Maintenance to prevent deformation of heat treatment of bearings

Use a reasonable cooling method:

The effect of the cooling process on the deformation of the metal after quenching is also an important cause of deformation. Hot oil quenching is less than quenching of cold oil and is generally controlled at 100±20 °C. The cooling capacity of the oil is also critical to deformation. Both the quenching mode and the speed affect the deformation. The faster the metal heat treatment cooling rate, the more uneven the cooling, the greater the stress generated, and the larger the variable bearing shape of the mold. Pre-cooling can be used as much as possible under the premise of ensuring the hardness requirement of the mold; using graded cooling quenching can significantly reduce the thermal stress and microstructure stress generated during quenching of metal, and is an effective method for reducing the deformation of some complex shapes; for some special or For workpieces with higher precision requirements, austempering can significantly reduce deformation.

Use the appropriate medium:

Under the premise of ensuring the same hardness requirements, oily medium should be used as much as possible. Experiments and practice prove that under the premise of no difference in other conditions, the cooling rate of oily medium is slower, while the cooling rate of aqueous medium is relatively faster. Moreover, compared with the oily medium, the change of the water temperature has a great influence on the cooling characteristics of the aqueous medium. Under the same heat treatment condition, the deformation of the oily medium relative to the aqueous medium bearing after quenching is relatively small.

The structure of the part should be reasonable:

After the metal is heat treated, during the cooling process, the thin portion is always cold and the thick portion is cold. In order to meet the actual production needs, the thickness of the workpiece should be minimized, and the cross-section of the parts should be uniform to reduce the distortion and cracking tendency of the transition zone due to stress concentration; the workpiece should keep the symmetry of the structure and material composition and structure as much as possible to reduce Distortion caused by uneven cooling; the workpiece should avoid sharp edges and corners, grooves, etc., and there should be rounded corner transitions at the thick and thin junctions and steps of the workpiece; minimize the asymmetry of the holes and the groove structure on the workpiece; Parts are processed by a reserved amount.

Bearing maintenance: In order to maintain the original performance of the bearing in a good condition for as long as possible, maintenance, overhaul, and accident prevention are required to ensure the reliability of operation and improve productivity and economy.

Maintenance should be carried out on a regular basis in accordance with the operating standards for the corresponding mechanical operating conditions. The content includes monitoring of operating conditions, replenishment or replacement of lubricants, and periodic disassembly inspections. The maintenance items in operation include the rotation sound of the bearing, vibration, temperature, and the state of the lubricant.

Overhaul of the bearing: Cleaning of the bearing: When disassembling the bearing for inspection, first record the appearance of the bearing, confirm the residual amount of the lubricant, and wash the bearing after sampling the lubricant for inspection. As a cleaning agent, gasoline and kerosene are commonly used.

The cleaning of the removed bearings is divided into coarse cleaning and fine cleaning. They are placed in the container respectively, and the metal mesh bottom is placed first so that the bearing does not directly contact the container. In rough cleaning, if the bearing is rotated with dirt, it will damage the rolling surface of the bearing and should be noted. In the rough cleaning oil, use a brush to remove the grease and the adhesive. After it is almost clean, it is transferred to the fine wash.

Fine washing is to carefully clean the bearing while rotating it in the cleaning oil. In addition, the cleaning oil should always be kept clean.

Bearing inspection and judgment: In order to judge whether the removed bearing can be used, it should be checked after the bearing is cleaned. Check the raceway surface, the rolling surface, the state of the mating surface, the wear of the cage, the increase of the bearing clearance, and the damage and abnormality that are irrelevant in dimensional accuracy. For non-separable miniature ball bearings, use one hand to support the inner ring horizontally and rotate the outer ring to check if it is smooth.