There are many grades of steel used for gears of medium and heavy-duty trucks in our country, mainly to meet the requirements of the introduction of advanced foreign automobile technology at that time. In the 1950s, our country introduced the production technology of medium-sized trucks (that is, the original model of the "Liberation" brand) from the former Soviet Union Rikhachev Automobile Factory, and also introduced the 20CrMnTi steel grade of automobile gears produced in the former Soviet Union.

After the reform and opening up, with the rapid development of our country‘s economic construction, in order to meet the rapid development needs of our country‘s transportation, since the 1980s, our country has planned to introduce various advanced models from industrialized countries, and various foreign advanced medium and heavy cargo vehicles have also been introduced. At the same time, our country‘s large automobile factories cooperate with foreign famous automobile companies to introduce foreign advanced automobile production technology, including automobile gear production technology.

At the same time, the level of steel smelting technology in our country is also constantly improving, using advanced smelting technologies such as secondary smelting of ladle and fine-tuning of composition and continuous casting and rolling, so that steel mills can produce high-purity, hardenability band narrowed gear steel, thus realizing the localization of the introduction of automotive gear steel, so that the production level of gear steel in our country has reached a new level. Domestic heavy-duty automobile gear steel with nickel and high hardenability suitable for our country‘s national conditions has also been applied and achieved good results.

The heat treatment technology of automotive gears has also developed from the original well gas carburizing protection in the 1950s and 1960s to the current widespread use of computer-controlled continuous gas carburizing automatic lines, box-type multi-purpose furnaces and automatic production lines (including low-pressure (vacuum) carburizing technology), gear carburizing pre-oxidation treatment technology, gear quenching control cooling technology (due to the use of special quenching oil and quenching cooling technology), gear forging isothermal normalization technology, etc. The adoption of these technologies not only allows gear carburizing and quenching distortion to be effectively controlled, gear processing accuracy to be improved, and service life to be extended, but also meets the needs of large-scale production of modern heat treatment of gears.

Relevant literature points out that the life of automotive gears is mainly assessed by two major indicators, one is the contact fatigue strength of the gear, and the other is the bending fatigue strength of the gear. The former is mainly determined by the quality of carburizing and quenching, and the latter is mainly determined by the gear material. Therefore, it is necessary to have a comprehensive understanding of the requirements, properties and heat treatment characteristics of carburizing steel for automotive gears.