Application optimization of back-up roll bearing of 1050 rolling mill

　　Abstract: the use of backup roll bearings of 1050 rolling mill in a company was tracked and recorded. It was found that 90% of the bearing consumption was concentrated in the lower roll box, which was abnormally damaged in a short time, seriously affecting the normal operation of the rolling mill.
 

　　1、 Bearing damage and characteristics

　　1. All the damaged bearings are lower roll box bearings, and the outer ring bearing area, peeling or cracking occurs.

　　2. At the same time, the seal ring of the bearing housing gland is damaged, chapped, hardened and deformed.

　　3. The wear groove of labyrinth ring at the corresponding sealing ring lip at the roll diameter.

　　4. A large amount of coolant accumulates in the bearing housing.

　　5. The inner ring has run off, and the end face of the inner ring is abnormally worn.

　　6. The bore surface of the bearing housing corresponding to the outer ring of the bearing is seriously damaged.

　　2、 Analyze the cause

　　From the above 2/4 phenomenon, it can be directly judged that there is a problem in the sealing and lubrication of the whole bearing roll system, because the upper roll is relatively superior to the lower roll, in addition to the relatively small rolling load, the most important thing is that the working environment is relatively superior and is not infringed by the coolant or cleaning fluid, that is, there is no problem in the lubrication of the upper roll bearing, and the bearing should not be damaged under the same rotating speed and similar rolling force, Therefore, it can be determined that one of the main factors that the lower roll bearing is particularly easy to be damaged is the problem of sealing and lubrication. When the seal is invalid, the coolant and outer diameter pollutants directly enter the lower roll bearing housing and accumulate in the bearing area of the bearing, which always infringes the bearing grease, resulting in complete failure of the lubrication effect, resulting in friction between metal and metal, and bearing spalling in a short time.

　　The cracking of the outer ring of the bearing can be judged as the direct cause of phenomenon 6. The outer ring of the bearing is matched with the outer diameter of the roller box (with large defects), and a series of factors such as less contact area, bumps, ellipses, etc. lead to the damage and cracking of the outer ring.

　　3、 Rectification suggestions

　　1. It is recommended to install a waterproof labyrinth to effectively drain the harmful liquid without directly damaging the bearing, restore the outer diameter surface accuracy of the roll labyrinth ring (roll diameter waterproof sleeve), and prevent the short-term damage of the sealing ring caused by the clamping or wear of the labyrinth ring (roll diameter waterproof sleeve).

　　2. During the repair of the bearing housing hole of the lower roll, due to the bearing damage, disassembly and scratch, the bearing housing hole has deformation ellipse, which seriously affects the normal use of the bearing and limits the normal operation of the rolling mill. Through the repair, the precision coordination between the bearing housing hole and the outer ring of the bearing is restored to improve the stable operation performance of the bearing.

　　3. Repair and grind the surface damage of the roll diameter caused by race and jamming, especially the extrusion bulge and burr in the contact area of the inner diameter end face of the bearing inner ring, so as to prevent the surface corrosion of the roll diameter.

　　4. The outside micrometer for measuring the roll diameter of the backup roll shall be equipped to re measure and record the roll diameter (the repaired roll diameter of the bearing position) in the factory and control the reasonable tolerance range. Therefore, it must be tested before the installation of the bearing inner ring.

　　5. Replace the labyrinth ring that is worn out of the concave and convex on site, and make a reasonable fit with the size of the sealing ring.