Grinding heat
Grinding wheel and work piece contact area, consume a lot of energy to produce large amounts of grinding heat to cause local transient high temperature of the grinding zone. Use of linear movement heat source heat transfer theory formula derivation, the method of calculation or application of infrared and thermocouple method measured experimental conditions, the instantaneous temperature can be found in the instantaneous temperature of the grinding zone can be as high as 1000 ~ 1500 ℃ 0.1 ~ 0.001ms. This instantaneous high temperature, sufficient to enable the work surface to a certain depth of surface layer of high temperature oxidation, amorphous organization, high-temperature tempering and secondary quenching, and even burn a variety of changes such as cracking.
(1) the surface oxide layer
Instantaneous under high temperature steel surface and the role of oxygen in the air or into very thin (20 ~ 30nm) thin layer of iron oxide. It is noteworthy that the oxide thickness and surface grinding of the metamorphic layer total thickness of the test results showed a corresponding relationship. This shows that the oxide layer thickness and grinding process is directly related to an important symbol of the grinding quality.
(2) Amorphous tissue layer
Instantaneous high temperature of the grinding zone to the surface of the molten state, the molten metal molecular flow is evenly coated on the surface of the work, and the base metal to be cooled extremely rapidly, forming a very thin layer of amorphous tissue layers. It has high hardness and toughness, but it is only about 10nm, it is easy to be removed in precision grinding.
(3) Layer of high temperature tempering
Instantaneous high temperature of the grinding zone can make the surface a certain depth (10 ~ 100nm) is heated to a temperature higher than that of the work piece tempering heating. With the improvement of the heating temperature in the case did not reach the austenitizing temperature, the surface layer will result in organizational changes that correspond with the heating temperature to return fire or high temperature tempering, the hardness decreases. The higher the heating temperature, the decrease in hardness is also more powerful.
(4) The second floor of hardened layer
When the instantaneous temperature of the grinding area of the surface layer is heated to above the austenitizing temperature (the Ac1), the austenitizing organization of the layer in the subsequent cooling process, but also be re-quenching into martensite. Where there are secondary quenching the work piece burn, the secondary hardening layer under high temperature tempering layer must be very low hardness.
(5) Grinding cracks
Secondary quenching burn will make the surface layer of stress changes. Secondary quenching zone in compression, the following high-temperature tempering zone material existence of the maximum tensile stress, here is the most likely to crack the core. Crack is most likely to spread along the original austenite grain boundaries. Serious burns can cause the entire grinding surface cracks (mostly cracks) caused by the work piece scrapped.



Other News:
Filled needle bearing installation
FAG bearings grinding deterioration affect reasons for introduction
Bearing radial load
Thrust needle roller and cage assemblies
Metal Forming Lubricant selection
Installation method
Measurement of the bearing clearance
The cylindrical bore radial bearings