Effects Of Process Parameters On Microstructure Of Workpiece In Closed-open Joint Rolling

As a new type of shaft forming technology proposed by our project group,closed-open joint rolling can effectively solve the problem of the bottleneck of the material utilization rate(usually no more than 85%)in the conventional cross wedge rolling(CWR).The study of the molding process has practical engineering significance an application value to save the cost and improve the efficiency.The rolling technology needs to have a certain guarantee for the performance of the products at the time of meeting the size requirement.The closed-open joint rolling with more process parameters combines with two technology of closed and open rolling.The effects of process parameters on microstructure of rolled piece are studied,which helps to control the change of microstructure in the process of rolling and ensure the mechanical properties of the final product.In this paper,the structure of the die in the closed rolling is improved and the influence of the process parameters on the microstructure of the rolled piece is studied by means of numerical simulation and experiments.42 CrMo is taken as the research material.The finite element model of coupled heat,force and microstructure is established by using the existing constitutive model,dynamic recrystallization model and grain growth model in Deform-3D.The distribution of the temperature field,the stain rate field and the microstructure field is analyzed.The influence law on the average grain size of the workpiece by the rolling temperature,roll speed and remain length of open-rolling is obtained by the method of single factor.The influence of the section shrinkage,the forming angle and the broadening angle of both closed rolling and open rolling on the average grain size during the process is summarized by the uniform test design.At the end,the closed-open joint rolling experiments and the metallographic experiments are carried out.The results of the experiments are analyzed to verify the reliability of finite element simulation.The research results of this paper provide the guidance advice for improving the microstructure property,optimizing the process parameters and controlling the final product quality.The research findings offer a theoretical basis for further extension of closed-open joint rolling without stub bar.