According to the FAG bearings metamorphic layer formation mechanism of surface grinding, main factors influencing the grinding degenerating layer of heat is grinding and grinding force role. Below we have to analyse the causes of bearing failure.
1.FAG bearing grinding heat
FAG bearings grinding, grinding wheel and workpiece contact zone, consume large amounts of energy, produce a lot of grinding heat, causing local instantaneous temperature of grinding zone. Applying the theory of linear motion-heat-source heat transfer formula, calculate, or application of infrared measurement and thermocouple method under experimental conditions the instantaneous temperature, can be found at 0.1~0.001ms in grinding zone of instantaneous temperature can be as high as 1000~1500℃. Such a transient high temperature enough to make the certain depth temperature on the surface layer of oxide on the surface, non-crystalline, high-temperature tempering, quenching for the second time, or even burn crack a variety of changes.
(1) surface oxide layer
Steel surfaces under transient high temperature and oxygen in the air, rising into very thin (20~30nm) thin-layer iron oxides. Worthy of note is the thickness of the oxide layer and surface grinding of degenerating layer corresponds to the total thickness of test results is related. This shows its directly related to the thickness of the oxide layer and grinding are important signs of grinding quality.
(2) amorphous tissue layers
Grinding zone of instantaneous heat the workpiece surface to a molten state, molecular flow of molten metal is coated evenly to a work surface, metal cooling at an extremely fast rate and substrate, forming a very thin layer of amorphous organization. It has high hardness and toughness, but it has only about 10nm, in precision grinding is easily removed.
(3) high-temperature tempering
Transient high temperature can make the surface of the grinding zone a certain depth (10~100nm) by heating above the tempering temperature of heating the workpiece inside. Does not meet the of austenite temperature case, with the improvement of heating temperature, its surface layer-by-layer corresponds to the heating temperature and high temperature tempering or tempered microstructure transformation, decline the hardness. Higher heating temperature, hardness and also more powerful.
(4) the second layer hardening layer
When grinding area of instantaneous heat the workpiece surface heated to a temperature of austenite (Ac1) above, the layer of austenitic organization in the subsequent cooling process and again quenched martensite organizations. Wherever the second workpiece quenching Burns, the secondary hardening layer must be very low hardness at high temperature tempering under layer.
(5) the grinding crack
Secondary hardening Burns will make the workpiece surface stress change. Quench zone for the second time in the compression state, high-temperature tempering material below it there is a maximum tensile stress, crack the core place here is most likely to occur. Crack spread easily along the original austenite grain boundaries. Serious burns can cause the entire ground surface cracks (crack) cause the workpiece scrapped.
FAG bearings in use, vibration, noise, improper use of lubricants will cause serious damage to bearings, directly affect the service life of bearings, FAG bearings in order to better, improve production efficiency we need to understand some improper use of FAG bearings bad bearings and some simple maintenance.
Different of FAG bearing parts of components, and shape, and design, and size, on mechanical of performance requirements are is different of, used of are is different of quenching method, generally each species bearing steel has fixed of c curve, and cooling media decided has bearing quenching Hou of organization and mechanical performance is compliance, therefore on these factors is specific of do focus consider analysis, in actual produced process in the FAG bearing parts of heat treatment defects of produced, and cooling bearing of media are is has directly of relationship.
In heat treatment furnace of FAG bearings after heating to full refinery, in order to strictly technical parameters requirements, are subject to quenching treatment, after cooling of FAG bearings from martensite organizations, bearing the cooling rate must be greater than the critical cooling speed, but speed too fast you make cold volume shrinkage and microstructure transformation of violent, caused a great deal of stress. In the conditions of access to martensite "f", so make sure you note the cooling speed, so you can receive qualified martensite.
Choose a suitable quenching media is particularly important, it determines the Organization and performance of bearing parts after quenching, quenching media usually have three solid, liquid and gas, when you press the FAG bearing quenching medium physical state changes in the physical state changes are divided into category and physical state change does not occur.
Throughout in the ease of making choice of quenching media is the most important, it determines the FAG bearing quenching after integral and performance of an organization, General of quenching medium gas and liquid, solid, gas with a relatively small number of relatively, in addition in quenching time of change, in turn, can be divided into biological change of physical state change does not occur and the two types.


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