"staining of cold rolled sheet"

Question:

"From time to time we experience staining with our full hard steel sheet. The material is usually aisi 1035 with a finish of Ra<20. We do not have this problem with a rougher finish or material that gets annealed. Some people think its related to coolent carry over. I am relatively new to this sector of the industry; I would like to know the best way to tackle this problem and if there is any information on the subject to get me started."

Answer:

Regarding an approach for solving the problem, you might want to consider the following: (1) Verify whether the staining is an external deposit or an in-situ corrosion product. (2) Conduct an EDS elemental and X-ray diffraction analysis of the stain to verify its composition. (3) Analyze your coolent for chlorides and pH. (4) Metallographically observe the sheet in stained and non stained areas to verify whether variations in sheet properties are contributing the to staining.

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