Research On The Simulation Of Forging Process For Heavy Disk Forgings Used In Nuclear Power Plants

As heavy disk forgings used in nuclear power plants, tube-sheet, head and end cap are important parts of nuclear reactor and steam generator, working in hard condition. The forging qualities of heavy disk forgings is related to the safety of the nuclear power plants. The process scheme of prior upsetting and finish forging were made by the forging technoledy keys. Based on the DEFORM-3D, the finite element model was built and forging process was simulated. The wide flat anvil upsetting, frustum anvil upsetting and finish forging with different parameters were studied from the aspect of the stress and strain field distribution and changing law. The rational forging scheme and parameters were obtained, providing the theoretical basis for the process design of heavy disk forgings.The stress and strain field of wide flat anvil upsetting was analyzed with different initial height-diameter ratio. Results indicate that the hard-deformation zone in double end planes was broad and the proportion was linear increased with reduction ratio. The strain in forging center increased rapidly lead to the sharp decline of deformation homogeneity, causing the layered cracks. In order to get three-dimensional compressive stress in center, control the tangential stress in side surface and avoid the strain condition causing cracks in center, the reduction ratio must be controlled in a rational range.Inorder to solve the deformation nonuniformity in wide flat anvil upsetting, prior upsetting was split into upsetting of frustum anvil and surface flattening of flat anvil. Based on the simulation result of stress and strain field in forging, upsetting and surface flattening were respectively studied from the parameters of frustum degree, reduction ratio, rotation mode of flat anvil and the down anvil shape. The dead zone of double end planes was deformed apparently by frustum anvil, and the range of large deformation was increased, resulting into a high deformation uniformity; the forging load and tangential stress in side surface were decreased meanwhile. As for the billet of Ho/Do=2.0, the parameters of 60% reduction and 14°-15° frustum anvil was rational. In surface flattening, using up narrow flat anvil and down frustum anvil with the flat edge rotation model lead to a three-dimensional compressive stress in center and deformation uniformity.4 parall anvil forging schemes and 2 rotation forging schemes of finish forging were simulated and analyzed. Results indicate that symmetrical parallel anvil process made forging center get a high mean press stress state, contribute to close the defects; crossing configuration in adjacent pass can increase the deformation uniformity and decline the tendency of crack in forging center. The parameters with 15% reduction and the feed value exceeding critical value resulted into deformation uniformity and compressive stress state.