How many kinds of stainless steel materials are there?
Stainless steel materials are divided into martensitic stainless steel, ferritic bai type du stainless steel, austenitic stainless steel, zhi duplex stainless steel, precipitation hardening stainless steel and so on.
1. Martensitic stainless steel
Martensitic stainless steel is 13% Cr steel, commonly known as 420 stainless steel. 420 stainless steel is \"cutting tool grade\" martensitic steel, similar to the earliest stainless steel such as Brinell high chromium steel. 420 has a certain degree of wear resistance and corrosion resistance, high hardness, and its price is the lower category of stainless steel balls. It is suitable for working environments that generally require stainless steel. The improvement of standard martensitic steel contains additional elements such as nickel, molybdenum and vanadium. The corrosion resistance of martensitic stainless steel comes from \"chromium\", which ranges from 11.5 to 18%. The higher the chromium content, the higher the carbon content is required to ensure the formation of martensite during heat treatment.
2. Ferritic stainless steel
Ferritic stainless steel is commonly known as 430 stainless steel, and ferritic stainless steel contains 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. Chromium is the main element in ferritic stainless steel. Because of its high chromium content, ferritic stainless steel has better corrosion resistance and oxidation resistance. However, the mechanical properties and process properties are poor, and it is mostly used for acid-resistant structures with little stress and as anti-oxidation steel. This type of steel can resist corrosion from the atmosphere, nitric acid and salt solutions, and has the characteristics of good high-temperature oxidation resistance and low thermal expansion coefficient. It is used in nitric acid and food factory equipment, and can also be used to make parts that work at high temperatures, such as gas turbine parts, etc. .
3. Austenitic stainless steel
Austenitic stainless steel is commonly known as 304 stainless steel. Austenitic stainless steel refers to stainless steel with austenitic structure at room temperature. When the steel contains about 18% Cr, 8%-10% Ni, and about 0.1% C, it has a stable austenite structure. The austenitic chromium-nickel stainless steel includes the famous 18Cr-8Ni steel and the high Cr-Ni system developed by adding Cr and Ni content and adding Mo, Cu, Si, Nb, Ti and other elements on this basis. Austenitic stainless steel generally belongs to corrosion-resistant steel and is the most widely used type of steel. Among them, 18-8 stainless steel is the most representative. It has good mechanical properties and is convenient for machining, stamping and welding.
4. Duplex stainless steel
Duplex stainless steel refers to a stainless steel whose ferrite and austenite each account for about 50%, and generally the content of less phases needs to reach at least 30%. In the case of low 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, Nb, Ti, and N. This type of steel has the characteristics of austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, and significantly improved intergranular corrosion resistance and welding performance, while still maintaining iron The 475℃ brittleness, high thermal conductivity, and superplasticity of element 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.
5. Precipitation hardening stainless steel
A precipitate phase is formed. The matrix structure of precipitation hardening stainless steel can be martensite or austenite, depending on the composition and processing process. Age-hardening martensitic stainless steel has both good corrosion resistance and simple heat treatment. Age hardening martensitic stainless steel is sensitive to chloride stress corrosion cracking. Sensitivity depends to some extent on steel grade and aging temperature.
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