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Cold Rolled Steel Coil – Common Causes of Surface Defects
What are the surface defects of the cold rolled steel coil as a color-coated steel sheet substrate. What is the reason for this?
Common surface defects and causes of cold rolled steel coil include:
1. Scratch. The mechanical equipment is scratched on the surface of the strip to cause strips or strips, continuous or intermittent, with deep and shallow scratches.
2. Sliding injury. When the unwinding tension of the steel coil is greater than the original take-up tension of the steel coil, during the unwinding process, the slack steel coil generates a large area of slippage caused by the interlayer shift.
3. Embossing. The roll or other pressure roller is adhered to foreign matter or mechanically damaged, causing a certain periodic impression on the corresponding position of the strip surface.
4. Roll printing. Due to various defects on the surface of the roll, such as grinding marks, roll peeling, etc., the periodic defects formed by the surface of the strip are copied.
5. Oxidizing color. A yellow or blue oxidized plaque on the strip surface due to annealing oxidation.
6. Emulsion spot. After rolling, the unrolled rolling liquid remains on the surface of the strip, and the residual plaque remaining on the surface of the strip is not completely volatilized or reduced during annealing.
7. Wrinkles. Often produced in the edge of a thinner strip, the crease perpendicular to the length of the strip is the yield deformation of the strip due to uneven tension.
8. Corrosion. The rust of the finished product of the cold-rolled steel coil is mainly caused by the rust of the board which is not oiled or unevenly coated during storage and transportation.
9. Mixed. Internal defects such as oxide inclusions or gases generated during smelting and continuous casting, and defects exposed to the surface after rolling.
10. Iron oxide skin is pressed. The iron oxide scale produced in the pre-hot rolling section is rolled into the matrix of the hot rolled steel coil after rolling, and the defects are still not removed by pickling and cold rolling.