Maintenance and judgment of preventing bearing heat treatment deformation

In order to prevent the deformation of bearing during heat treatment, we need to use reasonable cooling method, appropriate medium and reasonable part structure. Here is our company's experience.

Use reasonable cooling method
The influence of cooling process on the deformation after metal quenching is also a very important deformation reason. The deformation of hot oil quenching is smaller than that of cold oil quenching, which is generally controlled at 100 ± 20 ℃. The cooling capacity of the oil is also crucial for deformation. The way and speed of quenching affect the deformation. The faster the cooling rate of metal heat treatment is, the more uneven the cooling is, the greater the stress is, and the greater the deformation of the die is. Pre cooling can be used as far as possible on the premise of ensuring the hardness requirements of the die; step cooling quenching can significantly reduce the thermal stress and structural stress produced during metal quenching, which is an effective method to reduce the deformation of some workpieces with complex shape; isothermal quenching can significantly reduce the deformation of some workpieces with particularly complex shape or high precision requirements.
Using suitable medium
On the premise of ensuring the same hardness requirements, try to use oily medium. Experiments and practice show that under the premise of no difference in other conditions, the cooling speed of oily medium is slower, while the cooling speed of aqueous medium is relatively faster. Moreover, compared with oil-based medium, the change of water temperature has a greater influence on the cooling characteristics of water-based medium. Under the same heat treatment conditions, the deformation of oil-based medium bearing is smaller than that of water-based medium bearing after quenching.
The structure of parts should be reasonable
During the cooling process of metal after heat treatment, the thin part always cools faster than the thick part. In the case of meeting the actual production needs, the thickness difference of the workpiece should be reduced as far as possible, and the cross section of the parts should be uniform as far as possible to reduce the distortion and cracking tendency caused by stress concentration in the transition zone; the symmetry of the structure and material composition and organization should be maintained as far as possible to reduce the distortion caused by uneven cooling; the sharp edges, grooves, etc. should be avoided as far as possible There should be fillet transition at the boundary and steps; the asymmetric structure of holes and groove bars on the workpiece should be minimized; the method of reserving processing capacity should be adopted for parts with uneven thickness.
Bearing maintenance: in order to maintain the original performance of the bearing in good condition for as long as possible, it is necessary to maintain, overhaul and prevent accidents, ensure the reliability of operation and improve the productivity and economy. The maintenance should be carried out regularly according to the operation standard of corresponding mechanical operation conditions. The contents include monitoring the running state, replenishing or replacing the lubricant, and regular disassembly inspection. Maintenance items in operation include rotating sound of bearing, vibration, temperature, state of lubricant, etc.
Maintenance of bearing: cleaning of bearing: when disassembling the lower bearing for maintenance, first record the appearance of the bearing, confirm the residual amount of lubricant, and then clean the bearing after sampling the lubricant for inspection. Ordinary gasoline and kerosene are used as cleaning agents. The cleaning of the removed bearing is divided into coarse cleaning and fine cleaning, which are respectively placed in the container. First, the metal mesh is put on the bottom, so that the bearing does not directly contact the dirt of the container. During rough cleaning, if the bearing rotates with dirt, the rolling surface of the bearing will be damaged, which should be paid attention to. In the crude cleaning oil, use a brush to remove the grease and adhesion. After the oil is roughly clean, turn to the fine cleaning. Fine cleaning is to rotate the bearing in the cleaning oil and clean it carefully at the same time. In addition, the cleaning oil should always be kept clean. Maintenance and judgment of bearing: in order to judge whether the disassembled bearing can be used, it should be checked after the bearing is cleaned. Check the condition of raceway surface, rolling surface and mating surface, wear condition of cage, increase of bearing clearance and damage of irrelevant dimension precision decline. For non separating small ball bearing, use one hand to support the inner ring horizontally and rotate the outer ring to confirm whether it is smooth.
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