Deformation Analysis of Surface Defect on Plate Rolling

Abstract

Micro-defects sometimes appear on the surface of rolled plate and they affect the surface quality and cause the breakdown and cracks in the rolled sheet and strip. It is very difficult to make defect free products now. The shape of defect after rolling changes variously due to the rolling conditions. If the relation between the shape of the defect before rolling and that after rolling is clear, it leads to the effective method to predict the reason of the surface defect and to develop the process to remove the defect. The finite element analysis seems to be an influential technique, but it is difficult to calculate the deformation of micro-defects since the size of the defect is very small and the deformation is concentrates in small area. In this study, finite element analysis with an effective meshing and adaptive remeshing system was newly applied to calculate the change of surface micro-defects in plate rolling. A small mesh under sub-millimeter size was used around the defects. Rolling of plate with several types of surface defects, for instance V-shaped and rectangle scratch or denticle was calculated and the existing defect after rolling was investigated. The validity of simulated results was checked by experiments. There were mainly two cases in the change of defect shape in rolling i.e. opening type and closing type. The influence of rolling condition (roll diameter, lubrication and pass schedule etc.) on existing defects after rolling was revealed and the optimum condition to eliminate defects was discussed.