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The best material for stainless steel pipes depends on what it is used for because different stainless steels have different characteristics. The best fit is the best.
Stainless steel is often divided into martensitic steel, ferritic steel, austenitic steel, austenitic-ferritic (duplex) stainless steel, and precipitation hardening stainless steel according to the organizational state. In addition, it can be divided into chromium stainless steel, chromium-nickel stainless steel, and chromium manganese nitrogen stainless steel. There is also special stainless steel for pressure vessels "GB24511_2009_Stainless steel plates and strips for pressure equipment".
1. Ferritic stainless steel
Chromium 15% to 30%. 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, such as Crl7, Cr17Mo2Ti, Cr25, Cr25Mo3Ti, Cr28, etc. Ferritic stainless steel has good corrosion resistance and oxidation resistance because of its high chromium content, but its mechanical properties and process performance are poor. It is mostly used in acid-resistant structures with low stress and as anti-oxidation steel. This type of steel can resist the corrosion of the atmosphere, nitric acid, and salt solution, and has the characteristics of good high temperature oxidation resistance and a small 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..
2. Austenitic stainless steel
It contains more than 18% chromium, and also contains about 8% nickel, and a small amount of molybdenum, titanium, nitrogen, and other elements. Good overall performance, resistant to corrosion by various media. Common grades of austenitic stainless steel are 1Cr18Ni9, 0Cr19Ni9, and so on. The Wc of 0Cr19Ni9 steel is less than 0.08%, and the steel number is marked as "0". This type of steel contains a large amount of Ni and Cr, which makes the steel austenitic at room temperature. This type of steel has good plasticity, toughness, weldability, corrosion resistance, and non-magnetic or weak magnetic properties. It has good corrosion resistance in oxidizing and reducing media. It is used to make acid-resistant equipment, such as corrosion-resistant containers and equipment. Linings, pipelines, nitric acid-resistant equipment parts, etc., can also be used as the main material of stainless steel watch accessories. Austenitic stainless steel generally adopts solution treatment, that is, the steel is heated to 1050-1150°C, and then water-cooled or air-cooled to obtain a single-phase austenite structure.
3. Austenitic-ferritic duplex stainless steel
It has the advantages of both austenitic and ferritic stainless steels and has superplasticity. Austenite and ferrite each account for about half of the stainless steel. In the case of low carbon content, the content of chromium (Cr) is 18%~28%, and the content of nickel (Ni) is 3%~10%. Some steels also contain alloying elements such as Mo, Cu, Si, Nb, Ti, and N. This type of steel 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 at the same time maintains iron The body of stainless steel is brittle at 475°C, has high thermal conductivity, and has the characteristics of superplasticity. 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 nickel-saving stainless steel.
4. Precipitation-hardened stainless steel
The matrix is austenite or martensite, and the commonly used grades of precipitation-hardening stainless steel are 04Cr13Ni8Mo2Al and so on. It is stainless steel that can be hardened (strengthened) by precipitation hardening (also known as age hardening).
5. Martensitic stainless steel
High strength, but poor plasticity and weldability. The commonly used grades of martensitic stainless steel are 1Cr13, 3Cr13, etc., because of the high carbon content, it has high strength, hardness, and wear resistance, but the corrosion resistance is slightly poor, and it is used for high mechanical properties and corrosion resistance. Some general parts are required, such as springs, steam turbine blades, hydraulic press valves, etc. This type of steel is used after quenching and tempering. Annealing is required after forging and stamping.
6. Stainless steel plates and strips for pressure equipment
Stainless steel for pressure vessels has clear requirements for its classification and code, size, shape and allowable deviation, technical requirements, test methods, inspection rules, packaging, signs, and product quality certificates. Mainly used in food machinery, pharmaceutical machinery, and other sanitary equipment.
Dingshang Stainless Steel Co., Ltd. is a stainless steel pipe manufacturer and welded stainless steel pipe supplier in China, specializing in wholesale sales of U-stainless steel welded pipes, welcome to consult.