Prediction of camber formation, suppression and control of wedge-shaped hot rolled slabs by analytical concepts and finite elements

For today's process automation systems for hot strip mills, wedge reduction without generating camber is still a big challenge. By utilizing suitably positioned edging rolls, the corresponding side force acting on the strip induces a lateral material flow inside the roll gap, leading to stress-redistributions such that the outgoing camber is drastically reduced. Systematic parameter studies performed so far by utilizing the commercial FEM-package ©Abaqus Explicit revealed the dependence of the lateral edging force and the resulting strip centerline-curvature on characteristic rolling parameters, such as slab width, thickness, initial wedge and thickness reduction. To understand the underlying highly non-linear elasto-viscoplastic forming processes inside the strip or slab in more detail, and to develop fast simulation tools, semi-analytical model reduction approaches were developed. This enables a quantitative analysis of the induced lateral material flow and the occurring stress-redistributions inside the roll bite. By introducing a lateral material transfer parameter directly correlated to the centerline-curvature, an analytical relation could be derived for the bending moment, respectively for the external work, that has to be applied to eliminate the camber of the strip or slab. These analytical predictions, although based on rough simplifications, correspond quite satisfactorily with those attained by 3D-FE simulations.