The workload of metallographic sample preparation mainly focuses on the grinding and polishing steps, and usually metallographic sandpaper is used for grinding. Especially in teaching and quality testing laboratories, the use of metallographic sandpaper is very large. How to fully utilize the performance of metallographic sandpaper to make samples ground quickly and well, as experienced colleagues know, it is crucial to seize the opportunity to update metallographic sandpaper. If the update is too early, it is too wasteful; Overuse and delayed updates can affect the grinding effect of the sample, not only prolonging the sample preparation time, but also increasing the difficulty of subsequent polishing.


How to seize the opportunity to update metallographic sandpaper? The summary of the pulse detection editor combined with work practice is as follows:

The purpose of using metallographic sandpaper to grind the surface of the sample is to remove the deformation layer on the sample surface. Generally, three steps are used to remove the deformation layer. The sandpaper particle size is gradually ground from coarse to fine, and the next layer of finer sandpaper is ground to remove the scratches on the previous layer of coarser sandpaper until it meets the technical requirements.

The above figure shows a comparison between the new sandpaper and the worn sandpaper. From the figure, it can be seen that the grinding particles in the new sandpaper are very sharp, while the surface of the worn sandpaper has been basically ground flat, and the grinding particles have basically been embedded in the paper based bonding layer.


For metallographic sandpaper, the surface of the sample is quickly ground by the sharp edges of the grinding medium particles above the paper based bonding layer. While grinding the surface of the sample, the grinding particles are broken due to force, and the sharp edges and corners are removed. The remaining part is not in the bonding layer, and the sandpaper surface becomes blunt, resulting in weaker grinding ability and lower removal rate. If we continue to use it for grinding at this time, the chances of deep contact between the sample surface and the paper base will increase, and the blunt grinding medium particles will bring new damage to the sample surface, as is often said" Plastic Rheology; That's the situation. Also, the surface of the sample ground with this worn old sandpaper looks smoother and the effect is good to the naked eye. However, experienced metallographers all know that this is a fake. Place it under a microscope for magnification observation, and the actual effect is as follows:

The left image shows the surface of the sample after being ground with worn old sandpaper, while the right image shows the surface of the sample after being ground with brand new sandpaper. It is obvious that the grinding marks of the new sandpaper are clearer and have a three-dimensional morphology that overlaps with each other. The depth of the deformation layer is the visible depth. The grinding marks on the old sandpaper are blurry and basically on the same plane, but in reality, the deformation layer depth of this sample is deeper. Due to the planarization of the grinding marks and their good reflectivity, the visual perception is a false image caused by the mirror effect.

So, how to seize the opportunity to update metallographic sandpaper? The experience of the Kemai Testing editor is that when a sample is ground with metallographic sandpaper of a certain particle size, if you need to repeat it more than three times to produce a qualified surface, then it is time to replace it with a new one. At this point, the old sandpaper is already at its best. The sample must be ground faster and better, and it is necessary to seize the opportunity to update the metallographic sandpaper. If you have any questions or want to learn more at work, you can contact the engineer of Kemai Testing at any time for consultation. The contact information can be found on the Kemai Testing official website.