Research On Centrifugal Forward And Backward Composite Extrusion Process Based On Hollow Billet

In recent years,as the fields of transportation,aerospace,and new equipment manufacturing have developed towards modularization,integration,and lightweight,the demand for high-performance and low-cost development of thin-walled cylindrical components,which are widely used in engineering,has become increasingly high.This article takes the "H" shaped cylindrical parts with a central hole as the research object,selects 7075 aluminum alloy,and proposes a centrifugal forward and backward composite extrusion forming process based on hollow billets to address the problems of complex processes,low strain levels,and difficulty in meeting service conditions in traditional preparation of "H" shaped cylindrical parts with a central hole.This process achieves the formation of "H" shaped cylindrical parts with a central hole while avoiding multi-pass heating of the billets.Based on the actual production situation and the requirements for strengthening and toughening the extruded parts,the process flow design from the blank to the overall forming of the extruded parts has been completed.By analyzing the metal flow law of composite extrusion of hollow billets,the metal flow characteristics during the composite extrusion process were mastered.The formula for calculating the extrusion force during the extrusion process was derived using the upper limit method.The differences between traditional solid billets and hollow billets were analyzed.By changing the process parameters during the extrusion process of hollow billets,the ultimate goal was to increase the average equivalent strain,reduce peak load,and change the upper and lower forming height.The degree of influence of a single process parameter on the objective function was obtained.By combining orthogonal experiments with numerical simulation,the process parameters such as punch feed speed,friction coefficient,and billet aspect ratio were first optimized,and the optimal process parameters were given.Secondly,a height prediction model for the "H" shaped cylindrical part with a central hole is provided through calculation.According to the optimal process parameters,physical forming experiments were conducted to prepare extruded parts with good surface quality.The accuracy of the forming force calculation formula and height prediction model was verified.By sampling and observing the microstructure of the final extruded parts,the grain structure distribution,grain size distribution,and grain boundary orientation difference angle in the extruded and heat treated states were studied.The mechanical properties of the extrusion direction were tested through tensile experiments.Compared to the extrusion state,the T6 state greatly improved anisotropy,elongation at break,tensile strength,and yield strength.