Chromium oxide on the surface - 1.4016
Non metallic inclusions, in this case chromium oxides, branch-on through the casting process, can occur in the steel. If these occur as large chunks on the pre-material surface, they are rolled with the material and afterwards they can stay on the rolled piece surface. A removal at the pickling produces strong holes in these places.
Rod wire 9,00 mm round - annealed , pickled