The Study Of Key Parameters On Thick-wall Tube Forming By Open-die Cold Extrusion With Mandrel

Open-die cold extrusion is a forming process of saving material and high efficiency. The shaft and sleeve parts applied in machine manufacturing, transportation, aerospace and other industries are still produced by pure cutting or hot forging and cutting process now. Materials are wasted seriously, and still it is low efficient. Shaft and Sleeve part is an important part of the machinery manufacturing, its annual output reaches hundreds of millions of tons, it very suitable for open-die cold extrusion production. Open-die cold extrusion is divided into pen-die cold extrusion without mandrel with mandrel open-die cold extrusion by whether the inner hole is constrained or not. A lot of research about the open-die cold extrusion without mandrel has been carried out by this research group. But for sleeve parts with size requirements of inner hole, open-die cold extrusion with mandrel is more appropriate. But research of open-die cold extrusion with mandrel has not been reported in the available literature, open-die cold extrusion with mandrel is researched.The combination of theoretical modeling, numerical simulation and experimental study is used in this article. The main research content and outcomes are as follows:1) Three types of the external contracting, the bore enlarging, the external contracting and bore enlarging are synthesized, forming parameters, mechanics parameters, mold structure parameters, physical parameters and so on is established by the analysis of deformation process.2) Based on the theory of fluid mechanics, a dynamic volume velocity field, is established by combining stream function and upper bound method, then a general theoretical model applicable to three process types is also established.3) Important parameters, such as extrusion, extrusion power, deforming limit and so on, are calculated by using theoretical models established, and the effects of various parameters (aspect ratio, friction coefficient, die angle) on above parameters are explored.4) In the context of theory parameters feasible, a lot of numerical simulation is put up, stress field, strain field, velocity field and strain velocity field are analyzed. And typical parameters are applied to experiments, comparison among theory, simulation and experimental results is analyzed.5) The best die angle and the range of deforming limit under different parameters are determined by lots of above research, a foundation for mould and process design of open-die cold extrusion with mandrel is laid.