Lubrication and sealing of bearings for high speed wire rolling mill

Whether the working performance of rolling mill bearings can be effectively utilized depends on the lubrication conditions to a large extent. Lubricating oil is called "the fifth component of bearings". More than 40% of mill bearing damage is caused by poor lubrication. Therefore, in order to reduce the consumption of rolling mill bearings, it is necessary to choose suitable lubrication methods and high-quality lubricants for the conditions of use, and prevent the intrusion of foreign bodies such as water and oxidation scale during design and installation. It means sealed.
At present, rolling mill bearings are mainly lubricated by grease and oil and gas lubrication. At present, most manufacturers use simple grease lubrication methods. If possible, oil and gas lubrication technology can be used to make the rolling mill bearings work under ideal lubrication conditions, which will greatly reduce the consumption of bearings.

1, grease lubrication
The grease lubrication method has the characteristics of simple operation, convenient roll replacement, etc., and is widely used. The suitable grease should be selected according to the working temperature, speed, rolling force, sealing and waterproof performance, the size of shock and vibration, and the supply method of grease. Grease produced by regular manufacturers 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 procurement cost of high-performance grease is high, the amount is small, the bearing life is long, and the total comprehensive cost is reduced. In addition, the amount of grease to be filled must be appropriate and filled in place. Different grades of grease can not be mixed, so that the working surface of the rolling mill bearing is always in a normal oil film state.

2, fat filling amount
When the grease is first filled, the inner space of the bearing can be filled. For vertical or inclined rollers, the upper and lower covers of each bearing seat should be filled with sufficient grease. After each roll change, check whether the grease is hard and black, 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 sealing parts and sealing structure should be replaced or improved in a timely manner; If the situation is OK, you can continue to use after adding new grease.

3, oil and gas lubrication
Oil and gas lubrication is an ideal lubrication method for bearings. During operation, compressed air carries oil droplets into the bearing at regular intervals. The lubricating oil stays inside the bearing. During the operation of the bearing, the air takes away the heat to prevent external impurities. Water vapor seeps into the bearing. Oil does not atomize, does not pollute the environment.

4. Sealing device
The seal of the bearing is to maintain a good internal lubrication state, prevent cooling water, iron oxide scale and impurities from entering the working surface, in order to extend the service life of the bearing. Due to the sealing problem of rolling mill bearings, the most damaged bearings are those close to the side of the roll body. Bearings often cause grease contamination and loss, so that the working surface of the parts wear, spalling or even broken, especially the penetration of the emulsion of the cold strip mill makes the grease fail faster.

Bearing seals are divided into self-sealing and external sealing. The outer seal is mainly designed with the combination of labyrinth and contact. The more maze series (not less than the two poles), the smaller the gap, the better the sealing effect. According to the size of the bearing, the clearance of the maze is 0.6 to 1.5mm on the radial side and 4 to 6mm on the axial side.
Contact frame oil seal: widely used in rolling mills, in order to increase the effect, two or three can be used in parallel. The oil seal is oriented and cannot be installed in reverse. The hot rolling mill is generally equipped with two oil seals, and the two oil seals must face the bearing seat outside to prevent the infiltration of external dirt. The cold strip mill is generally equipped with three oil seals, and the lip of an oil seal near the bearing should be inward to prevent oil from spilling and affecting the quality of the rolling material. Be careful when using the oil seal to avoid damaging the lip when installing the roller and affecting the sealing effect.