Description of the phenomenon：

Netizens have reported that for the hot-rolled materials used in the FC5678220 and FC4054170 bearings, there are occasional unstable phenomena during use. Sometimes, there are occasional incidents of the rollers burning out online. Sometimes, when the rolling machine is taken offline for inspection, cracks or fragments can be found on the inner sleeve, as shown in the following pictures:

Reason analysis:

1. On-site, valuable bearing inner sleeve samples were taken for inspection. The hardness and metallographic structure of these samples met the process requirements.

2. Judging from the shape of the crack, this phenomenon occurred due to the excessive interference fit between the bearing inner sleeve and the roller neck, resulting in a burst fracture.

3. The chamfer R value of the roller neck is greater than that of the inner hole of the bearing inner sleeve. Although it seems that the inner sleeve can be installed properly at first glance, this end of the bearing inner sleeve has a tendency to be suspended. The alternating rolling force during use will cause radial circular micro-cracks on this end face of the bearing inner sleeve. The development of the crack depth can lead to the aforementioned damage of the inner sleeve.

Corrective and preventive measures:

1. Measure the actual size of the roller diameter and calculate the interference value for the fit.

2. Measure the actual R value size of the chamfer at the roller diameter, and compare it with the actual R value size of the inner hole of the bearing sleeve. Determine whether there is a situation where the R value at the roller neck is greater than the R value of the inner hole of the bearing sleeve. Of course, when the two R values are matched, it is also necessary to ensure the length of the chamfer of the inner hole of the bearing sleeve (axial and radial), which is also very crucial.

Conclusion：

Due to the diverse installation conditions and on-site usage environments of hot rolling, it is necessary to produce rolling machine bearings that are tailored to actual applications, so as to achieve a win-win situation for both the manufacturer and the users.