Grinding cracks on the surface of integral cemented carbide tools are mainly caused by the shallow compressive stress distribution in the grinding surface layer and the excessive tensile stress value in the near surface layer which exceeds the breaking strength of the material due to the excessive local instantaneous temperature in the grinding contact zone during the grinding process. Therefore, the instantaneous stress should be minimized and avoided as far as possible in the grinding process. The generation of high temperature also reduces and avoids the existence of residual tensile stress.
The instantaneous high temperature in the grinding process often causes the change of the mechanical properties of the grinding surface layer. This instantaneous high temperature can reach more than 1000 degrees Celsius, causing grinding burn to the tool surface layer. Grinding burn will destroy the surface layer structure of the tool, deteriorate the quality of the workpiece surface, seriously affect the strength, wear resistance and service life of the tool; serious cracks will also occur. Therefore, not only to prevent grinding cracks, but also to avoid grinding burn. In diamond machining, the local instantaneous temperature of the tool surface will depend on the machining method, the characteristics of the diamond tool and the grinding system.
Practice has proved that the higher the linear velocity and radial feed rate of diamond grinding wheel, the higher the hardness of fast cheap metal grinding disc, the finer the grain size of fast cheap metal grinding disc, the lower the thermal conductivity of cutting tool material and the worse the 180*6*22mm metal grinding disc wear, the higher the grinding temperature, the easier the grinding cracks and burns will occur.
To control and avoid grinding cracks and grinding burns, two measures must be taken: one is to reduce the generation of grinding heat, and the other is to accelerate the transmission of grinding heat. The ways to reduce grinding heat are to reduce the linear velocity of the diamond grinding wheel, reduce the radial feed (roughing-finishing-polishing), select the softer diamond grinding wheel, reduce the contact area between the workpiece and the 180*6*22mm metal grinding disc, reasonably select the high quality metal grinding disc size according to the grinding requirements, and often keep the fast cheap metal grinding disc in sharp conditions.
Sharpening and selecting suitable grinding coolant to reduce friction between abrasive particles and workpiece. The measure to speed up the grinding heat release is to adopt effective cooling methods besides the proper speed and axial feed rate. In order to improve the cooling effect, spray cooling, high pressure cooling, internal cooling and low viscosity oil are adopted. In addition, in the fine grinding process, reducing the feed and proper grinding can effectively reduce the residual stress in the surface.
In summary, in order to improve productivity and grinding efficiency, and at the same time to obtain better grinding surface quality, our method is to start with a lower wheel linear speed and larger radial feed, the last few feeds reduced and the wheel linear speed increased, and polishing, which can improve the grinding surface quality. In order to further improve the surface quality of grinding, spray cooling and high pressure cooling can be used to select suitable cutting fluid, and the fast cheap metal grinding disc and 180*6*22mm metal grinding disc are selected according to the processing objects.
The selection principle of grinding parameters is: the grinding parameters are to ensure that the grinding temperature is low, grinding surface roughness is high, as far as possible to select a lower wheel linear speed, larger radial feed, axial feed and workpiece speed. Because the linear speed and radial feed rate of high quality metal grinding disc have the greatest influence on the quality of grinding surface layer, the selection of grinding parameters is as follows: first select the larger workpiece speed, then choose the axial feed, and finally choose the linear speed and radial feed rate of fast cheap metal grinding disc.
