3 ways to increase the heat resistance of stainless steel flanges

How to increase the heat resistance of stainless steel flanges? Heat resistance refers to the resistance to oxidation or gas medium corrosion (ie thermal stability) at high temperatures, and sufficient strength (ie thermal strength) at high temperatures ). In addition to corrosion resistance, stainless steel flanges also have excellent high and low temperature resistance. Many stainless steels can be used as heat-resistant steel or low-temperature steel. The editor below shares 3 ways to increase the heat resistance of stainless steel flanges

① To ensure the anti-oxidation requirements, a higher chromium content is required to form a dense oxide film. The mass fractions of chromium that can maintain thermal stability at 800°C, 1000°C, and 1100°C are 10%-12%, 22%, and 30%, respectively. The higher the Cr content, the stronger the oxidation resistance. Adding alloying elements such as Al and Si to the steel helps to enhance the influence of Cr. Make the steel surface form an oxide film with a dense structure and firmly bond with the steel surface, such as alloy oxide film such as Cr2O3, Al2O3, and SiO2. This alloy oxide film has a good protective effect, which can prolong the service life of steel or increase the use temperature. In stainless steel flanges, if the oxide film is mainly in the form of (FeCr)2O3, its ability to resist sudden changes in oxidation temperature is the most superior.

　　② Measures to ensure the thermal strength requirements a. Increase Ni to obtain a stable austenite structure, and use Mo and W solid solution strengthening to increase the interatomic bonding force. However, the addition of Mo is unfavorable for oxidation resistance. b. The second phase mainly formed of carbides (MC, MC6), for which the carbon content should be appropriately increased. c. Add trace boron or rare earth to control the grain size and strengthen the grain boundary, such as heat-resistant austenitic stainless steel flange 0Cr15Ni25Ti2 MOAIVE.

　　③High temperature embrittlement problem. Heat-resistant stainless steel will produce various embrittlement phenomena during hot working or long-term work at high temperature, such as the temper brittleness of MoCr13 steel at about 550 ℃, the grain growth of high-chromium ferritic steel and the embrittlement of austenitic steel. The embrittlement caused by the precipitation of carbides on the grain boundary and the brittleness of ferritic steel at 475℃, the σ phase precipitation embrittlement near 850℃, even the high CrNi austenitic steel also has the problem of σ phase precipitation embrittlement. When heat-resistant steel is used at high temperature, it should be considered that embrittlement and high-temperature fatigue failure may occur during long-term high-temperature work. Fatigue failure is generally caused by the formation of cracks on the surface or some defects under the surface. The cracks gradually expand under the action of alternating loads until they break. The applicable temperature ranges and main uses of several heat-resistant steels are listed.