Usually, when we perform metallographic polishing, the sample undergoes several stages, such as rough grinding, fine grinding, rough polishing, fine polishing, corrosion, cleaning, and so on. These steps are linked step by step, step by step. How to ensure reasonable connection of operations? How to determine if the previous process was executed properly? This has become a concern for operators.

This article will preliminarily introduce the method of visually observing each grinding and polishing step to determine whether it is qualified. To help operators solve some operational problems and difficulties. Of course, this article also takes this opportunity to offer valuable insights. If there are any mistakes or omissions, readers are welcome to point them out and work together to learn and progress.

1、 Grinding section

In most cases, metallographic sandpaper is used during the polishing stage. Only a few high hardness materials need to be used, such as special tools such as diamond grinding discs. However, whether it is sandpaper or diamond tools, the principle is the same. The method of visual observation is also the same, and the qualification criteria are consistent.

Usually, as long as the scratch direction is consistent, you can proceed to the next step. Alternatively, all scratches on the entire grinding surface are parallel. Specifically, the grinding surface is flat, the direction of the grinding marks is consistent, and the previous grinding marks are covered.

Note that do not repeat each step in the same direction to avoid the failure of the judgment method mentioned above. Every time a layer of sandpaper is replaced, the sample is rotated at an angle (90°) to make the grinding marks of the previous pass perpendicular to the direction of the grinding marks of the current pass. This can cover the scratches from the previous step and ensure effective observation and judgment.

However, the observation and judgment method mentioned above is only applicable to manual polishing. If it is automatic grinding and polishing, the scratches are intertwined with each other, without a specific direction, presenting&# quo; Mi” The disordered order of characters. At this point, it is recommended to observe and determine as follows: 1. The scratches and grinding surface are uniform and consistent. 2. There are no coarse scratches mixed in it. 3. The traces left by the previous process have been removed (or covered).

Here's a point to add: generally speaking, in the final state of polishing, at the end of the next layer of sandpaper, the surface of the sample has a mirror like appearance when observed by the naked eye, but is covered with even and small scratches.

2、 Polishing section

The effect of rough polishing (initial polishing) and intermediate polishing is similar to that of sandpaper polishing, so the same standard can be used to determine whether it is qualified. Note that at the end of this step, although scratches still exist, there is generally a significant improvement and reduction, and the mirror effect begins to appear.

Although a few scratches can still be seen on the 1-micron polished surface, it has already shown a mirror like appearance. Except for a few difficult to polish materials, they are mostly mirror shaped with a few scratches.

And the surface of the final polished (precision polishing) sample cannot be observed with the naked eye, which is basically; Brightness, glossiness, and mirror finish;.

The above standards can be used to visually judge the quality of grinding and polishing, reducing the workload. If your automatic polishing equipment comes with observation capability (or device), then the actual situation shall prevail.

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