DECISION ON ALUMINA PARTICLE SIZE
While working with cutting disc or grinding wheel, choosing a proper model is the primary step. Brown fused alumina is one of the most ordinary abrasives, how will we decide the ingredient corundum size in wheel or disc?
The choice of alumina abrasive particle size mainly considers the requirements of grinding efficiency and workpiece surface roughness. Generally can be selected according to the following factors.
The workpiece machining accuracy is high, and when the surface roughness value is low, abrasive tools with fine alumina abrasive grains should be selected. The smaller the alumina particle, and the more alumina particle that is involved in cutting, the smaller the residual abrasive grain cutting marks on the workpiece surface and the lower the surface roughness value. However, the choice of abrasive grain size must also be considered in conjunction with the grinding conditions used. If the selected grinding amount is small and the dressing of the grinding wheel is fine, the coarser abrasive grain size can also be used to obtain a lower workpiece surface roughness value.
When the contact area between the grinding tool and the workpiece surface is relatively large, or when the grinding depth is large, coarse abrasive material should be used. The coarser abrasive material and the workpiece surface have less friction and less heat. Therefore, when grinding with the end face of the grinding wheel, the selected abrasive grain size may be coarser than when grinding with the periphery of the grinding wheel.
usually. Grinding grinding using 36 # ~ 46 # grinding wheel, workpiece surface roughness Ra can reach 0.8 ~ 0.4μm. If the grinding wheel speed vs is increased and the grinding depth ap is reduced, the surface roughness Ra of the workpiece can reach 0.4μm~0.2μm. When grinding, 150#~240# abrasives are used for grinding, and the workpiece surface roughness Ra is reached. Or lower. In the mirror grinding, graphite grinding wheels with fine powder W10~W7 resin binder were selected.
When rough grinding, the machining allowance and the grinding depth used are relatively large, and the grain size of the abrasive should be coarser than that of the grinding, so that the production efficiency can be improved.
Cutting and trenching procedures should use coarse-grained, loose-grained, and harder abrasives.
When grinding tough metals and soft metals, such as brass, copper, soft bronze, etc., the surface of the grinding tool is easily blocked by the chips, so the coarse-grained abrasive should be used.
Grinding materials with high hardness, such as quenched steel, alloy steel, etc., should use coarse-grained abrasives. When grinding hard alloys, due to the poor thermal conductivity of the material, it is prone to burns and cracks. Therefore, it is advisable to use coarser abrasives. For the grinding of thin and thin-walled workpieces, abrasives with coarser grain sizes should be used because of their easy heating and deformation.
For the small cutting allowance, or the workpiece with small contact area between the grinding tool and the workpiece, the finer abrasive material can be used. The wet grinding can be finer than the grinding tools used for dry grinding.
When processing on a rigid grinding machine, coarser abrasives may be used.
When forming and grinding, it is desirable to keep the shape of the grinding wheel working surface better, so it is advisable to choose a finer grain size for the abrasive.
In high-speed grinding, in order to increase the grinding efficiency, the grain size of the abrasive is rather finer than that of the ordinary grinding by 1 to 2 grain sizes. Because the fine-grained abrasive particles are sharper, it is easier to cut into the workpiece. At the same time, the number of working abrasive grains per unit area of the grinding wheel is larger, and each grain of abrasive grain is less on the contrary, so it is not easy to be dulled. In addition, even if individual abrasive grains fall off, the effect of unevenness on the wear of the grinding wheel is not as great as that of the coarse grain, so it is advantageous to maintain the smoothness of the grinding process. However, the grain size of the grinding wheel during high-speed grinding cannot be too fine. Otherwise, the chip removal conditions deteriorate, which is not conducive to improving the grinding efficiency.
Above details the principle of choosing ingredient brown fused alumina, following the principle accordingly and evaluation the workpiece correctly, efficiency and quality will be promising.