Bearing model: 380640

Use part: 1380 mill work roll

Lubrication method: oil and gas lubrication

Rolling speed: 1000m/min

Overview: The operating side bearing of the work roll was found to be damaged during maintenance after 90 days of operation. The analysis is summarized as follows after checking the bearing and related mating parts:

1 Bearing structure and performance

The bearing structure is 380000 type structure four-row tapered roller bearing, which is composed of two double-row inner rings, one double-row outer rings and two single outer rings plus one inner spacer ring and two outer spacer rings. Due to the clearance between the inner diameter and the shaft diameter, it is often selected as a rolling mill roller bearing, which can meet the characteristics of fast loading and unloading, strong bearing capacity and simultaneous action of axial and radial combined loads. However, the relative self-aligning performance is poor, and the shaft is generally not allowed to tilt relative to the housing hole, if there is a maximum tilt of not more than 2 ". If the bearing bears the bending roll force and the inclination of the axis exceeds the requirement of 2 ", the roller and raceway of the bearing will produce additional stress, resulting in bearing off-load and other conditions, which will increase the bearing single row rolling element load and shorten the service life of the bearing.

2 Site damage characteristics

1, four rows of rolling body single row serious damage, individual fracture;

The damage is mainly concentrated on the edge of the rolling body (the rolling body is a convex roller, and the edge is a non-stressed area).

2. Bearing edge outer ring outer raceway force trace skew, corresponding to the end of the rolling body force trace is more obvious;

Outer edge ring A: The wide end has obvious force marks, and the force contact width is about 20% of the edge ring. And there is slight corrosion on the surface, and the narrow end is bright and has no force contact marks.

3, bearing inner ring edge stress and wear marks are serious;

In the whole set of bearings, the inner diameter wear of the half inner ring is slight, the wear of the half inner ring is serious, and the edge is serious.

3 Analysis and judgment

Comprehensive bearing structural characteristics and the above site damage characteristics analysis and judgment:

1, the bearing in the working state of the partial load is serious, the inclination of the central axis of the inner and outer rings of the bearing is far more than the 2 "requirement, especially when the raceway is in the working state, the surface 20% of the contact mark between the outer ring and the inner hole of the box is stressed, which will lead to additional stress on the roller of the bearing and the raceway, resulting in the bearing partial load wear resulting in the edge of the rolling body peeling off.

2, at the same time from the edge of the rolling body stress, the edge of the outer ring 40% stress and feature 3 inner ring edge stress wear can be proved, bearing in the working state of the partial load image is serious.

4 Symptomatic measure

According to the above field situation, the bearing off-load force is the main cause of the bearing damage, and the following analysis and improvement can prevent the occurrence of such phenomena:

1. Improve bearing housing and matching with bearing

If there is a defect in the inner hole of the bearing housing, please repair it in time to avoid uneven contact with the bearing outer diameter and insufficient rigid support.

2, check the roll neck (with the inner ring of the bearing), especially the small roll neck that has been used for many times, due to repeated wear and creep wear with the inner ring of the bearing, is bound to cause the difference in linearity, before installation, check the roll neck to see if there is an irregular diameter change, to avoid the uneven force of the inner ring, resulting in the bearing's load bias.

3, optimize the bearing

3.1 Control bearing inner diameter tolerance at 0 position to avoid excessive clearance between inner diameter and journal;

3.2 Control bearing outer diameter tolerance in lower tolerance, easy installation.

3.3 Adjust the convex value of the rolling element so that the maximum stress point of the rolling element, inner ring and outer ring is controlled in the middle position after loading.

3.4 Adjust the hardness of the bearing clearance spacer to avoid wear changes after repeated use, resulting in uneven clearance, single column force, bearing load bias.