Failure bearing model: four-row cylindrical roller bearing for rolling mills, FC4666206,
Dimension: 230×330×206mm,
Failure position: the inner ring
Failure mode: the bearing inner ring cracks along with the axial direction,
Failure: the inner ring cracks after using for a certain period of time, and that appears at any position of the sorting.
Analysis:
Technicians clean the bearing and check the bearing damage. It is found that there are friction marks on one side of the bearing end face, but not on the other side. Take the inner ring back to the factory for pickling inspection, and take two end faces of the same inner ring respectively.
Observe the bearing end face after pickling, There are friction marks and many cracks on one of the end faces. And not on the other end. Therefore, it is concluded that the bearing cracking is caused by thermal cracks caused by end friction. The parts that rub with the end face of the bearing the inner ring are only roller cone sleeves. Therefore, the cone sleeve is fixed with the roller to ensure that the cone sleeve does not run and prevents sliding friction with the inner ring.
After fixing the cone sleeve for a period of time, it is found that the problem of inner ring cracking has not been completely solved.
The technician measured the roll diameter on site and found that the roll diameter was too large.
Measure the diameter of the new unused roll more than 10 pieces;
Measure more than 5 new unused bearing inner rings.
The data obtained are as follows:
The roll diameter size of the roller is ø 230 + 0.09; ø 230 + 0.08; ø 230 + 0.10; ø 230 + 0.09; and ø 230 + 0.07
The diameters of the rolls are in the range of (ø230 + 0.07 ~ 0.10).
The inner diameter of inner ring is Ф 230-0.00; Ф 230-0.01; Ф 230-0.00; Ф 230-0.01; and Ф 230-0.00
The inner diameter of the bearing shall meet the size range specified in GB / T308.1.
It can be seen from the above data that the interference between the bearing inner ring and roll diameter is 0.07 ~ 0.11mm.
It can be seen that the interference of bearings with an inner diameter of (230) is 0.05 ~ 0.079mm in the P6 tolerance zone and 0.084 ~ 0.113 in the R6 tolerance zone.
The interference is in the R6 tolerance zone.
This bearing is used in the high-speed hot rolling mill, and the P6 tolerance should be selected. Therefore, the roller diameter size should be modified to be Ф 230 + 0.05 ~ 0.07 in cooperation with the roller manufacturer.
After 3 months of service tracking, the bearing inner ring crack did not happen again.
Therefore, the reason for bearing inner ring cracking is hot crack caused by end-face friction and improper selection of fit tolerance. Bearing failure should be found from many aspects to solve the problem from the root.
TEDIN produces four-row cylindrical roller bearings and four-row tapered roller bearings for cold or hot rolling mills:
Diameter range: ID 80-1200mm;
Precision Grade: Class P5, Class P4;
Tapered rollers: with logarithmic profile, which prolongs the bearing's service life.
Material: imported TIMKEN steel, or OVAKO steel, high purity;
Custom internal design and dimensions.
Please check the Product Guide to select suitable bearings for your machinery.
Check more types of Rolling Mill Bearings!
E-mail: sales@tedin-bearing.com