RollerMaintenance of bearings

Roller bearings need to be taken out of the mill regularly for inspection and maintenance to improve the service life of roller bearings. The frequency of bearing maintenance should be adjusted according to the operation of the rolling mill, mainly based on experience. The usual maintenance frequency is once every three months at full load, most rolling mills once every six months, and light rolling mills once a year in December. After the first 1000 hours of operation, the roller bearings should be disassembled and inspected. During operation, it is necessary to clean the bearing and check the oil seal. If necessary, replace the oil seal completely. If no abnormality is found, the interval of the secondary examination may be extended.

The general steps for roll bearing maintenance are: 1. Track and record the position of the bearing in the mill. It is recommended to use a special record card for roller bearing maintenance services. It is also necessary to pay attention to special lifting methods and tools when removing the bearing from the bearing seat or inspecting the bearing. 2. Clean the bearing. During the cleaning of the bearing, all flaking, water, residual lubricant and any other dirt that can cause serious bearing wear should be removed. 3. Check the bearings, including visual inspection and minor repairs. Pay attention to check and repair the bearing seat, and put the bearing back into the bearing seat as needed. 4. Lubricate the bearing. The existing common rolling mill has the characteristics of large rolling force and high rolling speed, which requires the lubricant to have excellent viscosity-temperature performance, oxidation stability, rust resistance and wear resistance. Therefore, the lubricant with better performance should be selected as far as possible to lubricate and maintain the roll bearings.

CommonRollerFailure forms and causes

1. Cracks. The cracks are mainly caused by excessive local pressure and rapid cooling and heating of the rolls. On the rolling mill, if the emulsion nozzle is blocked, resulting in poor local cooling conditions of the roll, cracks will occur. Because the temperature is low in winter, it is easier to crack than in summer.

2, peeling. If the crack continues to develop, it will form a block or flake. Those with light peeling skin can be polished again, and those with serious peeling skin will be scrapped.

3. Pit marks. Pit marks are mainly due to the weld or other debris of the strip into the rolling mill, leaving different shapes of pit marks on the surface of the roll. Usually, the grooved roller needs to be replaced. When the quality of the strip steel weld is not good, when the rolling operation passes through the weld, it should be raised and pressed to prevent scratches.

4, sticky roller. The reason why sticky rolls are also called sticky rolls is that there are broken pieces, wave folds and broken edges in the cold rolling process, and the bonding between the steel strip and the rolls is easy to form under high pressure and instantaneous high temperature, resulting in small area damage to the rolls. Through grinding, after eliminating surface cracks, the roller can still be used, but the service life is significantly reduced, and peeling accidents are prone to occur in future use.

5, clip stick. It is mainly due to the heavy skin of the strip steel caused by excessive pressure or slight folding and the heavy skin caused by the deviation of the strip steel. When the roller is severely clamped, the roller will be stuck and the strip will crack. When the pinch roller is slight, there are pinch marks on the strip and the roller.

6, broken.RollerThe main causes of fracture are overpressure (I. e. excessive rolling pressure), internal defects of the roll and the stress field caused by the uneven temperature of the roll.