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Abstract. Finite element analyses of rolling processes have been carried out for many years. Most of the simulations focus on deformation of metal plates/sheets without taking into consideration flexibility of rolls and the machine frame. In our paper, we present a unique approach to simulation of rolling of thick plates where compliance of rolls and the complete structure of a roll leveler is taken into account. This approach makes it possible to accurately predict shape distortion of steel plates and gives valuable, practical information on how to prevent shape defects in a rolled product. In this paper, roll leveling of steel plates after continuous casting, is analyzed. Our approach is universal and can be applied to other types of rolling processes. As a simulation tool, we used a non-linear FEM code. INTRODUCTION Continuous casting is the process whereby molten steel is solidified into a steel plate through subsequent cooling and rolling - Fig.1. In recent years, technological advances in continuous casting technology made possible to produce shapes that substantially conforms to the finished product (the near-net-shape casting).[1] FIGURE 1. Continuous Casting Process. There are a few phenomena, as for example non-uniform temperature distribution during solidification or local deformations at rolling, which may cause geometrical distortion of the product shape. To deal with these type of defects, a roll leveler is used at the last stage of the production process. 50293
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Operation of the roll leveler requires very sophisticated skills – not only shape distortion of plates coming into roll leveling has to be taken into account, but also elastic deformation of rolls and deformation of leveler structure - frame affect product shape. To understand influence of various parameters of roll leveling process on the final shape of a product we decided to use finite element method. In our simulation we focused on roll leveling of thick plates, however our simulation techniques can be applied to products of any shapes. Typical approach to analyze compliance of rolls during leveling is to use 3D solid elements to describe roll geometry. We found this approach not acceptable – long computation times for models with huge number of degrees of freedom made FEM simulation very unproductive. In this paper we present approach where rolls are described using beam elements, rigid links and contact segments. Also the complete structure – frame of a roll leveler is taken into account. Due to the non-linear character of plastic deformations in metal plates as well as non-linear character of contact phenomena between rolls and plate we decided to use non-linear FEM code ADINA. Our simulation models made possible to establish relation between residual, shape distortion of a thick plate and compliance of rolls and roll leveler structure. ROLL LEVELING PROCESS In the roll leveling process, as shown in Fig.2, two rows of rolls bend top and bottom surfaces of steel plate alternatively. Through this process, localized plastic strain is created just beneath the top and bottom surfaces of the plate. This additional strain compensate initial shape distortion of the plate. FIGURE 2. Roll Leveler. Due to a high level of forces necessary to initialize plastic deformation of the plate, deflection of rolls and structure - frame of a leveler becomes significant, as shown in Fig.3. FIGURE 3. Roll Deformation. That may cause a non-uniform initial strain distribution along the plate width, as shown in Fig.4. FIGURE 4. Non-Uniform Strain . To achieve required shape quality, deflection of rolls has to be compensated by a pre-determined – counter-deformation of rolls. This is done usually with an aid of the wedge mechanism, as shown in Fig.5. Production process requires to adjust position of the wedge mechanism frequently, for every different type of plates.