There are two main factors affecting the grinding deterioration layer of SKF Bearing,
Grinding force
In the grinding process, the surface layer of the workpiece will be affected by the cutting force, compression force and friction force of the grinding wheel. In particular, the role of the latter two makes the surface layer of the workpiece form a highly directional plastic deformation layer and work hardening layer. These metamorphic layers will inevitably affect the change of residual stress in the surface layer.
Cold plastic deformation layer
In the grinding process, each moment of abrasive grain is equivalent to a cutting edge. However, in many cases, the rake angle of the cutting edge is negative. In addition to the cutting effect, the abrasive particles make the workpiece surface bear the extrusion effect (ploughing effect), leaving an obvious plastic deformation layer on the workpiece surface. The deformation degree of this deformation layer will increase with the blunt degree of grinding wheel and the increase of grinding feed.
Thermoplastic deformation (or high temperature deformation) layer
The instantaneous temperature formed by grinding heat on the working surface makes the elastic limit of the workpiece surface layer at a certain depth drop sharply, even to the extent that the elasticity disappears. At this time, the free extension of the working surface layer caused by the grinding force, especially the compression force and friction force, is limited by the base metal, and the surface is compressed (more plough), resulting in plastic deformation in the surface layer. High temperature plastic deformation increases with the increase of workpiece surface temperature under the condition of unchanged grinding process.
Work hardening layer
Sometimes, it can be found that the hardness of the surface layer increases due to machining deformation by microhardness method and metallographic method.
Grinding heat
In grinding, the contact area between grinding wheel and workpiece consumes a lot of energy and generates a lot of grinding heat, resulting in local instantaneous high temperature in the grinding area. It can be found that the instantaneous temperature in the grinding area can be as high as 1000 ~ 1500 ℃ in 0.1 ~ 0.001ms. Such instantaneous high temperature is enough to make the surface layer at a certain depth of the working surface produce high-temperature oxidation, amorphous structure, high-temperature tempering, secondary quenching, and even burn cracking.
SKF bearing surface oxide layer
Under the action of instantaneous high temperature, the steel surface reacts with oxygen in the air to form an extremely thin (20 ~ 30nm) thin layer of iron oxide. It should be noted that there is a corresponding relationship between the thickness of oxide layer and the total thickness of surface grinding metamorphic layer. This shows that the thickness of oxide layer is directly related to the grinding process and is an important symbol of grinding quality.
Amorphous structure layer
When the instantaneous high temperature in the grinding area makes the workpiece surface reach the molten state, the molten metal molecular flow is evenly coated on the working surface and cooled by the base metal at a very fast speed to form a very thin amorphous structure layer. It has high hardness and toughness, but it is only about 10nm, which is easy to be removed in precision grinding.Main factors affecting grinding deterioration layer of SKF Bearing
High temperature tempering layer
The instantaneous high temperature in the grinding area can make the surface heated to a certain depth (10 ~ 100nm) higher than the tempering heating temperature of the workpiece. When the austenitizing temperature is not reached, with the increase of the heating temperature, the surface layer by layer will produce the microstructure transformation of re tempering or high-temperature tempering corresponding to the heating temperature, and the hardness will also decrease. The higher the heating temperature, the more severe the decrease of hardness.Main factors affecting grinding deterioration layer of SKF Bearing
When the instantaneous high temperature in the grinding area heats the surface layer of the workpiece above the austenitizing temperature (AC1), the austenitized structure of the layer is re quenched into martensitic structure in the subsequent cooling process. For the workpiece with secondary quenching burn, the high-temperature tempering layer with very low hardness must be under the secondary quenching layer.Main factors affecting grinding deterioration layer of SKF Bearing
For the workpiece with secondary quenching burn SKF Bearing
The second quenching burn will change the stress of the surface layer of the workpiece. The secondary quenching zone is under pressure, and there is a large tensile stress in the material of the high-temperature tempering zone below it, which is the place where the crack core may occur. Main factors affecting grinding deterioration layer of SKF Bearing
The crack is easy to propagate along the original austenite grain boundary. Severe burns can lead to cracks (mostly cracks) on the whole grinding surface, resulting in scrapping of the workpiece. Proper material selection is still a factor that must be considered in bearing failure analysis.Main factors affecting grinding deterioration layer of SKF Bearing
The main task of NSK bearing failure analysis is to find out the main factors causing bearing failure according to a large number of background materials, analysis data and failure forms, so as to put forward targeted improvement measures, prolong the service life of the bearing and avoid sudden early failure of the bearing. The installation condition is one of the primary factors in the use factors. Main factors affecting grinding deterioration layer of SKF Bearing
The improper installation of the bearing often leads to the change of the stress state between the parts of the whole bearing, and the NSK bearing operates in an abnormal state and fails early. Main factors affecting grinding deterioration layer of SKF Bearing
According to the technical requirements of bearing installation, use, maintenance and repair, monitor and inspect the load, speed, working temperature, vibration, noise and lubrication conditions borne by the running bearing, find out the cause immediately and adjust it to make it return to normal.Main factors affecting grinding deterioration layer of SKF Bearing
First of all, the reasonable design and advanced nature of the structure will lead to longer bearing life. The manufacturing of bearings generally goes through multiple machining processes such as forging, heat treatment, turning, grinding and assembly. The rationality, advanced nature and stability of all the processing technologies will also affect the life of bearings. Main factors affecting grinding deterioration layer of SKF Bearing
Among them, the heat treatment and grinding processes that affect the quality of finished bearings are often more directly related to the failure of bearings. In recent years, the research on the metamorphic layer of the working surface of NSK bearing shows that the grinding process is closely related to the surface quality of the bearing.Main factors affecting grinding deterioration layer of SKF Bearing
The metallurgical quality of SKF Bearing material was once the main factor.
With the progress of Metallurgical Technology (such as vacuum degassing of bearing steel), the quality of raw materials has been improved.Main factors affecting grinding deterioration layer of SKF Bearing
The proportion of raw material quality factor in bearing failure analysis has decreased significantly, but NSK bearing is still one of the main influencing factors of bearing failure. Raceway noise is a kind of stable and continuous noise excited by the rolling body rolling in the raceway when the fag imported bearing rotates. Main factors affecting grinding deterioration layer of SKF Bearing
People pay attention to it only when its sound pressure level or tone is extremely high. In fact, the sound energy excited by the raceway sound is limited. For example, under normal conditions, the high-quality 6203 bearing raceway sound is 25 ~ 27db. The sound generation source of raceway is caused by the natural vibration of ferrule after being loaded. The elastic contact between the ferrule and the rolling body constitutes a nonlinear vibration system. Main factors affecting grinding deterioration layer of SKF Bearing
When the lubrication or machining accuracy is not high, the natural vibration related to this elastic feature will be excited, and when it is transmitted to the air, it will become noise. As we all know, even if the contemporary superb manufacturing technology is used to process fag imported bearing parts, there will always be small geometric errors in varying degrees on the working surface, resulting in small fluctuations between the raceway and the rolling body and exciting the natural vibration of the vibration system.Main factors affecting grinding deterioration layer of SKF BearingMain factors affecting grinding deterioration layer of SKF Bearing
Although the raceway noise of fag imported bearings is inevitable, high-precision machining of the working surface of parts, correct selection of bearings and accurate use of fag imported bearings can be adopted to reduce noise and vibration. Main factors affecting grinding deterioration layer of SKF Bearing
The thermal sensor can monitor the working temperature of the bearing at any time, and automatically alarm or stop when the temperature exceeds the specified value to prevent the occurrence of combustion shaft accident. Main factors affecting grinding deterioration layer of SKF Bearing
The metallurgical quality of SKF Bearing.
High temperature often indicates that the bearing is in an abnormal condition. High temperature is also harmful to the lubricant of the bearing. Sometimes bearing overheating can be attributed to the lubricant of the bearing. If the temperature of the bearing exceeds 125 ℃ for a long time, the service life of the bearing will be reduced.Main factors affecting grinding deterioration layer of SKF Bearing
The causes of high temperature bearings include insufficient or excessive lubrication and lubricant. It contains impurities, excessive load, bearing ring damage, insufficient clearance, high friction caused by oil seal, etc.Main factors affecting grinding deterioration layer of SKF Bearing
Therefore, it is necessary to continuously monitor the bearing temperature. NTN bearing is used to measure the bearing itself or other important parts. If the operating conditions remain unchanged, any temperature change can indicate that a fault has occurred. The periodic measurement of bearing temperature can be aided by thermometer, such as digital thermometer, which can accurately measure the bearing temperature and display it in ℃ or Fahrenheit.
Generally, the temperature of the bearing can be inferred from the temperature outside the bearing chamber. If the oil hole can be used to directly measure the temperature of the outer ring of the bearing, NTN bearing is more suitable. Usually, the temperature of the bearing starts to rise slowly with the operation of the bearing, and reaches a stable state after 1-2 hours. Main factors affecting grinding deterioration layer of SKF Bearing
The normal temperature of the bearing varies with the heat capacity, heat dissipation, speed and load of the machine. If the lubrication and installation parts are appropriate, the bearing temperature will rise sharply and abnormal high temperature will occur. At this time, the operation must be stopped and necessary preventive measures must be taken.Main factors affecting grinding deterioration layer of SKF Bearing
Plastic deformation: uneven pits appear on the contact surface between raceway and roller of INA Bearing, indicating plastic deformation of bearing. The reason is that under the action of large static load or impact load, the local stress on the working surface of the bearing exceeds the yield limit of the material, which generally occurs on ina bearings rotating at low speed.Main factors affecting grinding deterioration layer of SKF Bearing
INA Bearing Race crack: the crack of bearing race may be caused by too tight bearing fit, loose bearing or inner ring, deformation of INA Bearing containing parts, poor surface processing of ina bearing installation, etc.Main factors affecting grinding deterioration layer of SKF Bearing
Broken cage: the reason is insufficient lubrication, broken rolling element, seat ring skew, etc.Main factors affecting grinding deterioration layer of SKF Bearing
The metal of the cage adheres to the rolling element, which may be due to the rolling element being stuck in the cage or insufficient lubrication.Main factors affecting grinding deterioration layer of SKF Bearing
Serious wear of race raceway: foreign matters may fall into the race, insufficient lubricating oil or inappropriate lubricating oil brand. In order to ensure the performance of rolling bearings and maintain long-term use under good conditions, NTN imported bearings must be inspected and maintained. This inspection and maintenance is very important to prevent faults in advance.Main factors affecting grinding deterioration layer of SKF Bearing
It is hoped that regular inspection and maintenance can be carried out according to the operation standards suitable for the operating conditions of the machine. Generally, the following methods are adopted: the inspection under the operating state is based on the rolling sound, vibration Check the temperature and the nature of the lubricant, and judge the supplement or replacement time of the lubricant.Main factors affecting grinding deterioration layer of SKF Bearing
NTN imported bearing inspection: fully observe the bearings removed due to the regular inspection and replacement of the machine, and check the condition of the raceway surface, whether there is damage and whether it can be reused. Due to the clearance of NSK imported bearing, the inner and outer rings will move relatively under the action of load, which will reduce the stiffness of NSK imported bearing, cause the radial and axial vibration of the shaft, and affect the working accuracy and service life of the machine.Main factors affecting grinding deterioration layer of SKF Bearing
In order to reduce this vibration, for high-precision and high-speed mechanical equipment, the preloading method is often adopted when installing NSK imported bearing, that is, a certain load (radial or axial) is given to NSK imported bearing in advance during installation to eliminate its original clearance, and make NSK imported bearing body and inner and outer rings produce elastic deformation, so as to prevent relative movement between inner and outer rings during operation. Main factors affecting grinding deterioration layer of SKF Bearing
Main factors affecting grinding deterioration layer of SKF BearingThe temperature of IKO imported bearing can generally be inferred from the temperature outside the bearing chamber. It is more appropriate if the oil hole can be used to directly measure the temperature of the outer ring of the bearing.Main factors affecting grinding deterioration layer of SKF Bearing
Generally, the temperature of SKF Bearing starts to rise slowly with the operation of the bearing.
and reaches a stable state after 1-2 hours. The normal temperature of IKO imported bearing varies with the heat capacity, heat dissipation, speed and load of the machine. If the lubrication and installation parts are appropriate, the bearing temperature will rise sharply and abnormal high temperature will occur. At this time, the operation must be stopped and necessary preventive measures must be taken.Main factors affecting grinding deterioration layer of SKF Bearing
The working temperature of IKO imported bearing can be monitored at any time by using the thermal sensor, and the automatic alarm or stop when the temperature exceeds the specified value can be realized to prevent the occurrence of combustion shaft accident.Main factors affecting grinding deterioration layer of SKF Bearing
High temperature often indicates that IKO imported bearing is in abnormal condition. High temperature is also harmful to the lubricant of IKO imported bearings. Sometimes bearing overheating can be attributed to the lubricant of the bearing. If the temperature of the bearing exceeds 125 ℃ for a long time, the service life of the bearing will be reduced. The causes of high temperature bearings include insufficient or excessive lubrication and lubricant. It contains impurities, excessive load, bearing ring damage, insufficient clearance, high friction caused by oil seal, etc.Main factors affecting grinding deterioration layer of SKF Bearing
Therefore, it is necessary to continuously monitor the bearing temperature, whether it is measuring the bearing itself or other important parts. If the operating conditions remain unchanged, any temperature change can indicate that a fault has occurred.Main factors affecting grinding deterioration layer of SKF Bearing
The periodic measurement of IKO imported bearing temperature can be aided by thermometer, such as IKO imported bearing digital thermometer, which can accurately measure the bearing temperature and display it in ℃ or Fahrenheit.
The important IKO imported bearing means that when it is damaged, it will cause the shutdown of the equipment. Therefore, this kind of bearing should be equipped with temperature detector.
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