Anti rust management and new anti rust technology of Koyo bearing
Anti rust management and new anti rust technology of Koyo bearing
2022年4月26日
New method of SKF imported bearing heating assembly
New method of SKF imported bearing heating assembly
2022年4月27日

Diagnosis and management of NTN imported bearings

  • At this time, bearings with accuracy above grade 5 should be used.
  • The installation and disassembly frequency and methods of regular inspection of installation and disassembly. When the installation and disassembly are frequent, the cylindrical roller bearing with separable inner ring and outer ring, needle roller bearing and tapered roller bearing are more convenient.Diagnosis and management of NTN imported bearings
  • The speed can adapt to the NTN imported bearing type of mechanical speed [the limit value benchmark of bearing speed is expressed by the limit speed, and its value is contained in the bearing size table] the limit speed of bearing is not only taken from the bearing type, but also limited to the bearing size, cage type, accuracy grade, load conditions and lubrication mode. 

  The speed can adapt to the  NTN imported bearings

  • Therefore, these factors must be considered in the selection. Ina bearing temperature is too high: when the mechanism is running, the part where the bearing is installed is allowed to have a certain temperature. When touching the mechanism shell by hand, it should be normal not to feel hot. Otherwise, it indicates that the bearing temperature is too high.Diagnosis and management of NTN imported bearings
  • The reasons for the high temperature of INA Bearing are: the quality of lubricating oil does not meet the requirements or deteriorates, and the viscosity of lubricating oil is too high; The mechanism assembly is too tight (insufficient clearance); The bearing assembly is too tight; The bearing race rotates on the shaft or in the shell; Excessive load; Broken bearing cage or rolling element, etc.Main factors affecting grinding deterioration layer of SKF Bearing
  • INA Bearing Noise: the rolling bearing is allowed to make slight running noise during operation. If the noise is too loud or there is abnormal noise or impact sound, it indicates that the bearing is faulty. The reason for the noise of rolling bearing: it is more complex. It is the wear of the mating surfaces of the inner and outer rings of the bearing. Due to this kind of wear, the matching relationship between INA Bearing and shell, bearing and shaft is damaged, resulting in the axis deviation from the correct position and abnormal noise when the shaft moves at high speed. Main factors affecting grinding deterioration layer of SKF Bearing
  • Metal spalling on the raceway surface: the rolling element of INA Bearing and the raceway surfaces of inner and outer rings are subjected to periodic pulsating load, resulting in periodic contact stress. When the number of stress cycles reaches a certain value, it will be produced on the working surface of rolling element or inner and outer race raceway
  • Fatigue peeling. If the load of ina bearing is too large, this fatigue will be exacerbated. In addition, improper bearing installation and shaft bending will also produce raceway spalling. The fatigue spalling of bearing raceway will reduce the operation accuracy of shaft and cause vibration and noise of mechanism. 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. 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.Diagnosis and management of NTN imported bearings
  • 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 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. Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearingsain factors affecting grinding deterioration layer of SKF Bearing

Purpose of Preloading,imported bearings

  • Preload the NSK imported bearing of the main shaft to eliminate the original clearance between the ball and the raceway and form a certain elastic deformation. When bearing the external load, the NSK imported bearing has a certain rigidity. For the NSK imported bearing installed in the opposite direction of the external load, there will be no clearance between the ball and the raceway due to the external load, so as to improve the rotation accuracy of the main shaft, The rigidity of the main shaft is strengthened, the service life is improved, and the noise can be reduced at the same time.Diagnosis and management of NTN imported bearings
  • Principle of Preloading
  • The size of preload is generally determined according to the size of working load, spindle rotation accuracy and speed.Main factors affecting grinding deterioration layer of SKF Bearing
  • If the spindle load is small, the rotation accuracy is high and the speed is low, a larger preload can be taken.
  • If the working load is large and the speed is high, it is easy to heat and expand, so a small preload should be taken. The 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.Diagnosis and management of NTN imported bearings
  • Generally, the temperature of IKO inlet 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.Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearings
Diagnosis and management of NTN imported bearings

 Work hardening layer SKF Bearing

  • 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.Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearings
  • Thermoplastic deformation (or high temperature deformation) layer。Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearings
  • Sometimes, it can be found that the hardness of the surface layer increases due to machining deformation by microhardness method and metallographic method.Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearings
  • High temperature tempering layer
  • The instantaneous high temperature in the grinding zone can make the surface heated to a certain depth (10 ~ 100nm) higher than the tempering 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.

SKF Bearing second layer quenching layer

  • 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.Diagnosis and management of NTN imported bearingsimported bearings

 used Diagnosis and management of imported bearings

  • Deep groove ball bearing, contact ball bearing, cylindrical roller bearing
  • Rotation accuracy the type of bearing with the required rotation accuracy [the dimensional accuracy and rotation accuracy of the bearing have been standardized by GB according to the bearing type]? The spindle of machine tool, gas turbine and control machine require high rotation accuracy, high speed and low friction respectively. At this time, bearings with accuracy above grade 5 should be used.Diagnosis and management of NTN imported bearings
  • The installation and disassembly frequency and methods of regular inspection of installation and disassembly. When the installation and disassembly are frequent, the cylindrical roller bearing with separable inner ring and outer ring, needle roller bearing and tapered roller bearing are more convenient.Diagnosis and management of NTN imported bearings
  • The speed can adapt to the NTN imported bearing type of mechanical speed [the limit value benchmark of bearing speed is expressed by the limit speed, and its value is contained in the bearing size table] the limit speed of bearing is not only taken from the bearing type, but also limited to the bearing size, cage type, accuracy grade, load conditions and lubrication mode. Diagnosis and management of NTN imported bearings
  • Therefore, these factors must be considered in the selection. Ina bearing temperature is too high: when the mechanism is running, the part where the bearing is installed is allowed to have a certain temperature. When touching the mechanism shell by hand, it should be normal not to feel hot. Otherwise, it indicates that the bearing temperature is too high.Diagnosis and management of NTN imported bearings
  • The reasons for the high temperature of INA Bearing are: the quality of lubricating oil does not meet the requirements or deteriorates, and the viscosity of lubricating oil is too high; The mechanism assembly is too tight (insufficient clearance); The bearing assembly is too tight; The bearing race rotates on the shaft or in the shell; Excessive load; Broken bearing cage or rolling element, etc.Diagnosis and management of NTN imported bearings
  • INA Bearing Noise: the rolling bearing is allowed to make slight running noise during operation. If the noise is too loud or there is abnormal noise or impact sound, it indicates that the bearing is faulty. The reason for the noise of rolling bearing: it is more complex. It is the wear of the mating surfaces of the inner and outer rings of the bearing. Diagnosis and management of NTN imported bearings
  • Due to this kind of wear, the matching relationship between INA Bearing and shell, bearing and shaft is damaged, resulting in the axis deviation from the correct position and abnormal noise when the shaft moves at high speed. When the bearing is tired, the metal on its surface will peel off, which will also increase the radial clearance of the bearing and produce abnormal noise. Insufficient bearing lubrication, dry friction and bearing breakage will produce abnormal sound. 3) After the bearing is worn and shaken, the cage is loose and damaged, which will also produce abnormal noise and damage to the bearing. During the disassembly and inspection of rolling bearing, the fault and damage cause of bearing can be judged according to the damage of bearing.Diagnosis and management of NTN imported bearings
  • Metal spalling on the raceway surface: the rolling element of INA Bearing and the raceway surfaces of inner and outer rings are subjected to periodic pulsating load, resulting in periodic contact stress. When the number of stress cycles reaches a certain value, it will be produced on the working surface of rolling element or inner and outer race raceway.Diagnosis and management of NTN imported bearings
  • Fatigue peeling. If the load of ina bearing is too large, this fatigue will be exacerbated. In addition, improper bearing installation and shaft bending will also produce raceway spalling. The fatigue spalling of bearing raceway will reduce the operation accuracy of shaft and cause vibration and noise of mechanism. 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. 

  • 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.
  • 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 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. Diagnosis and management of NTN imported bearings
  • 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.Diagnosis and management of NTN imported bearings

Purpose of Preloading,SKF Bearing

  • Preload the NSK imported bearing of the main shaft to eliminate the original clearance between the ball and the raceway and form a certain elastic deformation. When bearing the external load, the NSK imported bearing has a certain rigidity. For the NSK imported bearing installed in the opposite direction of the external load, there will be no clearance between the ball and the raceway due to the external load, so as to improve the rotation accuracy of the main shaft, The rigidity of the main shaft is strengthened, the service life is improved, and the noise can be reduced at the same time.Diagnosis and management of NTN imported bearings
  • Principle of Preloading
  • The size of preload is generally determined according to the size of working load, spindle rotation accuracy and speed.Diagnosis and management of NTN imported bearings
  • If the spindle load is small, the rotation accuracy is high and the speed is low, a larger preload can be taken.
  • If the working load is large and the speed is high, it is easy to heat and expand, so a small preload should be taken. The 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.Diagnosis and management of NTN imported bearings

Generally, the temperature of IKO inlet 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.
  • 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.
  • 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.
  • 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.
  • 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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