On the surface of the steel plate, there are irregular warped metal sheets, showing leaf, feather, strip, etc. After the metal sheet falls off, it is pitted and shaped like a roll print. Scar holes generally have different macroscopic morphology; Poor reproducibility on the same and different steel coils; Generally, there is no peeling feature, and the defects remaining on the surface of the steel plate are mostly stratified. Generally, the linear extension of the defect along the rolling direction is not strong; The difference between different parts of the defect is large, some places have cracked into holes, and some places have almost the same thickness as the normal parts of the steel plate; Often accompanied by pits and holes with different rules; The junction between the defect and the steel base is not smooth and often has a certain step; Along with the occurrence of edge cracks, there are pits, holes, delamination and other defects with different depth and not obvious extension characteristics.

This defect is caused by the inability to cut off the hot rolled coil and flow down to the electrical steel sheet factory, so its cause is the same as the cause of scarring on the raw material hot rolled plate. The original defects such as scarring, heavy skin and cracks on the slab surface are not cleaned up, and remain on the surface of the steel plate after rolling, and the residue is left on the slab surface, which is generated during rolling.

The preventive measure is to strengthen the inspection and acceptance of the slab, do not use the slab with scar surface and heavy skin depth exceeding the standard. The specific treatment method is that the local scar can be eliminated by grinding, but it can not exceed the depth and scope specified in the relevant standards.

Heavy skin is one of the common defects, some mild, some severe, and accompanied by cracks or holes, long strips of wide peel can be uncovered, uncovered often found that there is a layer of white and gray material between the skin and the substrate. Such defects are mainly caused by brittle inclusions or slag inclusion in steel, and inclusions can often be found in the defect site. Such defects can occur on both sides of the coil, with the highest incidence of defects at 1/4 and 3/4 of the width of the coil, followed by the middle of the coil, and then the edge of the coil. The occurrence law of such defects is very consistent with the distribution law of large non-metallic inclusions in the casting billet, that is, the inclusions content in the head and tail of the casting billet is higher than that in the middle billet, and the inclusions in the width direction of the casting billet are the most at 1/4 or 3/4, followed by the middle and the least at the edge.