This article analyzes the reasons for burning bearings in rolling mills, explains the damage principles, and proposes several control measures based on actual operating experience, so as to reduce the number of burning bearings in rolling mills, thereby saving production costs and improving production efficiency.
Rolling mill bearing burning refers to the phenomenon of bearings getting stuck due to excessive wear during operation. It is usually caused by plastic deformation caused by a surge in heat generated by sliding between parts. Once the roller bearings are damaged, the rolling mill will not be able to operate normally. In this case, rolling bearing failure may occur. Overview of Rolling Mill Bearing Burning Rolling mill bearing burning refers to the jamming phenomenon of bearings due to excessive wear during operation. It is usually caused by plastic deformation caused by a surge in heat generated by sliding between parts. Bearing burning in the rolling mill will reduce the service life of the bearing. Generally speaking, each bearing has a budgeted service life. The rolling bearings used in rolling mills can operate normally before fatigue corrosion spots appear. The total number of working hours of the rolling elements of the rolling bearing running on the raceway is its service life. Once the roller bearings are damaged, the rolling mill will not be able to operate normally. In this case, three types of rolling bearing failure will occur. First, fatigue pitting corrosion. It refers to the fatigue pitting corrosion phenomenon that occurs on the surface of the inner and outer raceways or rolling elements due to the influence of the cyclic contact stress between the bearing track and the rolling elements after the rolling mill has been running for a certain period of time; second, plastic deformation. It refers to the uneven surface at the contact position between the rolling element and the raceway. This is mainly because the bearing needs to carry large static loads and impact loads, which will cause local stress to exceed the endurance limit of the material, leading to plastic deformation. At the same time, plastic deformation is often accompanied by noise. Third, bearing wear. If the working environment is harsh, the lubrication used in the bearings will often cause bearing wear if the seal is not good.
Reasons for premature bearing failure
Irregular operations during assembly and disassembly
Based on practical operating experience, the most obvious reason why bearings cannot reach their expected service life is irregular operations during assembly and disassembly. Correct tools should be used when assembling and disassembling bearings. If the tools do not meet the requirements, there will be a gap between the bearing seat and the bearing assembly. The remaining gap will cause wear of the bearing raceways and rolling elements. This also shows that correct tools must be used during the assembly and disassembly of bearings, so that the force can be evenly distributed during installation and reduce wear between bearings. In addition, a certain gap should be left between the bearing shaft and the bearing seat according to the gap between the short stress rolling mill bearing seat and the bearing assembly. However, this gap should not be too large, because if the gap between the roller bearing seat and the frame is too large, the shaking of the bearing seat will also increase, causing excessive impact loads to act on the bearings, causing the bearings to The service life is reduced. At the same time, excessive impact loads will also affect the positioning of the bearing seat, change the force distribution of the bearing seat, and deepen the damage to the bearing.
Improper use of lubrication
The reason for lubricating the bearing is to use the oil film to protect it. After adding lubrication, the oil film can isolate the surface of the moving rolling elements, so that the bearing can perform stably during operation and increase the accuracy of rotation. Once the lubrication is used improperly, too little or unevenly distributed, the bearing will wear out, resulting in bearing failure.
Grease pollution
A small part of the reason is pollution, which mainly refers to the decline in the quality of oil. If the grease is contaminated due to poor sealing or the quality of the grease itself is not up to standard, the quality of the lubrication will be reduced and the ideal performance will not be achieved. The rolling mill’s rolls are cooled by turbid ring water, which easily contaminates the lubricating grease, increases the wear between the bearings, and reduces the service life.
Negligence in maintenance work
Improper maintenance is a major reason, and it is also easier for people to ignore. About 40% of bearing failures are caused by insufficient later maintenance. Bearing spare parts need maintenance work after long-term use. At this time, the bearing has been overloaded. If it is not maintained in time, fatigue damage will occur. In addition, friction often occurs during the crawling process of the rolling mill. The pull-welding rolling groove will discharge the welding current. The lubricating film of the bearing cannot withstand the impact of the current, so electrical corrosion will occur in the bearing track, causing unevenness on the bearing surface. . In this way, the friction on the bearing surface increases even more. The direct consequence is that the bearing inner ring, bearing outer ring, and rolling elements are all worn, and this wear is uneven, resulting in a reduction in the service life of the bearing.
Control measures to prevent bearing burning in rolling mills
Burning of rolling mill bearings is a common problem in the actual production process. Frequent damage to rolling mill bearings not only has a negative impact on the production schedule, but also increases production costs. The author believes that the following measures can be taken to reduce the phenomenon of rolling mill bearing burning. The emergence of rolling mills reduces the number of burned bearings, thereby saving production costs and improving production efficiency.
Offline assembly and debugging of rolling mill bearings
First of all, we must ensure that the rolling mill off the line is in good overall condition, carefully check the bearing seats of the rolling mill, clean the bearing seats, and ensure that there are no foreign objects inside. Before assembly, recheck whether there are foreign objects or component deformations in the bearing seat. If found, they should be solved immediately. If the component deformation is very serious, it should be replaced according to the assembly requirements of the bearing seat. In addition, it is necessary to ensure that the roll balancing device of the rolling mill is intact, and the adjustment device must be inspected, cleaned and lubricated in the preliminary work. A gap is created between the nut and the downwardly pressing nut, which causes the roller to shake to a large extent and affects the force distribution.
Enhance details
Before inspection and assembly, it is necessary to ensure that there are no foreign objects in the bearing seat, that the bearing frame is well sealed, that a suitable gap distance is left between the rolling elements and the raceways, and that the bearing inner sleeve and the rolling mill bearing seat are aligned. The rolls must be kept clean, the roll neck must be clean, and oil stains and other foreign matter on the surface must be removed. The inner sleeve of the bearing needs to be heated before installation. The heating temperature needs to be controlled within the specified temperature. The entire assembly process must ensure the integrity of the surface finish of the equipment. After the assembly is completed, the rolling mill must be inspected axially and radially, and the axial adjustment amount should be controlled within 5mm. The fixing situation related to the bearing seat should also be checked to ensure that all parts are in an effective fastening state, and the parts that need lubrication should be lubricated to ensure that the roll bearings are evenly stressed.
On-line assembly and debugging of rolling mill bearings
During the on-line assembly process of rolling mill bearings, it is necessary to ensure that the rolling line is consistent with the center line. Only in this way can the upper and lower rollers rotate in parallel and ensure that the axial force of the bearing is relatively uniform. Under normal circumstances, the slide rails of the rolling mill base will be worn and need to be checked in advance. Otherwise, the rolling mill will shake during operation, causing the rolls to bear impact loads beyond the endurance range and shortening the service life.
Rolling mill bearing seats and bearings are used online
Staff should promptly record the use information of roll chocks and bearings, analyze their use in the actual production process, and replace bearings that have been severely worn and failed. Online operations should require standardized operations, adjust the tension step by step, and assist in adjusting the speed to avoid impact forces that exceed the yield limit of the material. Regularly repair the lubrication points of the rolling mill to minimize long-term uninterrupted welding work on the rolling mill. At the same time, pay attention to detecting the temperature around the bearings, report any abnormal phenomena in a timely manner and be prepared to solve the problem. Control the rolling speed within a reasonable range and do not allow low-temperature steel to be rolled in unreasonable low-temperature environments to ensure that the rolls can maintain efficient operation. Staff on duty need to perform operations in accordance with the operating specifications and frequently check the temperature of the roll surface to prevent the temperature of the roll surface from being too high, otherwise the protective effect of the lubricating grease on the roll surface will be reduced. Deformation will also occur during the operation of the rolling mill. Workers should also observe frequently to reduce deformed rolling parts and avoid affecting the bearing seat.
Prevention and rectification of accidents
First of all, it is necessary to do a good job in hardware maintenance. Spare parts must be of high quality. Analyze the use of bearings based on actual conditions. If spare parts are found to have failed, they must be cleaned up in time and the maintenance and protection of spare parts must be done. Once a production accident occurs, we must keep in mind the handling principle of “equipment is the foundation and operation is the key”, conduct analysis based on the actual situation, and organize professionals to solve the problem. At the same time, it is also necessary to strengthen the training of professional staff, improve workers’ standardized and operational work skills, cultivate a sense of responsibility and trust, improve the production process supervision system, and prepare for accident prevention.
