Heat-resistant steel refers to steel with high temperature oxidation resistance and high temperature strength. High temperature oxidation resistance is an important condition to ensure that the workpiece works for a long time at high temperature. In an oxidizing environment such as high-temperature air, oxygen reacts chemically with the steel surface to form a variety of iron oxide layers. The oxide layer is very loose, loses the original characteristics of steel, and is easily peeled off. In order to improve the high temperature oxidation resistance of steel, alloying elements are added to the steel to change the oxide structure. Commonly used alloying elements are chromium, silicon, aluminum and so on. They react with oxygen to form a dense and stable oxide layer on the surface of the steel, or a passivation layer of Cr2O3, SiO2 or Al2O3, to protect the steel from further oxidation. If the amount of chromium, silicon, and aluminum is large, the high temperature oxidation resistance of steel is good, but if the amount of silicon and aluminum is too large, the mechanical properties and processability of the steel will deteriorate. Therefore, heat-resistant steel uses chromium as the main alloying element and silicon and aluminum as auxiliary elements. In short, the high temperature oxidation resistance of steel is only related to the chemical composition.