Bending process for producing uniform angle distribution from ultra-high strength steel sheets having thickness distribution

Abstract

Because of the elastic deformation of rolling mills in rolling, the edge drop in thickness of rolled ultra-high strength steel sheet was remarkable, thus the thickness distribution was not uniform. The distribution of angle before and after unloading in V-bending of the ultra-high strength steel sheets having such a thickness distribution was measured. The bend angle was nonuniformly distributed by the insufficient bend angle at the bottom dead centre and springback during unloading. The effects of the bent angle and thickness distribution on the springback in thin and thick edges were discussed. The distribution of bend angle was reduced by bottoming with a three-piece die using a rubber pad. It was found that bottoming with a divided die using a rubber pad in bending is effective in improving the dimensional accuracy of ultra-high strength steel sheets having a thickness distribution by finite element simulation and experiment.