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.
High carbon chromium bearing steel
1. Grades, characteristics and uses of high carbon chromium bearing steel
High carbon chromium bearing steels have high contact fatigue strength and wear resistance, many grades are fully hardened steels such as GCr15
GCr15SiMn, GCr15SiMo, GCr18Mo. However, since some bearings require good toughness in the core and high hardness on the surface, a hardened bearing steel such as GCr4 has been developed.
1 GCr15 (fully hardened steel) GCr15 is a typical steel grade of high carbon chromium bearing steel, which has high hardness, wear resistance and contact fatigue strength after quenching and tempering. Its hot workability and workability are good, the hardenability is moderate, but the weldability is poor. GCr15 has a large white point sensitivity, but this defect can be eliminated in bearings that are vacuum degassed. It is used to manufacture rolling bearing rings with wall thickness ≤12mm and diameter ≤250mm, or to manufacture cones, cylinders, spherical rollers and all sizes of needles with diameter ≤22mm. It can also be used to make molds, gauges and woodworking tools as well as mechanical parts with high elastic limit and high fatigue strength.
2 GCr15SiMn (highly hardened steel) improves the content of silicon and manganese on the basis of GCr15 steel, so the hardenability, elastic limit and wear resistance are better than GCr15. The rolling bearing parts produced therefrom should not be used above 180 °C. It is used for the manufacture of rolling bearing rings with wall thickness >12mm, outer diameter >120mm, steel balls with diameter >50mm and cones, cylinders, spherical rollers and all sizes of needles with diameter >22mm. Other uses are the same as GCr15.
3 GCr15SiMo (highly hardened steel) increases the silicon content based on GCr15 and adds molybdenum. It has high hardenability, good wear resistance, high fatigue strength and good overall performance. It is suitable for the manufacture of rolling bearing rings and steel balls, rollers and the like in a large size range.
4 GCr18Mo (high-hardenable steel) adds molybdenum with a mass fraction of 0.15%~0.25% on the basis of GCr15, and increases the content of each, so the hardenability and wear resistance are improved. The lower bainite austempering can be performed to achieve hardness and wear resistance similar to martensite quenching, and the impact, fracture toughness and flexural strength of the steel are improved, thereby improving the overall mechanical properties and life of the steel. A rolling bearing ring with a wall thickness of up to 20 mm can be produced, and the size range of the rolling bearing member is also expanded.
5 GCr4 (restricted hardened steel) GCr4 is a low-hardenability rolling bearing steel. It has the properties of GCr15 fully hardened bearing steel and low carbon alloy carburized steel after being heated by volumetric tip and surface quenched and tempered. After quenching, the surface hardness is high, the surface resistance is good, the fatigue resistance is good, the core hardness is only 35~40HRC, the toughness is good and the impact resistance is good. It is mainly used to manufacture rolling bearing rings and rollers of various sizes and loads.
The difference between spindle bearings and tension disc bearings in SKF bearings
SKF spindle bearings and tension disk bearings are mostly used in textile machinery. The textile machine SKF bearing has a harsh environment and requires long life, heavy load, high speed, low noise and stable operation. The textile machine developed by SKF Bearing has outstanding performance, high speed and most of the tolerance class is 5, which has been supplied to many textile machinery factories. The following mainly introduces two kinds of textile machinery bearings, spindle bearings and tension disc bearings:
The SKF spindle bearing is one of the main components of the twisting and winding on the spinning machine. It is a combination of the two-point supported slender rotary shaft, which is used to twist the fiber into a yarn and wind the yarn around the bobbin. shape. The quality of SKF bearing spindle bearings is closely related to yarn quality, power consumption, environmental noise, labor productivity and so on.
SKF tension disc bearings are high precision ball bearings with single or double row rolling elements. Due to their low moment of inertia, the spindle can be accelerated to the working speed quickly, with a gap seal and low friction. The SKF tension disk unit is used for guiding and tensioning the textile machinery drive belt.
KOYO company bearing code
Core Tip: KOYO's bearing code consists of basic code, pre-code and post code. The basic code indicates the bearing series and dimensions. The front code indicates the bearing type and bearing parts.
The bearing code of KOYO Company consists of basic code, pre-code and post code. The basic code indicates the bearing series and dimensions. The front code indicates the bearing type and bearing parts. It is located before the basic code. The rear code indicates the structure of the bearing, cage, sealing and dustproof, tolerance, oil gap, heat treatment and other technical requirements. After the basic code. 1. Front code C- cylindrical roller bearing attachment (or bearing itself), for example: C00210 45C- Paired mounting tapered roller bearings, face to face installation, eg 45C30210 46C- Paired installation of tapered roller bearings, back to back installation, Example: 46C30210 4CRI- four-row cylindrical roller bearing inner ring, for example: 4CRI4560F 4CRO- four-row cylindrical roller bearing outer ring, for example: 4CRO660AF E- magnetic motor ball bearing, outer diameter is positive tolerance, for example: E10 EN- magnetic Motor ball bearing, outer diameter is negative tolerance, for example: EN10 IR- needle bearing inner ring (inch), for example: IR1212 IRA- needle bearing inner ring, wider than IR series (imperial), for example: IRA20 IRM- needle roller Bearing inner ring, for example: IRM710 M- maximum load capacity ball bearing, for example: M6311 OR- needle bearing, only outer ring, for example: OR10876 F- deep groove ball bearing with flange, for example: F603 TR- size non-standard Single row tapered roller bearings, for example: TR060702 W- wide, deep groove ball bearings, for example: W602ZZX 2. Rear code (1) Internal structure A- angular contact bearing, contact angle 30 degrees (not marked), for example : 7210 B- Angular contact bearing, contact angle 40 degrees, for example: 7210B C- angle Contact bearing, contact angle 15 degrees, for example: 7210C C- tapered roller bearing, contact angle 20 degrees, for example: 30303C D- tapered roller bearing, contact angle 28 degrees 30 minutes, for example: 30305D G- compression axial oil gap Self-aligning and tapered roller bearings J- Tapered roller bearings, in accordance with ISO grouping, for example: 30206J N- Tapered roller bearings, special noise requirements, eg 30208N R- Sizing for increased load capacity, conical and cylindrical rollers Sub-bearings, eg 22228R (2) Sealed and dust-proof OR-ball bearings with O-rings, eg 6201+OR RK- single-sided, double-lip contact synthetic rubber seals, eg 6210RK 2RK- double-sided, double Lip contact synthetic rubber seal, eg: 6210.2RK RS- single-sided, contact-type synthetic rubber seal, eg 6210RS 2RS- double-sided, contact-type synthetic rubber seal, eg 6210-2RS RSA- single-sided, with metal cover contact Synthetic rubber seal, eg: 88107RSA 2RSA- double-sided, with metal cover contact synthetic rubber seal, eg: 88107-2RSA RSB- single-sided, contact-type synthetic rubber seal with Gaga metal cover, eg: 88107RSB 2RSB- double Face, contact synthetic rubber seal with Gaga metal cover Example: 88107-2RSB RSC- silicone rubber RS seal, for example: 6210RSC RSD- polypropylene rubber RS seal, for example: 6210RSD RSE- single-sided, rib-guided contact synthetic rubber seal, for example: 6206RSE 2RSE- double Face, rib guide contact synthetic rubber seal, for example: 6206-2RSE RSF- RS type fluorinated rubber seal, for example: 6210RSF RU- single-sided, non-contact synthetic rubber seal,
Principles and functions of grease in NTN bearings
Our customers always have some improper use methods when using all kinds of NTN bearing grease. Today we will explain the principle and function of the grease in the bearing.
1, the principle of the use of grease
Everyone is a liquid solution that is a very thick solution. This grease is composed of a reticulated soap fiber whose structure determines that it can adsorb a large amount of lubricating oil and make it work properly. But as you can imagine, if a sponge is squeezed, the water will flow out. Grease is also squeezed out of the lubricating oil, but the grease in the NTN bearing is rarely directly squeezed and drained, because a freshly lubricated imported bearing is moving in the inner space of the bearing during running. Its main working principle is "temperature".
2, the practical function of grease
The main reason for draining grease to the sliding surface is the increase in temperature of the grease around the NTN bearing. When the bearing starts to run normally, the grease will reach the sliding friction surface. Lubrication begins to work as the temperature increases.
Advantages of NTN imported bearings with grease lubrication:
1) Individual bearing points must be refueled by hand. If the grease is used, it will save trouble and avoid accidents caused by lack of oil.
2) The grease itself has a sealing effect, which allows the use of a mechanism with a low degree of sealing to achieve a simplified design.
3) Experience has shown that lithium grease lubrication has a lower temperature rise and longer bearing life than a drop method in a certain speed range (n<20000r/min or dn<20000mm.r/min).
2, NTN imported bearing lubrication theory basis: the lubrication mechanism of the bearing is the theory of elastic fluid dynamic pressure lubrication.
3. NTN bearing failure type and lubrication relationship: Most of the failure causes are caused by faults in the assembly and poor sealing. A small number of failures are caused by wear, gluing, corrosion and overheating due to lack or excess of lubricant or quality failure.
4. Basic characteristics of grease and general criteria for selecting grease:
When selecting grease, it is necessary to select the grease that is compatible with the conditions of use (temperature, speed, load, environment, etc.), which are related to the basic characteristics of the grease, and the basic characteristics of the grease depend on the thickener and base oil. kind of.
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The effect of grease on the service life of KOYO bearings
The use factors mainly refer to whether the installation adjustment, use and maintenance, maintenance and repair, etc. meet the technical requirements. According to the technical requirements of KOYO bearing installation, use, maintenance and maintenance, monitor and check the load, speed, working temperature, vibration, noise and lubrication conditions of the bearing in operation, find out the cause and immediately adjust the cause, make adjustment It returned to normal. The installation condition is one of the primary factors in the use factor. The bearing is often changed due to improper installation, and the force state between the parts of the whole bearing changes. The bearing is operating in an abnormal state and the end of the service life is early. Refers to the three major factors that determine the quality of the bearing, such as structural design, manufacturing process and material quality.
The metallurgical quality of imported bearing materials was once the main factor affecting the early failure of rolling bearings. With the advancement of metallurgical technologies (such as vacuum degassing of bearing steels), the quality of raw materials has improved. The proportion of raw material quality factors in bearing failure analysis has dropped significantly, but it is still one of the main factors affecting bearing failure. The proper selection of materials is still a factor that must be considered in bearing failure analysis.
Bearings are generally manufactured through multiple processes such as forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of each processing technology will also affect the life of the bearing. The heat treatment and grinding processes that affect the quality of the finished bearing often have a more direct relationship with the failure of the bearing. In recent years, research on the metamorphic layer of bearing working surface shows that the grinding process is closely related to the bearing surface quality.
The main task of KOYO bearing service life analysis is to find out the main factors causing bearing failure based on a large amount of background materials, analysis data and failure modes, so as to propose improvement measures in a targeted manner, prolong the service life of bearings and avoid bearing protrusion. Early failure of the hair.
In general, the grease filling amount in the KOYO bearing always exceeds the actual required amount of direct participation in lubrication, in the cavity of the holder and the bearing cover, and forms a contour on the periphery of the rolling element. During this process, the bearing temperature rises rapidly due to the resistance of the excess grease. Although most of the excess grease is squeezed out at the beginning of the run, the grease that is squeezed into the raceway attachment may still be carried by the rolling element into the raceway. In the early stages of bearing operation, most of the grease is squeezed out of the raceway very quickly (less than a minute), and the build-up grease is discharged a small amount while circulating along with the bearing rotor. At this time, the bearing temperature continues to rise until the excess bearing grease is completely discharged, which can be called the walking phase of the grease. According to the grease quality and filling amount in the bearing structure, this time may last for more than ten. Minutes, even hours.
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The latest method of daily maintenance and maintenance of KOYO bearings
First, the problems of the maintenance technology of KOYO imported bearings:
The two major problems related to KOYO's imported bearing maintenance technology are: 1. When to change the oil. 2. How much oil should be changed? If the oil change is too small, the bearing will be scrapped in advance; if the oil change is too much, KOYO bearings will be in trouble or long-term damage to the power coil and coil.
Second, KOYO imported bearing maintenance technology:
The way to determine when to lubricate and when to stop oiling is simple: monitor when developing a baseline, setting up an observation schedule, and filling the oil.
1. Develop a basic line
The KOYO imported bearing base line reflects the decibel strength under normal operating conditions, no visible errors, and sufficient lubrication.
Three ways to develop a baseline:
1), comparison method: If there are multiple KOYO bearings of the same type, these bearings can be put together for comparison. Use the same test method or observe each bearing from the same angle. Analyze the decibel intensity and sound quality. If there is no essential difference (less than 8 dB), we can set it as the base decibel strength of each KOYO bearing.
2) Set the basic line when adding lubricating oil: When adding lubricating oil, listen to the intensity of the sound, when the sound intensity drops and then rises. At this time, do not add too much oil, and set it as the basic line.
3) History: Observe the decibel strength of KOYO bearings, record them daily, and then compare the results of 30 days. If the decibel intensity changes little or no (less than 8 decibels), we can set this as the baseline and use it for later comparisons.
2, set the observation timetable
Equipment criticality associated with total production, environmental results, and operational results is a major factor in selecting and setting up an evaluation mechanical system. It is very necessary to test once a month after the basic observation line is established. For high-decibel KOYO bearings that are to be lubricated, the frequency should be detected more frequently so that changes that may occur are observed. If a KOYO bearing is in a state of destruction, the lubricant can only temporarily cover up the error. However, the decibel intensity will rise quickly to show the existence of the error. In some cases, this phenomenon will appear in a few minutes, while others will take several days.
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