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FAG bearing

January 16, 2020

FAG bearings

FAG bearings are technical FAG spindle bearings : spindle bearings are single-row angular contact ball bearings consisting of a solid inner ring, outer ring, ball, and a cage assembly with a solid window cage . They cannot be removed. These bearings can be open or sealed. Spindle bearings have limited tolerances. They are particularly suitable for bearing arrangements that require very high guiding accuracy and speed capability. They are particularly suitable for bearing arrangements of shafts in machine tools.
 
Chinese name
FAG bearings
Foreign name
FAG bearing
Type
Ball, roller, etc.
Advantages
Low friction coefficient and high transmission rate
Application
Equipment
Missing point
Small carrying capacity and high noise

Introduction

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Since 2001, FAG bearings have played an active and important role in the group's aerospace, automotive and industrial fields, covering all applications in the production machinery, power transmission and railway, heavy industry and consumer goods industries.
FAG bearings produce all kinds of ball and roller bearings with outer diameters from 3 mm to 4.25 meters , including standard products based on samples and non-standard products based on user's special requirements .

Reason for failure

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According to the formation mechanism of the grinding metamorphic layer on the working surface of the FAG bearing , the main factors affecting the grinding metamorphic layer are the effects of grinding heat and grinding force. Let's analyze the reasons for the failure of FAG bearings.
1. FAG bearing grinding heat
In the FAG bearing grinding process , a large amount of energy is consumed in the contact area between the grinding wheel and the workpiece, and a large amount of grinding heat is generated, resulting in a local instantaneous high temperature in the grinding area. Using linear motion heat source heat transfer theoretical formulas to deduce, calculate or apply the infrared method and thermocouple method to measure the instantaneous temperature under experimental conditions, it can be found that the instantaneous temperature in the grinding zone can be as high as 1000-1500 ° C within 0.1-0.001ms. Such instantaneous high temperature is enough to cause high-temperature oxidation of the surface layer at a certain depth on the working surface , amorphous structure, and high-temperature tempering.
(1) Surface oxide layer
The surface of the steel under the action of transient high temperature interacts with oxygen in the air and rises to a very thin (20-30 nm) thin layer of iron oxide . It is worth noting that the test results of the thickness of the oxide layer and the total thickness of the surface grinding metamorphic layer are in a corresponding relationship. This shows that the thickness of the oxide layer is directly related to the grinding process and is an important symbol of grinding quality.
(2) Amorphous structure layer
When the workpiece surface reaches the molten state due to the instantaneous high temperature in the grinding zone, the molten metal molecular stream is evenly coated on the work surface and cooled by the base metal at a very fast rate, forming an extremely thin layer of amorphous state. Organizational layer. It has high hardness and toughness, but it is only about 10nm, which can be easily removed in precision grinding .
The instantaneous high temperature in the grinding zone can cause the surface to be heated to a temperature higher than the tempering temperature of the workpiece within a certain depth (10 to 100 nm) . When the austenitizing temperature is not reached , as the heated temperature increases, the surface layer by layer will produce a re-tempering or high-temperature tempering microstructure transformation corresponding to the heating temperature, and the hardness will also decrease. The higher the heating temperature
(4) Two hardened layers
When the workpiece surface layer is heated above the austenitizing temperature (Ac1) by the transient high temperature in the grinding zone, the austenitized structure of this layer is re-quenched into a martensitic structure in the subsequent cooling process . For any workpiece with a secondary quench burn, the high-temperature tempering layer with a very low hardness must be under the secondary quench layer.
The secondary quenching burn will change the stress on the surface layer of the workpiece. The secondary quenching zone is under pressure, and the material in the high temperature tempering zone below it has the largest tensile stress . This is the place where crack cores are most likely to occur. Cracks are most likely to propagate along the original austenite grain boundaries . Severe burns will cause cracks (mostly cracks) on the entire grinding surface, which will cause the workpiece to be scrapped.
2. The deterioration layer of FAG bearing
During the grinding process, the surface layer of the workpiece will be affected by the cutting, compressive and frictional forces of the grinding wheel. Especially the effect of the latter two makes the surface layer of the workpiece form a highly directional plastic deformation layer and work hardening layer. These metamorphic layers inevitably affect the change of the residual stress in the surface layer .
(1) Cold plastic deformation layer
In the grinding process, each moment of abrasive particles is equivalent to a cutting edge. However, in many cases, the rake angle of the cutting edge is negative. In addition to the cutting action, the abrasive particles are subject to the surface of the workpiece under a squeezing action (plowing action), leaving a significant plastic deformation layer on the surface of the workpiece. The degree of deformation of this deformed layer will increase as the grinding wheel becomes dull and the grinding feed increases.
(2) Thermoplastic deformation (or high temperature deformation) layer
The instantaneous temperature formed by the grinding heat on the work surface sharply reduces the elastic limit of the workpiece surface layer to a certain depth , even to the extent that the elasticity disappears. At this time, the free extension of the working surface layer caused by the grinding force, especially the compressive and frictional forces, is limited by the base metal, and the surface is compressed (more plowed), causing plastic deformation in the surface layer . The high-temperature plastic deformation increases with the increase of the surface temperature of the workpiece without changing the grinding process.
(3) Work hardened layer
Sometimes the microhardness method and metallographic method can be found to increase the hardness of the surface layer due to processing deformation.
In addition to the grinding process, if the surface decarburization layer caused by casting and heat treatment heating is not completely removed in subsequent processing, the surface remaining on the workpiece will also cause the surface to soften and deteriorate, leading to the early failure of the bearing.

Main type

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Black series

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FAG black series ball bearings are composed of bearing housings and corresponding ball bearings. These products are particularly suitable for applications in agricultural machinery, drive technology, pumps and the steel industry. It has the following characteristics: The bearing ruler is manufactured in strict accordance with Japanese industrial standard JIS B 1559. The gray cast iron bearing seat is painted black. The radial seat ball bearing is based on the ball bearing 62 series. The black oxide on the bearing surface is greatly enhanced. Corrosion resistance, pore size series includes metric and imperial, using lip seals, etc.
FAG deep groove ball bearings are universal, self- retaining , with solid outer ring, inner ring and ball and cage assembly
FAG deep groove ball bearings
Bearings. These products are simple in design, have a long service life and are easy to maintain; they can be divided into single-row and double-row designs and open and sealed designs. Due to the production technology used, the open bearing can still be turned into a recess on the outer ring for sealing or protection. Due to their low friction torque , they are suitable for high speeds.
Single-row angular contact ball bearings are self-retaining units with solid inner and outer rings, and balls and nylon, steel or brass cage components. The inner and outer ring raceways are offset from each other in the axial direction of the bearing. There are open and sealed bearings. Their self-aligning ability is very small. Many sizes of angular contact ball bearings are designed by X-life. These bearings are shown in the dimension table. X-life quality bearings have improved raceway shapes and optimized surfaces. This makes the bearing's fatigue limit load significantly improved. In the revised service life calculation, the service life value has been increased by more than 50%. Therefore, in certain applications, smaller bearings can be used if necessary.
Double row angular contact ball bearings by the inner and outer rings of the entity, and a ball and a polyamide, stamped steel sheet, or brass made of holder units. They are similar in structure to a pair of single-row angular contact ball bearings arranged in an O-shape , but with a more compact structure. They have different contact angles and bearing ring designs. The bearings can be open and sealed. Due to the production technology used, the open bearing outer ring has cutting grooves for sealing or