Due to the continuous improvement of the market's requirements for the surface quality, thickness tolerance, and flatness of cold-rolled products, the requirements are especially strict for plates and strips. It drives the development of rolling mill equipment from two rolls to multiple rolls (eight rolls, twelve rolls, eighteen rolls, twenty rolls, and thirty-six rolls), so as to be able to roll thinner thicknesses, smaller tolerances, and better surface quality.
Therefore, higher requirements are placed on the bearings, especially the bearings of the backing rolls. The backing bearing is currently recognized worldwide as the first choice for back-up roll bearings for multi-roll mills, which requires the backing bearing to have high precision.
characteristic:
◎Can bear larger radial load
◎The operation accuracy level is better than p4 level
◎The outer diameter of the bearing is directly used as the roller surface
◎Separable and repairable
Installation features:
◎Inner ring and shaft are loose fit
◎Every 3 to 7 sets are a group, which is installed on the shaft as a group
◎Each set of bearings has a sequence number, which should not be disturbed during installation
◎The mark on the maximum wall thickness of the bearing inner ring must be in the same position when installing.
Assembly accuracy:
The accuracy required by the bearing itself is very high, especially the cross-sectional height (T value) from the inner diameter to the outer diameter after the radial clearance is eliminated. Keep it within 0.006 mm
Lubricating:
The effect of lubrication is directly related to the service life of the bearing. In addition to the performance and lubrication method of the lubricant, the lubrication effect is good or bad. The lubrication structure design of the bearing is the main factor. The number, size and location of the oil holes directly affect the lubrication effect. The lubricant should be confirmed before the design of the backing bearing Performance and lubrication method.
Three lubrication methods for backing bearings
◎Rolling emulsion lubrication
The most economical lubrication method, the non-sealed backing bearing mostly adopts its lubrication method, which requires a large flow of emulsion to quickly pass through the inside of the bearing to achieve lubrication and cooling.
◎Circulating oil lubrication
Mainly lubricate the backing bearing with lip seal, the lubricating oil flows through the inside of the bearing to take away heat, and then circulates to the lubricating oil base station for cooling and recirculation. Lubricants with higher viscosity can be used, which greatly improves the bearing life relative to emulsion lubrication.
◎Oil-air lubrication
Mainly lubricate backing bearings with lip seals. Clean and dry compressed air is used to blow the lubricating oil into the bearing to form pressure inside the bearing to make the lubricant adhere to the bearing surface while preventing the intrusion of foreign objects. The lubrication cost High, but the lubrication effect is the best.
Maintenance and repair:
Since the backing bearing is installed on the back-up roll of a multi-roll mill, the different distribution positions of the rolls will inevitably receive different forces, which results in different degrees of wear of the bearing. The backing bearing should carry a higher load after 2 cycles of use The position of the bearing on the support roller and the bearing on the lower supporting roller should be exchanged. The inner ring should be rotated by 90° in each cycle, so that the wear of the bearing can be kept as much as possible.
Because the rolling material requirements of the multi-roll mill are relatively high, after a certain period of time, due to the wear of the bearings, the accuracy of all aspects is reduced. When the requirements of the rolling materials cannot be met, the bearings need to be reground to restore the accuracy. Before the inner ring and rolling elements have obvious pitting and peeling tendency, only the outer ring needs to be ground (due to the special heat treatment process, the outer ring can be ground several times to maintain the same hardness as the original) surface to restore the bearing accuracy.
For the entire leased backing bearing with intact outer ring, missing or peeling rolling elements, and serious pitting or peeling of the inner ring, new parts and regrouping are required for repair.
EGI-BEARING has rich technical experience in the manufacturing and repair of backing bearings for multi-roll mills. For specific technical data, please contact the EGI-BEARING Technical Department.
