1. grinding heat
In grinding, grinding wheel and the workpiece contact zone, can consume a large amount of, a lot of grinding heat, causing local instantaneous temperature of the grinding area. Application of linear movement formula, calculation, or apply an infrared heat source heat transfer theory method and method of thermocouple measuring instantaneous temperature of the experimental subject, can be found in 0.1~0.001ms in the grinding zone of instantaneous temperature can be as high as 1000~1500℃. Such instantaneous temperature, sufficient to enable the work surface a certain depth of high temperature oxide layer on the surface, non-crystalline, high-temperature tempering, quenching for the second time, or even burn crack and other changes.
(1) the oxide layer on the surface
Steel surfaces under transient high temperature and oxygen in the air, up into very thin (20~30nm) thin-layer iron oxides. Worth noting is the thickness of the oxide layer and surface grinding of metamorphic total layer thickness of test results is correspondence. This indicates that the oxide layer thickness and directly related to the grinding process, are important signs of grinding quality.
(2) amorphous organization
Transient high temperature of grinding zone bring the workpiece surface to melt when the molten metal flow is evenly coated on the surface of the work, and by base metal to very fast cooling, forming a very thin layer of amorphous organization. It has high hardness and toughness, but it only has about 10nm, in precision grinding of very easily removed.
(3) high-temperature tempering
Transient high temperature can make the surface a certain depth of grinding zone (10~100nm) is heated above the workpiece heating tempering temperature. Do not reach under the temperature of austenite, followed the progress of heated temperature of, the surface layer-by-layer corresponds to the heating temperature or high temperature Tempering Tempering microstructure transformation of hardness also declined. Higher heating temperature and decline in hardness and the more powerful.
(4) the second layer hardening layer
When grinding area transient high temperature heating to the workpiece surface temperature of austenite (Ac1) above, the layer of austenitic organization during the subsequent cooling process, and again quenched martensite organizations. Wherever the second workpiece quenching Burns, the secondary hardening layer must be under extremely low temperature tempering hardness.
(5) the grinding crack
Second burn the workpiece surface quenching stress changes. Quench zone for the second time in a pressure, high temperature tempered material beneath it there is a maximum tensile stress, here is where the most likely crack the core. Crack most easily along the original dissemination of austenite grain boundaries. Severe burns will cause the entire ground surface formed the crack (crack) cause the workpiece scrapped.
2. grinding force formed of metamorphic layers
In the grinding process, the layer will be cut by grinding wheel on workpiece surface forces, the role of compression and friction. Especially for the latter role, the workpiece surface layer form directional strong plastic deformation and hardening. These degenerating layer must affect the change of residual stress in the surface layer.
(1) cold plastic deformation
During the process of grinding, abrasive is commensurate to a cutting edge with every moment. In much cases, cutting edge angle is negative, other than cutting abrasive, is to keep the workpiece surface subjected to compression (plough), leaving significant plastic deformation on the workpiece surface layer. That level of deformation and deformation of grinding blunt and grinding feed rate and increased with the increase of the degree.
(2) hot plastic deformation (or high-temperature deformation)
Instantaneous temperature of grinding heat work surface to form, making certain depth workpiece surface layer of sharp decline in the elastic limit, or even the elastic extent of the disappears. Work surface layer on grinding force at this time, especially under the action of compression and friction, cause freedom stretch, subjected to base restrictions, the surface is compressed (plow), resulting in surface plastic deformation. High temperature plastic deformation in grinding the same cases, but increased with surface temperature.



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