Improvement of the dishing process in ring rolling using conical guide rolls

Abstract

Ring rolling is an incremental bulk forming process for producing seamless rings, which are suited for high loads. For seamless dish shaped rings, there are applications in different areas such as offshore, aeronautics and the mining industry. At the moment, dish shaped rings are produced by machining of rings with rectangular cross section, by (open die) hollow forging on a conical mandrel, by using a shaped main roll and mandrel in ring rolling or by casting. These ways of manufacturing have different disadvantages, such as high material waste, long process time, geometrical limitations or a cast structure with poor mechanical properties. If dish shaped rings can be produced on conventional radial-axial ring rolling mills, the range of products for ring producers could be expanded without the disadvantages of the current manufacturing processes. In prior studies dish shaped rings were successfully generated by ring rolling. However, a problem was the achieved poor form accuracy and reproducibility of the process. Thus, the goal of this investigation is to improve the geometrical accuracy of dish shaped rings produced on conventional radial-axial ring rolling mills by replacing the lower cylindrical part of the guide rolls by a conical module. Using this improved rolling strategy, the dishing angle deviation was reduced from 5° to 1°. In addition to the experiments, the influence of the most important numerical and process related parameters on the final geometry and the climbing height was investigated by finite element-simulations.