کاهش مصرف انرژی در فرآیندهای رولینگ حلقه ای : تجزیه و تحلیل FEM

Ring Rolling is a very high energy consuming hot forming process used for the production of shaped ring, seamless and axis symmetrical workpieces. Different production steps (Upsetting, Piercing, Ring Rolling) are involved in generating the desired ring shape. In particular the Upsetting and Piercing steps generate a hollow circular preform that will be subsequently enlarged by the rolling mills (Driver, Idle and Axial Rolls) during the Ring Rolling step. In order to reduce the energy and the force needed to produce the workpiece it must be observed that they are strictly affected by the speed laws imposed to the rolling mills which depend on the preform and the final ring geometry. As a consequence the setup of the Upsetting and Piercing steps became fundamental because they impose the preform geometry of the workpiece. Starting from this assumption, in the present work different preforms geometries, characterized by different initial heights, are considered to simulate the Ring Rolling process focusing the results analysis not only on the part feasibility, but also on the energy and force required which affect the equipment dimensioning. An industrial case was considered to validate the FE model. The maximum load and the energy needed for the ring production are considered as main figures for optimizing the process.

Ring Rolling is a hot forming process used for the production of shaped ring, seamless and axis symmetrical workpieces. In this process the metal is rolled between two rolls which move toward each other to form a continuously reducing gap. In Ring Rolling, the rolls are of different diameters and geometries. The Ring Rolling process is basically used in the production of railway wheels, anti-friction bearing and different ring shaped workpieces for automotive, aerospace and wind industry applications. A typical ring produced by means of this process can have a final diameter equal to 3 m and an height equal to 0.5 m [1]. It could be either a hot or cold process and different alloys as steels, light alloys and titanium can be worked. The advantages of Ring Rolling process include short production time, uniform quality, close tolerances and considerable saving in material cost. This process, compared to others as casting or plasma cutting, could provide lower working temperature, less material required and, consequently, a reduction in energy consumption. Moreover, the main advantage of the workpieces produced by Ring Rolling process, compared to other technological processes, is given by the size and orientation of grains, especially on the worked surface which give to the final product excellent mechanical properties [2]. On the other hand, as the ring to be produced increases in dimensions, the force and the energy needed to carry out the process require a more powerful plant/equipment. Moreover, according to the production setup and phases, the total energy required can be heavily changed. In a world in which the environment impact of production activities becomes every day more and more important, it is necessary to understand if there is any possibility of reducing the energy consumption. Also the ability of obtaining the desired part is very important for reducing material scrapping and useless material heating. This means that the correct definition of the geometry of the intermediate parts is a fundamental task for achieving both the desired objectives.

Ring Rolling is a complex deformation process where different steps: Upsetting, Piercing and Ring Rolling are involved to produce a seamless ring starting from a bar. The process parameters must be carefully selected in order to guarantee a good quality ring reducing undesired axial deformation that results in a defect known as fishtail. Moreover, the possibility of reducing the energy consumption of the ring production is still an open challenge in order both to optimize the process and to increase the productivity of the plant. In this paper the authors focused their research on the importance of the upset height setting in the Ring Rolling process. The importance of this parameter has been evidenced since it affects the energy and the loads needed to produce the workpiece, and the milling curve. The problem was investigated via numerical approach starting from an industrial case study and the results underline that a decrease of the upset height could guarantees: • Less energy and loads: it was demonstrated that a decrease of the upset height leads to a decreasing of the load and energy of the Piercing step and of the Ring Rolling step, that results the most critical for the ring production, with an exception to the Idle Roll energy. On the contrary the Upsetting step load and energy increase. • Less defect: it was measured that the lower the upset height, the more precise the final height and the more reduced the fishtail defect. • Material saving: an upset bar characterized by a lower upset height will generate a minor scrap when a preform is generated in the Piercing step. Moreover, all the obtained results are very important because of the required energy, the required loads and the ability of obtaining sound parts can lead to a reduction of the environment impact for the considered technology.