What is it?
This defect looks like a straight line cut parallel to the rolling direction of the steel. It is caused by a foreign object that is present in the pass line of a rolling mill, pickle line, etc., and comes in contact with the coil surface resulting in a scratch. It is important to note that a scratch on a hot-rolled band is characterized under the microscope as having excessive steel grain growth under the scratch since it was caused when the coil was over 1200 degrees Fahrenheit. If grain growth is absent, the defect occurred later in cold processing of the coil.