Process and Key Points for Machining Stainless Steel Bearings

Changzhou Mechanical Processing Summary Forging Process Specification Steel contains complex carbides (Fe, Cr) 7C3, which dissolve slowly in austenite during heating, while the steel has poor thermal conductivity. Therefore, the forging heating speed should be slow. If the heating temperature is too high or the residence time in the high temperature zone is too long, it is easy to generate twins and damage the properties of the steel.

"Because the steel has good hardenability and poor thermal conductivity, the cooling after forging must also be slow, otherwise it is prone to cracks.". If the stop forging temperature is too high, it is easy to generate network carbide, and the coarse network carbide structure cannot be eliminated in the subsequent annealing process. This material has high deformation resistance, low plasticity, and poor forging performance at high temperatures, requiring special requirements for the material and structure of the mold.

In order to better evaluate the noise level of bearings, in actual measurements, vibration values at three points evenly distributed on the front and back sides of each set of bearings are measured, and the larger test value is taken as the effective vibration value of the bearing.

(1) Low noise lubricating grease can greatly reduce the vibration and noise of bearings. After greasing, 00% of them meet the requirements of Group Z2 (40 dB), and 98% meet the requirements of Group Z3 (38 dB). The product has a certain reserve accuracy. Due to some factors that are difficult to avoid in the system, such as the stability of the machine tool, the uneven quality of the grinding wheel and the dressing quality of the grinding wheel during the grinding process, and the uneven quality of the replacement and dressing of the oilstone and oilstone during the channel superfinishing process, the entire process system has certain fluctuations while meeting the processing accuracy requirements of the process, so the vibration value data in Table 2 has a certain degree of dispersion.

(2) During the testing process, it was found that the vibration value of 5 sets of bearings tested on one side was relatively high, and the lubricating grease was removed. After disassembly, it was found that one side of the groove had poor ultra-precision quality and left grinding wheel marks.

This indicates that there is a certain deviation between the swing center of the oilstone and the curvature center of the groove after grinding, which affects the surface processing quality of the groove. Judging from the amplified sound signal of the speaker, it was found that there were obvious abnormal sounds in 5 sets. By observing the lubricating grease inside, it was found that there were foreign matters invading, and the superfine quality of the channel was not high.

(1) Through the trial production of 2000 sets of 6204E using a new process, the final vibration value test results verify the feasibility and effectiveness of this process, accumulating valuable production experience for the production of low noise bearings.

(2) Improve the positioning accuracy of the end face and outer diameter, provide a good process benchmark for grinding and superfinishing the bearing channel, and facilitate the processing of good channel surface quality. Adjusting the ultra-fine process parameters of the channel to form uniform and delicate stripes on its surface can effectively reduce the vibration and noise levels of the bearing.

(3) Improving the assembly quality of bearings, strictly implementing process specifications, and eliminating bumps on the working surface of bearings are also effective measures to reduce bearing vibration and noise.