A: 

1. Insufficient bearing lubrication will cause high temperature discoloration of the bearing.

2. Bearings are prone to scratches and peeling under high load and low speed applications or continuous high temperatures. This phenomenon is due to the thin or insufficient lubricating oil film that will accelerate the problem.

3. The bearing rollers are overheated. The rupture of the lubricating film will cause direct contact between the parts and cause local scratches. Thermal damage to the tapered roller caused by metal-to-metal contact.

4. The bearing is completely locked. Insufficient lubrication can lead to extreme local heating, and then produce metal flow in the bearing, changing the original material and geometric structure of the bearing.