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Analysis of Common Causes of Bearing Damage
Due to its own quality and external conditions, the bearing capacity, rotation accuracy and friction reduction performance of rolling bearings will change. When the performance index of the bearing is lower than the usage requirements and cannot work normally, it is called bearing damage or failure. Once a bearing is damaged and other unexpected situations occur, various abnormal phenomena such as machine and equipment stalling and functional damage will occur. If the bearing is broken, you must first analyze the cause of the damage and then find a solution. Therefore, it is necessary to find out the cause of the occurrence in a short time and take corresponding measures.
Bearings are wear-and-tear parts. They only show signs of wear after accumulating to a certain extent, that is, they only break after a certain amount. Of course, the damage to rolling bearings is much complicated than the damage to general mechanical parts. Rolling bearing damage is characterized by multiple manifestations and complex causes. In addition to the internal factors of bearing design and manufacturing, bearing damage is mostly caused by improper use, such as unsuitable selection, unreasonable design, improper installation, poor lubrication, poor sealing and other external factors. The following 8 points are the main factors causing bearing failure:
If there is a lack of lubrication, the bearings will be easily oxidized and rusted by the air. To prevent bearing corrosion, do not soak with water. The bearings are made of chromium steel and stainless steel, but they are also afraid of water. When handling the bearings by hand, wash off the sweat on your hands and apply high-quality mineral oil before operating. Pay special attention to rust prevention during the rainy season and summer.
The specific reasons for natural bearing corrosion and wear are mainly as follows:
①Oxidative wear. The tiny peaks and valleys on the friction surface squeeze each other, causing the brittle surface layer to gradually fall off and wear. The tiny peaks and valleys on the relative motion surface of the bearing combine with oxidation in the air to form brittle oxides that are not firmly bonded to the base metal. This oxide easily falls off during friction, and the resulting wear is called oxidative wear.
② Friction generates heat and wear. When the bearing operates under high speed, heavy load and poor lubrication, high temperatures will occur due to friction at the peaks and valleys of the surface, the hardness and wear resistance of the contact points will decrease, and adhesion and tearing may even occur. This kind of wear is called frictional thermal wear.
③ Hard particle wear. If the bearings make relative motion. The structure of the moving surface of the bearing is uneven, there are hard particles, or impurities such as sand, friction chips, and chips fall into the moving surface of the bearing. During the relative motion of the bearing, hard particles or impurities can cause scratches or even grooves on the surface of the bearing. This kind of wear is called hard particle wear.
④Pitting corrosion wear. The rolling contact surfaces of gears, bearings, etc. are periodically subjected to large contact pressure during the relative process. After a long period of time, fatigue occurs on the metal surface, causing micro cracks and erosion on the bearing surface. This kind of wear is called pitting wear.
Causes rust or corrosion, wear and tear caused by chemical corrosion. The bearing surface is corroded by acids, alkalis, salt liquids or harmful gases. The wear process is accelerated, and this wear is called wear caused by chemical corrosion. Corrosion damage due to temporary contact with liquids such as water, acids, alkalis, salts, or harmful gases: non-moving bearings on equipment. Damage caused by rust or corrosion is called corrosion damage.
Bearing load is too large or improper use
Do not exceed the load of the bearing during use. In the case of a car, the load may be too heavy and the bearings may be easily damaged. Therefore, trucks have problems than cars, which is caused by the failure of many parts.
Bearing clearance is too small
The front wheel of the car uses a tilt-type bearing, and the clearance needs to be adjusted. If it is too loose, it will cause abnormal noise, deflection, and wheel shaking. Too tight will accelerate wear, both of which are bad. For old bearings, check whether there are burrs, scratches, or cracks on the ball (column) surface. Whether the radial clearance and axial clearance of the old bearing are qualified, generally only the radial clearance is measured. For new bearings, first check whether the bearing model is correct. Refer to Table 1 for the radial clearance standards of rolling bearings. For example: Model 6318 deep groove ball bearing, the inner diameter of the bearing is 90mm, the radial clearance range is 0.016~0.046mm, and the maximum wear amount of the bearing can also be found to be 0.25mm.
Use inferior bearings
The production process of the bearings does not meet the requirements. The accuracy of the shaft or bearing box is poor, and the bearing steel is pressed and produced without heat treatment, so the produced bearings are not durable.
Reckless driving may also cause damage to car bearings.
But this reason is a bit far-fetched. Because if you drive carelessly, other parts will break before the bearings.
Poor installation
When installing bearings, you must follow the installation steps of the bearings and do not install and disassemble them wildly. Whether the bearing is installed correctly is related to the service life of the bearing, so everyone must pay attention to it. When installing the bearing, avoid holding it directly with your hands, because the sweat on your hands may also cause corrosion. Don’t ignore the small details. When installing the bearing, the most important thing is not to allow strong stamping or to directly hit the bearing with a hammer. This is not because you are afraid of smashing it, but because you are afraid that it will be deformed. If the bearing is deformed, it will become unusable. Also, pressure is not allowed to be transmitted through the rolling elements.
Foreign body invasion
Try to use special tools and try to avoid using cloth and short fibers to prevent fine fibers from entering the bearing and causing unnecessary damage. For another example, when installing bearings, the staff once used the copper rod tapping method, which could easily cause uneven axial force on the bearing, cause deformation of the cage, damage to the rolling elements, and increase the clearance. In addition, during the tapping process, the copper rod Copper debris flies into the bearing cage, which can easily cause bearing failure.
Wear caused by high temperature
The hardness caused by abnormal high temperature changes the metallographic structure or chemical composition of the metal, which reduces the wear resistance and hardness of the bearing surface and accelerates the wear process. This kind of wear is called wear caused by high temperature action. Wear caused by high temperature. When the bearing is temporarily operated at high temperature.
Too much oil causes the bearing rolling elements to slip.
Too much oil in the bearing and box will cause the bearing rolling elements to slip, causing the rolling friction to change from rolling friction to sliding friction, damaging the bearing rolling elements. Because there is too much oil in the bearing, the free space in the bearing box will be small, and the operating temperature of the bearing will increase. As it rises, the grease density decreases. The lubricating oil film on the rolling elements becomes thinner and the lubrication conditions are poor, which can easily cause abnormal noise in the bearing, cause surface slippage, and shorten the life of the bearing.
Generally, there is a bearing oil chamber on the side of the motor end cover (except for motors designed with double-sealed bearings). According to the motor speed, the amount of oil that can be filled into the bearing chamber can refer to the following standards: When the motor speed is <1500r/min, the amount of oil added to the bearing chamber is 2/3 of the volume. When the rotation speed is between 1500 and 3000r/min, it is 1/2 of the bearing chamber volume. When the rotation speed is >3000r/min, it should be less than or equal to 1/3 of the bearing volume. In the actual working process, for bearings operating at high temperatures and high speeds, bearings with sealing surfaces should be used as little as possible, the oil storage capacity of the motor oil cap should be increased, and a grease nozzle should be installed to extend the operating life of the motor bearings.
If the bearing insulation is destroyed during installation, the very thin bearing oil film will be broken down by the shaft voltage. After the oil film is broken down, not only will the rolling element lubrication conditions be poor, but the generated sparks will cause electric corrosion of the bearing rolling elements, causing the rolling elements to malfunction. The surface is not shiny and accelerates bearing wear. Bearing wear can be repaired in this way. The solution is: it is necessary to re-study the use conditions or re-select the bearings, observe the clearance and check the machining precision between the shaft and the bearing strip, check the design around the bearing, study and check the installation method, lubricant and lubrication method.
Solutions for bearing failure
1. Carry out preliminary preparations, that is, dismantle equipment, to ensure sufficient construction space and a safe working environment;
2. Preliminary cleaning of the shaft surface is to wipe off the oil stains on the surface of the bearing position and positioning surface, and remove high spots, burrs, rust layers, etc., and use 99.7% absolute ethanol to clean the surface of the bearing position to ensure that there is no dirt. dry;
3. Wipe the inner and outer surfaces of the mold clean, and wipe a thin layer of SD7000 release agent on the inner surface of the mold, discharge chute, bolts, bolt holes, positioning pins, and positioning pin holes. The thinner, the better, dry and set aside;
4. Strictly blend the material SD7101H according to the volume ratio of 2:1. The blending is complete and there is no color difference. Apply the blended material quickly to the surface of the bearing position;
5. Quickly install the mold in place, tighten the bolts and install the positioning pins. During the installation of the mold, pay attention to the mold to avoid axial movement of the mold. At the same time, use a rubber hammer to hit the mold in the circumferential direction when tightening the mold to make the material distribution even and avoid deformation of the mold;
6. Material curing: When the ambient temperature is 24°C, it is recommended to remove the mold for no less than 4 hours; when the ambient temperature is below 24°C, it is recommended to use an iodine tungsten lamp for heating for no less than 3 hours;
7. Be careful when dismantling the mold to avoid material damage or falling off during the disassembly process. After disassembling the mold, use a saw blade or cutting blade to remove the excess material extruded from the discharge chute (no knocking or breaking off by hand), and at the same time Sand this area lower than the overall surface;
8. Assembling components: When assembling components, it is recommended to apply a thin layer of release agent on the mating surface of the component in advance, apply a thin layer of material on the surface of the bearing position, and install it quickly in strict accordance with the assembly process.
Studying the formation and causes of rolling bearing damage is of great significance. On the one hand, it can improve the use method, use the bearing correctly, and give full play to the performance of the bearing. On the other hand, it can help develop new products with better performance. In addition to describing the precautions, installation methods, operation monitoring, etc. in the use of rolling bearings, this article also focuses on the forms and causes of bearing damage and the countermeasures that should be taken.
Bearings have a certain life span. If we use them properly and pay attention to the above usage precautions, the bearings will fully play their role. Generally, regular manufacturers provide after-sales service for brand bearings. If it is a quality problem, you can go to the corresponding store to exchange it.