Regarding the problem of spots appearing on the surface of copper alloy parts
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Dear Masters, after the recent batch of copper alloy parts in the factory were processed by the vertical turning machine (with cutting fluid), drilled with drilling machine (tapping oil), and then ultrasonic cleaned to remove oil and degreasing, fire-stained markings appeared on the surface of the parts, which cannot be erased. As shown in the photos, can you help me find out what is the reason?
Is it caused by local overheating caused by uneven heat treatment after the material is formed?
Look for cutting fluids and cleaning agents used for ultrasonic cleaning, and find out what ingredients in these two should corrode the workpiece. As you can see from the second picture, you can wipe off the attachments on the surface. It is recommended to check the cause from corrosion.