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FAG imports the main influence factor of layer of going bad of bearing grinding

28th January 2011 Bearing Technology 1 Comment

FAG imports the main influence factor of layer of going bad of bearing grinding: According to the formation mechanism of layer of going bad of superficial grinding of FAG bearing work, influence FAG bearing grinding to go bad the key factor of layer is grinding heat and action of force of grinding. About importing the nonserviceable reason of the bearing, please see ” Which are the nonserviceable reason of importing the bearing ” Introduction to the article.

1.Grinding is hot

In grinding is processed, in emery wheel and work piece contact zone, consume a large amount of energy, it is hot to produce a large amount of grinding, cause the some instant high temperature of the grinding area. Use the heat source heat transfer theory formula derivation of the linear movement, calculate or employ infrared rays law and thermocouple law to survey the instant temperature under experiment terms, can find the instant temperature of the grinding area can be up to 1000- 1500 ℃ in 0.1- 0.001ms. Such instant high temperature, it is enough to make the superficial layer of certain depth of surface of job produce high temperature oxidation, amorphous organization, high temperature tempering, quench while being two-shot, even burn many kinds of changes of fracturing etc..

1 Oxide layer of surface

Oxygen function in steel surface and air under the high-temperature function of the instant, poling rises thinly 20- 30nm Iron oxide lamina. The test result of one layer of overall thickness is corresponding relation that what merits attention is to oxidize layer thickness and surface grinding and go bad. It means it oxidizes layer thickness and directly relates to grinding craft, it is the important sign of the grinding quality.

2 Amorphous layer of tissue

When the instant high temperature of the grinding area makes the surface of the work piece reach the fusing state, the molten metal molecular flow is plated on the job surface evenly, and is cooled for the extremely quick speed by the metal of matrix and formed a layer of extremely thin amorphous layers of tissue. It has high hardness and toughness, but it has about 10nm only, it is very easy to be remove in accurate grinding is processed.

3 High temperature tempering floor

The intersection of instant and high temperature of grinding area can enable the intersection of the surface and sure depth ‘ 10- 100nm It if you can’t heat work piece to, higher than inside temperature of heating. In case of not reaching the austenitizing temperature, with the improvement the heating temperature, it is superficial in its layer-by-layer last corresponding to heating temperature one or high-temperature organization tempered change, the hardness is thereupon decline too. The higher the heating temperature is, the hardness drops the more terrible.

4 Bilaminar to quench fire bed

The instant high temperature that in the grinding area heats the work piece superficial layer to the temperature Ac1 of austenitizing When the the above, this layer of organization of austenitizing is in the subsequent cooling process, quenched into a martensite and organize again. Every have, quench work piece that burn while being two-shot, its it quenches to be must the intersection of hardness and extremely low the intersection of high temperature tempering and layer under the fire bed while being two-shot.

5 Crackle of grinding

Two-shot superficial layer stress alternation of the work piece of quenching and burning enabling. Quench district to be in pressing state while being two-shot, following the intersection of high temperature tempering and the intersection of district and material its have tensile stress of maximum, here is the place where most likely the crackle core happens. The crackle is the easiest to spread along the grain boundary of original austenite. Severe burn will lead to the fact whole the intersection of grinding and surface flaw ‘ Present more full of cracksly Cause the work piece to scrap.

2.Formative deterioration floor of grinding strength

In bearing grinding, the work piece superficial layer will be influenced by cutting force, compressive force and frictional force of the emery wheel. Especially after function of the two,last work piece surface stratification directivity getting stronger very plastic deformation layer and work hardening layer. One layer of changes that must influence the residual stress of the superficial layer that these go bad.

1 Floor of plastic deformation of cold

In grinding, the abrasive grain is equivalent to a cutting edge every quarter. But under many circumstances, the hook angle of the cutting edge is the negative value, the abrasive grain just makes the surface of the work piece bear and push function plough and plow function except cutting function ,Make the surface of the work piece leave the obvious plastic deformation floor. This kind of deformation intensity of deforming layer will increase as the emery wheel will feed the increase of quantity if the emery wheel will rub obtuse intensity and grinding.

2 Hot the plastic deformation ‘ Or the high temperature is out of shape Layer

The hot temperature during job surface formative wink of grinding, make the work piece superficial layer elastic limit of certain depth drop suddenly, even reach the intensity disappearing in elasticity. The superficial layer of the job, in grinding strength, especially compressive force and rubing under the action of force at this moment, the freedom caused is spread, receive the metallic restriction of matrix, the surface is compressed plow even more ,Have caused plastic deformation on the superficial layer. High-temperature plastic deformation increases with increase in temperature of surface of the work piece under the invariable situation of the grinding craft.

3 Work hardening floor

Can be found with microhardness law and metallography law sometimes, the hardness of superficial layer caused by processing the deformation rises.

Except that grinding is processed, casting and heat treatment heat the surface decarburization floors caused, have complete destination in the for the future processing, remain on the intersection of work piece and surface causing surface soften deterioration too, facilitate the early failure of the bearing.

Source: Internet.

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