Ring Rolling of Pre-forms Made by Wire-arc Additive Manufacturing

Ring rolling is a flexible forming process used to produce seamless rings with various dimensions and cross sections. For smaller rings of up to 500 mm diameter, mechanical ring rolling machines can be used. A special design is a 4-mandrel-table rolling mill, which achieves high productivity due to the fact that the precursor rings are continuously conveyed through the roll gap by rotation of the table. The mechanical machines are usually integrated into a process chain that involves shearing of blocks, forging of blanks and ring rolling as the final process step. Especially profiled cross sections may require multiple forming steps to reach the final ring geometry. To increase the flexibility of the process, it seems viable to use highly productive additive manufacturing processes such as wire-arc additive manufacturing (WAAM) to produce preforms for the ring rolling process. WAAM is based on arc welding and allows for processing various materials with high deposition rates. In this case, a more complex cross section can be manufactured, so that a single ring rolling stage may be sufficient. However, no previous research on ring rolling of additively manufactured pre-form is known. The present contribution aims at analyzing the hot forming behavior of pre-forms made by WAAM during ring rolling. The microstructure evolution and the achieved mechanical properties will be evaluated. (C) 2020 The Authors. Published by Elsevier Ltd.