Heat treatment method for automobile transmission gear

Abstract

The invention discloses an automobile transmission gear heat treatment method. The method includes the steps of carburization, carbonitriding, quenching, cleaning, low temperature tempering and air cooling. The carburization technique is combined with the carbonitriding technique, abrasion resistance, fatigue strength and corrosive resistance are improved by a layer of highly hard nitride layer obtained on the carburized layer on the surface of a gear, and comprehensive performance of a product is good; meanwhile, the problems of massive carbide appearing under the high carbon potential state and network carbide appearing in the cooling process are avoided, and early-age cracking of the surface of the gear is avoided; moreover, by the method, the technological process is simplified, heating and cooling links and discharge links are reduced, carburization deformation and quenching deformation are reduced, generation of black structures is reduced as well, and anti-fatigue performance is guaranteed; finally, by the method, production cycle is shortened greatly, energy consumption is lowered, and production efficiency is improved highly.

Description

technical field [0001] The invention relates to a heat treatment method, in particular to an automobile gearbox gear heat treatment method which effectively combines carburizing technology and carbonitriding technology, and belongs to the technical field of heat treatment. Background technique [0002] Automobile transmission gear is one of the parts with the highest technical requirements in the automobile transmission system. During the operation of the gear, there are both rolling and sliding between the tooth surfaces that mesh with each other. At the same time, the gear is also subjected to pulse stress and alternating bending stress. Therefore, the gears are required to undergo heat treatment to have good hardness, wear resistance, fatigue resistance, high dimensional accuracy, and low noise performance during operation. [0003] At present, the most important heat treatment method for surface strengthening of automobile gearbox gears is carburizing and quenching. The...

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Problems solved by technology

[0005] 1. Due to the high carburizing carbon potential, the austenite carbon content in the carburizing surface layer is too high, and it is easy to precipitate large carbides from the austenite during the cooling and heat preservation process. Precipitation of the tenite grain boundary forms a network carbide, which is easy to cause early cracking of the gear surface;

[0006] 2. The high-temperature heating and cooling times of the gear are twice, and the carburizing deformation and quenching deformation are superimposed, so the deformation of the gear is relatively large;

[0007] 3. After carburizing and cooling out of the furnace, it is very easy to cause surface oxidation and decarburization. After quenching, there are black structures in the surface structure, which reduces the fatigue resistance of the gear and shortens the service life;

[0008] 4. The production cycle of heat treatment is long, the production efficiency is low, and the energy consumption is large

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