Methods for increasing the heat resistance of stainless steel flanges

 What are the methods for increasing the heat resistance of stainless steel flanges?

　　1. A higher chromium content is required to ensure oxidation resistance to form a dense oxide film. The mass fraction of chromium that can maintain thermal stability at 800 ° C, 1000 ° C, and 1100 ° C is 10% - 12%, 22%, and 30%, respectively. The higher the Cr content, the stronger the oxidation resistance. The addition of alloying elements such as Al and Si to steel helps to enhance the impact of Cr. The surface of steel is formed as an oxide film with a dense structure and firmly binds to the surface of steel, such as alloy oxide films such as Cr2O3, Al2O3, and SiO2. The alloy oxide film has a good protective effect, which can extend the service life of steel or increase the service temperature. In stainless steel flanges, if the oxide film is mainly in the form of (FeCr) 2O3, its ability to resist sudden changes in temperature is most outstanding.

　　2. Measures to ensure thermal strength requirements a. Adding Ni to obtain a stable austenitic structure and using Mo and W solid solution strengthening to increase the bonding force between atoms. However, the addition of Mo is not conducive to antioxidant activity. b。 The formation of a second phase dominated by carbides (MC, MC6) should be appropriately increased in carbon content. C。 Add trace amounts of boron or rare earth to control grain size and enhance grain boundaries, such as heat-resistant austenitic stainless steel flange 0Cr15Ni25Ti2 MOAIVE.

　　3. High temperature embrittlement problem. Heat resistant stainless steel can produce various embrittlement phenomena during high-temperature hot working or long-term work, such as the tempering embrittlement of MoCr13 steel at about 550 ℃, the growth of high chromium ferrite steel, and the embrittlement of austenitic steel. Brittleness caused by precipitation of grain boundary carbides at 475 ℃ and brittleness of ferritic steels σ Phase precipitation brittleness exists even in high CrNi austenitic steels σ Phase precipitation brittleness. When using heat-resistant steel at high temperatures, consideration should be given to the possibility of embrittlement and high-temperature fatigue damage during long-term high-temperature work. Fatigue failure is usually caused by the formation of surface cracks or certain defects beneath the surface. Under the action of alternating load, the crack gradually propagates until it ruptures.