CV shaft: Dual quenching and tempering for excellent performance

In the precision world of mechanical transmission, the CV shaft (constant velocity joint shaft) is a key component connecting the power source and the drive wheel. Its performance is directly related to the efficiency and stability of the entire transmission system. The excellent performance of the CV shaft is inseparable from the two crucial links in the production process-quenching and tempering. This double quenching not only gives the shaft body high hardness and high strength, but also effectively balances the mechanical properties of the material through fine regulation, ensuring the long-term stable operation of the CV shaft under complex working conditions.

Quenching, this ancient and exquisite heat treatment process, is the first key process in the manufacturing process of CV shafts. It fundamentally changes the atomic arrangement inside the shaft body by heating the shaft body to the austenitizing temperature, that is, the temperature required for the material's organizational structure to transform into austenite (a stable phase at high temperature). After reaching the predetermined temperature, the shaft body will be quickly immersed in a cooling medium, such as oil, water or brine, to achieve rapid cooling. This rapid temperature change forces the atoms inside the shaft to not have time to rearrange into a stable low-temperature phase, but to be "frozen" in a highly distorted, high-energy state, thus giving the shaft extremely high hardness and strength.

However, just like the two sides of a coin, while quenching improves the performance of the shaft, it also brings side effects that cannot be ignored. Due to the rapid cooling rate, huge internal stresses will be generated inside the shaft. These stresses are like latent undercurrents and may destroy the structural stability of the shaft at any time. In addition, the shaft after quenching often shows high brittleness and weak resistance to impact loads, which to a certain extent limits its scope of application.

In order to solve the problems of the shaft after quenching, tempering treatment came into being. Tempering, as the name suggests, is the process of reheating and keeping the shaft after quenching, but the temperature is much lower than the quenching temperature. The essence of this step is to control the heating temperature and insulation time to make subtle changes in the internal structure of the shaft, so as to achieve the purpose of eliminating internal stress, improving toughness and impact resistance.

During the tempering process, the residual austenite inside the shaft body begins to gradually transform into a more stable organizational form, such as pearlite, bainite or tempered martensite. These newly generated organizations not only retain the high hardness characteristics of the shaft body after quenching, but also effectively reduce the internal stress level and improve the toughness and plasticity of the shaft body by optimizing the microstructure. At the same time, tempering can also form a dense oxide film on the surface of the shaft body, further enhancing its corrosion resistance.

The selection of tempering temperature and time has a crucial impact on the performance of the final product. Too high temperature or too long holding time may cause the shaft body hardness to drop too much, affecting the transmission efficiency; while too low temperature or too short holding time may not be able to fully eliminate internal stress and improve toughness. Therefore, in the production process of CV shafts, precise control of tempering process parameters is particularly important.

Quenching and tempering are the two core processes in the production of CV shafts. They do not exist in isolation, but complement each other and are indispensable. Quenching provides the basis for high hardness and high strength for the shaft body, while tempering further optimizes the mechanical properties of the shaft body on this basis, making it more in line with the actual needs of the transmission system. Through the perfect combination of this double quenching, the CV shaft can not only maintain stable transmission performance under high speed and high load conditions, but also effectively resist impact load and fatigue damage, extend service life and reduce maintenance costs.

The excellent performance of the CV shaft is inseparable from the support of the two key processes of quenching and tempering. Through precise control and clever coordination, they have successfully raised the mechanical properties of the shaft such as hardness, strength, toughness and impact resistance to a new level. In the future development, with the continuous progress of materials science, heat treatment technology and precision machining technology, we have reason to believe that the performance of the CV shaft will be more comprehensively improved and optimized, providing a more solid guarantee for the efficient and stable operation of the transmission system.