SKF imported bearings (especially rolling bearings) are of two structures with cage and without cage. Among them, large SKF imported bearings are generally required to bear a large load, often without cage, but filled with rolling elements between the inner and outer raceways. Most small and medium-sized rolling bearings have cages.Performance of Koyo bearing material after heat treatment
In the processing process of SKF imported bearings, how do the outer ring, inner ring, rolling element and cage of the bearing fit together. To put it simply, first place the inner and outer rings of SKF imported bearing, place the inner ring next to the side, then place the rolling element (put it aside), then adjust the position of the rolling element, and then place the cage. Cage is also involved in the processing of bearing, so what is the main function of bearing cage?Performance of Koyo bearing material after heat treatment
The purpose of the cage is:Koyo bearing material
And drive the rolling body to roll on the correct raceway;Performance of Koyo bearing material after heat treatment
The cage separates the rolling elements at an equal distance and evenly distributes them on the circumference of the raceway to prevent mutual collision and friction between the rolling elements during operation;
In the release bearing, the rolling element and a ferrule are combined to prevent the rolling element from falling off.
SKF imported bearing is called the window, which is used to isolate and the rolling element. The pocket clearance makes the cage have a certain amount of activity in the radial and axial directions. The total amount of activity in the radial direction is called the clearance of the cage.Performance of Koyo bearing material after heat treatment
In roller cage, there are many structural types and complex shapes. There are many pockets with equal distance on the cage. The pocket shape includes spherical, circular, elliptical, rectangular and tooth shape. Its size is larger than the size of the rolling body. The difference between the two is the pocket gap. Sometimes the connecting part between the windows of the rolling cage is called lintel, which plays the role of connecting and increasing the strength of the cage.Performance of Koyo bearing material after heat treatment
Key points for good use of bearings:Performance of Koyo bearing material after heat treatment
SKF imported bearing is a kind of precision mechanical support element. Bearing users deeply hope that the bearing installed on the main engine will not be damaged and maintain its dynamic performance within the predetermined service life, but the objective facts are sometimes not satisfactory. Sudden SKF imported bearing failure accidents will cause great losses to users.Performance of Koyo bearing material after heat treatment
The failure analysis and research of a large number of rolling bearings show that the short life or premature loss of accuracy of bearings are caused by material defects or improper manufacturing, but to a large extent, it is due to the failure to install and maintain in strict accordance with the use requirements of SKF imported bearings, or the improper selection of SKF imported bearings or the actual load exceeding the rated load of SKF imported bearings, resulting in the abnormal damage of SKF imported bearings, for example.Performance of Koyo bearing material after heat treatment
The fatigue spalling of SKF imported bearing parts is largely caused by impurities in the lubricating oil. It can be seen that in order to achieve a longer service life and precision retention period of rolling bearings, in addition to requiring the bearing manufacturer to improve the product quality, users of SKF imported bearings must also use SKF imported bearings with scientific methods and procedures, otherwise, the best bearings will die prematurely under the harsh and arbitrary use conditions.Performance of Koyo bearing material after heat treatment
The early failure forms of rolling bearing mainly include fracture, plastic deformation, wear, corrosion and fatigue. Under normal conditions, it is mainly contact fatigue.Performance of Koyo bearing material after heat treatment
In order to better use SKF imported bearings, the following points should be noted:Performance of Koyo bearing material after heat treatment
Preparation before installation
Selection and requirements for installation site
The installation site shall be at a distance from lathes, grinders and other mechanical equipment. The site shall be cleaned and kept dry and clean frequently to prevent iron filings, sand, dust and moisture from entering the SKF imported bearing.Performance of Koyo bearing material after heat treatment
Check the model of SKF imported bearing and prepare installation tools
Check whether the bearing model and size meet the installation requirements, select the appropriate assembly method and prepare the tools and measuring tools for installation according to the structural characteristics of SKF imported bearings and the matching parts. The commonly used installation tools include hand hammer, copper rod, sleeve, special backing plate, screw mosquito fixture, press, etc., and the measuring tools include vernier caliper, micrometer, dial indicator, etc.Performance of Koyo bearing material after heat treatment
Inspect the bearing assembly surface
If there are bumps, rust layers, wear debris, sand particles, dust and soil on the assembly surface of SKF imported bearings and the surfaces of matched parts, one is that the bearing installation is difficult, resulting in incorrect assembly position; Second, these attachments form abrasives and are easy to wear the working surface of the bearing, affecting the assembly quality. Performance of Koyo bearing material after heat treatment
Therefore, before installation, carefully inspect the surface of journal, bearing housing hole, shoulder end face and the mating surface of connecting parts such as bushing, washer and end cover. If there is any rust layer, file it off with a fine file and polish it with a fine abrasive cloth. At the same time, remove the attachments on the assembly surface of SKF imported bearing and its connecting parts. Timken bearing corrosion is mainly divided into metal corrosion and human hand sweat. Performance of Koyo bearing material after heat treatment.Performance of Koyo bearing material after heat treatment
Metal corrosion accounts for the vast majority and can not be avoided in many cases. Hand sweat can also cause Timken bearing corrosion, which is mainly due to the sweat film on its surface when it comes into contact with sweat. The interaction will lead to electrochemical reaction and lead to corrosion, but it can be avoided, such as wearing professional gloves and other tools to take parts.Performance of Koyo bearing material after heat treatment
Metal corrosion mainly includes:
① Surface finish; ② Chemical structure and composition of metal materials; ③ Solution composition and pH value of metal surface; ④ Environmental media; ⑤ Ambient humidity and temperature.
Rust prevention pretreatment method:
Keep the surface clean and use appropriate methods for cleaning. General methods include chemical treatment cleaning, mechanical cleaning and solvent cleaning. Dry the surface with compressed gauze at 170 ℃ and then dry it with compressed air.Performance of Koyo bearing material after heat treatment
For example, some large antirust substances cannot be oiled by immersion method, which is mainly applicable to thin-layer antirust oil or solvent diluted antirust oil, but pay attention to labor and fire protection measures.
Brush coating method
When brushing, it is not only necessary to avoid accumulation, but also to prevent coating leakage. It is generally applicable to some special shaped products or outdoor construction equipment that are not suitable for soaking or spraying.Performance of Koyo bearing material after heat treatment
Immersion method Koyo bearing material
The thickness of oil film can be achieved by controlling the temperature or viscosity of antirust grease. Some small items are soaked in antirust grease to make the surface adhere with a layer of antirust grease.
The lubricating grease adsorbs the acid components volatilized from the paint, causing the deterioration of the lubricating grease, and this acid component promotes the hydrolysis of the grease. As a result, the concentration of the acid component increases, causing the corrosion of Timken bearing.
The working principle of grease is to separate the steel ball from the inner and outer raceways by using the grease layer, adhere to the surface of the steel ball and raceway by using the viscosity characteristics of grease, separate the metal interface between the steel ball and the inner and outer raceways, reduce the wear of the metal surface, protect the metal from air and moisture corrosion, reduce vibration and noise, and enable Timken bearing to rotate smoothly.Performance of Koyo bearing material after heat treatment
However, after the grease deteriorates, the viscosity will change, the oil film will break through, and the separation function and adhesion characteristics of the grease will disappear, resulting in serious consequences
First, the acid components produced by insulating paint directly oxidize the metal surface, causing Timken bearing corrosion.Performance of Koyo bearing material after heat treatment
Second, it causes the steel ball to directly touch the inner and outer raceways and wear during rotation, resulting in increased noise.Performance of Koyo bearing material after heat treatment
As the main components of the locomotive, especially traction motor and axle box bearing, its function plays an important role in transportation. When the locomotive is running on the line, once the bearing fails, the whole train will not run, blocking the main line of transportation, especially the passenger train, which will have a greater negative impact. Performance of Koyo bearing material after heat treatment
At the same time, once the locomotive bearing fails, it is also very difficult to rush repair the locomotive, Therefore, it is very important to prevent and reduce the occurrence of locomotive bearing faults for locomotive transportation. Whether the bearings with potential faults can be detected before Koyo bearing loading and ensure that qualified Koyo bearing accessories are put on the train is the focus of this paper.Performance of Koyo bearing material after heat treatment
Failure of Koyo bearing
The serious damage of Koyo bearing is often not caused by a single cause, but by the combined action of several aspects, a vicious cycle occurs under bad operating conditions, resulting in the serious burning loss of the bearing. Therefore, after the accident, it is often difficult to judge the cause, which brings us some difficulties in formulating relevant measures. For the convenience of discussion, first analyze the causes of the failure of Koyo bearing from several aspects.Performance of Koyo bearing material after heat treatment
Effect of installation on Koyo bearing
When assembling the bearing, the copper hammer is not used to impact the bearing according to the process requirements, resulting in the deformation of the cage, the incorrect installation of the inner and outer rings of the Koyo bearing of the traction motor, or the disappearance of the axial transverse momentum due to other reasons, resulting in the extrusion of the bearing shaft.
Improper assembly and fit clearance of Koyo bearing can also easily lead to bearing failure. Small clearance can easily lead to friction and heating of rollers and raceways. With the continuous rise of temperature, the temperatures of inner ring, body, cage, outer ring and end cover of Koyo bearing are different, and there is a temperature difference between them. Performance of Koyo bearing material after heat treatment
Therefore, the expansion amount is also slightly different, which will further reduce the fit clearance and increase the heat generation of Koyo bearing. If the clearance is too large, the vibration of the roller will increase, which will aggravate the impact of the roller and the raceway. At the same time, it is easy to cause uneven internal load distribution, reduce the bearing roller and overload the central roller.Performance of Koyo bearing material after heat treatment
The interference of the fit clearance between the inner ring of Koyo bearing and the shaft is inconsistent, which is also easy to cause bearing failure. Large interference is easy to cause the inner ring of Koyo bearing to crack due to excessive tensile stress, and too small interference is also easy to cause “Relaxation” of the inner ring of Koyo bearing.
Abnormal wear of Koyo bearing
When the Koyo bearing is used for a period of time, certain defects and scars will appear on the inner ring, body, cage, outer ring and raceway of the bearing, resulting in poor bearing lubrication and bearing heating. Long-term heating will lead to:
dilution of Koyo bearing lubricating oil. Therefore, when running on the line, if it is found that the bearing is seriously hot and smoking, do not stop, but keep running to the front station, because at this moment, the overheated Koyo bearing is in the melting state. Performance of Koyo bearing material after heat treatment
Once it is stopped and cooled, it can no longer walk and block the main line. Due to the above reasons, a vicious circle is further formed, which accelerates overheating and burns the bearing. Accelerate the fatigue of materials and reduce the hardness. Serious bearing inner ring displacement, body out of round, collision and heat generation, and finally welded together.Performance of Koyo bearing material after heat treatment
Oil supply and maintenance of locomotive bearings is very important. In particular, proper oil filling of bearings can ensure good lubrication of Koyo bearings. Lack of oil and excessive oil filling are also easy to cause bearing failure. Adding less oil is easy to cause poor lubrication and heating of Koyo bearings, and adding more oil is also easy to cause overheating of mixing. Therefore, proper oil supply in maintenance and cleaning of bearing lubricating grease are also very important, Once other impurities and moisture fall into the grease, it will affect the normal clearance and establish the necessary oil film.
The service time of Koyo bearing is too long, which exceeds the service life of Koyo bearing and is easy to cause material fatigue. In addition, the material is deformed due to strong impact, resulting in peeling and grinding of rollers and raceway surfaces, resulting in poor lubrication and increased vibration. Contact fatigue failure is the main form of normal failure of Koyo bearing.Performance of Koyo bearing material after heat treatment
When the rolling bearing is running, the rolling element rolls between the raceways of the inner and outer rings of the bearing, and its contact part bears periodic alternating load, which can reach hundreds of thousands of times per minute. Under the repeated action of periodic alternating stress, fatigue spalling occurs on the contact surface. After the rolling bearing begins to peel off.Performance of Koyo bearing material after heat treatment
it will cause the vibration and noise of Koyo bearing to increase, and the working temperature will rise sharply, resulting in the final damage of Koyo bearing. This damage form is called contact fatigue damage. Therefore, Koyo bearings require that the steel used for rolling bearings should have high contact fatigue strength.Performance of Koyo bearing material after heat treatment
When the rolling bearing works normally, it is accompanied by sliding friction in addition to rolling friction. The main parts of sliding friction are: the contact surface between the rolling element and the raceway, the contact surface between the rolling element and the pocket hole of the cage, between the cage and the retaining edge of the ferrule, and between the end face of the roller and the retaining edge of the ferrule. Performance of Koyo bearing material after heat treatment
The existence of sliding friction in Koyo bearing rolling bearing inevitably causes the wear of Koyo bearing parts. If the wear resistance of bearing steel is poor, the rolling bearing will lose its accuracy prematurely due to wear or increase the vibration and reduce the service life of Koyo bearing due to the decline of rotation accuracy. Therefore, Koyo bearing steel is required to have high wear resistance.Performance of Koyo bearing material after heat treatment
The basic requirements for materials of rolling bearings largely depend on the working performance of Koyo bearings. The selection of suitable materials for manufacturing rolling bearings will have a great impact on its service performance and service life. Generally, the main failure form of rolling bearing is fatigue spalling under alternating stress, bearing and loss of bearing accuracy due to friction and wear. Performance of Koyo bearing material after heat treatment
In addition, there are cracks, indentation, corrosion and other reasons that cause abnormal damage to Koyo bearings. Therefore, rolling bearings should have high plastic deformation resistance, less friction and wear, good rotation accuracy, good dimensional accuracy and stability, and long contact fatigue life.Performance of Koyo bearing material after heat treatment