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

Whether the working performance of rolling mill bearings can be used effectively depends to a great extent on the lubrication situation, and the lubricant is called "the fifth largest component of the bearing". More than 40% of the damage to rolling mill bearings is caused by poor lubrication. Therefore, to reduce the consumption of rolling mill bearings, it is necessary to select a lubrication method and high-quality lubricant suitable for the conditions of use, and to design and install a reliable installation to prevent the intrusion of foreign objects such as water and scale. Sealing means.
At present, rolling mill bearings mainly use 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 is widely used. The appropriate lubricating grease should be selected according to the working temperature, rotating speed, rolling force, sealing waterproof performance, impact vibration size, grease supply method, etc. of the rolling mill bearings. The grease from a regular manufacturer with high temperature resistance, strong viscosity, good extreme pressure performance and high water resistance should be selected. According to the working characteristics of rolling mill bearings, 2#, 3#, lithium 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 the grease is filled for the first time, the inner space of the bearing can be filled up. For vertical or inclined rollers, sufficient grease should be filled 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, new grease can be added to continue to use.
3, oil-air lubrication
Oil-air lubrication is an ideal way to lubricate bearings. Compressed air drops into the bearing with lubricating oil drops at regular intervals during the operation of the bearing. The lubricating oil remains inside the bearing. The air takes away heat from the bearing during operation 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 seal of the bearing is to maintain a good internal lubrication state, and prevent cooling water, oxide scale, and impurities from immersing in the working surface to extend the service life of the bearing. Due to the sealing problem of the rolling mill bearing, the most damaged bearing is the part near the roll body. The bearing is often caused by grease pollution and loss, which makes the working surface of the part worn, peeled or even broken, especially the emulsion of the cold strip mill 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 design combining labyrinth and contact. The more the maze level (not less than 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 skeleton oil seal: It is widely used in rolling mills, in order to increase the effect can be used in parallel two or three. The oil seal is directional and cannot be reversed. Hot rolling mills are generally equipped with two oil seals, and the lips of both oil seals must be outside the bearing seat 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 for rolling mill bearings, which has been widely used in recent years. The RBR seal ring adopts an axial sealing method, and its lip is attached to the base surface of the gland, and is not affected by the roll bounce. The old grease inside the bearing can overflow, and the external cooling water, iron oxide scale and impurities are blocked by the lip Enter, 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.