Grain Refinement Of Metal Tubes With Cyclic Rotating Bending Process

The hollow components that were produced by bending,cutting and bulging or other methods have been applied to the field of transport machinery manufacturing,which promote the application of metal tubes in the field of modern industry.The weight of transportation machinery can be greatly reduced by the application of metal tubes.To ensure the safety and reducing the complexity of the manufacturing process,the metal tubes that were used to produce hollow components must have high strength,meanwhile,good mechanical and forming properties are also needed.However,the metal tubes produced with the existing technologies are often accompanied with the grain coarsening,uneven microstructure,and fibrous micro structure as well as poor mechanical properties.This limits the application of metal tubes in industry severely.On the other hand,this is a serious waste of existing resources.Therefore,how to use a simple and universal method to eliminate microstructure defects existing in the metal tubes,and improve the comprehensive mechanical properties is the problem needs to be solved urgently.Research contents of this paper belongs to the projects which are supported by the National Natural Science Foundation of China(Grant No.51304046)and the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20130042120031).Cyclic rotating bending(CRB)process is newly proposed in these projects to refine and control the microstructure as well as improve the mechanical properties of metal tubes.The microstructure evolution in the deformation process under different experimental conditions was focused on in this paper.The main contents of the research are summarized as follows.(1)To confirm the general applicability of the CRB to the different kinds of metal tubes,three kinds of materials of H65 brass,6061 aluminum alloy,STKM17C were used to carry out CRB process.The experimental results under the combination of multiple experimental conditions were successfully obtained.(2)The microstructure evolution of metal tubes including grain size and distribution,grain orientation changes was studied under different cyclic rotating bending deformation conditions(including deformation temperature,displacement of upper plate)with the optical microscopy and EBSD technology.(3)The mechanical properties of selected sample after the cyclic rotating bending process were studied with a tensile test machine at room temperature.The influences of different experimental conditions on the microstructure and mechanical properties of metal tubes in the cyclic rotating bending deformation process were obtained by analyzing the experimental results of selected sample.(4)The cyclic rotating bending process is found to be able to refine the grain structure and improve the mechanical properties of the metal tubes by the analysis of the experimental results.