In order to obtain low friction torque, high rigidity and good rotary accuracy of the bearings, small size steel balls are used and hollow shafts are used to ensure light weight and space for wiring.Thin-walled bearings have realized extremely thin section bearings, as well as miniaturization and light weight of products. The variety of products extends their range of applications.
1. The main cause of heat treatment deformation:
One of the main reasons for bearing rings is the uneven thermal expansion and contraction of the ring surface and the internal thermal expansion and contraction during the heat treatment and cooling process, as well as the thermal stresses and large tissue stresses resulting from different tissue transformations.When the overall plastic deformation of the collar, the deformation is manifested as the expansion or reduction of the diameter direction, and when there is a local plastic deformation is manifested as the increase of roundness or cylindricity error.Because the cooling rate is much faster than the heating rate of the ring in the furnace, while the thin-walled bearing ring stiffness is poor, so the vast majority of the deformation is generated during the cooling process.
Many factors affect the bearing collar heat treatment, where the heat treatment process can reduce the heat stress and tissue stress generated during the method, can reduce the amount of deformation of the collar.From the perspective of heat treatment process, appropriate control of insulation time, can effectively reduce the deformation of the collar. The outer diameter of the larger thin-walled bearing collar, due to its own poor stiffness, heat treatment in a certain thermal stress and tissue stress, it may produce a large deformation, to control its deformation must develop a suitable heat treatment process, control the thermal stress and tissue stress.
2. Original heat treatment process:
The original heat treatment process of the thin-walled bearing is: quenching temperature 855℃, heating time 30min, quenching oil temperature 100℃, a set of ring turning process after increasing the appropriate stress relief annealing.In the quenching stage to properly control the quenching heating temperature, reasonable control of quenching and cooling speed, quenching and heating before the oil groove with water glass, asbestos rope or refractory clay to block.The use of protective atmosphere heating, etc. can reduce the generation of oil groove cracks, improve the structure of the oil groove or the shape of the oil groove, avoid straight oil groove and sharp angle effect also has a positive effect on the control of the generation of oil groove cracks.