Numerical Simulation On Forging Process For Integrated Head Of RPV

The integrated head which is obtained by forging process is one of the most important equipment in the nuclear power forgings which demand good mechanical properties. It is helpful for the process designing through the numerical simulation which can improve the efficiency and shorten the development cycle. In this paper, numerical simulation for the forging process is completed by which can predict the problems in the actual forging ahead. The main results are as follows.The flat-bottom pot with good shape can be obtained from either constant temperature conditions or inconstant temperature conditions in the first stage. Under Constant temperature conditions, the diameter at the bottom of the basin is more than 4700mm, and the height is about 1300mm, with the thickness of 860mm. When the conduction of heat is considered, the diameter at the top of the flat-bottom basin is more than the one under the constant temperature conditions, and the height of the flange decreased 60mm-100mm more. The results show that the distribution of efficient strain after a forging circle is inhomogeneous both under constant temperature conditions and inconstant temperature conditions, the deformation of the flange with constant temperature conditions which is distributed as rings is higher than that under inconstant temperature conditions which is distributed as layers. When the top die worked per pass, the hydrostatic pressure in forging within the formation zone is similar with an ellipsoid shape, and its long half-shaft on the anvil along the length direction, the short axle direction along the width of the anvil, and the shape changes with the increased value of the press. Under constant temperature, hydrostatic pressure distribution is less than that with inconstant temperature conditions. According to the characteristics of forging deformation, it is divided into two steps at the second stage. In the first step, the hydrostatic pressure at the bottom of basin is "dumbbell" shape, which is changed at the second step. The value of hydrostatic pressure under constant temperature conditions is larger than that in the inconstant temperature conditions. After the completion of forging under constant temperature, the efficient strain of the flange is 8.42% to 54.1% by contrast with the value of 1.71% to 62.2% under inconstant temperature condition. It shows that the height of the flange reduced 60mm-100mm compared with the one under the constant temperature conditions in the first stage. It is advised that the height of the original billets should be increased to ensure that the final upper and lower bottom of the flange has sufficient allowance. The results show that the grain size of the flange is refined by 1-2 grades after the second stage. In order to maintain the grain size, the holding time should be controlled within 2 hours before the stretching process, and the heating temperature must be less than 1200℃in other forging stages, which will be great helpful for controlling the grain size. In the stretching process, the " step " have been caused by the uneven stretching deformation, which lead that the thickness of the large deformation zone decreased too much. The "step" issue is taken over by optimizing the parameters of the basin. The results show that the distribution of the thickness for the cap is improved after the solution. By contrast with three different stretching values, it is recommended that the value for stretching should be around 760mm.