Carburizing process for heat treatment of Automobile Gears

Heat treatment carburizing process can make gears have good comprehensive mechanical properties, so it is most widely used in the production of automobile gears. At present, the heat treatment carburizing process used in the production of automobile gears in the world is mainly gas carburizing. Gas carburizing is the most widely used surface hardening process in the production of low carbon steel. In foreign countries, it has been realized that the carburizing depth and surface hardness of heat treatment can be controlled by computer, so as to obtain the best carburizing layer depth and minimum deformation of heat treatment.

As the conventional heat treatment carburizing process often forms a thin layer of non martensitic structure on the surface of carburized gear, which significantly affects the fatigue performance of gear, and the heat treatment carburizing temperature is high, the cycle is long and the deformation is large, while vacuum carburizing has the characteristics of energy saving, fast heat treatment carburizing speed, simple control, safety and environmental protection. However, for a long time, the problems of carbon black damage to insulation and carburization uniformity after vacuum carburization have not been effectively solved, which affects the popularization and application of vacuum carburization technology. In recent years, catalytic infiltration process has been paid more and more attention because of its advantages of increasing infiltration rate, reducing process temperature, refining microstructure, reducing gear distortion and reducing cost. At present, BH catalytic infiltration technology has been applied in FAW heat treatment plant and FAW Dongfeng Seiko gear plant.

Through the long-term efforts of research units at home and abroad, the low-pressure vacuum carburizing technology with the control pressure range of 600 ~ 1000Pa has effectively solved the above problems, especially the use of high-pressure inert gas cooling and quenching can greatly reduce the gear distortion. The process has experienced great development in recent years and has reached the mature stage of industrialization. One of the most striking advantages of low-pressure vacuum carburizing compared with gas carburizing is that the oxygen free treatment medium makes the heat-treated carburized parts do not produce internal oxidation.

At present, many new heat treatment carburizing processes are emerging. The application of vacuum high-pressure gas quenching and plasma carburizing process to automobile gear processing has achieved great success.

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