Optimized Die Design And Numerical Simulation For Hot Extrusion Process Of The Valve

The valve is the kernel part of an automobile engine. With the development of the engine's coming to the high-speed and high-power direction, the standards, varieties and quantities of the valve are becoming more and more, and the requirement of their mechanical properties are becoming higher and higher. Compared with other manufacturing process, using hot extrusion technology to manufacture valves has a lot of advantages such as higher technologic stability, better products'surface and higher products'dimension precision, better products'structure and mechanical properties and higher production efficiency, et. Nowadays, hot extrusion has become the trend of manufacturing valves especially the valves of the car. Based on the rapid development of our native car's manufacture and the project requirement of the'The Research of the Valve Hot Extrusion Technology and Electric Screw Stress that is taken on by our research team, this paper mostly discusses process optimization and numerical simulation of hot extrusion for the valve DCI11.Although hot extrusion has such advantages, it does have some disadvantages, such as short extrusion dies'life and strict demands of heating. Short dies'life is the main problem which does exist in hot extrusion process for automobile valves. The problem needs to be solved urgently.Based on the summarization of the current status and the developing trend of valve producing technique, the author discusses the principle, characteristics and existing problems of hot extrusion in this paper.Rigid viscous-plastic material model is summarized after an analysis of plastic procedure of metal, constitutive law of one-dimensional viscous-plastic and in complex stress state, flow stress model, the variational principles of rigid viscous -plastic deforming and the finite element formula are emphatically discussed in the article, which offers the theory that the simulation of valves hot forming can be based on.After analyzing the reason and mechanism how abrasion too fast affects the service life of traditional hot extrusion dies, the author summarized four theoretical, semi-theoretical and semi-empirical design methods of impression profile. The author put forward an optimized method based on Series Quadrate Planning Theory and designed the dies of hot extrusion and final forging that have utilized construction.This paper is specially for the short dies'life of DCI11 valves. Based on the above all, by using rigid viscous-plastic material model and thermodynamics coupled FEM simulation, the author simulated the process of hot extrusion and final forging through a commercial software of DEFORM. The result indicates the inner stress field, strain field, strain rate field, damages and temperature distribution and how the metal flows in the part during hot extrusion and final forging deforming procedure, the forming status. The author analyzed residual stress, causation of defect of the work piece, and so on. All of these results can offer a qualitative and quantitative theoretical basis in improving the process of hot extrusion and final forging for valve and prolonging the dies'service life of two procedures.