In severe cases, metal peeling and large-area random scratches occur on the contact surface; In general, the mechanical damage of Koyo imported bearing refers to the appearance of groove marks at different levels on the alloy surface of bearing bush. Contact surface damage and ablation exist at the same time. The main reason for bearing mechanical damage is that the bearing surface is difficult to form oil film or the oil film is seriously damaged.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Plastic deformation and cold work hardening occur on the outer surface layer, and Koyo imported bearing is under the repeated action of cylinder pressure (impact load). The deformation capacity is lost locally, and the grain is gradually formed and continuously expanded. Then, with the falling off of wear debris, the loaded outer layer forms a hole. Generally, when the bearing bush is pitted, the pit first appears, and then the pit gradually expands and causes the cracking of the alloy layer interface. Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
The crack extends along the parallel direction of the interface until it peels off. The main reason for bearing cavitation is that the sudden change of the cross section of structural elements such as oil groove and oil hole causes strong disorder of oil flow. Bubbles are formed in the vacuum area with disorder of oil flow, and then cavitation occurs due to the collapse of bubbles due to the increase of pressure. Cavitation usually occurs in the high load area of the bearing, such as the lower bearing bush of the crankshaft main bearing.
Due to the overload of the engine, the fatigue pitting corrosion of Koyo imported bearings refers to. Make the bearing overheat and the bearing clearance is too large, resulting in fatigue damage, fatigue pitting or fatigue falling off in the middle of the bearing. This kind of damage is mostly caused by overload, excessive bearing clearance, or unclean lubricating oil and foreign matters mixed in it. Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Therefore, when using, attention should be paid to prevent the bearing from overload and do not run at too low or too high speed; Adjust the engine to a stable state at idle speed; Ensure the normal bearing clearance and prevent the engine speed from being too high or too low; Check and adjust the working condition of the cooling system to ensure that the working temperature of the engine is appropriate.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
The chemical impurities (acid oxides, etc.) in the lubricating oil oxidize the bearing alloy to form acidic substances. The corrosion area of the bearing alloy is generally impure lubricating oil. Cause the bearing alloy to fall off locally and form irregular small cracks or pits. Improper use of bearing oil and lubricating alloy is the main reason for poor corrosion resistance of the engine.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Local high temperature is formed, and there is a small convex metal surface in direct contact between the journal and the friction pair of Koyo bearing. In case of lack of lubrication and poor cooling, the bearing alloy will be blackened or partially burned. This fault is often caused by too tight fit between journal and bearing; Lack of lubricating oil pressure is also easy to burn the bearing. Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
As we all know, in addition to the adverse phenomena of the bearing in use, the noise also lies in the bearing itself. Different types of NTN bearings have different noise, so how do we choose the bearing with low noise?Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Bearings with relatively low noise: when the above two types of low noise bearings cannot be used, bearings with relatively low noise can be used. The specific comparison basis is as follows:
The noise of ball bearing is lower than that of roller bearing, and the (friction) noise of bearing with less sliding is lower than that of bearing with more sliding; If there are many balls, the outer ring is thick and the noise is small;
The noise of bearings with solid cages is relatively lower than that of bearings with stamping cages;Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
The noise of bearings with plastic cages is lower than that of bearings with the above two cages;Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
The noise of bearings with high precision, especially those with higher rolling element precision, is relatively lower than that of bearings with low precision;Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
The noise of small bearings is relatively lower than that of large bearings.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Rolling bearings with low noise requirements include: among the standard bearings produced in China, some single row radial ball bearings and short cylindrical roller bearings have low noise varieties for motor bearings. The inner diameter of ball bearing φ 2.5mm to φ There are several varieties of 60mm with three suffixes of ZL, Z2 and Z3, which correspond to three different low-noise requirements respectively. Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Among the roller bearings, there are eight models from n309 to n322, which are also manufactured according to the low-noise standard. These bearings can be fully applicable to other machines with low noise requirements, and the price is cheap. If the type and size can meet the requirements, try to use these two types of low noise bearings.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
There are two kinds of noise caused by problems in bearing application: scar sound and dust sound, which are described as follows:Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Scar sound and its control method
If there is crack, indentation or corrosion on the rolling surface of rolling bearing, periodic vibration and noise like riveting rivets will occur. Its cycle may be fixed, but most of it has a certain corresponding relationship with the rotating speed. The scars will occur continuously on the channel, and the scars will appear on the steel ball from time to time, and this noise will change with the installation and lubrication conditions.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
The control methods of this kind of noise are as follows: do not knock the NTN bearing during installation. When the bearing is assembled with the shaft and then installed into the bearing seat, prevent the bearing from being installed obliquely; Prevent NTN bearings from rusting during storage and impact vibration during transportation; Use grease with high viscosity.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Dust sound and its control method
If there are dust and other foreign matters in the rolling bearing, aperiodic vibration and so-called dust sound will occur. The magnitude of vibration and noise is uncertain, and there may or may not be.
The control methods of dust noise include: improving the cleaning method of NTN bearing, and strictly cleaning the NTN bearing, shaft, seat hole and matching parts before installation; Remove foreign matters in the lubricant; Improve the sealing of NTN bearing; Avoid using plastic cages with impure materials or embedded foreign matters.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Noise caused by lubrication factors and Its Countermeasures
Incorrect lubricant selection, insufficient lubricant or aging hardening can lead to vibration and noise of NTN bearing, and this noise has no certain law. In this case, only select the appropriate lubricant, adjust the amount of lubricant, prolong the service life of lubricant and reasonably determine the replacement cycle.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Noise related to main engine and Its Countermeasures
This kind of noise is not caused by NTN bearings alone, so it is futile to find the reason only from the bearing. We should pay full attention to the main engine and improve the performance of the main engine if necessary. This paper mainly describes the common buzzer sound and frame resonance sound in the motor.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
Buzzer of motor and Its Countermeasures
The axial vibration of the motor shaft will cause great high-frequency noise – buzzer, and its frequency is the same as the axial vibration frequency, which can be constant or variable. The method to prevent the buzzer is the same as that to prevent the axial vibration.
Resonance sound of NTN bearing frame and Its Countermeasures
When the axial natural vibration of NTN inlet bearing frame is caused by the axial natural vibration of the above-mentioned outer ring mass, a noise called resonant sound will be generated. The method of pre tightening can improve the axial natural frequency of the outer ring mass system, destroy the resonance condition and reduce the noise. Proper material selection is still a factor that must be considered in bearing failure analysis. Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
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. Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
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. 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.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
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 processing 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.
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.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
The metallurgical quality of NSK bearing material was once the main factor affecting the early failure of rolling bearing. With the progress of Metallurgical Technology (such as vacuum degassing of bearing steel), the quality of raw materials has been improved. 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.Common sense of Koyo bearing temperature inspectionCommon sense of Koyo bearing temperature inspection
The use factors of Koyo bearings mainly refer to whether the installation, adjustment, use and maintenance, maintenance and repair meet the technical requirements. According to the technical requirements of Koyo bearing installation, use, maintenance and repair, monitor and inspect the load, speed, working temperature, vibration, noise and lubrication conditions of the running bearing, find out the causes immediately and adjust them to make them return to normal.
The installation condition is the primary factor in the use factors. The bearing often changes the stress state between the parts of the whole bearing due to improper installation. The bearing operates in an abnormal state and ends its service life early. The internal factors mainly refer to the three factors that determine the quality of Koyo bearing, such as structural design, manufacturing technology and material quality. NTN bearing is a precision part of imported bearings.
The system realizes the optimization of workshop asset efficiency and maintenance work for the decision support of mechanical service, preventive maintenance means, condition monitoring and a series of maintenance work. Therefore, bearing plays a vital role in some industries. The shaft parts of machine tools, especially the spindle, are generally assembled with NSK Bearings or sliding bearings and rotate at a high speed, sometimes generating high heat.
If this phenomenon is not eliminated in time, it will lead to overheating of the bearing and increase the temperature of the corresponding parts of the machine tool, resulting in thermal deformation. In serious cases, the height of the spindle and tailstock will be unequal, which will not only affect the accuracy and machining accuracy of the machine tool itself, but also burn out the bearing. The causes of main shaft bearing heating and its troubleshooting are shown in Table 1. In order to ensure the working condition of NTN bearing, it is necessary to avoid damage as much as possible. What should we do?
Generally, if the bearing is used correctly, it can be used until the fatigue life is reached. However, there will be accidental and premature damage, which can not be resistant to use. This early damage, as opposed to fatigue life, is called the quality service limit of failure or accident. Most of them are caused by careless installation, use and lubrication, foreign matters invading from the outside, and insufficient research on the thermal effects of shafts and shells.
As for the damage state of NTN bearing, for example, the clamping damage of the ring retaining edge of roller bearing can be considered as the reason. These reasons can also coincide with insufficient lubricant, unsuitable, defects of oil supply and drainage structure, intrusion of foreign matters, bearing installation error and excessive deflection of shaft.
Therefore, only investigating the bearing damage, it is difficult to know the real cause of the damage. However, if you know the use machinery, service conditions, the structure around the bearing, the situation before and after the accident, and combined with the damage state of the bearing and several causes, you can prevent the recurrence of similar accidents. In order to ensure the working condition of NTN bearing, it is necessary to avoid damage as much as possible. What should we do?
Generally, if the bearing is used correctly, it can be used until the fatigue life is reached. However, there will be accidental and premature damage, which can not be resistant to use. This early damage, as opposed to fatigue life, is called the quality service limit of failure or accident. Most of them are caused by careless installation, use and lubrication, foreign matters invading from the outside, and insufficient research on the thermal effects of shafts and shells.
As for the damage state of NTN bearing, for example, the clamping damage of the ring retaining edge of roller bearing can be considered as the reason. These reasons can also coincide with insufficient lubricant, unsuitable, defects of oil supply and drainage structure, intrusion of foreign matters, bearing installation error and excessive deflection of shaft.
Therefore, only investigating the bearing damage, it is difficult to know the real cause of the damage. However, if you know the use machinery, service conditions, the structure around the bearing, the situation before and after the accident, and combined with the damage state of the bearing and several causes, you can prevent the recurrence of similar accidents. The structural design, manufacturing process and material quality of ina imported bearings are analyzed.
INA imported bearings have reasonable design and advanced nature, so that long service life of INA bearing will be longer. The manufacturing of bearings generally goes through multiple processing 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.
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 on the working surface of bearing shows that the grinding process is closely related to the surface quality of bearing.
The metallurgical quality of ina imported bearing materials was once the main factor affecting the early failure of rolling bearings. With the progress of Metallurgical Technology (such as vacuum degassing of bearing steel), the quality of raw materials has been improved. The proportion of raw material quality factor in bearing failure analysis has decreased significantly, but it is still one of the main influencing factors of bearing failure. Proper material selection is still a factor that must be considered in bearing failure analysis.
The main task of ina imported 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. For the use of bearings, noise is very common. Even the low-noise bearings in the imported Koyo bearings have the same situation. So why does it make noise? Today I will introduce its essence to you.
The raceway sound of Koyo imported bearing and its control method raceway sound is a smooth and continuous sound generated by the rolling body rolling on the raceway surface when Koyo imported bearing is running. It is a unique basic sound that will occur in all rolling bearings. The general bearing sound is the sound of raceway plus other sounds. The raceway sound of ball bearing is irregular, and its frequency is above 1000Hz.
Its main frequency does not change with the speed, but its total sound pressure level increases with the speed. For the bearing with loud raceway sound, the sound pressure level of raceway sound decreases with the increase of viscosity; For bearings with low raceway noise, the sound pressure level changes from decrease to increase when the viscosity increases to more than 20mm2 / s.
The greater the rigidity of the bearing pedestal, the lower the total sound pressure level of the raceway sound. If the radial clearance is too small, the total sound pressure level and dominant frequency of raceway sound will increase sharply with the decrease of radial clearance. The methods to control the sound of raceway are: select low-noise bearings, that is, bearings with small waviness, and carefully select the service conditions. Raceway noise often affects the noise of the whole machinery. Reducing raceway noise can reduce the noise of the whole machinery.
Impact sound of rolling element and its control method when the ball bearing or cylindrical roller bearing of larger model runs at low speed under pure radial load, due to the small centrifugal force of the rolling element, the rolling element in the non load area will impact the cage or raceway and make noise. But as the speed increases, the sound will disappear. The control methods of impact sound of rolling elements are: appropriately reduce the radial clearance, and use the bearing of cage with reasonable structure and flexible material.
The rolling sound of imported Koyo bearings and its control method rolling sound is the harsh metal friction sound that can occur in cylindrical roller bearings on all occasions. Most of it occurs in larger types of grease lubricated bearings, which is more likely to occur in greases with degraded base oil performance and hardly occurs in oil lubrication. In addition, it is easy to occur in winter.
When bearing pure radial load, it is easy to occur in the case of large radial clearance, and it is easy to occur in a specific speed range with different models and sizes, both continuously and intermittently. Special processing methods for the outer ring raceway can prevent the occurrence of rolling sound. If necessary, this kind of bearing can be selected, or the radial clearance of the bearing can be appropriately reduced, the lubricating grease with excellent performance can be used and the rigidity of the parts matched with the bearing can be improved.
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