Method to prevent deformation of bearing during heat treatment

We in heat treatment processing of bearing parts, there is the thermal stress and organization stress, the internal stress can overlay or partially offset each other, is complex and changeable, because it can as the heating temperature, heating rate, cooling, cooling speed, parts of the change of the shape and size changes, so the heat treatment deformation is inevitable.

Three methods to prevent deformation of bearing during heat treatment:

1. Use reasonable cooling methods:

The influence of cooling process on metal deformation after quenching is also an important reason for deformation. The quenching deformation of hot oil is smaller than that of cold oil, generally controlled at 100±20℃. The cooling capacity of the oil is also critical to deformation. The stirring mode and speed of quenching affect the deformation. The faster the cooling rate of metal heat treatment, the more uneven the cooling, the greater the stress, the larger the bearing shape of the mold. Under the premise of ensuring the hardness requirements of the mold, precooling can be used as far as possible; The use of fractional cooling and quenching can significantly reduce the thermal stress and microstructure stress generated during metal quenching and is an effective method to reduce the deformation of some workpiece with more complex shape. Isothermal quenching can be used to reduce deformation of the workpiece with high precision or complexity.

2. Use appropriate media:

Under the premise of ensuring the same hardness requirements, try to use the oil medium, experiment and practice have proved that under the premise of no difference in other conditions, the oil medium cooling rate is slower, while the water medium cooling rate is relatively faster. Moreover, compared with oil medium, water temperature change has a greater impact on the cooling characteristics of water medium. Under the same heat treatment conditions, the deformation of oil medium is relatively small compared with water medium NSK bearing after quenching.

3. Reasonable parts structure:

During the cooling process after metal heat treatment, the thin part always cools quickly, while the thick part cools slowly. In order to reduce the distortion and cracking tendency in the transition zone due to stress concentration, it is necessary to reduce the uneven thickness of the workpiece and make the section of the part uniform. The workpiece should keep the symmetry of structure and material composition and structure as far as possible to reduce the distortion caused by uneven cooling. The workpiece should try to avoid sharp edges, grooves, etc., in the thickness of the workpiece at the junction, steps to have a rounded corner transition; To minimize the structural asymmetry of holes and grooves in the workpiece; Non - uniform thickness parts using the method of reserved processing.