I. Unit parameters:

Mill model: 850 20-high reversible single machine

Maximum linear speed of unit: 600m/min

Product specification: Precision stainless steel thin tape

Maximum width: 750mm

Thinnest thickness: 0.1mm

Common rolling force: 3500KN

Lubrication method: rolling oil

Bearing type of support roll: NNCF2045130

Ii. Assembly structure and site fault overview

In the first cycle (about 22 days per cycle) when the bearing runs on the machine, it is found that the bearing end face of the second set of B roller is worn, leading to cracks in the bearing end face, wear of the saddle gear piece and damage to the wear gasket.

3. On-site problems and phenomena

1. After the B roll was disassembled, it was found that friction occurred on the B end face of the bearing outer ring, regular strip cracks in the radial direction and metal friction burns in the circumferential direction were generated on each circle, and normal wear on the A end face of the outer ring was not abnormal.

2. wear on both sides of the wear gasket, and compression subsidence step;

3, the corresponding saddle gear plate guard end face wear is serious, installation of wear-resistant gasket groove bottom abrasion;

4. Check that the cage, inner ring and rolling body are normal except the bearing ring B end face wear;

5, wear-resisting gaskets are divided into two thickness specifications, a nominal size of 8mm, a nominal size of 4.5mm, respectively installed on ADEH and BCFG saddle component end face, used to separate the bearing end face and saddle end face to avoid metal sliding friction, but also limit the axial displacement of the bearing outer ring, bearing all the axial thrust generated during rolling;

Check the installed roller system, the whole group and disassembly measurement found: ADEH installation of 8mm wear-resistant gasket roller system, bearing end face distance from the saddle and the head end are more than 5.5mm, the installation of the bearing outer ring after the axial movement of 1-1.6mm, can effectively and safely separate the bearing end face and the saddle component end face, eliminate the problem of metal interference friction.

Check the roller system of BCFG installation of 4.5mm wear-resisting gasket, bearing end distance from the saddle gear plate and the boss end face spacing is small, the minimum distance of measurement is 1.2mm, the axial channel momentum of the outer ring of the bearing after installation is 1-1.9mm, although the bearing end face and the saddle component end face separation, but because the distance is too small, There is a problem of metal interference friction between bearing end face and saddle end face during operation.

After measuring the thickness of the wear gasket, it is found that the thickness tolerance of the nominal size of 4.5mm is seriously out of tolerance, and the minimum size is 4mm.

Iii. Reason analysis

In summary, analysis of the above problems and phenomena: Bearing outer ring B end face friction, outer ring A end face normal wear without any abnormal, wear on both sides of the wear-resisting baffle plate and sink step, it can be judged that there is heavy mutual sliding friction between outer ring B end face and wear-resisting gasket, friction high temperature leads to the bearing end face B thermal crack. Under the action of friction and axial force, wear, high temperature, height and size of the wear gasket will occur. As a result, the isolation effect is lost, resulting in metal friction between the B end face of the second set of bearing B of B roller and the gear end face of the corresponding saddle, resulting in this failure.

Iv. Preventive measures

1. Strictly control the thickness and size of wear-resisting baffle, especially the thin baffle with BCFG configuration;

2. Check the used baffle plate and replace it if the thickness is out of tolerance;

3. On the premise of no axial clamping and interference bearing outer ring rotation after installation, increase the thickness of the baffle plate and re-determine the size;

4, the use of high hardness and high wear resistance of the baffle; (electrical wood, high hard tetrafluoroethylene);

5. Strictly control the accuracy of bearing, saddle and mandrel to reduce the occurrence of axial force during rolling.