Support roller bearing damage reasons and examples

A, supporting roller bearing damage reason analysis of tandem mill roll radial supporting roller bearings with cylindrical roller bearing, rolling process, the effect on the working roller and supporting roller axial force, respectively, by the work roll bearings and back-up roller thrust bearing, the main reason of abnormal supporting roller bearing damage is axial force is too large, causing the axial positioning locking plate damage. 1, axial force causes the common four roll strip mill, ideally, can think of no axial force, PC mill because of the cross roll system, in the process of PC in itself will produce a part of the axial force and so on PC mill supporting roller selection is considered part of the axial force, also due to mill manufacturing and assembling error, raw material with transverse thickness error, mill using relevant parts wear and deformation in the process of a series of factors such as the role of the mill will inevitably produce axial force. 2, the main axial force generated factors due to the distance between the roll is produced, in the process of rolling, supporting roller is always rely on tight entrance on one side of the memorial arch, work roll on export on one side of the memorial arch. Analysis of site condition, resulting in search for the cause of support roller large axial channeling force, found a PC running wide cross head position, due to lines to work roller and support roller is not parallel, produce certain Angle between two roller line, as shown in figure 1. Figure 1 illustrates the work roll surface linear velocity along the axis of the supporting roller and axis vertical decomposition, the income of Vb is equal to the linear velocity on the surface of the support roller Vb, Vb = Vwcosa = Vb1 also got the component in supporting roller line of Vw Vwc for Vwc = Vwsina. In the process of rolling, roll system under the effect of rolling force P, two roller contact surface is - Ribbon, on this ribbon, two roll along the axis of the supporting roller has a relative sliding speed Vwe, according to the theory of friction can be know: supporting roller is bound to give work roll a and Vwc in the opposite direction of the effect of sliding friction, which itself was a and Vwc direction at the same time instead of sliding friction role, namely, the axial force produced by crossing Angle. Three axial force and other factors in addition to the axial force caused by the axis is not parallel, the following factors also can produce axial force: A) Roll caused work roller and back-up roller cone axis angular velocity is different at both ends and make cross; B) Arch with roller assembly; C) Support roller friction coefficient increase or both ends of the oil film bearing oil film bearing lubrication conditions; D) Universal shaft obliquity caused by the horizontal component of the work roll shaft head suffered but these force and roll system axis of cross compared the friction effect is very small. Second, supporting roller bearing damage forms for example 1, supporting roller bearing retainer scratch card injury and causes of ring guard and the end of the roll body scratch called card, due to the rolling body hard, generally cause retaining ring surface roughness, accompanied by small soluble apply, inner ring surface transverse scratch ( See figure 2) 。 Figure 2 ring and inner ring hurt the cause of the scratch card: ( 1) Retaining ring size design is unreasonable, assembly process contact ke injury; ( 2) Qualitative hard foreign invasion; ( 3) Bearing tilt of skew roller; ( 4) Produce sliding rolling. 2, bearing indentation and the reason analysis card into the pits of solid foreign bodies or the impact surface and the scratch when the installation form of organization ( See figure 3) , the relative sliding friction between the bearing parts under the action of the indentation and wear. Continue to wear will make the parts size and shape change, bearing fit clearance increases, working surface morphology becomes bad, thus loss of rotating accuracy, bearing cannot work normally. FIG. 3 the main reason is the load is too large, poorly fitting ( Non linear) And large torque load, seal is bad, etc. 3, supporting roller bearing wear analysis support roller bearing per cycle use running time is 12 ~ 15 days, online running total time about 5 months each year, 12 ~ 16 months for an overhaul in oil, rotary load area. After overhaul, we found that the abrasion of the bearing and bearing wear regularity of other situations have bigger difference, As shown in figure 4, 5) 。 The Numbers for the No. 6, model for RZ - Typical 1040 aa of the bearing, the overhaul appraisal situation are shown in table 1, bearing is not normal wear and tear, not only reduce the movement precision of the bearing, the high precision of rolling plate is very bad, also make expensive bearing life. Figure 4 figure 5 the support rod mill bearings mainly has two reasons for abnormal wear: 1) Bearing internal clearance is larger contact Angle decreased, while working in the number of rolling element bearing is less, the local contact stress is too large, the bearing capacity of the bearing, and destruction of oil film, metal to metal contact type adhesive wear. 2) Clearance big result in rolling element bearings in the loading area and their contact is not close, not pure rolling, rolling body in keeping the tentacles, improve the bearing capacity, at the same time reduce the bearing wear.