Stainless Steel
In layman's terms, stainless steel is a 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 ** and other oxidizing media, the corrosion resistance increases with the increase of the chromium content in the steel water, when the chromium content reaches a certain percentage, the corrosion resistance of steel Mutations occur, from rust-prone to rust-free, from corrosion-resistant to corrosion-resistant. 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 resistant stainless steel, stainless steel, stainless steel, seawater resistant stainless steel, etc., according to the corrosion resistance type can be divided into corrosion resistant stainless steel, stress corrosion resistant stainless steel, corrosion resistant stainless steel, etc.; according to 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 steel: 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 well-known 18Cr-8Ni steels and high Cr-Ni series steels based on which Cr and Ni contents are increased and Mo, Cu, Si, Nb, Ti and other elements are added. 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, this type of steel is also resistant to corrosion by **, phosphoric acid, formic acid, acetic acid, urea, etc., if it contains elements such as Mo and Cu. If the carbon content in such steel is less than 0.03% or contains Ti, Ni, it can significantly improve its resistance to intergranular corrosion. High-silicon austenitic stainless steels have good corrosion resistance. Because austenitic stainless steel has comprehensive and good comprehensive performance, it has been widely used in various industries.
Ferritic stainless steel: Stainless steel mainly composed of ferrite in use. Chromium content is 11% to 30%, with a 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. These types of steels have high thermal conductivity, small coefficient of expansion, good oxidation resistance, and excellent resistance to stress corrosion. , 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 type of steel widely used.
Austenitic-ferritic duplex stainless steel: Austenitic and ferritic stainless steels that make up approximately one-half of each. In the case where the C content is low, 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, the strength and resistance to intergranular corrosion and chloride stress corrosion resistance are significantly improved. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-stainless steel.
Martensitic stainless steels: Stainless steels that can adjust their mechanical properties through heat treatment are, to put it plainly, 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.
In layman's terms, stainless steel is a 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 ** and other oxidizing media, the corrosion resistance increases with the increase of the chromium content in the steel water, when the chromium content reaches a certain percentage, the corrosion resistance of steel Mutations occur, from rust-prone to rust-free, from corrosion-resistant to corrosion-resistant. 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 resistant stainless steel, stainless steel, stainless steel, seawater resistant stainless steel, etc., according to the corrosion resistance type can be divided into corrosion resistant stainless steel, stress corrosion resistant stainless steel, corrosion resistant stainless steel, etc.; according to 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 steel: 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 well-known 18Cr-8Ni steels and high Cr-Ni series steels based on which Cr and Ni contents are increased and Mo, Cu, Si, Nb, Ti and other elements are added. 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, this type of steel is also resistant to corrosion by **, phosphoric acid, formic acid, acetic acid, urea, etc., if it contains elements such as Mo and Cu. If the carbon content in such steel is less than 0.03% or contains Ti, Ni, it can significantly improve its resistance to intergranular corrosion. High-silicon austenitic stainless steels have good corrosion resistance. Because austenitic stainless steel has comprehensive and good comprehensive performance, it has been widely used in various industries.
Ferritic stainless steel: Stainless steel mainly composed of ferrite in use. Chromium content is 11% to 30%, with a 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. These types of steels have high thermal conductivity, small coefficient of expansion, good oxidation resistance, and excellent resistance to stress corrosion. , 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 type of steel widely used.
Austenitic-ferritic duplex stainless steel: Austenitic and ferritic stainless steels that make up approximately one-half of each. In the case where the C content is low, 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, the strength and resistance to intergranular corrosion and chloride stress corrosion resistance are significantly improved. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-stainless steel.
Martensitic stainless steels: Stainless steels that can adjust their mechanical properties through heat treatment are, to put it plainly, 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.
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