Preload inspection method of Timken bearing
Preload inspection method of Timken bearing
2022年4月18日
Three criteria for judging the failure of ina imported bearings
Three criteria for judging the failure of ina imported bearings
2022年4月18日

NSK bearing limit speed and heat treatment bulging method

  • The speed of NSK bearing is mainly limited by the temperature rise caused by friction heating inside NSK bearing. When the speed exceeds a certain limit, NSK bearing will not continue to rotate due to burns, etc. The limit speed of NSK bearing refers to the limit value of continuous rotation without friction and heating causing burns.
  • Therefore, the limit speed of NSK bearing depends on the type, size and accuracy of NSK bearing, as well as various factors such as lubrication mode, quality and quantity of lubricant, material and type of cage, load conditions and so on. The limit speed of various NSK Bearings when grease lubrication and oil lubrication (oil bath lubrication) are respectively contained in the size table of each NSK bearing, and its value represents the limit value of speed of NSK Bearings of standard design when rotating under general load conditions (C / P > = 13, FA / FR < = about 0.25). In addition, the lubricant may be superior to other properties according to its type and brand, but it is not suitable for high-speed rotation.
  • When the corrected load condition C / P of the limit speed is less than 13 (i.e. the equivalent dynamic load p exceeds about 8% of the basic rated dynamic load C), or the axial load in the synthetic load exceeds 25% of the radial load, the limit speed shall be corrected with the following formula.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The quenched structure of NSK bearing steel consists of quenched martensite, a small amount of undissolved secondary carbides and about 12% ~ 14% retained austenite. Quenched martensite and retained austenite belong to unstable structure.
  •  During tempering, the decomposition of martensite shrinks the volume of steel, while the decomposition of retained austenite expands the volume of steel.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • With the increase of tempering temperature, the transformation and decomposition amount of residual austenite increases. Under the condition of ensuring the hardness required by the process, appropriately increase the tempering temperature to decompose the residual austenite and transform it into martensite structure with large specific volume, which can correspondingly increase the volume of the workpiece, that is, increase the external diameter grinding amount. Using this method, the parts with NSK bearing ring defects that become waste products under normal grinding conditions can be saved.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • This method is effective for thick and heavy workpieces with large residual austenite content (especially for self-aligning roller bearings). In the actual production, different tempering processes are formulated for parts with different specifications, sizes and thicknesses. On the premise of ensuring hardness and deformation, the microstructure is fully transformed to produce large bulge, and the grinding amount is increased accordingly to save the waste products. The function of ina inlet bearing coordination is to make the stationary ring and rotating ring of ina inlet bearing consolidate with the stationary part (usually ina inlet bearing seat) and rotating part (usually shaft) of the installation part respectively, so as to realize the basic task of transmitting load in the rotating state and limiting the position of the moving system relative to the stationary system. 
  • On the shaft and in the ina inlet bearing seat, the rolling ina inlet bearing is required to fix its position in three directions: radial, axial and tangent directions. Radial and tangential positioning is realized through tight fit of ina inlet bearing ring, and tight fit is adopted for axial positioning only in a few cases; NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Generally, axial limit parts, such as end caps and retaining rings, are used to limit the axial position within the clearance range. Check the vibration of NTN imported bearing during operation. The peeling, indentation, corrosion, crack, wear, etc. will be reflected in the vibration measurement of NTN imported bearing. NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The vibration of NTN imported bearing is very sensitive to the damage of NTN imported bearing. Therefore, the vibration can be measured by using a special NTN imported bearing vibration meter (frequency analyzer, etc.), and the specific abnormal situation can not be inferred by frequency division. NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Since the measured values are different due to the service conditions of NTN imported bearings or the installation position of sensors, it is necessary to analyze and compare the measured values of each machine in advance to determine its judgment standard.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Second, check the sound condition of NTN imported bearing during rolling. Because NTN imported bearing will emit abnormal sound and irregular sound even if there is slight peeling and other damage, it can be distinguished with a sound detector. The sound detector is used to check the rolling sound and sound quality of NTN imported bearing in operation, so as to prevent it in advance.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Third, check the temperature of NTN inlet bearing during rotation. It is more appropriate if the outer ring temperature of NTN inlet bearing can be directly measured by oil hole. Generally, the temperature of NTN inlet bearing can be inferred based on the temperature outside the NTN inlet bearing chamber.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • If the lubrication and installation parts are appropriate, the temperature of NTN inlet bearing will rise sharply and abnormal high temperature will occur. At this time, the operation must be stopped and necessary preventive measures must be taken.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Generally, the temperature of NTN imported bearing rises slowly with the start of operation and reaches a stable state after 1-2 hours. The normal temperature of NTN imported bearing varies with the heat capacity, heat dissipation, speed and load of the machine.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Check the axle and find out the faults existing in Peilin before long-distance or race. In the early stage, when Peilin lubrication is seriously deteriorated, eliminate these faults in advance for lubrication or replacement, so as to avoid affecting the level of play due to hardware problems, which is very important for professional drivers and amateur drivers.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Touch is a very simple method. In industry, the lubrication problem of Peilin can lead to high temperature, which can be felt by hand. This high temperature will be harmful to the lubricant in Peilin. It is difficult for the bicycle to rotate at that high speed, or even reach the ground that makes Peilin hot. The inspection touch of the bicycle is only the axis of the flower drum rotating with the hand mold, which can feel the situation inside, The vibration indicates that there are pits or the beads are not round, and the quicksand feeling is the lack of good lubrication.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method 
  • If the rotation is astringent and stuck, it indicates that the oil is dry or the wrong device has caused Peilin to be misaligned and too tight.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The observation is mainly aimed at the appearance of Peilin to see whether the rubber seal has been broken. Open the rubber seal to check whether the lubricating oil is dry. Blackening means that the lubricating oil is polluted or carbonized. Whiteness and turbidity indicates water inflow. In this case, the earlier it is found, the smaller the damage after oil change. However, the long-term use of such oil can cause irreversible damage to Peilin.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Listen, electronic stethoscope is commonly used in industry to check the condition of Peilin. The low whine indicates that Peilin is working normally, while the hiss, sharp chirp or other irregular business indicates that NTN imported bearings are in an abnormal working state.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The sharp chirp may be caused by improper lubrication, which causes metal friction, while the hissing sound may be the pollution of lubricating oil. The irregular noise is caused by the vibration caused by the indentation of the raceway. In the absence of an electronic stethoscope, the bicycle has a very simple method. Put a wooden stick on the front fork or rear fork and turn it. 
  • This method can also be used for the center axle, but it is difficult to judge because the sound of the center axle will be mixed with the rear axle. NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • There are two kinds of lubricants commonly used in Koyo bearings: lubricating oil and grease. When the circumferential speed of the shaft is less than 4-5m / s, or the parts on the vehicle that cannot be lubricated with lubricating oil, they shall be lubricated with grease. The advantage of grease lubrication is that the sealing structure is simple, the grease is not easy to lose, and it is not affected by temperature. Adding grease once can be used for a long time.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Two problems should be paid attention to when using grease. One is to select the appropriate brand of grease according to the requirements of the automobile manual. For example, nano base grease should not be selected for automobile water pump bearing because of its poor water resistance. The second is to add an appropriate amount of lubricating grease into the Koyo bearing. Generally, it is appropriate to fill only 1 / 2-L / 3 of the cavity of the Koyo bearing. NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Too much is not only useless, but also increases the running resistance of the Koyo bearing and heats it up. Special attention should be paid to the automobile hub bearing. It is necessary to advocate “empty hub lubrication”, that is, only apply an appropriate layer of grease on the Koyo bearing. Otherwise, it will not only waste and poor heat dissipation, but also overflow the grease by heating, which may affect the braking performance.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The advantage of lubricating oil lubrication is low friction resistance and heat dissipation. It is mainly used for Koyo bearings with high speed and high working environment temperature. The brand of lubricating oil shall be selected according to the requirements of the vehicle manual, and shall be replaced in time after the vehicle maintenance cycle. After discharging the old oil, the mechanism shall be cleaned before adding new oil. The oil shall be added to the specified marking line or flush with the oil filler (depending on the specific structure and requirements of the vehicle), and no more oil shall be added.
  • The assembly accuracy of cage is guaranteed by special assembly mould, which can fully meet the assembly accuracy requirements of Koyo bearing. The condition of small interference fit for the fixed ring is that both sides of the matching surface have high shape accuracy and small roughness, otherwise it will be difficult to install and more difficult to disassemble. In addition, the influence of thermal elongation of the main shaft needs to be considered.
  • Surface heat treatment is divided into two categories. One is surface quenching and tempering heat treatment, which uses vibration absorption or vibration isolation devices to reduce Koyo bearing noise or isolate Koyo bearing noise. The other is chemical heat treatment. Its hardness test method is as follows: chemical heat treatment is to make the workpiece surface infiltrate atoms of one or more chemical elements, so as to change the chemical composition, organization and performance of the workpiece surface. After quenching and low-temperature tempering, the surface of the workpiece has high hardness, wear resistance and contact fatigue strength, while the core of the workpiece has high strength and toughness.
  • The main technical parameters of chemical heat treatment workpiece are hardened layer depth and surface hardness. The depth of hardened layer shall be checked by Vickers hardness tester. Check the distance from the workpiece surface to the point where the hardness drops to 50HRC. This is the effective hardening depth. When the hardness of the surface of the bearing is less than 0.7mm, the hardness of the rolling Rockwell tester can not be used to check the hardness of the surface of the bearing which is not thicker than 0.7mm. 
  • If the local hardness requirements of parts are high, local quenching heat treatment can be carried out by means of induction heating. For such parts, the location of local quenching heat treatment and local hardness value shall be marked on the drawing. The hardness inspection of parts shall be carried out in the designated area. Rockwell hardness tester can be used to test HRC hardness value. Unbalanced rotating torque – cause: incorrect installation, installation error, etc.
  • Timken bearing for large machinery that cannot be turned by hand, it can be started under no-load state first, and then turn off the power immediately for inertial operation. At this time, after confirming that there is no abnormal vibration or noise and the rotation is normal, enter the power operation.
  • When entering power operation, start at low speed and no load and gradually reach the specified operating conditions. The power operation inspection is mainly based on the sound, temperature rise and vibration. The cause shall be found out immediately, and the one-way bearing shall be removed for inspection when necessary.
  • For the one-way sound inspection of Timken bearing, generally, a sound stick can be used.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The temperature inspection of one-way bearing can generally be speculated according to the shell temperature, but it is correct to directly measure the temperature of the outer ring of one-way bearing by using oil hole, etc.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The grinding layer, high-temperature layer and two-layer quenching of Timken bearing are treated in molten state. The molten metal molecular flow is uniformly coated on the working surface and cooled by the base metal at a very fast speed, forming an extremely 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.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The instantaneous high temperature in the grinding area of Timken bearing 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.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Timken 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 will be 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. When examining the advantages of chromium steel and stainless steel as fag bearing materials, it is found that they do not only have anti rust effect. NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Chromium steel is a common fag bearing material. It is harder than stainless steel, so it has a longer service life. However, at higher temperatures, its performance is not very good.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • At the high temperature of 120c, it will undergo huge deformation and reduce the load. The continuous high temperature of 150C can be tolerated, but the instantaneous temperature of 150C or higher will reduce the service life of fag bearing. Heat treatment can make fag bearing bear the high temperature of 170C at an instant.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The 440 stainless steel commonly used for fag bearing is hard and firm enough to carry load (20% less than Brass Steel), but it can prevent rust and can withstand the instantaneous high temperature of 250C and the continuous high temperature of 300C. We often mistakenly think that all stainless steel is non-magnetic, and 440 stainless steel is magnetic.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  •  It is not completely rustproof, but affected by salt, acid and alkali. Grade 316 has good antirust performance, no magnetism, but it is relatively soft, so it has less load. Because it is not firm, the accuracy of 316fag bearing is not high and feels rough. Timken imported bearings must be installed under dry and clean environmental conditions. Before installation, carefully check the machining quality of the mating surface of the shaft and housing, the end face of the shoulder, the groove and the connecting surface. NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • All mating connection surfaces must be carefully cleaned and deburred, and the unprocessed surface of the casting must be cleaned of molding sand.NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • Timken imported bearings shall be cleaned before installation and used after drying, and good lubrication shall be ensured. The bearings are generally lubricated with grease or oil. When grease lubrication is used, grease with excellent properties such as no impurities, oxidation resistance, rust prevention and extreme pressure shall be selected. NSK bearing limit speed and heat treatment bulging methodNSK bearing limit speed and heat treatment bulging method
  • The filling amount of lubricating grease is 30% – 60% of the volume of bearing and bearing box, which should not be too much. The double row tapered roller bearing with sealing structure and the shaft connecting bearing of water pump have been filled with grease, which can be directly used by users and can not be cleaned.NSK bearing limit speed and heat treatment bulging method
NSK bearing limit speed and heat treatment bulging method

NSK bearing limit speed and heat treatment bulging method

  • When installing the bearing, equal pressure must be applied on the circumference of the ferrule end face to press the ferrule in. It is not allowed to directly knock the bearing end face with hammers and other tools to avoid damaging the bearing. When the interference is small, press the end face of the bearing ring with the sleeve at room temperature, knock the sleeve with a hammer, and press the ring evenly through the sleeve. If it is installed in large quantities, hydraulic press can be used. When pressing in, ensure that the end face of the outer ring and the end face of the housing shoulder, the end face of the inner ring and the end face of the shaft shoulder are pressed tightly, and there is no gap.
  • When the interference is large, the bearing can be installed by oil bath heating or inductor heating. The heating temperature range is 80 ℃ – 100 ℃, and the height cannot exceed 120 ℃. At the same time, tighten the bearing with nuts or other appropriate methods to prevent the gap between the ferrule and the shaft shoulder caused by the width contraction of Timken inlet bearing after cooling.
  • The clearance of single row tapered roller bearing shall be adjusted after installation. The clearance value shall be determined according to different working conditions and the interference of the fit. If necessary, it shall be determined by test. The clearance of double row tapered roller bearing and water pump shaft connecting bearing has been adjusted at the factory, so it is not necessary to adjust it during installation.