Influence of Rolling Conditions and Chemical Compositions of Rolled Material on Strip Surface Flaw Caused by Surface Deterioration of Hot Work Rolls

The relationship between the strip surface flaw occurrence and rolling conditions in upstream stands together with the chemical compositions of rolled material are examined in the skinpass mill line. The ratio of the mean rolling pressure and the work roll surface in roll bite has a good correlation with the occurrence of the strip surface flaw. The strip surface flaw occurs frequently when the ratio exceeds the threshold value fixed by the chemical compositions of rolled strips. A slight addition of Si to Al-killed steel reduces remarkably the occurrence of the strip surface flaw. In order to clarify this phenomena, the influence of Si content on the behavior of scale formed on strip surface is investigated through laboratory tests. Moreover, the influence of the friction coefficient on the velocity difference between roll surface and strip surface is calculated by rigid-plastic FEM, as the friction coefficient changes with Si content.