. General parts are required, such as springs, steam turbine blades, hydraulic valve valves, etc. This type of steel is used after quenching and tempering. Annealing and annealing are required after stamping.
5. Precipitation hardening stainless steel:
The title base is austenite or martensite, and the commonly used grades of precipitation hardened stainless steel are 04Cr13Ni8Mo2Al. It can be treated with precipitation hardening (also known as age hardening) to make it hard (strong) stainless steel.