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Alloy steel with high strength and good chemical stability at high temperature. It includes two kinds of anti-oxidation steel (or high-temperature non skinning steel) and heat-resistant steel. Oxidation resistant steels generally require good chemical stability, but bear lower load. High temperature strength and corresponding oxidation resistance are required for hot strength steel. Heat resistant steel is often used in the manufacture of boiler, steam turbine, power machinery, industrial furnace, aviation, petrochemical and other industrial sectors working under high temperature. In addition to high temperature strength and high temperature oxidation corrosion resistance, these parts also require enough toughness, good machinability and weldability, and certain structural stability according to different applications. In addition, some new low chromium nickel anti-oxidation steels have been developed.