Lubrication and sealing of bearings for high-speed wire rod mills

Summary:   Whether the working performance of rolling mill bearings can be effectively used depends on the lubrication to a larg...

   Whether the working performance of rolling mill bearings can be effectively used depends on the lubrication to a large extent. Lubricants are called "the fifth largest component of bearings". More than 40% of the damage of rolling mill bearings is caused by poor lubrication. Therefore, to reduce the consumption of rolling mill bearings, it is necessary to select lubrication methods and high-quality lubricants suitable for the conditions of use, and design and installation to prevent the intrusion of foreign matter such as water and scale. Sealing means.

   At present, the rolling mill bearings mainly adopt grease lubrication and oil-air lubrication. At present, most manufacturers use simple and easy grease lubrication methods. If possible, oil-air lubrication technology can be used to make rolling mill bearings work under ideal lubrication conditions, which will greatly reduce bearing consumption.

  1, grease lubrication
  The method of grease lubrication has the characteristics of simple and easy operation, convenient roll replacement, and wide application. The suitable lubricating grease should be selected according to the working temperature, speed, rolling force, sealing and waterproof performance of the rolling mill bearing, the magnitude of shock and vibration, and the method of grease supply. It is necessary to choose the grease from a regular manufacturer with high temperature resistance, strong viscosity, good extreme pressure performance and high water resistance. According to the working characteristics of rolling mill bearings, 2#, 3#, lithium-based grease or polyurea grease containing EP additives should be selected.

   Although the purchase cost of high-performance grease is high, the amount is less, the bearing life is long, and the total comprehensive cost is reduced. In addition, the filling amount of grease must be appropriate and filled in place. Different grades of grease cannot be mixed, so that the working surface of the rolling mill bearing is always in a normal state of oil film.

  2, fat filling amount
   When filling the grease for the first time, just fill the inner space of the bearing. For vertical roll or inclined roll, fill enough grease in the upper and lower covers of each bearing seat. After each roll change, check whether the grease is hardened and blackened, whether it is contaminated by impurities, and whether it is oxidized and emulsified. If the above situation occurs, the grease should be completely replaced and the seals and sealing structure should be checked and replaced or improved in time; if the situation is still good, you can continue to use it after adding new grease.

  3, oil-air lubrication
Oil-air lubrication is an ideal lubrication method for bearings. The compressed air brings lubricating oil drops into the bearing at intervals during the operation. The lubricating oil stays inside the bearing. The air takes away the heat during the operation of the bearing and prevents external impurities. Water vapor penetrates into the bearing. The oil is not atomized and does not pollute the environment.

  4, sealing device
  The bearing's seal is to maintain a good internal lubrication state and prevent cooling water, iron oxide scale, and impurities from entering the working surface to extend the service life of the bearing. Due to the sealing problem of rolling mill bearings, the most damaged parts of the bearings are near the side of the roll body. Bearings are often contaminated and lost due to grease pollution, which makes the working surface of the parts worn, peeled and even broken, especially the emulsion of cold strip rolling mills. Penetration makes the grease fail faster.

  Bearing seals are divided into two types: self-contained seal and external seal. The external seal mainly adopts a combination of labyrinth and contact design. The more stages of the labyrinth (not lower than the two poles), the smaller the gap, the better the sealing effect. The gap of the labyrinth is 0.6~1.5mm on one side in the radial direction and 4~6mm in the axial direction according to the size of the bearing.

   Contact type skeleton oil seal: It is widely used in rolling mills. In order to increase the effect, two or three can be used in parallel. The oil seal is directional and cannot be installed reversely. Hot rolling mills are generally equipped with two oil seals, and both oil seal lips must be directed to the outside of the bearing housing to prevent the infiltration of external dirt. Cold strip rolling mills are generally equipped with three oil seals and one oil seal lip close to the bearing should be inward to prevent the overflow of grease and affect the quality of the rolled material. Be careful when using the oil seal to avoid damaging the lip when installing the roller, which will affect the sealing effect.

   RBR seal ring: This is a rubber lip seal ring specially used for rolling mill bearings, which has been widely used in recent years. The RBR seal ring adopts the axial sealing method, and its lip is attached to the base surface of the gland, and is not affected by the roll beating. The old grease inside the bearing can overflow, and the external cooling water, iron oxide scale and impurities are blocked by the lip Into it, there is a better sealing effect. Moreover, it is easy to use, and the roll is installed in the bearing seat without any influence when changing the roll.