Three-dimensional thermo-mechanical coupled FEM simulation for hot continuous rolling of large-diameter mandrel bar

Based on the important boundary conditions of rolling simulation including friction, heat conduction and interactions of the workpiece and rolls, the hot continuous rolling processes of large-diameter mandrel round bar (200 mm in diameter) in 6VH-stand hot tandem mill are successfully simulated by three-dimensional coupled thermomechanical elastoplastic finite element method (FEM). The distributions of stress, strain, temperature and the rolling force and torque for the two-pass and four-pass continuous rolling are calculated respectively. Thus, the two and four-pass roll schedules are verified, respectively. The simulation results show that it is safe to produce 200 mm round bar by the two-pass (oval pass and round pass) continuous rolling on the existing equipment compared to the four-pass continuous rolling. There are concave surfaces and increased widths occurring at the end of rolled billet due to uneven deformations between the outside and inside of the workpiece as well as the free spreading close to the roll gap of the final pass.