Forming Conditions And Die Structure Of Multi-roll Rotary Forging For The Super Large Ratio Of Diameter And Thickness Circular Plates

The super large ratio of diameter and thickness circular plates are widely used in the fields of aerospace,nuclear energy,deep submarine research and so on.However,the manufacturing process is usually difficult.Multiple conical rollers rotary forging（MCRRF）is a new technology for high performance and high efficiency to manufacture the circular plates.This technology not only retains the advantages of traditional rotary forging,such as saving labor,small vibration and impact,good forming quality and high precision,but also improves the problem that traditional rotary rolling forming cannot form large workpiece due to the limitation of the size of pendulum head.This paper studies the theoretical basis and mold design of this technology,mainly including the following parts:（1）This paper introduces the principle of multiple conical rollers rotary forging,and gives the design method of die structure through geometry and kinematics analysis.On this basis,the deformation characteristics of MCRRF are analyzed,and several main parameters of active deformation area are solved,so as to better understand and control the forming process of MCRRF;（2）By using the knowledge of statics,mathematics and plastic mechanics,the stable rolling and forging models of MCRRF are established,and the theoretical expressions of the two conditions are derived.On this basis,the design requirements of process parameters are given and the influence laws of related die structure parameters and process parameters on these two conditions are analyzed.The reliability of the theoretical analysis is verified by finite element analysis.These two conditions ensure the stability of MCRRF;（3）Finite element model of MCRRF is established,and the reliability of the model was validated by test,on this basis,using the finite element model to study the multiple roll roll system structure of the workpiece in the process of pendulum rolling equivalent strain field,temperature field,equivalent stress field,the forming force and the structure of the artifact ultimately shape,center,thinning degree of influence mechanism.The results show that the roller structure has a great influence on the deformation and temperature uniformity of the workpiece,and the necessity of optimizing the roller structure is determined,while the lower die structure mainly affects the shape of the workpiece and the degree of center thinning,and the parameters of the lower die h_c=H and h_g=H are determined.（4）The optimization objective is to minimize the SDP of equivalent strain uniformity of the workpiece and the structural parameters of the roller system of the die are determined.Using the orthogonal test to determine the cone Angle of second roller,cone Angle of third roller and cone Angle of forth roller as the optimization goal of the most significant roll structure parameters,on this basis,the response surface design,combined with the finite element analysis results to solve the optimal solution,so as to optimize the roll structure.A set of optimal roll combinations were determined asφ₂=59.7°,φ₃=67.2°and φ₄=45.9°.