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How to choose the right rolling mill bearing for the steel mill? (Part Ⅲ)

Feb 21, 2023
1 Establish the bearing use file and adjust the bearing stress area
Establish bearing use files, clean and inspect the bearings regularly, check the wear of the inner and outer raceways and the surface of the rolling elements, check the clearance, replace it if it exceeds the standard, and rotate the outer ring of the bearing by 120°-180° to replace the force Location. When the equipment needs to replace the bearings, the original bearings of the same manufacturer should be selected first, and the rest should be selected and combined after careful measurement.

2 Adjust the roller assembly accuracy
Regularly inspect and adjust the side slide plates of the bearing housings of the work rolls and backup rolls to ensure that the axes of each roll are parallel. In order to reduce the additional axial force caused by the cross-rolling surfaces of the rolls, the bearing seat of each set of rolls should be strictly controlled in the use range, and should not be used with each other at will. In addition, the transmission system, especially the universal joint shaft, should be replaced regularly, otherwise, additional axial force will be generated due to oscillation caused by excessive total clearance.

3 Improve the bearing seal structure
There are two suitable methods for improving the bearing sealing structure. Method 1: Change the installation direction of the seal ring, and the lip of the seal ring faces outwards to prevent external dirt from entering; Method 2: Add a seal ring on the end face, which can effectively prevent the emulsion from entering the inside of the bearing.

4 Reasonable selection of lubricating oil
Roll bearings are mostly lubricated with grease, and oil lubricated at high speeds.
The purpose of bearing lubrication is to form an oil film on the rolling surface and sliding surface, and to form an elastohydrodynamic lubricating oil film between metal surfaces. When the lubricant is selected correctly, the lubricant is clean enough, and the speed, temperature, and load are appropriate, the service life of the bearing will far exceed the calculated life. Therefore, reasonable selection of lubricants is crucial to the service life of roll bearings.
Grease selection points:
(1) The higher the rotation speed, the grease with larger penetration should be selected;
(2) When the ambient temperature is low, grease with high penetration should be selected;
(3) When the ambient temperature is high, a grease with a higher dropping point should be selected;
(4) If strong water resistance is required, sodium-based grease cannot be used, because sodium-based grease is easy to emulsify;
(5) The cleanliness, corrosion resistance, water content and oil separation of grease should pay attention to its indicators.
Based on the above points, according to different seasons, different working conditions, different product specifications and other conditions, the type of grease can be adjusted in time to achieve economy and efficiency. Under other conditions, oil mist lubrication can also be used. Oil mist lubrication will greatly reduce the working temperature of the bearing and improve the lubrication conditions. The life of the bearing will be greatly improved, but the relative cost is higher than that of grease.

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