What is the main reason affecting the FAG bearing grinding transformation layer?

According to FAG bearing grinding work appearance transformation layer formation mechanism, the main elements affecting the FAG bearing grinding transformation layer is a function of grinding and grinding force. 1, the grinding heat in the grinding, grinding wheel and workpiece contact zone, consuming energy, produce a large number of grinding heat and form a grinding zone of instantaneous high temperature. On the basis of the theory of linear motion heat source heat transfer formula derivation, calculation or by the method of infrared ray and measured experiment under the condition of instantaneous temperature thermocouple method, hair is 0. 1 to 0. The grinding area within 001 ms instantaneous temperature up to 1000 ~ 1500 ℃. The instantaneous high temperature, enough to make certain depth work looks outside surface to produce high temperature oxidation, amorphous group, high temperature tempering, secondary hardening, cracking and burns, etc. （ 1) Appearance under the action of transient high temperature oxide layer of steel appearance and oxygen in the air, rises into extremely thin ( 20～30nm） The iron oxide thin layer. Keep in mind oxide layer thickness and the appearance of grinding metamorphosis layer is the total thickness test results in corresponding relation. This clarify the thickness of oxide layer, is directly related to the grinding process is an important symbol of grinding quality. （ 2) Amorphous layer organization grinding the instantaneous high temperature parts arrived in molten state, appearance of molten metal molecular flow is evenly coated in appearance, and base metal cooling at breakneck speed, form a very thin layer of amorphous tissue layers. It has high hardness and toughness, but it's only about 10 nm, it is easy to be removed in the fine grinding process. （ 3) High temperature tempering layer of instantaneous high temperature can make the grinding area looks certain depth ( 10 ~ 100海里) Be heated to a temperature higher than the workpiece temperature tempering heat. In did not reach the austenitizing temperature conditions, with the progress of heated temperature, its appearance will produce one by one and heating temperature corresponding to the organization transformation, or high temperature tempering tempering hardness also fall subsequently. The higher the heating temperature and hardness of the land is also increasingly fierce. （ 4) Transient high temperature quenching layer when the grinding area on the second floor outside the workpiece surface heating to the austenitizing temperature ( Ac1） Above, the layer of austenitizing group in the subsequent cooling process, the quenching into martensite structure anew. Burn artifact, whoever has the secondary hardening second time hardening layer must be under very low temperature tempering hardness layer. （ 5) Grinding crack secondary hardening burns will make the workpiece surface layer stress changes. Secondary hardening zone is in compression state, the high temperature data back to the fire area underneath there are the largest tensile stress, this is most likely to attack the center of the crack. Crack is the most easily spread along the original austenite grain boundary. Serious burns will cause the entire surface grinding is crack ( Formed a crack) Formed workpiece scrapped. Layer 2 metamorphosis of grinding force in grinding process, the outer surface of workpiece will be tight by grinding wheel cutting force, force and friction force. In particular, the role of the latter two, make the outer surface of workpiece directional strong plastic deformation and strain hardening layer. The transformation layer inevitably affected the change of surface residual stress. （ 1) Cold plastic deformation layer in the process of grinding, every moment of abrasive is equivalent to a cutting edge. But in many cases, a cutting edge for negative rake Angle, abrasive besides cutting action, is to accept compression artifacts appearance ( The plough) , make the workpiece appearance left obvious plastic deformation layer. The deformation layer deformation grinding with grinding wheel dull level increases and grinding feed. （ 2) Thermoplastic deformation ( Or high temperature deformation) Layer of grinding heat in the work appearance of instantaneous temperature, make certain depth of the workpiece outside surface elastic limit down sharply, to reach the elastic dying of the light levels. Outside their work surface on the grinding force, especially under the action of tightening force and friction force, provoked comfortable stretch, was the limitation of the matrix metal, appearance is tightening ( More plough) Outer surface formed plastic deformation. High temperature plastic deformation on the conditions of the grinding process, with the temperature increasing of workpiece appearance. （ 3) Sometimes work hardening layer microhardness and metallographic method can be found that due to the machining deformation provoked outside surface hardness increases. In addition to grinding machining, casting and heat treatment of decarburization layer formed by the heating of appearance, again after processing in the if is not complete, residues in workpiece looks will also form they softening disintegration, contribute to FAG bearing early failure.