Since the root of the gear is not ground during the general gear grinding process, the decarburization layer generated during the carburizing process remains on the surface of the workpiece, which reduces the bending fatigue strength of the tooth root of the gear, and the entire tooth is broken from the root of the gear during use. When heat treatment is performed by ordinary normalizing high temperature tempering, the hardness of the gear forging blank can be basically guaranteed.
However, when the position of the gear forging blank is different during the heat treatment process, there is a significant difference in the hardness of the fire-extinguishing oil-cooled electric drum forging blank, so that the fiber structure of the gear after heat treatment is significantly different, and local bainite is even present. It affects the machining performance of the gear, resulting in problems such as deformation rebound, increased pressure angle and helix angle after carburizing.
The change of the helix angle of the gear directly affects the strength of the gear during use. After assembly and use, the axial force of the gear will increase, which will affect the service life of the gear, and eventually lead to early failure of the gear. The change of the pressure angle will cause noise during the operation of the gear, and also change the position of the meshing area of ​​the gear, which affects the accuracy of the movement of the gear.
The proper core hardness can prevent the early failure of the bevel gear. It is generally best to use 35-40HRC. The core hardness is too low and the strength is too low and the core too high toughness (low impact value) is too bad, which will cause early failure of the bevel gear.