Investigation of flexible radial ring rolling for production of non-axially symmetric seamless rings on radial axial ring rolling mills

• Applicant: Professor Dr.-Ing. Gerhard Hirt
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2021 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454751242

The ring rolling process is used to produce seamless rings made of different materials in a wide geometric spectrum. The geometric flexibility is one of the main advantages of this production process. Demand for near net shape geometries to reduce material and post-processing costs led to the development of processes to manufacture rings profiled in radial and axial directions by applying shaped tools. By using innovative tool and process control concepts the producible geometric variety was increased without reducing the process flexibility, as is the case for shaped tools. All of these process variants allow manufacture of profiled rings with constant cross sections around their circumference. There is also demand for seamless rings with non-constant cross sections around the circumference, e.g. for eccentric bearings, but these cannot yet be produced in the ring rolling process.The project described here aims to further develop the ring rolling process in order to enable near net-shape production of such eccentric ring geometries. This can be achieved by performing a targeted closing and opening movement of the mandrel depending on the circumferential motion of the ring in the machine. A necessary mechanism to measure the ring’s rotation was already installed in both guide rolls of the ring rolling machine at the Institute of Metal Forming of the RWTH Aachen University. The provided information will then be transmitted into the machine’s control to allow for real-time control of the tool’s motions based in this information. Additionally, by use of an existing finite element model the producibility of such ring geometries was shown in principle by using the aforementioned process control, which was done in a simplified way using a reference point on the ring to control the mandrel movement. Here it is necessary to implement the method used in the experiments into the simulation to consider potential loss of contact of the guide roll(s) with the ring. In further steps, process influences and boundaries will be investigated by use of the simulation. After successful implementation of the measurement system as well as realisation of the tool motions the numerical results will be verified experimentally by producing two ring geometries with different height-to-wall thickness ratios and potential additional influencing parameters will be identified. The first geometry is expected to be comparatively easy to produce while the second geometry shows more narrow boundaries resulting from a lower ring stiffness. In a second phase the project’s focus will be improvement of the process control, production of rings with several thick sections and the effect of locally different strains on the microstructure of the rings.

• DFG Programme: Research Grants