Stainless steel is steel that does not easily rust. In fact, a part of stainless steel has both stainless and acid resistance (corrosion resistance). The stainless steel's stainless and corrosion resistance is due to the formation of a chromium-rich oxide film (passivation film) on its surface. This stainless steel and corrosion resistance are relative. Tests have shown that steel in the atmosphere, water and other weak media and nitric acid and other oxidizing media, its corrosion resistance increases with the increase of water content of chromium in the steel, when the chromium content reaches a certain percentage, the corrosion resistance of steel occurs Mutation, that is, from rust to rust, from corrosion resistance to corrosion. There are many ways to classify stainless steel. According to the room temperature structure classification, there are martensitic, austenite, ferritic and duplex stainless steel; according to the main chemical composition, can be divided into chromium stainless steel and chromium nickel stainless steel two major systems; by purpose There are nitric acid-resistant stainless steel, sulfuric acid-resistant stainless steel, seawater resistant stainless steel, etc., according to corrosion resistance type can be divided into corrosion resistant stainless steel, stress corrosion resistance is not {TodayHot} stainless steel, resistance to intergranular corrosion of stainless steel, etc.; classified by functional characteristics Can be divided into non-magnetic stainless steel, free-cutting stainless steel, low-temperature stainless steel, high-strength stainless steel and so on. Due to its excellent corrosion resistance, formability, compatibility, and toughness over a wide temperature range, stainless steel materials are widely used in industries such as heavy industry, light industry, daily necessities, and architectural decoration. . Austenitic stainless steels have austenitic stainless steel at room temperature. When the steel contains about 18% of Cr, 8% to 10% of Ni, and about 0.1% of C, it has a stable austenite structure. Austenitic chromium-nickel stainless steels include the famous 18Cr-8Ni steel and high Cr-Ni series steels developed on the basis of increasing Cr and Ni contents and adding Mo, Cu, Si, Nb, Ti and other elements. Austenitic stainless steels are non-magnetic and have high toughness and plasticity, but they have low strength and cannot be strengthened by phase transformation. They can only be strengthened by cold working. Such as adding S, Ca, Se, Te and other elements, it has good free-cutting properties. In addition to corrosion of such oxidation-resistant acid media, such steels may contain elements such as Mo and Cu that are resistant to corrosion by sulfuric acid, phosphoric acid, and formic acid, acetic acid, and urea. If the carbon content of such steel is less than 0.03% or contains Ti, Ni, it can significantly improve its resistance to intergranular corrosion. High-silicon austenitic stainless steel concentrated nitric acid may have good corrosion resistance. Because austenitic stainless steel has comprehensive and good comprehensive performance, it has been widely used in various industries. 316 and 316L Stainless Steels 316 and 317 Stainless Steels (see below for properties of 317 stainless steels) are molybdenum-containing stainless steels. The molybdenum content of 317 stainless steel is slightly higher than that of 316 stainless steel. Due to the molybdenum content in the steel, the overall performance of the steel is better than that of 310 and 304 stainless steel. Under high temperature conditions, when the concentration of sulfuric acid is lower than 15% and higher than 85%, 316 Stainless steel has a wide range of uses. 316 stainless steel also has good chloride attack properties, so it is commonly used in the marine environment. The maximum carbon content of 316L stainless steel is 0.03, which can be used in applications where annealing cannot be performed after welding and maximum corrosion resistance is required. Corrosion resistance is better than 304 stainless steel and has good corrosion resistance in the production of pulp and paper. And 316 stainless steel is also resistant to the erosion of the ocean and the aggressive industrial atmosphere. Heat resistance of 1600 degrees below the intermittent use and in 1700 degrees below continuous use, 316 stainless steel has good oxidation resistance. In the range of 800-1575 degrees, 316 stainless steel is preferably not continuously applied, but the stainless steel has good heat resistance when 316 stainless steel is continuously used outside this temperature range. The resistance to carbide precipitation of 316L stainless steel is better than that of 316 stainless steel, and the above temperature range can be used. The heat treatment is annealed at a temperature in the range of 1850-2050C, then rapidly annealed and then rapidly cooled. 316 stainless steel can not be hardened by heat treatment. Welding 316 stainless steel has good welding performance. All standard welding methods can be used for welding. Welding can be based on the use of 316Cb, 316L or 309Cb stainless steel filler rods or electrodes for welding. In order to obtain the best corrosion resistance, the welded section of 316 stainless steel needs post-weld annealing. If 316L stainless steel is used, post-weld annealing {HotTag} processing is not required. Typical applications Pulp and paper equipment heat exchangers, dyeing equipment, film processing equipment, pipelines, materials for the exterior of buildings in coastal areas. Ferritic stainless steel is mainly stainless steel with ferrite structure in use. Chromium content of 11% to 30%, with body-centered cubic crystal structure. This type of steel is generally nickel-free, and sometimes contains a small amount of elements such as Mo, Ti, and Nb. This type of steel has large thermal conductivity, small expansion coefficient, good oxidation resistance, and excellent resistance to stress corrosion, etc. , steam, water and oxidizing acid corrosion parts. Such steels have the disadvantages of poor plasticity, significantly reduced post-weld plasticity and corrosion resistance, which limits their application. The application of off-furnace refining technology (AOD or VOD) can greatly reduce the gap elements such as carbon, nitrogen, etc., thus making this kind of steel widely used. Austenitic-ferritic duplex stainless steel is about half of austenitic and ferritic stainless steel. In the case of lower C content, the Cr content is 18% to 28%, and the Ni content is 3% to 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 steels. Compared with ferrite, it has higher plasticity and toughness, no brittleness at room temperature, significantly improved resistance to intergranular corrosion and welding performance, and at the same time retains iron. The 475°C brittleness and high thermal conductivity of the ferritic stainless steel make it superplastic. Compared with austenitic stainless steels, they have high strength and resistance to intergranular corrosion and chloride stress corrosion resistance. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-stainless steel. Stainless steel, which can be adjusted to its mechanical properties by heat treatment of martensitic stainless steels, is, generally speaking, a type of hardenable stainless steel. Typical grades are Cr13 type, such as 2Cr13, 3Cr13, 4Cr13 and so on. High hardness after the fire, different tempering temperatures have different toughness combinations, mainly used for steam turbine blades, cutlery, surgical instruments. According to the difference in chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium nickel steel. According to different organization and strengthening mechanism, it can be divided into martensite stainless steel, martensite and semi-austenitic (or semi-martensitic) precipitation hardening stainless steel and maraging stainless steel.