Stainless steel weak corrosive medium of air, steam, water and acid, alkali, salt and other chemical etching medium corrosion resistance, also known as acid-resistant. Practical applications, it is often weak resistance to corrosion medium corrosion of steel called , the corrosion of steel known as the acid-resistant steel and the chemical resistance.
Due to both differences in the chemical composition, the former does not necessarily resistant to chemical corrosion, while the latter generally has asex. The corrosion resistance of stainless steel depending on the alloying elements contained in the steel. Stainless steel basic alloying elements as well as nickel, molybdenum, titanium, niobium, copper, nitrogen, etc., in order to meet the requirements of the various uses of the organization and performance of stainless steel. Stainless steel, easy ion etching by chlorine, chromium, nickel, chlorine is the same elements, same elements will be interchangeable assimilation thereby forming the corrosion of stainless steel.
- Major categories
Stainless steel often divided by organizational status: martensitic steels, ferritic steels, austenitic steels, austenitic – ferritic (duplex) stainless steel and precipitation hardening stainless steel, etc.. Can components be divided into: chromium stainless steel, chrome-nickel stainless steel and stainless steel and other CrMnN.
- ferritic stainless steels: chromium 12% to 30%. Its corrosion resistance, toughness and weldability with the increase of the amount of chromium improved resistance to chloride stress corrosion better than other types of stainless steel. Fall into this category Crl7, Cr17Mo2Ti, Cr25, Cr25Mo3Ti, Cr28, etc.. Ferritic stainless steel because of the high chromium content, corrosion resistance and oxidation resistance are better, but poor mechanical properties and process performance, used for the uneven force acid structure and for the use of antioxidant steel. Type of steel resistant to corrosion in the atmosphere, nitric acid, and the salt solution, and has good high temperature oxidation resistance, and thermal expansion coefficient for nitric acid and food factory equipment, parts of the work can also be produced at high temperatures, such as gas turbine parts .
- the austenitic stainless steel is greater than 18%: chromium, also contain about 8% of nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Good overall performance, resistance to a variety of media corrosion. Commonly used grades of austenitic stainless steel such as 1Cr18Ni9, 0Cr19Ni9. 0Cr19Ni9 steel Wc <0.08%, Steel No. marked as “0″. The type of steel contains a large amount of Ni and Cr, the steel at room temperature, austenitic state. Type of steel has good ductility, toughness, weldability and corrosion resistance, good corrosion resistance in oxidizing and reducing medium used to produce acid-resistant equipment, such as corrosion of containers and equipment lined pipeline resistance nitrate equipment parts. Austenitic stainless steels generally use the solution treatment, upcoming steel heated to 1050 to 1150 ℃, and then water-cooled, single-phase austenite.
- austenitic – ferritic duplex stainless steel: the advantages of both austenitic and ferritic stainless steel and has superplastic. Austenitic and ferritic structure each account for about half of the stainless steel. Cr content of 18% to 28%, the Ni content in the 3% to 10% in the case of C-containing lower. Some steel containing alloying elements such as Mo, Cu, Si, Nb, Ti, N. Both the characteristics of the austenitic and ferritic stainless steel type of steel, compared with ferrite, higher ductility, toughness, no ductility at room temperature, the resistance to intergranular corrosion and welding performance were significantly improved, at the same time maintain iron 475 ℃ brittleness of ferritic stainless steel and high thermal conductivity with superplastic characteristics. Compared with austenitic stainless steel, high strength and resistance to intergranular corrosion and resistance to chloride stress corrosion. Duplex stainless steel has excellent resistance to pitting corrosion, and also a section nickel stainless steel.
- martensitic stainless steel: high strength, but poor ductility and weldability. 1Cr13, 3Cr13 martensitic stainless steel commonly used grades, high carbon, it has high strength, hardness and wear resistance, corrosion resistance is somewhat less for high mechanical performance requirements, corrosion resistance requirements Usually some parts, such as a spring, turbine blades, the hydraulic machine valve. This type of steel is used after quenching and tempering treatment.
- Precipitation hardening stainless steel: the matrix austenite or martensite, precipitation hardening grades of stainless steel commonly used 04Cr13Ni8Mo2Al. Through precipitation hardening (also known as age hardening) of stainless steel handle make it hard (strong).