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Causes and remedial measures of deep scratches and drag marks on the contact surface of rolling bearings

by:JNSN     2021-12-26
In addition to local fractures, cracks and other pits on the surface of the raceway or rolling element, there are often large-area surface damage caused by wear caused by the sliding of the rolling bearing. In addition to the operating conditions, the degree of damage is essentially affected by the viscosity and cleanliness of the lubricant. 3.3.4.1 Wear phenomenon caused by poor lubrication: the contact surface is dark and rough, see Figure 28 and 66. The abrasive substance darkens the color of the lubricant; when a brass cage is used, the color of the lubricant turns yellow. Grease will also harden. In many cases, however, moisture reduces the consistency of the lubricant and becomes thinner. Wear causes a decrease in preload or an increase in bearing clearance. If foreign particles are the cause of wear, there will be severe scratches on the surface of the rolling elements, see Figure 67. Under unfavorable conditions, the raceways of rolling bearings will wear unevenly in their circumferential direction. The raceway surface is striped, see Figures 68 and 69. This wear causes fatigue damage, please refer to section 3.3.2.1 Fatigue caused by wear. Reason (1): Lubricating oil film that cannot be carried. Lubricant contamination (fine hard particles such as dust or water). Uneven wear caused by improper adjustment of tapered roller bearings. 42 Evaluate the running characteristics and damage of the removed bearing. Rolling Contact mode 66: worn, rough raceway 67: first signs of wear will be detected on the surface of the rolling element. Remedy: Use a higher load-bearing lubricant, such as a higher viscosity lubricant or the use of EP additives to shorten the lubricant replacement Cycle improvement, sealing and filtering lubricant to ensure the correct adjustment of the bearing 433.3.4.2 Scuffing on the outer diameter of the rolling element: the circumferential dent in the contact area of u200bu200bthe rolling element. There are parallel circumferential traces on the rollers, see Figures 70 and 71. For balls, yarn balls are often seen, see Figure 72. Not to be confused with edge marks (see section 3.3.2.6). The edge of the trajectory formed by the edge movement is smooth due to plastic deformation, and the abrasion has a sharp edge. Hard particles are often embedded in the cage pockets, causing scratches, see Figure 73. Reason (two): Contaminated lubricant; hard particles embedded in the cage pockets, which act like abrasive particles on the grinding wheel. Remedial measures: Ensure clean installation conditions, improve sealing, filter lubricant 44, evaluate the removed bearing Running characteristics and damage. Rolling contact mode 72: Scratches on the surface of the ball are like yarn balls. 73: External particles embedded in the crossbeam of the cylindrical roller bearing cage. Such as full complement bearings. Slip causes the raceway or rolling elements to become rough. The material is often piled up and accompanied by drag marks. It is usually not evenly distributed on the surface but in dots, see Figures 74 and 75. Small pitting corrosion is often found, please refer to section 3.3.2.1 of fatigue caused by poor lubrication. Reason (three): When the load is too low and the lubrication is poor, the rolling elements slip on the raceway. Sometimes because the load-bearing area is too small, the roller decelerates rapidly in the cage pockets of the non-load-bearing area, and then accelerates sharply when entering the load-bearing area. The speed changes rapidly. Remedial measures: Use bearings with low load carrying capacity to preload the bearings, such as using springs to reduce the bearing clearance and ensure sufficient load to improve lubrication scratches: For separable cylindrical roller bearings or tapered roller bearings, The rolling elements and raceways have missing materials that are parallel to the axis and equally spaced from the rolling elements. Sometimes there are several sets of marks in the circumferential direction. Usually there is this trace only in the circumferential direction of about B/d instead of the entire circumferential direction, see Figure 76. Reason (4): When installing a single ferrule and a ferrule with rolling elements, they are misaligned and rubbed against each other. It is especially dangerous when moving components with large masses (when the thick shaft equipped with the bearing inner ring and rolling element assembly is pushed into the outer ring already installed in the bearing housing). Remedy: Use suitable installation tools to avoid misalignment. If possible, rotate slowly when installing the components.
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