Carbon atoms are infiltrated into the surface of steel samples, and carburizing layer is formed on the surface of steel samples. This chemical heat treatment process is called carburizing treatment. The hardness and wear resistance of the sample surface are greatly improved by using this process. The famous Russian metallurgist Arnosov in 1837（ II.II.AHOCOB ）Gas carburizing was used for the first time in the United States of America in the early 20th century, and the Soviet Union began to study it in all aspects.
With the progress of the times, the rapid development of gas carburizing, on the basis of previous research, a new process “direct carburizing and quenching method” has been produced. This method greatly simplifies the heat treatment process and improves the quality of parts under the principle of reducing cost. Some new grades of steel suitable for carburizing and quenching have been developed gradually due to technological changes. Since then, the technology of carburizing has been developed rapidly. At present, gear and shaft parts are often used and one of the most important heat treatment processes for these parts is carburizing and quenching.
Gas carburizing is widely used in industry. Parts of various shapes are carburized by well furnace or multi-purpose furnace. Under this process, the quality of workpieces is stable and controllable. Gas, natural gas and ethanol are commonly used carburizing media. However, it is difficult to control the carbon concentration in the process. When the carbon concentration in the medium is high, the carbide structure generated in the carburizing layer is coarse, the surface is more brittle, and the surface layer is easy to peel off and has a very short life; when the medium carbon concentration is low, the surface layer is shallow, the surface hardness is low, and the wear resistance is poor; in addition, if the atmosphere circulation or air leakage occurs in the carburizing furnace, the carburizing layer will be uneven, and Therefore, the life is reduced and a series of uncontrollable results are obtained. In addition, the more commonly used carburizing methods are liquid carburizing and solid carburizing.