Heat treatment technology and service life of automobile and tractor gears

The service life of automobile and tractor gears is related to many factors, such as steel material, forging quality, precision of cold working, use, maintenance and lubrication after loading, but the quality of heat treatment of gears is very important to the service life of gears.

It has been proved that gears without carburizing and quenching heat treatment can not be used. As a result, the gears will be polished off immediately after the car starts. Generally, the gear after heat treatment can run thousands to tens of thousands of kilometers.

The quality of heat treatment has a great influence on the life of gears. There is a county agricultural machinery factory in Jiangsu province that produces walking tractor gears. Solid carburizing is used for heat treatment. Due to unstable soil technology and no metallographic inspection method, after the tractor gears are loaded, after several hours of operation, all the teeth of the tractor gears are polished. Finally, it is found that the carbon concentration on the surface of the gears is very high, and there are coarse network carbides, The quality of gas carburizing and quenching gear used in Changzhou gear factory is relatively stable, and its service life can be about 2000 hours.

In addition to ensuring the accuracy of the service life of the gear, the internal metallographic structure of the gear plays a decisive role in the service life. For example: for 18crmnit steel tractor gear, if the appropriate heat treatment process is adopted to ensure the metallographic structure to make the carbide level in the range of O ~ 3, the tractor gear life can be within 10000 hours, but when the heat treatment process is improper and the carbide level is out of tolerance, it can only be used within 4000 hours. The higher the carbide level is, the more serious the tooth chipping phenomenon is. After carburizing, the hardness of the gear core also has a direct impact on its service life. The hardness of the gear core is from rc30 to 37, and the service life is from 300 to 800 hours. The service life of gear is 3000 hours when the core hardness is in rc35, 6000-12000 hours when the core hardness is in rc37-47, and the ferrite is in the snow core. ~Class 3 range, low gear life. However, it can be used for about 10000 hours after the low carbon martensite is quenched in the caution part (all the above are the research and test data of a gear factory). Therefore, it is very important to select the heat treatment process correctly, make the process stable and adopt certain metallographic inspection, and strictly control the metallographic structure of the gear after carburizing, so as to ensure the internal quality and service life of the gear.

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