The consumables with a particularly high usage for metallographic grinding are metallographic sandpaper. The correct use and scrap level of metallographic sandpaper are directly related to the quality, efficiency, and cost control of sample preparation. To what extent is it more suitable to replace the metallographic sandpaper with a new one? The metallographic engineer of Kemai Testing told you that when using metallographic sandpaper, it should be replaced with a new one!

The purpose of using metallographic sandpaper grinding is to remove the deformation layer on the surface of the metallographic sample. The usual method is to grind from coarse to fine in 2-3 steps, and the last layer of each grinding is ground with finer sandpaper to remove the scratches generated by the previous grinding and obtain a good surface effect, laying a foundation for subsequent polishing.


The working principle of metallographic sandpaper grinding the surface of a sample is to quickly grind the surface of the sample using sharp grinding medium particles fixed on the paper base, thereby removing the surface deformation layer. At the same time, the grinding medium particles participating in the grinding are broken due to force, and the sharp edges and corners are removed, while the remaining part is in the bonding layer, making its surface dull. Therefore, using metallographic sandpaper for a long time weakens its grindability, reduces its removal rate, and blunt grinding medium particles can cause new damage to the surface of the sample. The following figure is a comparison between new sandpaper and worn sandpaper. It is obvious that the surface of the worn metallographic sandpaper has been basically ground flat。

When using worn old sandpaper to grind the sample, the surface of the sample will appear smoother to the naked eye and have better reflectivity than the surface ground with new sandpaper. However, this is indeed an illusion. If you look at it under a microscope, you will see" The True Face of Lushan Mountain; As shown in the following figure:

The left image in the comparison image shows the surface ground with old sandpaper, while the right image shows the surface of the sample ground with brand new metallographic sandpaper. Obviously, the grinding marks of the new sandpaper overlap more clearly with each other and present an image with a three-dimensional morphology; The surface ground by old sandpaper is almost flat, and the grinding marks are almost indistinct. The grinding marks are flattened and have good reflectivity, which seems to have a good mirror effect when observed with the naked eye. In fact, the deformation layer on this surface is deeper.

After countless experiments and comparisons, the suggestion of the metallographic engineer for pulse detection is that when the sample is ground with metallographic sandpaper, a grade of sandpaper needs to be repeated continuously for more than three times to produce a qualified surface. At this point, the old metallographic sandpaper used should be replaced, neither waste nor make full use of its resources, otherwise it will be uneconomical.


If you have any questions about the use of metallographic sandpaper, please feel free to discuss with our metallographic engineers at Kemai Testing to help you solve your problems and make your work better!