The bearing cage is broken, which can be easily solved by using medium frequency annealing equipment and adding a stress relief annealing process.

Bearing cage, also known as bearing cage, refers to a bearing part that partially wraps all or part of the rolling elements and moves with them to isolate the rolling elements. It usually also guides the rolling elements and keeps them within the bearing. Commonly used materials for its workpieces For 08 steel, the heat treatment uses gas nitrocarburizing surface strengthening treatment, but there are always fracture defects. After analyzing the reasons, it was found that adding a stress-relieving annealing heat treatment can avoid this defect, and the effect is good.

The bearing cage has a stamped corrugated shape, and the heat treatment uses gas nitrocarburizing surface strengthening treatment. The process is: 570℃x(3-4)h, oil cooling or water cooling. During production, it was found that some cages were broken, and the fractures were all at the rivet riveting area.

Analysis believes that the technical requirement for the depth of the nitrocarburizing layer of the cage is 0.005-0.012mm, and the depth of the nitrocarburizing layer of the failed cage reaches 0.050mm. This is due to the high nitrocarburizing temperature and too long time. In addition, the higher the co-infiltration temperature, the more uneven the compound in the co-infiltration layer, the thicker the loose layer, and the more serious the looseness. During metallographic observation, black tissue defects were found. This black tissue is a kind of cavity, which is generally distributed at a very shallow depth on the surface. It is a typical nitrocarburizing defective tissue. This structure reduces the surface density of the part, reduces its wear resistance, and makes it easy to peel off, even causing the workpiece to break. The black structure produced in the workpiece is caused by the high temperature of nitrocarburizing. Reasons for cage fracture: On the one hand, the nitrocarburizing layer is too deep to embrittle the surface tissue, and there are loose and black tissue defects in the tissue, which causes the material to peel off and the performance is greatly reduced; on the other hand, the comprehensive stress concentration of the workpiece is greater than the material strength. , causing the workpiece to break. Stamping processing causes the cage to have certain cold working stress. After nitrocarburizing, the workpiece is superimposed with the structural stress and thermal stress generated during the heat treatment. When the cage is riveted, the riveting stress is superimposed again, and the riveting part is obviously the stress concentration point and the weak point of the workpiece. The defective cage also has defects such as excessive penetration, embrittlement of the surface layer and loose black tissue. When the stress concentration is greater than the strength of the weakest part of the workpiece, cracks and fractures will occur there.

The process improvements are as follows:

(1) Based on the analysis of failed workpieces, reduce the depth of the nitrocarburizing layer, reduce the brittleness of the layer, and reduce and eliminate the risk of cracking.

(2) In order to reduce the stress generated during workpiece processing, stress relief annealing should be performed after the workpiece is stamped and riveted. After the workpiece is nitrocarburized, medium frequency annealing equipment should also be used for stress relief annealing to eliminate the structural stress and thermal stress generated during the heat treatment to reduce the risk of deformation and cracking of the workpiece.

After many tests, it was concluded that by adding a stress-relieving annealing process on the basis of the original heat treatment process, the produced bearing cage has no fracture defects, has good production performance, and is suitable for mass production.