Process and key points of processing stainless steel bearings

Steel contains complex carbides (Fe, Cr)7C3, which dissolve in austenite slowly when heated. Meanwhile, steel has poor thermal conductivity, so the forging heating speed should be slow. If the heating temperature is too high or the stay time in the high temperature area is too long, it is easy to produce twins and destroy the performance of the steel. And because the steel hardenability is better and poor thermal conductivity, the cooling after forging must be slow, otherwise it is easy to crack. If the forging temperature is too high, the network carbide is easy to produce, and the coarse network carbide structure can not be eliminated in the future annealing process. The material has high deformation resistance, low plasticity and poor forging performance at high temperature, so it has special requirements for the material and structure of the die.

In order to better evaluate the noise level of bearings, the vibration values of three uniform points on the front and back of each set of bearings are measured in the actual measurement, and the larger test value is taken as the effective vibration value of bearings.
(1) As can be seen from Table 2, low noise grease can greatly reduce the vibration and noise of bearings. After grease injection, 100% meets the requirements of Z2 group (40 dB), 98% meets the requirements of Z3 group (38 dB), and the product has a certain reserve accuracy. Affected by some unavoidable factors such as machine tool stability, uneven quality of grinding wheel and grinding wheel dressing quality in grinding process, uneven quality of oil stone and oil stone replacement and dressing quality in channel superfinishing process, the whole process system has a certain volatility when meeting the requirements of processing accuracy, so the vibration value data in Table 2 have a certain dispersion.
(2) During the test, it was found that the vibration value of 5 sets of bearings in single-side test was relatively high, and the grease was washed away. After disassembly, it was found that one side of the channel had poor superfinishing quality and left grinding wheel marks. This indicates that there is a certain deviation between the swing center of the oil stone and the curvature center of the groove after grinding, which affects the surface machining quality of the groove. According to the amplified sound signal of the speaker, there are 5 sets of obvious abnormal sound. Observing the grease inside, it is found that there is foreign body intrusion, and the superfine quality of the channel is not high.

(1) 2000 sets of 6204E were trial-produced by adopting the new process, and the final vibration test results verified the feasibility and effectiveness of this process, which accumulated preferable production experience for the production of low noise bearings.
(2) Improve the positioning accuracy of end face and outer diameter, provide a good process reference for grinding and superfinishing of bearing groove, and facilitate the processing of good groove surface quality. The vibration and noise levels of bearings can be effectively reduced by adjusting the process parameters of the groove superfinishing to form uniform and fine stripes on the surface.
(3) It is also an effective measure to reduce bearing vibration and noise to improve the assembly quality of bearings, strictly implement the process specifications and eliminate the bump on the working surface of bearings.