Forming Method And Experimental Research For Manufacturing Tubes With Nanocrystalline/Ultra-fine Grain Structure By Stagger Spinning

Power spinning is the most economic and fast method for producing thin rotationalsymmetry product because this sort of technology contain a bunch of advantages such as highaccuracy, great smoothness, high material utilization, excellent performance and so on, sopower spinning has played a great important part in many departments in our country. Withthe development of precision form technology, technology for producing certain product hasbeen asked for advanced requirements. With the nanocrystalline/ultra-fine grain materialsdeep research and the development of its technology in recent years, the method, using severeplastic deformation for nanocrystalline/ultra-fine grain structure to improve thecomprehensive properties of materials, has become a significant subject that the numerousmaterial scholars pay a attention to. Facts have shown that the nanometer metal by severeplastic deformation has many attractive performance characteristics and developmentprospect, which is considered one of the most effective methods to realize thenanocrystallization of block metal materials. This paper is financially supported by theNational Natural Science Foundation of China (NO.51075153) and the National NaturalScience Foundation of GuangDong province (NO.10151040301000000) Research on themethod and forming mechanism for nanocrystalline/ultra-fine grain tubes by powerspinning.In this paper, the nanocrystalline/ultra-fine grain tubes by stagger spinning are theresearchful central content, the reasonable process plan of stagger spinning was determinedand optimization algorithm was used to optima spinning process, researching the effect ofgrain grain refinement of spinning parts by the severe plastic deformation in the end. Themain research contents and conclusions of this paper are summarized as follows:Firstly, based on the theory of stagger spinning and design experience of productiontools, the production tools have been designed for spinning, and the reasonable processparameters were determined to research the forming process. The research providestheoretical foundation for experimental study of the stagger spinning forming method, it isvaluable on both theory and practical application.Secondly, this paper adopt orthogonal experimental method and take the ovality, straightness and wall thickness deviation as indexes, and analyse the process parameters oftubes stagger spinning forming. The result shows that in the processing of tubes staggerspinning forming, the influence sequence of the ovality and straightness is: feed rate>totalthinning ratio>axial offset; the influence sequence of the uniformity of thickness distributionis: total thinning ratio> feed rate> axial offset. By comparing these tubes form the orthogonalexperiment, analyzed the parameters influence law of the spinning defects, such as surfacefinish, bellmouth and so on.Thirdly, the orthogonal experimental design and the optimization algorithm of SVM(Support Vector Machine)+GA (Ganetic Algorithm) are integrated to optimize processparameters of tubes by stagger spinning, taking the feed ratio, total thinning rate and Axialoffset as optimizing parameters, the ovality, straightness and wall thickness deviation of thespinning tubes as optimizing objectives. Firstly, the nonlinear mapping models of SVM wereestablished bsed on data above orthogonal experiment. Secondly, through optimizing themodel by useness of GA, the optimum process parameters of stagger spinning have beengiven. At last, the verification tests are made using the optimized process parameters，theresults show that optimization method is reasonable.Fourthly, the analysis of the factors which may affect the mechanical property ofcylinder product and the law of the changing of property are significant for research.Therefore, test the property of20steal cylinder product after cold power spinning throughtensile and hardness test and the relationship between property and thinning ratio is describedby making curves. And obtain microstructure of different thickness part for20steal cylinderproduct through microscope and SEM (Scanning Electron Microscope). Test the changing ofgrain size of different thickness part for20steal cylinder product after cold power spinningwith microstructure, then the process of textures’ changing and the affection for organizationand textures to property are analyzed.