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Surface defect on steel strip/sheet from Chrome Plated work rolls

January 26, 2013

Q. I would really appreciate any advice or help on the matter described below.

We are currently experiencing a surface sheet defect appearing on the CAL line [continuous annealing line] when using chrome plated temper mill rolls in cold rolling. This defect does not seem to be apparent when using non-chrome plated rolls.

This surface defect appears on inspection during movement of the strip/sheet and seems to be an 'S' shaped wave form defect running along the long direction of the strip/sheet towards the middle of the strip/sheet. There is no buckling of the strip/sheet and the 'S' shaped defect seemingly disappears when the strip/sheet is static. This wave form appearance can vary in magnitude and occasionally in positioning on the strip/sheet ie. closer to the edge.

There also appears to be a color difference either side of this 'S', one side appearing darker and the other more bright.

Has anyone had experience of seeing this form of defect on the CAL line?

Any advice would be much appreciated as this defect is ruining the overall aesthetic of the finished product.

Nina J
- Valencia, Spain