How to distinguish scratches from cracks?

Cracks are generally not straight; they are rather irregular, and there is usually no depression at the site of the crack； Scratches are generally brighter, usually have a depression, and their shape is relatively regular. Additionally, cracks can be detected by surface inspection, but scratches cannot

I don’t think these things can be accomplished just by reading relevant text or asking questions on forums. . Overall, looking at the many questions asked by the original poster. . Just starting in the industry? Does the company where I work provide any relevant guidance or training? Try figuring it out on your own first. .

If you can’t be sure, the method is simple: use PT testing for austenitic materials and MT testing for ferritic materials. The shape of scratches is regular, with vertical and horizontal patterns; they arise during loading/unloading processes and in the preprocessing stages. The depth achieved through such grinding methods is not very deep (unless it’s a very severe mechanical damage); no visible changes will be detected upon re-inspection. Of course, the depth after grinding must not exceed the allowable negative deviation or the specified depth limit ； Crack patterns include surface cracks, internal cracks, etc.; their shape is generally longitudinal along the rolling direction of the tube sheet, and depending on the cause of their formation, they may also appear at 45 degrees or in a divergent pattern ； Hairline cracks and surface cracks can be removed using grinding wheels after they are detected by PT and MT tests; pay attention to whether the depth exceeds the allowable limit, as internal cracks or cracks that penetrate through the material cannot be removed.