Why 310 stainless steel can withstand high temperature?
At room temperature, the matrix structure of austenitic stainless steel 310 is pure γ。 The chemical composition in GB / T 24511-2017 is shown in the following screenshot. Because the nominal contents of chromium and nickel are 25% and 20% respectively, 310 is also called “2520”.
310 is often used as high temperature resistant material because of its good high temperature strength and low oxidation at high temperature; When the temperature is kept at 1200 ℃, the oxidation rate of 310 is very serious. In addition, it is also used in the transportation and storage of strong acids such as 65% – 85% nitric acid.
Why can 310 withstand high temperature?
In the high temperature environment, 310 heat-resistant stainless steel can maintain the stability of all aspects of its performance, and is not easy to be affected by some external corrosion, oxidation and other media. This is mainly due to the high content of Cr in 310 stainless steel itself. When encountering oxidation medium, Cr in the metal on 310 surface can combine with oxygen to form Cr2O3. This oxide film can prevent oxidation and corrosion.
As long as the content of Cr in stainless steel is sufficient, the Cr2O3 oxide film will continue to cover the surface of 310 steel. As the film becomes thicker and thicker, 310 steel is finally put on “protective clothing”, which can prevent the contact between internal 310 metal and the outside world, so as to prevent further oxidation. This is also the main reason why 310 steel can have good oxidation resistance at high temperature.
The role of Cr and Ni
Chromium (CR): for heat-resistant stainless steel, Cr can maintain its own stability at high temperature without oxidation and falling off. However, the content of Cr should not be too high. If it is too high, the toughness of stainless steel itself will also decrease, because CR can promote the toughness of stainless steel α The presence of components, rather than inhibition γ， Too many α It is easy to cause some brittle phases. Therefore, in austenitic stainless steel, we hope to keep the Cr content moderate, which can not only ensure all aspects of material properties, but also prevent the emergence of some brittle phases.
Nickel (Ni): Ni is a very important element in heat-resistant austenitic stainless steel and plays an important role in the promotion of heat resistance γ It plays a very positive role in the formation of the culture. In the phase diagram, with the increase of Ni content, it is possible to increase the Ni content γ towards α The transformation temperature becomes very low, which can enhance the stability of matrix austenite. In addition, proper adjustment of Ni content in stainless steel can significantly improve the comprehensive mechanical properties of stainless steel and ensure its good welding performance.
Source: China Flange Manufacturer – Yaang Pipe Industry (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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