Bearing is an important part of contemporary mechanical equipment.Its main function is to support the mechanical rotating body and reduce thefriction coefficient(frequency coefficient), and ensure its rotation accuracy.
Chinese name
Bearing
Foreign name
bearing
Role
Support rotating parts to reduce friction
Classification
Plain and rolling bearings
Application
Metallurgy, wind power, mining machinery, aerospace, auto parts
EarlyLinear motion bearingThe form is to place a row of wooden poles under a row of skids.Modern linear motion bearings use the same working principle, except that sometimes balls are used instead of rollers.The simplest rotating bearing is the sleeve bearing, which is just a bush clamped between the wheel and the axle.This design was later replaced by rolling bearings, which replaced the original one with many cylindrical rollersbushingEach rolling element is like a separate wheel.
An early example of a ball bearing was found on an ancient Roman ship built in 40 BC, which was found in the Italian Lake Nano: a wooden ball bearing was used to support a rotating table top.It is said that Leonardo·Da VinciA ball bearing was described around 1500.Among the various immature factors of ball bearings, a very important point is that there will be collisions between balls, resulting in additional friction.But you can prevent this phenomenon by putting the balls into small cages.In the 17th century,GalileoThe ball bearing of "cage ball" was first described.At the end of the 17th century, it was designed and manufactured by C. Warlow of EnglandBall bearing, and installed on the mail car for trial use, and the British P. Worth obtained a patent for ball bearings.The first practical one with cageRolling bearingIt was invented by the watchmaker John Harrison in 1760 to make the H3 hour meter.HR. Hertz published a paper on contact stress of ball bearings.On the basis of Hertz's achievements, R. Streitbeck of Germany, A. Palmgren of Sweden and others conducted a large number of tests, which contributed to the development of the design theory and fatigue life calculation of rolling bearings.Later, NP. Petrov applicationNewton's law of viscosityCalculate bearing friction.The first patent on the raceway is Camasson'sPhilip Vaughan Obtained in 1794.
In 1883, Friedrich Fisher proposed to use appropriate production machines to grindsteel ballThe proposition of the "" has laid the foundation of the bearing industry.The British O. Renault made a mathematical analysis of Thor's discovery and derivedreynolds equation , has been established since thenHydrodynamic lubricationTheoretical basis.
Industry Overview
According to the data of the National Bureau of Statistics, there were 1416 enterprises in China's bearing manufacturing industry in 2011 (with an annual sales revenue of more than 20 million yuan), and the total industrial output value of the year was 193.211 billion yuan, up 27.59% year on year;The sales revenue was 191.097 billion yuan, up 30.30% year on year;The total profit was 12.523 billion yuan, an increase of 26.54% over the previous year.It is estimated that by 2015, the output of bearings in China is expected to exceed 28 billion sets,Main business incomeIt is expected to reach 210 billion yuan, becoming the world's largest bearing production and sales base.
At present, the bearing industry in China mainly faces three prominent problems: low concentration of production, low R&D and innovation ability, and low level of manufacturing technology.
First, the industrial production concentration is low.Among the world's bearing sales of about 30 billion dollars, the world's eight largest multinational companies account for 75% - 80%.The two largest companies in Germany account for 90% of the national total, five in Japan account for 90% of the national total, and one in the United States accounts for 56% of the national total.However, the sales volume of the 10 largest bearing enterprises in China, such as bearing shaft enterprises, only accounted for 24.7% of the whole industry, and the production concentration of the top 30 enterprises was only 37.4%.
Second, the ability of R&D and innovation is low.Weak basic theoretical research in the whole industry, weak participation in the formulation of international standards, less original technology, less patented products.
At present, our design and manufacturing technology is basically imitation, and our product development ability is low, which is reflected in: although the matching rate of domestic main engines reaches 80%, the matching and maintenance bearings of important main engines such as high-speed railway passenger cars, medium and high-grade cars, computers, air conditioners, and high-level rolling mills are basically imported.
Third, the level of manufacturing technology is low.The manufacturing process and equipment technology of the bearing industry in China are developing slowly, the CNC rate of turning is low, and the automation level of grinding is low. There are only more than 200 automatic production lines in China.Advanced heat treatment processes and equipment that are critical to bearing life and reliability, such as controlled atmosphere protection heating, double refining, bainite quenching, have low coverage, and many technical problems have not been solved.The research and development of new steel grades of bearing steel, the improvement of steel quality, and the research and development of lubrication, cooling, cleaning, abrasive tools and other related technologies cannot meet the requirements of improving the level and quality of bearing products.As a resultProcess capability indexLow, poor consistency, large dispersion of product processing dimensions, and unstable internal quality of products affect the precision, performance, life and reliability of bearings.
Bearing parameters
life
Under a certain load, the bearingpittingThe number of revolutions or hours previously experienced is called bearing life.
Rolling bearingThe service life is defined by revolutions (or working hours at a certain speed): the bearing within this service life shall have initial fatigue damage (peeling or defect) on any bearing ring or rolling element.However, whether in laboratory tests or in actual use, it is obvious that the actual life of bearings with the same appearance under the same working conditions is quite different.In addition, there are several different definitions of bearing "life", one of which is the so-called "working life", which means that the actual life that a bearing can achieve before it is damaged is caused by wear and damage, which is usually not caused by fatigue, but by wear, corrosion, seal damage and other causes.
In order to determine the standard of bearing life, the bearing life is linked with reliability.
Due to the difference in manufacturing accuracy and material uniformity, even the same batch of bearings with the same material and size, used under the same working conditions, have different service life.If the statistical life is 1 unit, the longest relative life is 4 units, and the shortest is 0.1-0.2 units. The ratio of the longest life to the shortest life is 20-40 times.90% of bearings do not produce pitting corrosion, and the number of revolutions or hours experienced is called the rated life of bearings[1]。
Rated dynamic load
In order to compare the bearing capacity against pitting corrosion, the maximum load that the bearing can withstand isBasic dynamic load rating, represented by C.
That is to say, under the rated dynamic load C, the reliability of this kind of bearing working at one million revolutions (106) without pitting failure is 90%. The greater the C, the higher the bearing capacity.
3．radial thrust bearing Refers to the radial component that produces pure radial displacement
Industry status
Announce
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According to the data in the Forecast of Production and Marketing Demand, Transformation and Upgrading Analysis Report of China's Bearing Manufacturing Industry, the total industrial output value of China's bearing manufacturing industry showed an increasing trend year by year from 2009 to 2013.In 2013, the total industrial output value of the industry was 249.363 billion yuan, up 12.92% year on year.
Based on the analysis of the data in the past five years, it is found that the sales revenue of China's bearing manufacturing industry also increased year by year from 2009 to 2013.In 2013, the sales revenue was 249.012 billion yuan, up 11.80% year on year.
With the rapid development of the bearing industry in China, the variety of bearings has grown from few to many, the product quality and technical level have grown from low to high, and the scale of the industry has grown from small to large. A professional production system with basically complete product categories and reasonable production layout has been formed.
In 2023,The research team of the Engineering Ceramics Laboratory of the Korean Materials Research Institute has manufactured silicon nitride bearing balls for the drive module of electric vehicles.It is estimated that by 2026, the global market size of hybrid power bearings using silicon nitride bearing ball technology will grow to more than 1.3 trillion won.[2]
The sliding bearing has no inner and outer rings and no rolling element, which is generally composed ofWear-resistant materialmake.It is commonly used for low speed, light load, lubricating oil filling and mechanical rotating parts with difficult maintenance.
The sliding contact surface of the spherical plain bearing is spherical, which is mainly suitable for swinging, tilting and rotating movements.
Rolling bearing
Rolling bearings are classified according to the load direction or nominal contact angle they can bearRadial bearingandthrust bearing。amongRadial contact bearingIs the radial bearing with the nominal contact angle of 0,Radial angular contact bearingRadial bearing with nominal contact angle greater than 0 to 45.Axial contact bearingIs the thrust bearing with the nominal contact angle of 90, and the thrust angle contact bearing is the thrust bearing with the nominal contact angle of more than 45 but less than 90.
According to whether it can adjust the heart during operation, it can be divided intoSelf-aligning bearing----The raceway is spherical, which can adapt to the angular deviation and angular movement between the axis lines of two raceways and the bearings and non self-aligning bearings（Rigid bearing）----The bearing that can resist the deviation of axis axis angle between raceways.
It can be divided into separable bearing and non separable bearing according to whether its components (rings) can be separated.
According to its structural shape (such as whether there is filling groove, whether there is inner and outer ring, the shape of ferrule, the structure of rib, and even whether there is cage), it can also be divided into various structural types.
Divided intoMiniature bearing(<26mm), small bearings (28-55mm), medium and small bearings (60-115), medium and large bearings (120-190mm), large bearings (200-430mm) and extra large bearings (>440mm).
Deep groove ball bearing is the most representativeRolling bearing。Compared with other types of bearings with the same size, this type of bearing has small friction coefficient, high limit speed, simple structure, low manufacturing cost, high precision, no need for regular maintenance, and large size range and many forms. It is the most widely used type of bearing.It mainly bears radial load and can also bear certain axial load.When it only bears radial load, the contact angle is zero.
After the deep groove ball bearing is installed on the shaft, the axial displacement in both directions of the shaft or housing can be limited within the axial clearance range of the bearing, so the axial positioning can be made in both directions.When the deep groove ball bearing has large radial clearanceAngular contact bearingAnd can withstand large axial load.stayAxial loadDeep groove ball bearing ratio under high speed operation conditionThrust ball bearingMore advantages.In addition, this type of bearing also has a certain self-aligning ability. It can still work normally when it is inclined 2 ′ - 10 ′ relative to the shell hole, but it has a certain impact on the life of the bearing.
Generally, 36 and 46 bearings are the representative six types of bearings, and the angular contact is generally 15 degrees, 25 degrees, 45 degrees, etc.
The self-aligning ball bearing is the inner ring andRacewaySphericalOuter ringAnd a bearing equipped with spherical balls.The curvature center of the outer ring raceway surface is consistent with the bearing center, so it has the same centering function as the automatic self-aligning ball bearing.In case of deflection of shaft and housing, it can be adjusted automatically without increasing bearing load.Spherical Roller Bearings It can bear radial load and axial load in two directions.The self-aligning ball bearing has large radial load capacity and is suitable for heavy load and impact load.The inner diameter of the inner ring is a tapered bearing, which can be directly installed.Or install it on the cylindrical shaft with a set sleeve and a disassembly cylinder.The cage is pressed with steel platepolyamideFormingSelf aligning ball bearing is suitable for bearing heavy load and impact load, precision instrument and low noiseelectricmachine, automobiles, motorcycles, metallurgy, rolling mills, mines, petroleum, paper makingcement, sugar squeezing and other industries and general machinery.
Thrust ball bearings are divided into one-way and two-way.They can only bear axial load and can never bear any radial load.thrust bearingIt is divided into tight ring and live ring.The tight ring is tightly sleeved with the shaft, and the live ring is supported on the bearing seat.Ferrules and rolling elements usually adopt rolling with high strength and good wear resistanceBearing steelmanufacture,quenchaftersurface hardness It shall reach HRC60~65.Cage is usually made of mild steel stamping, orcopper alloyIt is made of cloth sandwiched bakelite or plastic.
The contact angle of thrust angular contact ball bearing is generally 60 °. The commonly used thrust angular contact ball bearing is generally two-way thrust angular contact ball bearing, mainly used forPrecision machine toolThe main shaft is generally used together with double row cylindrical roller bearings, which can withstand bidirectional axial load, with high precision and good rigidity,temperature riseLow speed, high rotating speed, easy assembly and disassembly, etc.
needle bearingIt is equipped with thin and long rollers (the roller length is 3~10 times of the diameter, and the diameter is generally not more than 5mm), so the radial structure is compact. Its inner diameter size and load capacity are the same as other types of bearings, and its outer diameter is the smallest. It is especially suitable for the support structure with limited radial installation size. Needle roller bearings can choose bearings without inner rings orNeedle roller and cage assemblyAt this time, the journal surface and housing hole surface matched with the bearing are directly used as the inner and outer rolling surfaces of the bearing. To ensure that the load capacity and operating performance are the same as those of the bearing with ring, the hardness, machining accuracy and surface quality of the shaft or housing hole raceway surface should be the same asBearing ring. PurposeCombined needle roller bearingIt is composed of radial needle roller bearing andthrust bearingThe bearing unit of component combination is compact in structure and small in size, with high rotation accuracy, and can bear a certain amount of axial load while bearing a high radial load.Moreover, the product has various structural forms, wide adaptability and easy installation.Combined needle roller bearings are widely usedMachine tool、Metallurgical machinery, textile machinery andPrinting machineryAnd other mechanical equipment, and can make the mechanical system design very compact and smart.
Spherical Roller Bearings There are two rows of symmetrical spherical rollers, which mainly bearRadial loadAt the same time, it can also bear axial load in any direction, but cannot bear pure axial load.The raceway of the outer ring of this type of bearing is spherical, so its centering performance is good, and it can compensate the coaxiality error. When the shaft is forced to bend or the installation is not concentric, the bearing can still be used normally. The centering performance varies with the bearing size series. Generally, the allowable centering angle is 1~2.5 degrees, and this type of bearing has a large load capacity,In addition to bearing radial load, the bearing can also bear two-way axial load, with good impact resistance. Generally speaking, the allowable working speed of self-aligning roller bearing is low.It is applicable to work under heavy load or vibration load.
Flange bearingThe outer wheel is provided with flange.The feature is to simplify the structure of the main engine, reduce the size of the main engine, and make the bearing easier to locate.
Bearing with seat
Radial bearingA kind of component combined with the seat, on the support surface parallel to the bearing axis, there is a base plate for mounting screws.
A set of bearings is composed of the above two or more bearing structuresRolling bearing。askingpinAnd thrust cylindrical roller combined bearing, needle roller and thrust ball combined bearing, needle roller and angular contact ball combined bearing, etc.
Metal linear bearing is a kind of linear motion system produced at low cost, which is used in combination with cylindrical shaft for unlimited travel.Since the bearing ball is in point contact with the shaft, the service load is small.The steel ball rotates with minimal friction resistance, so as to obtain high-precision and stable movement.
Plastic linear bearingIt is a linear motion system with self-lubricating characteristics. The biggest difference between the metal linear bearing and the metal linear bearing is that the metal linear bearing is a rolling friction, and the point contact between the bearing and the cylindrical shaft, so it is suitable for low load high-speed motion;The plastic linear bearing is sliding friction, and there is surface contact between the bearing and the cylindrical shaft, so it is suitable for high load, medium and low speed movement.
Under the action of periodic load, the contact surface of the bearing is easily damaged by fatigue, that is, cracks and spalling emerge, which is an important damage situation of the bearing.Therefore, in order to improve the service life of bearings, bearing steel must have high contact fatigue strength.
2、 Wear resistance
During the bearing task, not only rolling friction but also rolling friction will occur between the ferrule, rolling element and cagesliding frictionSo that the bearing parts are always worn.In order to increase the wear of bearing parts, maintain the stability of bearing accuracy and extend the service life, bearing steel should have good wear resistance.
3、 Hardness
Hardness is one of the important quality of bearing quality, which has indirect influence on contact fatigue strength, wear resistance and elastic limit.The hardness of bearing steel under application condition shall reach HRC61~65, and the bearing can achieve high contact fatigue strength and wear resistance.
4、 Rust resistance
In order to prevent bearing parts and finished products from being corroded and rusted during processing, storage and application, it is required that bearing steel should have good rust resistance.
5、 Processability
During the consumption process of bearing parts, there are many cold and hot working procedures. In order to meet the requirements of small quantity, high efficiency and high quality, bearing steel should have good processing performance.For example, cold and hot forming properties,Machinability, hardenability, etc.
In addition to the above basic requirements, bearing steel should also meet the requirements of proper chemical composition, average external structure, less non-metallic impurities, external defects conforming to the specification, and external decarburization layer not exceeding the regular concentration.
Application
Announce
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Bearing action
In terms of its function, it should be a support, that is, it is literally used for bearing, but it is only a part of its function. The essence of support is to be able to bearRadial load。It can also be understood that it is used to fix the shaft.The quick, easy and optimal automatic selection of bearings is included.It is to fix the shaft so that it can only rotate and control its axial and radial movement.The motor can't work without bearings.Because the shaft may move in any direction, and the motor requires that the shaft can only rotate during operation.Theoretically, it is impossible to realize the role of transmission. In addition, the bearing will also affect transmission. In order to reduce this impact, good lubrication must be achieved on the bearing of high-speed shaft. Some bearings already have lubrication, calledPrelubricated bearingMost bearings must have lubricating oil. When running at high speed, friction will not only increase energy consumption, but also easily damage bearings.It is one-sided to transform sliding friction into rolling friction, because there is a kind ofsliding bearingThings.
lubrication
Rolling bearingThe purpose of lubrication is to reduce the internal friction and wear of bearings and prevent burning and sticking;Extend its service life;Discharge friction heat and cooling to prevent bearing overheating and lubricating oil aging;It also has the effect of preventing foreign matters from invading the bearing interior, or preventing rust and corrosion.
Lubrication method
Lubrication methods of bearings are divided into grease lubrication and oil lubrication.In order to give full play to the function of the bearing, first of all, it is necessary to select the lubrication method suitable for the use conditions and purpose.If only lubrication is considered, the lubricity of oil lubrication is dominant.However, grease lubrication has the advantage of simplifying the structure around the bearing. Compare the advantages and disadvantages of grease lubrication and oil lubrication.Pay special attention to the amount of lubrication. Whether it is oil lubrication or grease lubrication, too little lubrication and insufficient lubrication will affect the life of the bearing. Too much lubrication will produce large resistance and affect the speed.
seal up
Bearingseal upIt can be divided into self sealing and external sealing.The so-called bearing self sealing is to make the bearing itself into a sealing device.Such as bearing with dust cover, seal ring, etc.This kind of seal has the advantages of small space, convenient installation and disassembly, and low cost.The so-called bearing external sealing performance device is installedEnd capThe sealing device with various performances is manufactured internally.Bearing external seal is divided intoNon-contact sealAnd contact seal.amongNon-contact sealIt is suitable for high speed and high temperature occasions, with different structures such as clearance type, labyrinth type and gasket type.Contact sealIt is applicable to medium and low speed working conditions, and commonly used structural forms include felt seal, cup seal, etc.
According to the requirements of bearing working conditions and working environment on sealing degree, various sealing forms are often used comprehensively in engineering design to achieve better sealing effect.The following main factors shall be considered for the selection of bearing external seal:
one
Bearing lubricant and type (grease and lubricating oil);
two
The working environment of the bearing and the size of the space occupied;
From the perspective of use, the following points should be paid attention to to ensure that the bearing can work reliably:
1. Improve lubrication quality, control oil pressure, temperature and flow, and strengthen oil filtration.
2. Use fuel and lubricating oil that meet the requirements.
3. ControlDiesel generatorThe temperature state of the group is unfavorable when working under the condition of supercooling and overheating.In cold weather, the diesel engine shall be preheated before starting, and the crankshaft shall be rotated manually to make the oil enter the friction surface.
4. Bearing andJournalThe surface quality and geometry shall be strictly guaranteed.
5. The bearing clearance should be appropriate. If the generator set is too large, it will produce impact. If the generator set is too small, it will cause poor lubrication and may burn the pads.
How to ensure the reliable operation of bearings
In general, the following points should be noted from the perspective of use:
1. The bearing clearance should be appropriate. If it is too large, the impact will occur. If it is too small, the lubrication will be poor and the bearing pad may burn;
2. The surface quality and geometric shape of bearing and journal shall be strictly guaranteed;
3. Improve the lubrication quality, control the pressure, temperature and flow of oil, and strengthen the oil filtration;
4. Use fuel oil and lubricating oil that meet the requirements.
In order to give full play to the bearing and maintain its due performance for a long time, regular maintenance (regular inspection) must be carried out.It is very important to improve productivity and economy to find faults early and prevent accidents before they happen through proper regular inspection.
install
Whether the bearing is correctly installed affects the accuracy, service life and performance.Therefore, the design and assembly department should fully study the installation of bearings.It is expected to install according to the operation standard.The items of operation standards are generally as follows:
It is hoped that the bearing packaging will not be opened until shortly before installation.commonlygreaseLubrication, without cleaning, directly fill with grease.For lubrication with lubricating oil, it is not necessary to clean normally, but for bearings used for instruments or high-speed applications, clean them with clean oil to remove the rust inhibitor on bearings.Bearing without rust inhibitor is easy to rust, so it cannot be left unattended.Moreover, bearings sealed with grease can be used directly without cleaning.
The installation method of bearing varies according to the bearing structure, fit and condition. Generally, the inner ring needs interference fit because it is mostly shaft rotation.Cylindrical hole bearing is usually pressed in by a press or hot assembly.In the case of taper hole, it is directly installed on the taper shaft or installed with a sleeve.
When mounted to the housing, generalClearanceThere are many fits, and the outer ring has interference, which is usually pressed in with a press, or there is a cold shrink fit method for installation after cooling.When dry ice is used as coolant, the moisture in the air will condense on the surface of the bearing in the case of cold shrink fitting.Therefore, appropriate rust prevention measures are required.
Maintenance
disassemble
The bearing is disassembled for regular maintenance and replacement.After disassembly, if it is necessary to continue to use or check the state of the bearing, its disassembly should also be carried out with the same care as the installation.Pay attention not to damage the bearing parts, especially the disassembly of interference fit bearings, which is difficult to operate.
It is also very important to design and make disassembly tools as required.During disassembly, research the disassembly method, sequence and investigate the matching conditions of bearings according to the drawings to ensure the safety of disassembly.
Outer ringTo remove the interference fit outer ring, set several screws for extruding the outer ring screw on the circumference of the shell in advance, tighten the screw evenly while removing.These screw holes are usually covered with blind plugs, tapered roller bearings and other separate bearings, and several notches are set on the housing retaining shoulder. Use cushion blocks to remove them with a press or gently knock them.
The removal of the inner ring can be easiest to pull out with a press.At this time, pay attention to let the inner ring bear its pulling force.In addition, the pulling fixture shown is mostly used. No matter what kind of fixture, it must be firmly clamped on the side of the inner ring.For this reason, it is necessary to consider the size of the shaft shoulder, or study the processing of the groove at the shoulder so as to use the drawing fixture.
The inner ring of large bearing is disassembled by oil pressure method.Oil pressure is applied through the oil hole of the bearing to make it easy to draw.For bearings with large width, oil pressure method and drawing fixture shall be used together for disassembly.
The inner ring of cylindrical roller bearing can be disassembled by induction heating.The method of drawing after heating the part in a short time to expand the inner ring.Induction heating is also used when a large number of such bearing inner rings need to be installed.
clean
When the bearing is disassembled for inspection, the appearance record shall be made by photography and other methods.In addition, confirm the amount of residual lubricant and sample the lubricant before cleaning the bearing.
a、The cleaning of bearings is divided into rough cleaning and fine cleaning, and a metal grid can be placed at the bottom of the used container.
b、During rough cleaning, use a brush in the oil to remove grease or adhesive.If the bearing is rotated in the oil at this time, be careful that the rolling surface will be damaged due to foreign matters.
c、During fine cleaning, rotate the bearing slowly in oil and carefully.
The commonly used cleaning agent is neutral and water freediesel oilorkerosene, and sometimes warm lye is used as required.No matter what kind of cleaning agent is used, always filter it to keep it clean.
After cleaning, immediately coat the bearing with antirust oil or grease.
Inspection and judgment
In order to judge whether the removed bearing can be reused, it is necessary to focus on its inspectiondimensional accuracy 、Rotation accuracy、Internal clearanceAnd mating surface, raceway surfaceHolderandseal ringEtc.Since large bearings cannot be rotated by hand, pay attention to the appearance of rolling elements, raceways, cages, retaining surfaces, etc. The higher the importance of bearings, the more careful inspection is required.
Low bearing accuracy: select bearings with specified accuracy level.
principal axisBending or case hole misalignment: repair the spindle or case.
Poor lubrication: lubricating materials of specified brand shall be selected and properly cleaned.
Low assembly quality: improve assembly quality.
Running ring of bearing inner shell: replace the bearing and relevant wearing parts.
The axial force is too large: the clearance of the sealing ring shall be 0.2~0.3mm after cleaning and adjusting, and the diameter of the impeller balance hole shall be corrected and the static balance value shall be verified.
Bearing damage: replace the bearing.
safekeeping
The bearings are coated with a proper amount of antirust oil and packed with antirust paper when leaving the factory. As long as the package is not damaged, the quality of the bearings will be guaranteed.However, for long-term storage, it is advisable to store it on a shelf 30cm above the ground under the condition that the humidity is lower than 65% and the temperature is about 20 ℃.In addition, the storage place shall be kept away from direct sunlight or cold walls.
Quality inspection
national standard
1. National standard for vibration acceleration (commonly known as Z standard)
This standard was formulated early. The quality level of bearings is determined by measuring the vibration acceleration value of bearings when they rotate. It is divided into three quality levels: Z1, Z2, and Z3 from low to high.At present, domestic bearing manufacturers are still using the vibration acceleration value to measure the quality of bearings, which simply reflects the fatigue life of bearings.
2. Vibration speed standard (commonly known as V standard)
Since the original vibration acceleration standard has not been abolished, this standard is based on the standard issued by the Ministry of Machinery Industry. It is formulated with reference to European standards in combination with the actual situation and needs of China, and is used to detect the vibration speed of bearings to classify the quality level of bearings (equivalent to the national standard).It is divided into five quality levels: V, V1, V2, V3 and V4.The quality grade of various ball bearings is V from low to highV1、V2、V3、V4 ；The quality grades of roller bearings (cylindrical and conical) from low to high are V, V1, V2 and V3.
It reflects the quality of bearings by detecting the vibration b speed of bearings in different frequency bands (low frequency, medium frequency, high frequency).It can be roughly analyzed whether there are geometric dimension problems of bearings (such as steel ring ellipses), quality problems of raceways/rollers, and quality problems of cages. Compared with the vibration acceleration, the bearing quality has been significantly improved.At present, domestic bearings exported to Europe, China's military and aerospace industry all carry out bearing quality inspection in accordance with this standard. At the same time, it provides a feasible means to detect the quality of bearings imported from Europe and identify counterfeit bearings.
There is a situation that two standards are parallel in bearing quality inspection. However, bearings with high "Z" quality level may not have good quality performance when tested with "V", and there is no corresponding relationship between the two.This should be paid special attention to in the quality inspection of bearings.
Quality identification
We usually identify the quality of equipment bearings from the following aspects:
1. Whether the outer package is clear
Double row tapered roller bearing
Generally, brands produced by regular manufacturers have their own special designers to design the external packaging, and arrange factories with qualified production conditions to produce. Therefore, the product packaging should be very clear and unambiguous from lines to color blocks.
2. Whether the steel seal is clear
Each bearing product will be printed with its brand words, label, etc. on the bearing product body.Although the font is very small, the products produced by formal manufacturers use steel printing technology to print and emboss before overheating treatment, so the font is small, but deeply concave and very clear.In general, the font of counterfeit products is not only vague, but also floating on the surface due to the rough printing technology. Some can even be easily erased by hand or the manual marks are serious.
3. Whether there is noise
Hold the inner sleeve of the bearing with the left hand, and rotate the outer sleeve with the right hand in a small amplitude to hear whether there is noise during the operation of the bearing.Because mostbrand copycat The production conditions are backward and the operation is completely manual workshop type. During the production process, impurities such as dust and sand will inevitably be mixed into the bearing body, so there will be noise or unsmooth operation when the bearing rotates.This is the key to judge whether the products are from the brand products of regular manufacturers with strict production standards and machine operation.
4. Surface
Whether there are muddy oil stains on the surface requires us to pay special attention when purchasing imported bearings.As there is still a certain gap between domestic anti rust technology and foreign advanced manufacturing countries, it is easy to leave thick oil stains when carrying out anti rust treatment on the bearing body. When touching with hands, it feels sticky and thick, while there is almost no trace of anti rust oil on the imported bearings.According to the insiders, the specially careful people can smell a special smell on the imported bearings, which is the smell of antirust oil.
5. Whether the chamfer is even
The so-called chamfer of bearing is the junction of transverse and vertical surfaces. Due to the limitation of production technology, the fake bearing products are not satisfactorily processed at these corners, which can be easily identified.
6. Packaging
Bearing packaging includes inner packaging and outer packaging
After the bearing is manufactured and inspected as qualified, it shall be cleaned and rust proof, and then put into the inner package to achieve the purpose of waterproof, moisture-proof, dust-proof, impact proof, maintaining the quality and accuracy of the bearing, and facilitating the use and sales.
The inner packaging of bearings is divided into three categories according to the rust prevention period:
① Short rust proof packaging: the rust proof period is 3~6 months. It is applicable to bearings that are shipped in large quantities to the same subscriber and put into use in a short time.According to the agreement of both parties, simple packaging is adopted in the principle of convenient use.
② General rust proof packaging: the rust proof period is one year, suitable for general purpose bearings.
③ Long term anti rust packaging: two years for special andPrecision bearing。
Bearing inner packing materials includePolyethylene plasticCylinder (box), kraft paper, plain and corrugated polyethylene composite paper, paper boxpolyethyleneOr polyethylene plastic filmnylonFastening belt or plastic woven fastening belt, waterproof high-strength plastic belt, linen bag, etc.All the above materials shall be corrosion resistantperformance testQualified.
