The key to operation:
Try to get the maximum polishing rate in order to remove as quickly as possible the layer of damage produced during polishing. It is also important that the polishing damage layer does not affect the final observed tissue, i.e. does not cause false tissue. The former requires the use of coarser abrasives to ensure that there is a large polishing rate to remove the grinding damage layer, but the polishing damage layer is also deeper; the latter requires the use of the finest material, so that the polishing damage layer is shallow, but the polishing rate is low. The best way to solve this contradiction is to divide the polishing into two stages. Rough polishing purpose is to remove the polishing damage layer, this stage should have the maximum polishing rate, roughing the formation of surface damage is a secondary consideration, but it should also be as small as possible; followed by fine polishing (or end of the throw), the purpose is to remove the surface damage produced by roughing the polishing damage to minimize the polishing damage.
Polishing machine polishing, specimen grinding surface and polishing disc should be absolutely parallel and uniform light pressure on the polishing disc, pay attention to prevent the specimen fly out and too much pressure to produce new wear marks. At the same time should also make the specimen rotate and move back and forth along the direction of the radius of the turntable to avoid localized abrasion of the polished fabric is too fast in the polishing process should be constantly added to the micro-powder suspension, so that the polished fabric to maintain a certain degree of humidity. Humidity is too large to weaken the polishing of the abrasive effect, so that the sample in the hard phase presents convex and non-metallic inclusions in steel and cast iron graphite phase produces "trailing" phenomenon; humidity is too small, due to friction heat will make the sample warming, lubrication is reduced, the grinding surface loses its luster, and even black spots, light alloy will be thrown on the injured surface. In order to achieve the purpose of rough polishing, the requirements of the turntable speed is low, preferably not more than 500r/min; polishing time should be longer than the time required to remove the scratches, because it is also necessary to remove the deformation layer. Rough polishing after grinding surface smooth, but dull, under the microscope to observe a uniform and detailed grinding marks, to be eliminated by fine polishing. Fine polishing when the turntable speed can be increased appropriately, polishing time to throw off the rough casting of the damage layer is appropriate. After polishing the grinding surface bright as a mirror, in the microscope bright field of view conditions can not be seen scratches, but in the contrasting lighting conditions can still be seen grinding marks.