Formation Mechanism And Control Of Geometric Defects In Electric Upsetting-forging Of Large Size Valve Billets

In the forming process of the valve parts,the electrothermal upsetting process,as an important process step,has a very important impact on the yield and performance of the valve parts.However,due to the unreasonable setting of technological parameters in the process of electrothermal upsetting,it is easy for electrothermal upsetting parts to produce various undesirable deformation or even defective structure.For the improvement of forming quality of valve parts,we must rely on systematic and detailed research.In addition,there are several process parameters which affect and restrict each other in the process of electric upsetting.The regulation of parameters is a common problem in actual production.Therefore,the regulation and collocation of different technological parameters in the process of upsetting are of great theoretical demand and practical significance.In this paper,the rules of process parameters are systematically studied for the defective structure of nickel-based superalloy valve in the actual forming process.According to these theoretical studies,targeted optimization schemes can be obtained,which provides theoretical basis and theoretical guidance for actual production.The major work and conclusions of this paper are as follows:(1)The feature of temperature,resistance and deformation in the process of electric upsetting,the analysis of defects and formation causes,the solution of multi-field coupled electrothermal force in the finite element solver and the principle of rigid-plastic model are explained.(2)The finite element model is established according to the various defects in the process of electrothermal upsetting,and the effect of defect structure on the process of die forging is analyzed.(3)A multiphysical field coupled finite element model based on finite element software MSC.Marc is established.The model solves the complex contact and boundary conditions,as well as the problems of non-linear loading by current and upsetting force.(4)Designing upsetting force and current schemes with different loading modes,studying the temperature,deformation and defect structure changes during the process of electrothermal upsetting under different loading schemes,and summarizing the influence and regularity of technological parameters in the process of electrothermal upsetting.(5)According to the influence of technological parameters on the upsetting process,the response surface of initial current,peak current and initial upsetting force to defect structure is established by designing experiments,and the optimum technological parameters can be obtained according to the response surface.In addition,the simulation of the die forging process of the valve parts is completed according to the actual production conditions,and the manufacturing validation study of the electric upsetting process and the die forging process is carried out based on the optimized process parameters.