Analysis and maintenance and lubrication of SKF imported bearings caused by high temperature
Bearing failures are often due to a variety of factors, all design and manufacturing process factors and SKF bearing failures, and their analysis is not easy to determine. Under normal circumstances, in general, you can consider and analyze factors and internal factors.
The main factors used for adjustment are installation, use and maintenance, maintenance, etc. in line with technical requirements. The mounting conditions are one of the factors that use the bearing is the primary factor that often causes the change in state of the state between the various parts of the package, the operation in the abnormal state and early failure. According to the technical requirements of the installation, use, maintenance and maintenance of SKF bearings, the bearing contact load, speed, temperature, vibration, noise and lubrication status are monitored and checked, and abnormalities are immediately found to find the cause and adjusted back to normal. In addition, the quality of the grease and the surrounding medium, the atmosphere is also very important for analytical testing.
Internal factors mainly refer to structural design, quality manufacturing processes and materials. There are three factors that determine the quality of the bearing.
First, the structural design and advanced will have a longer SKF bearing life. Bearing manufacturing is subjected to multiple processes of forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of the treatment will also affect the service life of the bearing. Affecting the heat treatment and grinding process of bearings, there is often a more direct relationship with the bearing faults associated with product quality. In recent years, studies of the deterioration of the surface layer of the bearing have shown that the grinding process is closely related to the quality of the bearing surface.
The influence of the metallurgical quality of SKF bearing materials is the main factor in the early failure of rolling bearings. With the advancement of metallurgical technology (such as bearing steel, vacuum degassing, etc.), the quality of raw materials has been improved. The proportion of raw material quality factors in bearing failure analysis has dropped significantly, but it is still one of the main factors of bearing failure. The choice of proper or not is still a bearing failure analysis that must be considered.
The main task of SKF bearing failure analysis is based on a large number of background materials, data and failure mode analysis to identify the main factors causing bearing failure, so that targeted improvements can be made to extend the service life of the bearing to avoid unexpected events of the bearing. Early failure.
The way alloy elements exist in steel
1. The alloying elements interact with the carbon in the steel to form carbides in the steel. The alloying elements interact with carbon in the steel. They can be divided into two categories:
(1) An element which does not form a carbide (referred to as a non-carbide forming element), and includes nickel, silicon, aluminum, cobalt, copper, and the like. Since these elements have a lower binding force to carbon than iron, they cannot be combined with carbon in steel, and they have no significant effect on the structure of carbides in steel.
(2) An element forming a carbide (referred to as a carbide forming element), and depending on the strength of binding to carbon, the carbide forming element can be classified into three types.
1) Weak carbide forming elements: Manganese manganese has a slightly stronger binding force to carbon than iron. Manganese is added to steel and generally does not form special carbides (carbides with a structure different from Fe3C are called special carbides) but are dissolved in cementite.
2) medium-strong carbide forming elements; chromium, molybdenum, tungsten
3) Strong carbide forming elements: vanadium, niobium and titanium have extremely high stability. For example, TiC starts to slowly dissolve above 1 000 C when quenching and heating. These carbides have extremely high hardness, for example, in high speed steel. Vanadium is added to the V3C to make it more wear resistant.
2. The alloying element is dissolved in ferrite (or austenite) and exists in steel as a solid solution.
3. Alloying elements are combined with nitrogen, oxygen, sulfur, etc. in steel, and are present in steel in the form of non-metallic inclusions such as nitrides, oxides, sulfides, and silicates.
4. Free form, ie insoluble in iron, insoluble in compounds: lead, copper
Why NSK bearings generate noise during work
It is impossible to absolutely eliminate friction in any bearing including NSK bearings, so noise is inevitable due to the presence of friction during operation. According to the standard, the noise should be within a certain range, and if the noise is high, it means that the bearing has a fault.
The cause of noise generated by NSK bearings is more complicated. One is the wear of the inner and outer rings of the bearing. Due to this wear, the coupling relationship between the bearing and the housing, the rolling bearing and the shaft is broken, causing the axis to deviate from the correct position and generate an abnormal sound when the shaft is moving at a high speed. When the automobile bearing is fatigued, the surface metal peeling off will also increase the radial clearance of the bearing to produce abnormal noise. In addition, insufficient bearing lubrication, dry friction, and bearing crushing can produce abnormal sounds. After the bearing wears loose, the cage is loose and damaged, and abnormal noise is also generated.
The bearing sound of the bearing and its control mode is the kind of slippery continuous sound that the moving body is moving on the raceway surface when the car bearing is running. What types of bearing seals are there? . It is the unique sound of the city that has no moving bearings. The general bearing sound is equal to the rolling sound plus other sounds. The ball bearing sound is unlawful, the frequency is above 1000Hz, its frequency does not change with the speed, but its sound pressure level is added with the acceleration of the speed. For bearings with large rolling sounds, the sound pressure level of the raceway sound is reduced with the addition of viscosity; and for a small bearing with small raceway sound, the sound pressure level is reduced by a viscosity of about 20 mm2/s or more. Turned to nothing to delete. The greater the rigidity of the bearing housing, the lower the sound pressure level of the raceway sound. If the radial play is too small, the sound pressure level of the raceway sound and the frequency will be sharply added to the cut of the radial play. There is no way to control the rolling sound: choose low-noise bearings, that is, bearings with small waviness, and carefully choose the premise. The raceway sound often affects zero mechanical noise, and the reduction of the raceway sound can reduce zero mechanical noise.
Impact sound of the moving body and its control mode When the larger ball bearing or NSK bearing is running at low speed under pure radial load, the dynamic body in the non-loading area will impact the connecting frame or roll due to the small centrifugal force of the moving body. The road emits noise. But with the advancement of the speed, the sound of that type will disappear. There is no control method for the impact sound of the moving body: the radial clearance is appropriately cut, and the bearing of the connecting frame without the reasonable layout and the material is not harmonious.
The basic code indicates the basic type of FAG bearing
Core Tip: The basic code indicates the basic type, structure and dimensions of the FAG bearing. The pre-code indicates that the bearing parts are placed before the basic code. FAG's bearing code is based on the basic code, pre-generation
The basic code indicates the basic type, structure and size of the FAG bearing. The pre-code indicates that the bearing part is placed before the basic code. FAG's bearing code consists of the basic code, the pre-code and the post code. The basic code indicates the basic type, structure and size of the bearing. The leading code indicates that the bearing part is placed before the basic code. The post code indicates the supplemental code added after the basic code of the bearing when the bearing structure shape, size, seal, cage, tolerance, clearance, heat treatment, packaging, technical requirements, etc. are changed.
1 pre-code
The pre-code R is placed directly before the basic code of the imported bearing, and the remaining pre-codes are separated from the basic code by small dots.
GS—Thrust cylindrical roller bearing race. Example: GS.81112
K – the combination of rolling elements and cages. Example: K.81108 assembly of thrust cylindrical roller and cage.
R – without bearings that separate the inner or outer ring. Example: RNU207 - NU207 bearing without inner ring.
WS—Thrust cylindrical roller bearing shaft ring. Example: WS.81112.
2 post code
The post code is placed after the basic code. When there are multiple sets of post code, it should be arranged from left to right in the order of the post code listed in the INA bearing code table. Some post-codes are separated from the base code by small dots.
Importance of lubrication for IKO bearings
1. The bearing oil bath is smooth
Smooth oil bath is a common smooth way in imported bearings, suitable for the smoothness of low and medium speed bearings. The IKO bearing is partially immersed in the groove, the smooth oil is brought up by the rotating bearing parts, and then flows back to the oil groove. The oil level should be slightly lower than the center of the lowest rolling element.
2. The smooth drop of the bearing
The drip smooth is suitable for the bearing parts that need to be quantitatively supplied with smooth oil. The amount of oil dripping is preferably every 3-8 seconds. Excessive oil quantity will cause the bearing temperature to increase.
3. The bearing's circulating oil is smooth
The oil is pumped to the bearing components by an oil pump, and then filtered and cooled by the smooth oil after the IKO bearing. Because the circulating oil can take away a certain amount of heat and cool the bearing, this method is used for bearing parts with higher rotational speed.
4. The bearing spray is smooth
The use of boring shrinking air is mixed with smooth oil through a sprayer to create an oil mist. In the radial bearing, the air flow can effectively cool the bearing and prevent the intrusion of impurities. This method is suitable for the smoothness of high speed and low temperature bearing components.
5. The bearing's radiation is smooth
The low pressure oil is injected into the bearing through the nozzle by the oil pump, and the oil injected into the bearing flows into the oil groove through the other end of the bearing. When the bearing rotates at high speed, the rolling element and the cage also cause airflow around the surrounding air at a relatively high rotational speed. It is difficult to send the smooth oil to the bearing in a smooth manner. In this case, it is necessary to spray the smooth oil with low-pressure radiation. In the bearing, the position of the nozzle should be placed between the inner ring and the center of the cage.
Different IKO bearing greases are not the same in the contours of the bearings. It is necessary to form a contour that is relatively straightforward. The running time is short. In the long-term operation, the bearing temperature is low and stable. This is an ideal one. Grease, so it is especially important for the grease.
Some so-called eddy-flow greases are not easy to form contours, and even if they are contoured, they are easy to collapse. At this time, the excess grease repeatedly returned to the raceway is in a state of being strongly stirred for a long time, and the bearing torque is large and the temperature is high. Unbalanced, noise may also be generated, and grease is also prone to deterioration and loss.
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What problems should I pay attention to when using FAG imported bearings?
Bearings are precision parts, so they require a very cautious attitude when using them. That is, they use high-performance FAG bearings. If they are not used properly, they will not achieve the expected performance and will easily damage the bearings.
First, the following matters should be noted when using bearings:
1. Keep the bearings and their surroundings clean
Even if the smiling dust that is invisible to the naked eye enters the bearing, it will increase the wear, vibration and noise of the bearing.
2, use the installation carefully
Strong stamping is not allowed. It is not allowed to directly hit the bearing with a hammer. It is not allowed to transmit pressure through the rolling elements.
3, use appropriate and accurate installation tools
Try to use special tools and try to avoid using cloth and short fibers.
4, to prevent bearing corrosion
When taking the bearing directly by hand, wash off the sweat on your hands and apply high-quality mineral oil before handling. Pay special attention to rust prevention during the rainy season and summer.
However, under certain special operating conditions, FAG bearings can achieve longer life than traditional calculations, especially at light loads. These special operating conditions are when the rolling surfaces (tracks and rolling elements) are effectively separated by a lubricant film and the surface damage caused by contaminants is limited. In fact, under ideal conditions, so-called permanent bearing life is possible.
Second, bearing life:
The life of a rolling bearing is defined by the number of revolutions (or the number of hours of operation at a certain speed). Bearings within this life are subject to initial fatigue damage (flaking or missing) on any of their bearing rings or rolling elements. However, whether in the laboratory test or in actual use, it can be clearly seen that the same bearing under the same working conditions has a different actual life. In addition, there are several different definitions of FAG imported bearings "life", one of which is the so-called "working life", which means that the actual life that a bearing can reach before it is damaged is caused by wear and damage, usually not caused by fatigue. It is caused by wear, corrosion, seal damage and other reasons.
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Introduce several common maintenance methods after FAG universal joint bearing damage
Usually, our FAG universal joint bearing will be seriously damaged after using it for a period of time. In this case, what should we do? We should find some common methods for daily maintenance of FAG universal joint bearings. We will introduce them today. Several so that everyone can use it later. One-third of the bearing damage is caused by fatigue damage, the other third is due to poor lubrication, and the other third is due to contaminants entering the bearing or improperly installed.
In this case, we have especially experimented with FAG universal joint bearings with increasing temperature. When inspecting FAG universal joint bearings that have been removed during regular maintenance and operation of bearing equipment and replacement of peripheral parts, it is necessary to judge sequentially. Whether secondary bearing parts can be reused and recorded better than bad. Most FAG universal joint bearings are damaged for many reasons, such as excessively small bearing clearances due to previously estimated loads, ineffective seals, and tight fits. Any of these factors have their particular type of damage and leave a special mark of damage.
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