2013年6月7日星期五

Comparison of sliding bearings and rolling bearings


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In the work of bearing rolling friction. Rolling easy maintenance, reliable, good starting performance at moderate speeds higher carrying capacity. Compared with the sliding bearing, radial bearing a larger size, poor damping capacity, high speed, low life sound bigge r. Rolling in the radial bearings (mainly radial force) usually consists of inner and outer rings, rolling and rolling element cage four parts. Inner sleeve in the journal together with the shaft rotates, the outer ring mounted in the bearing bore. In the inner and the outer periphery of the inner periphery of the outer ring are formed with raceway. When the relative rotation of the inner and outer rings, the inner and outer rings of the rolling element raceway, are separated by the cage, to avoid friction. Thrust bearings are divided into a tight circle and live ring in two parts. Tight circle and sleeve tight, live ring bearing in the bearing housing. Rings and rolling elements commonly used high strength, wear resistance, good bearing steel, surface hardness after quenching should reach HRC60 ~ 65. Cage mostly made of mild steel stamping, copper alloys can also be used bakelite cloth or plastic manufacturing.slewing b earing suppliers

Many different types of rolling bearings.
       1, according to the direction of load can be divided into radial bearings (radial force and small axial force), thrust bearing (only bear axial force) and radial thrust bearing (can withstand the radial and axial force).
       2, according to the shape of the rolling elements can be divided into ball bearings, roller bearings and needle roller bearings.
       3, according to the working conditions can be divided into plain bearings, high-speed bearings, high temperature bearings, bearing temperature, vacuum bearings, magnetic bearings, corrosion-resistant bearings, precision miniature bearings and oversize bearings. The various types of bearings into China B, C, D, E, G 5 个 accuracy level, B is the highest accuracy level, G is the general level of accuracy, the most common.

Rol ling is the standard, by special bearing factory mass production. Design choices are often factors to be considered life, load, precision, clearance (radial and axial), the limit speed, friction torque, aligning performance, preload and rigidity, vibration and noise.

With the sliding bearing, bearing the advantages
       1, under normal conditions, the efficiency and hydrodynamic bearings lubricated bearings pretty, but more mixed lubricated bearings should be higher;
       2, the radial clearance is relatively small, radial angular contact bearings can be used preload preload to eliminate backlash, high running accuracy;
       3, for the same size shaft, bearing a width smaller than the sliding bearings, make the machine compact in the axial direction;
       4, most of the rolling bearing can be subject to both radial and axial loads, so bearing composite structure is simple;
       5, less lubricant consumption, easy to seal, easy to maintain;thin wall bearings
       6, no useful for non-ferrous metals;
       7, the high degree of standardization, mass production and low cost.

With the sliding bearing, bearing disadvantages:
       1, less able to withstand impact loads;
       2, high-speed heavy load bearing lower life;
       3, vibration and noisy;
       4, the radial dimension than the sliding bearings.

2013年6月3日星期一

Rolling bearing material


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Rolling bearing rings and rolling elements, side repeatedly exposed to high contact pressure side accompanied by sliding rolling contact. Holder, side rings and

Rolling on both sides of the body, or a party sliding contact side of the tension and compression force. Accordingly, the bearing rings, rolling elements and cage material, performance
, The main requirements are as follows.

    Rings, rolling material required performance: rolling fatigue strength, high hardness, high wear resistance;slim bearings

The required performance of the cage material: good dimensional stability and mechanical strength; also need good workability. According to different purposes, as well as its impact resistance
Resistance, heat resistance, good corrosion resistance.

    Rings and rolling material: rings and rolling commonly used carbon chromium bearing steel.

    Further impact-resistant case, used as a bearing material chrome steel, chrome molybdenum steel, nickel-chromium-molybdenum steel, carburizing quenching the steel from the surface to the appropriate
The depth of a hardened layer. With appropriate hardeni ng depth, fine tissue, an appropriate hardness of the surface and core hardness of the carburizing bearing, than the axis of the bearing steel
Order of the chemical composition having excellent impact resistance, the carburizing bearing steel.

The embodiment of the vacuum degassing treatment, Therefore, the high degree of purity of the material used, the oxygen content of less good quality. Further appropriate heat treatment, so that the roller bearing
The amount of dynamic fatigue life improved significantly.
 
   The above-mentioned steels, in accordance with the special use, but also the use of high-speed steel having excellent heat resistance, good corrosion resistance of stainless steel.

The cage material: punched retainer material, the use of low carbon steel. According to different purposes, brass, stainless steel plate. Cut cage material,thin bearings
The high-strength brass, carbon steel, in addition also the use of synthetic resin.

About rolling bearing clearance and rolling bearing material


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Effective clearance, or clearance work is rolling bearings installed on the host to achieve stable operation state of a certain temperature rise in certain loads, scroll
Bearing in the presence of the actual clearance. Obviously, the effective clearance is smaller than the clearance wo rk. The original rolling bearing clearance is rolling bearing sets installed in the front of the machine,
Which in the free state clearance. In fact, the original clearance measurement is difficult to know. Original clearance often use the inspection and clearance instead.china bearing supplier

  The rolling bearing rings and rolling commonly used carbon chromium bearing steel. The most of the bearings, the use of JIS SUJ2 steel species. Large bearing SUJ3. SUJ2
Chemical composition, in the world, as imported bearing materials have been normalized.

  Rolling bearing rings and rolling elements, side repeatedly exposed to high contact pressure side accompanied by sliding rolling contact. Holder, side rings and roll
Moving on both sides of the body, or a party sliding contact side of the tension and compression force. Therefore, bearing rings, rolling elements and ca ge materials, performance,ball bearing suppliers
The main requirements on imports bearing rings, the required performance of rolling material: rolling fatigue strength, high hardness, high wear resistance.

Needle bearing surface off the cause of abnormal


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Bearing part of the move surface material like fish scales fall off, a phenomenon known as fatigue spalling. Withstand a certain load, move the bearings during operation,
Even if the static load, but the balls and raceways purposes, but their stress cycle of reciprocat ion, material fatigue will occur to move so that the bearing life is reached. In addition,
Several kinds of bearings of the type defined in the "Life", one of which i.e. the so-called "working life", it means that a needle bearing can be achieved before the damage actual TING
Life by wear and tear, damage is usually not caused by fatigue, but by wear, erosion, damage to the seal causes.bearing suppliers

However, whether in laboratory testing or in actual use, can be significant to see that the appearance in the same work under the premise of the same bearing, very different from the actual life
. The life of the bearing revolutions (or the number of hours of work under a certain speed) Definition: within needle roller bearings in this life, in any of its bearing ring or move
Body on the initial fatigue damage (peeling or defect). Most of the bearings pumping b ad a lot of reasons - beyond the original estimate of load, an effective seal, over
The tight fit as a result of too small bearing clearance.

    Any factor of these factors has a special type of damage and will leave special signs of damage. To view the damage to the bearings, in most of the cases can be
To discover its possible causes, in general, one-third of the needle bearing damage due to fatigue damage, another one-third due to poor lubrication
The other one-third due to contaminants from entering the bearing or install mishandled.

However, these types of damage with Industry. For example, the pulp and paper industry is mostly because of poor lubrication or contamination caused by damage to the bearing and not because
Due to material fatigue.

Large metal noise

  Reason 1: abnormal load, countermeasures: correction with research bearing clearance, adjust the load, fix the housing should er block position.

  Reason 2: Install the adverse responses: axis, the machining accuracy of the housing, improve installation accuracy, installation method.

  Reason 3: Lack of lubricant or unsuitable responses: add lubricant to select the proper lubricant.

  Reason 4: rotating parts in contact, the contact part of the Solution: Modify the labyrinth seal.

Rules noise

  Reason 1: As the foreign body causing rolling surface indentation, corrosion or scars, countermeasures: Replace the bearings, cleaning the parts, to improve the sealing device, use a clean
Lubricant.

  Reason 2: (after carburizing steel) surface deformation Solution: replace the bearings, pay attention to its use.

  Cause 3: The raceway surface stripping, Solution: Replace the needle bearing.

Irregular noise

   Reason 1: The clearance is too large, Countermeasures: R esearch with the bearing clearance, modify the amount of preload.

   Reason 2: foreign invasion, countermeasures: replacement of bearings, cleaning the parts, to improve the sealing device, the use of clean lubricant.

   Reason 3: spherical injury, peel, Solution: Replace the bearings.

Abnormal temperature rise

   Reason 1: too much lubricant measures: reducing lubricant, used in moderation, choose the hard grease.thin section ball bearings

   Reason 2: Lack of lubricant or unsuitable responses: add lubricant to select the proper lubricant.

   Reason 3: abnormal load responses: changes along with research bearing clearance, adjust the pre-load, modify the position of housing shoulder block.

   Reason 4: poor installation, countermeasures: to improve the machining accuracy of shaft and housing, mounting accuracy, the installation method.
 
  Reason 5: creep, seal friction and the mating surface is too large, Solution: replace the needle roller bearings, with research, to modify the shaft and housing, to change the seal form.

The vibration (axis beating)

   Reason 1: (after carburizing steel) surface deformation responses: Note bearing replacement operation.

   Reason 2: Peel Solution: replace the bearings.

   Reason 3: Install adverse responses: modification the shaft housing shoulder block at right angles to the side of the liner straight angle.

   Reason 4: foreign invasion, Solution: replace the bearings, cleaning the parts, to improve the sealing device.

Excessive lubricant leakage, discoloration

  Reason: too much lubricant, foreign invasion, foreign body wear powder, measures: appropriate use of lu bricants, study the change in lubricant research and needle roller shaft
By Order of the replacement, cleaning the enclosure.

Deep groove ball bearing lubrication mechanism of friction and wear analysis


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The bearing friction mechanism and the other bearing significantly different friction factors vary depending on the radial load, the wobble frequency, the oscillating frequency and oscillating angle, the temperature of the contact surface and the surface roug hness. General deep groove ball bearing movement within the outer ring relative to sliding friction, a larger friction; while the other bearing is in motion relative sliding friction compared to the cushion layer and the inner or outer ring, the friction coefficient small. Research shows that a significant difference in the skf bearing friction coefficient of the different materials under the same conditions, in the gasket material.bearing suppliers
With the continuous development of the bearing, the wear mechanism and form changing. Ships lubricated bearings in the work process, due to the relative sliding of the inner and outer rings, causing the bearing surface layer material is continuously loss, resulting in the bearings is not working properly. The main wear adhesive wear, abrasive wear and corrosion and wear 3 types. Deep groove ball bearing wear work due to the liner and the relative sliding of th e inner and outer rings, which led to the shedding of the liner, tearing, extrusion and other failure modes, the bearing does not work.
Bearing lubrication can be briefly described as follows:
a. layer of film is formed between the two rolling surfaces or sliding surfaces in contact with each other and spaced from the second surface to reduce friction and wear of the contact surface.
using oil lubrication, especially circulating oil lubrication, oil mist lubrication and injection lubrication, lubricating oil can take away most of the internal friction heat of the deep groove ball bearings, play an effective role in heat dissipation.
lubricated with grease, you can prevent external dust and other foreign matter from entering the bearing and sealing effect.
d. lubricant has a role to prevent metal corrosion.
e extend the fatigue life of the bearing.
As we all know, the appearance of the work always kept the dial gauge against the end face of the deep groove ball bearings or shaft proper position, even with the contemporary the highest manufacturing technology and processing skf bearing parts. Observe the reading changes with the pretension load method. The preload method has its negative aspects, such as imported bearing friction torque increases, increased temperature rise, shortened life expectancy and so on, so take full account of different levels of tiny geometric error, roller bearings and measurement clearance, shaft or bearing housing need in different directions rotation for several weeks, the ball ends deep groove ball bearings with inner ring on the leading edge in order to ensure proper contact.thin section ball bearing
Self-lubricating layer thinning, leading to the SKF bearing wear depth increases. Thus, bearing failure due to its continuous PTFE is extruded during the swing, the lubrication function decline, eventually leadi ng to knit substrate material wear.

About the bearing in the application of the various problems


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Transmission machinery bearings are indispensable parts of general use. Wrong choice, poor installation, improper use, maintenance is not timely will affect their life, causing equip ment failure, resulting in significant economic losses.

Bearing normal life called "narrow life." Bearing operation bearing inner and outer raceway and roller rolling surface, due to repeated load, material fatigue pitting.

Paper Machinery loss most bearings: dryer bearings, drive gear bearing, press roll, drive roll and other large roller type bearings.

First, the dryer

Such as: the operating side using 3,113,740 bearings, drive side bearing using 3,113,748. Bearing with the bearing outer ring is designed to transition fit, the inner adapter using shifting sets. In actual use, most bearing temperature is high, some up to 100 ℃ or more, or even burning phenomenon, and forced downtime.contact ball bearing

Second, the bearings used in the process several situations

1, the installation of the bearing preload does not meet the requirements, the inner ring and shaft relative rotation, causing severe wear of the journal; sometimes too large an adapter, the bearing during operation, due to thermal expansion is not enough space, leading to bearing inner ring burst.

2, bearing and bearing outer rings with improper tightening is too large, because the two different materials, different coefficient of expansion, bearing multi-cast iron or cast steel, the bearing, the outer ring of carbon chromium steel, in a certain temperatures, the transition fit into a tight fit when the interference exceeds a certain range, it will cause the outer ring burst; while the gap is too large, the bearing outer ring and bearing relative rotation, causing the bearing housing is worn, causing severe roller vibration, resulting in broken paper or paper cited difficulties.

3, the analysis, the load, high speed devices, such as bearing and shaft insufficient interference (preload not meet the requ irements), then the load bearing inner ring rotates, the inner circumference of the bearing generated between sliding direction of the creep phenomenon, so that the degree of wear increases with the surface, the shaft and the casing is damaged. Meanwhile, the invasion of the powder worn the bearing, causing the bearing to heat and vibration. Due to bearing friction heat generated by the rotation, the shaft and bearing chamber circulated out. Bearing chamber thermal conditions better than the shaft, so that the bearing outer ring than the inner ring, the rolling element low temperature 5-10 ℃. Moreover, since the hollow shaft through the steam dryer, the heat from the shaft to the bearing, and in the production operation, the bearing inner and outer temperature difference is even greater.high speed bearing

Third, bearing installation does not regulate the operation of the common

For bearing installation, many operators use "red cap" (barbecue heated) violations approach is very wrong. Broiled only difficult to control the temperature, the more important it is easy to change the bearing material resulting in "injuries", local heating and the bearing inner ring, the stress concentration easily deformed or even burst, shorten life. Recommended cooking oil or electric heating method installed bearings.

Check the correct method of bearing failure


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For just use bearing novice, will often have no experience. They do not know how to operate them bearing potential problems. Today, I put these experiences with you a rough introduction.

(1) observation. Rolling with the naked eye, there should be no external raceway spalling traces and severe wear, and was an arc-shaped groove; all rolling surface should be no spots, cracks and peeling phenomenon; cage should not be loose, no damage, not worn , but a large gap with the rolling elements.ball roller bearing

(2) texture method. Normal bearing inner and outer ring and rolling gap of 0.005 to 0.010 mm. Have used a stage for rolling bearing inner race with your fingers axial shaking, there should be no obvious Kuang moving sound.

(3) Turn France. With one hand holding the bearing inner race, the other hand turning outer race, the bearings should be flexible rotation, and should not feel the radial shaking.china bearing manufacturer

Inspection, the three kinds of empirical methods should combine in order to facilitate the technical state of rolling bearings to make the right judgments. The tapered roller bearing , the rolling element is also observed in the middle of the outer ring, if the forward, shall not more than 1.5 mm.

The choice of bearing material bearing performance will be affected


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Bearing material selection affect bearing performance: When the detection of chromium bearing steel and stainless steel as a material advantage, and found them not only with rust eff ect. Chromium bearing steel is the most common material. It is harder than stainless steel, so longer. However, at higher temperatures, its performance is not how.bearing roller bearings
At 120C under a high temperature, it will happen enormous deformation, the load decreases. Sustained high temperatures it can tolerate 150C, 150C or higher but the moment the temperature will reduce bearing life. Heat treatment can make the bearings to withstand high temperature instantaneously 170C.
The most common stainless steel for the bearing 440, which hard and strong enough to load, (20% less than steel, brass), but it can rust and can tolerate high temperature 250C and 300C of the instant continuous high temperature. We often mistakenly thought that all of the stainless steel is not magnetic, 440 stainless steel is magnetic, it is not completely rust, but by salts, acids, alkalis. 316 levels of anti-rust per formance is very good, not magnetic, but relatively soft, low load, since it is not strong, so the accuracy of the bearing 316 is not high, feeling rough.deep grove ball bearing

Bearing axial load carrying capacity limit is how much


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Bearing axial load carrying capacity limits:

1, deep groove ball bearings such as in pure axial load, the axial load should generally not exceed 0,5 C0 values.bearing roller bearings

2, small bearings (diameter of about 12 mm or less) and light series bearings (diameter series 8,9,0 and 1) shall not be greater than 0,25 C0 withstand axial load.

3, the axial load is too large, it will greatly shorten bearing life.bearing manufacturers

4, if the deep groove ball bearing certain radial load, the axial load it can withstand extreme? Usually if deep groove ball bearings can bear radial load, but also bear certain axial load.