During gear heat treatment, carburizing and quenching, a reasonable furnace charging method shall be adopted according to the specific conditions such as the shape and requirements of parts, so as to ensure uniform gear heating, quenching and carburizing atmosphere, so as to reduce deformation and ensure quality.
Generally, there are two charging methods for gears: flat loading and hanging loading. Different charging methods should be selected for gears with different shapes and requirements to reduce deformation. For example, for disc gears with large diameter and thickness ratio, the hanging warpage is smaller than that of flat loading, and the flat loading is required for internal splines with high precision. Compared with the m-value ellipse of cross bar distance of hanging splines
Less roundness.
Affected by the wetting kinematics of quenching medium, there is uneven wetting between single gear and gears, resulting in the change of hardness and plastic deformation. Therefore, the charging mode of carburized gear has a great influence on the change of the shape of gear ring and spline hole, the change of key width and common normal length. The research shows that when the cylindrical gear with modulus of 4-12 is carburized, the torsional deformation of the spline hole and gear ring is increased by 0.5 ~ 1.5 times on average compared with that of the flat gear. The research shows that some helical gears and ring sleeve gears have small flat deformation. However, not all gears are placed horizontally. During direct quenching, thin-walled gears with a diameter of about 200 mm or gears with large tooth width that are easy to cause uneven cooling due to the lack of convection of quenching liquid in the wheel width groove during horizontal quenching can reduce end face warpage, tooth alignment error and the limit variation of common normal length. For some deformable parts, the influence of high-temperature state without self weight shall be considered during furnace loading. High stiffness multi-point suspension mandrel shall be used for hanging and placing. When placing heavy parts horizontally, it is best to use special fixture to make it bear only the self weight of the part. For different carburizing and quenching equipment, the charging mode of gear shall be determined through test.
Foreign countries pay great attention to the charging mode of axial parts, which is intended to reduce the difficulty of straightening and reduce the loss of waste products. Generally, the axial parts are placed vertically in the hanger. In order to reduce the bending deformation caused by mechanical vibration and oil impact and swing back and forth, and prevent the deformation caused by the dead weight of the workpiece and additional bundle, it is best to place it vertically by three plane loose limit method.
In short, reasonable gear placement, rational use of tooling, reasonable loading clearance space and so on are effective ways to reduce gear quenching deformation.