Definition and appearance: The scale of the strip surface is not completely washed in the pickling process; or the impression left by the scale of the iron oxide is not completely eliminated during the cold rolling process, and the appearance of such defects may be pitting , line marks or large areas of indentation, can appear in any part of the strip surface.
Cause: The high-pressure water nozzle before the hot-rolling mill is clogged; the iron oxide skin is not blown clean and is rolled in; the hot-rolled high-temperature coil takes up the material, and the scale is not enough when pickling and pulling, and the pickling is not clean.
Eliminate countermeasures: ensure that the descaling high-pressure water device of the hot rolling mill works normally; the top of the hot-rolling frame should be cleaned to prevent the iron oxide scale from falling on the surface of the strip and then rolled in; for high-temperature coiling, strengthen the scale when pickling Improve the ability to clear.
Identification: Discrimination by means of its appearance and metallographic detection.
May be misjudged: sometimes confused with scratches or pickles.
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