The hottest stainless steel Knowledge Series 3

2022-08-14
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Stainless steel knowledge (Series 3)

professional terms of stainless steel

generally speaking, stainless steel is steel that is not easy to rust. In fact, some stainless steel has both rust resistance and acid resistance (corrosion resistance). The rust resistance and corrosion resistance of stainless steel are due to the formation of chromium rich oxide film (passive film) on its surface. This rust resistance and corrosion resistance are relative. The test shows that the corrosion resistance of steel in weak media such as atmosphere and water and oxidizing media such as nitric acid increases with the increase of chromium content in steel. When the chromium content reaches a certain percentage, the corrosion resistance of steel changes abruptly, that is, from easy to rust to not easy to rust, from non corrosion to corrosion resistance. There are many ways to classify stainless steel. According to the structure classification at room temperature, there are martensite, austenite, ferrite and duplex stainless steel; According to the classification of main chemical components, it can be basically divided into two systems: chromium stainless steel and chromium nickel stainless steel; There are nitric acid resistant stainless steel, sulfuric acid resistant stainless steel, seawater resistant stainless steel, etc. according to the purpose, they can be divided into pitting corrosion resistant stainless steel, stress corrosion resistant stainless steel, intergranular corrosion resistant stainless steel, etc; According to the functional characteristics, it 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 strength and toughness in a wide temperature range, stainless steel has been widely used in heavy industry, light industry, household goods industry, architectural decoration and other industries

austenitic stainless steel: stainless steel with austenitic structure at room temperature. When the steel contains about 18% Cr, 8%~10% Ni and 0.1% C, it has stable austenite structure. Austenitic chromium nickel stainless steel includes the famous 18Cr-8Ni steel and the high Cr Ni series steel developed by increasing the content of Cr and Ni and adding Mo, Cu, Si, Nb, Ti and other elements. Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but its strength is low. The probe is 7993 series, which belongs to positive voltage power supply mode. It cannot be strengthened by phase transformation, but only by cold working. If s, CA, Se, TE and other elements are added, it has good machinability. In addition to the corrosion resistance of oxidizing acid medium, this kind of steel can also resist the corrosion of sulfuric acid, phosphoric acid, formic acid, acetic acid, urea, etc. if it contains Mo, Cu and other elements. If the carbon content in this kind of steel is less than 0.03% or contains Ti and Ni, its intergranular corrosion resistance can be significantly improved. High silicon austenitic stainless steel has good corrosion resistance with concentrated nitric acid. Austenitic stainless steel has been widely used in all walks of life because of its comprehensive and good comprehensive properties

ferritic stainless steel: stainless steel with ferritic structure in service. The chromium content is 11% - 30%, with body centered cubic crystal structure. This kind of steel generally does not contain nickel, and sometimes contains a small amount of Mo, Ti, Nb and other elements. This kind of steel has the characteristics of high thermal conductivity, low expansion coefficient, good oxidation resistance, excellent stress corrosion resistance and so on. It is mostly used to manufacture parts and components resistant to atmospheric, steam, water and oxidative acid corrosion. This kind of steel has some disadvantages, such as poor plasticity, significantly reduced plasticity and corrosion resistance after welding, which limits its application. The application of outside furnace refining technology (AOD or VOD) can greatly reduce the interstitial elements such as carbon and nitrogen, so this kind of steel is widely used

austenite ferritic duplex stainless steel: it is a stainless steel with about half of austenite and half of ferrite. When the content of C is low, the content of Cr is 18% - 28%, and the content of Ni is 3% - 10%. Some steels also contain Mo, Cu, Si, Nb, Ti, N and other alloy elements. This kind of steel only operates in strict accordance with the instructions and has the characteristics of both austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, significantly improved intergranular corrosion resistance and welding performance, and also maintains the 475 ℃ brittleness, high thermal conductivity and Superplasticity of ferritic stainless steel. Compared with austenitic stainless steel, it has high strength and significantly improved resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel saving stainless steel

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martensitic stainless steel: its mechanical properties can be adjusted through heat treatment. 3. According to the industry and functional characteristics, it can be divided into stainless steel, which is a kind of hardenable stainless steel. The typical brand is Cr13 type, such as 2Cr13, 3Cr13, 4Cr13, etc. The hardness after quenching is high, and different tempering temperatures have different combinations of strength and toughness. It is mainly used for steam turbine blades, tableware and surgical instruments. According to the difference of chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium nickel steel. According to the different structure and strengthening mechanism, it can also be divided into martensitic stainless steel, martensitic and semi austenitic (or semi martensitic) precipitation hardening stainless steel and maraging stainless steel

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