Cause analysis of burning loss of working roll operating side bearing of aluminum foil rolling mill

Generally, the plane of the two backup roll axes of the four high rolling mill does not coincide with the plane of the two work roll axes (except for the reversible rolling mill). The offset distance of the work roll from the outlet direction is 3mm for the 1550 aluminum foil rolling mill. This position relationship is guaranteed through the archway window. The bearing pedestal on the operation side is constrained by the roll, roll bending plunger, axial baffle and frame. Ideally, the axial force generated on the work roll is very small, about 0.5% ~ 1% of the rolling force. It is generally considered that the main factors of axial force during rolling are different thickness (cross section), uneven wear of work roll and backup roll, the non parallelism of rotation axis between rolls caused by the matching tolerance and circular runout of work roll and backup roll, and the excessive gap between work roll and backup roll bearing seat and archway in the state of heat balance. When the roll cross angle reaches 0.05 °, the axial force caused can reach 5% of the rolling force [1], which will seriously exceed the bearing load capacity and cause bearing burning.

1.2 insufficient bearing lubrication

Generally, the aluminum foil rolling mill is high-speed and high-temperature rolling, which generates large heat during production. Oil mist lubrication can be evenly lubricated to each friction pair. In addition, the specific heat of compressed air is small, the flow rate is high, it is easy to take away the friction heat, the oil consumption is low, and there is a sealing effect. Generally, the aluminum foil rolling mill adopts oil mist lubrication. Poor oil mist lubrication will lead to huge heat generated during high-speed rotation of the bearing, and the thermal expansion of the bearing ball will reduce the bearing clearance, resulting in increased wear of the inner and outer rings of the bearing, insufficient lubrication of the bearing, unable to take away the heat generated during high-speed rotation of the bearing in time, and finally lead to bearing locking and even fire of the rolling mill.

1.3 improper assembly of work roll bearing box

Aluminum foil products have very high requirements for plate shape and surface quality. The rolling mill needs to replace the work roll frequently and disassemble the bearing box for many times. When disassembling the bearing housing, pay full attention to the clearance of roll bearing. The control of bearing clearance is very important, because when the roll is running at high speed, the size of clearance has a great impact on the fatigue life, temperature rise, noise, vibration and so on. In terms of temperature rise, when the clearance is too large, it will cause uneven friction, which will lead to local fatigue damage of the bearing and reduce the service life of the bearing; When the clearance is too small and the rolling mill rotates at high speed, the sliding friction of the bearing ball is serious, the wear is intensified, and the bearing temperature rises rapidly, resulting in bearing sintering. After the rolling mill is loaded with a new work roll and started, the bearing will be locked in a very short time.

1.4 reasons for bearing quality

The quality problem of the bearing itself is also one of the reasons for the locking of the roll bearing. Sometimes after removing the locking bearing of the work roll, it will be found that the cage of the tapered roller bearing is completely broken. This situation can be determined to be caused by the quality problem of the bearing itself. Through many times of practice, it is found that if the cage of the bearing has slight cracks and continues to be used, when the bearing rotates at high speed and bears the load, the cage breaks and the roller cannot rotate normally, resulting in bearing burns and finally bearing locking.

1.5 influence of aluminum foil rolling process

In the process of aluminum foil rolling, work roll bending and tilting are frequently used, especially in the aluminum foil roughing mill. When the blank shape is poor in the opening pass, the tilting force is too large, or the blank is too narrow, the wave efficiency of the bending roll to the edge is insufficient, and the sudden belt break will lead to excessive axial load on the bearing, easy damage and bearing locking. With the continuous improvement and improvement of blank quality and rolling process, the burning loss of work roll bearing caused by this reason has rarely occurred.