In the production process of the quick return lever hoist HSH-A, carburizing and quenching is a crucial process step. In this step, the choice of cooling medium has a decisive influence on the performance of the internal gear. The cooling medium not only determines the cooling rate of the gear, but is also closely related to its hardness, toughness, residual stress and other properties.

Influence of cooling rate
The choice of cooling medium directly affects the cooling rate of the carburized gear. Fast cooling media such as water have a fast cooling rate, which helps the gear surface to cool down quickly and form a fine grain structure, thereby improving the hardness and wear resistance of the gear. However, too fast cooling rate may also cause greater thermal stress inside the gear, increasing the risk of deformation and cracking. In contrast, slower cooling media such as oil have a slower cooling rate, which helps to reduce the thermal stress inside the gear and reduce the risk of deformation and cracking.

Changes in gear performance
1. Hardness: The cooling rate of the cooling medium directly affects the hardness of the gear. Fast cooling media can make the gear obtain higher hardness, while slower cooling media can keep the gear at a certain toughness. Therefore, when selecting a cooling medium, it is necessary to balance the relationship between hardness and toughness according to the use environment and requirements of the gear.
2. Toughness: In addition to hardness, toughness is also an important indicator of gear performance. Although fast cooling medium can increase the hardness of gears, it may also reduce its toughness and make it more brittle. Slower cooling medium helps to maintain the toughness of gears and improve their impact and fatigue resistance.
3. Residual stress: The cooling rate of the cooling medium will also affect the residual stress inside the gear. Too fast cooling rate may cause large residual stress inside the gear, affecting its service life and safety. Slower cooling medium helps to reduce residual stress and improve the stability and reliability of gears.

In the carburizing and quenching process, it is very important to choose a suitable cooling medium. For the internal gears of HSH-A lever hoist, it is necessary to comprehensively consider its material, size, heat treatment process and other factors to select the peerless cooling medium. For example, for gears with smaller size and higher hardness requirements, a fast cooling medium such as water can be selected; for gears with larger size and better toughness requirements, a slower cooling medium such as oil can be selected.