Evolution Law Of Longitudinal Weld During Extrusion Of Automobile Hollow Aluminum Profile

With the intensification of greenhouse effect and the shortage of fossil energy,the global ecological environment and future development are not optimistic,so it is imperative to reduce energy consumption and carbon emissions.Vehicle lightweight can effectively reduce the quality of vehicle preparation,thus reducing fuel consumption and exhaust emissions.Aluminum alloy profile has the advantages of high specific strength,easy to form,low price,easy to recycle and so on.It is the ideal material to realize the lightweight of automobile body.Hollow profiles occupy a large proportion in automotive aluminum profiles.Hollow aluminum profile often by shunt extrusion molding,forming process of metal materials first shunt and then welding,will inevitably produce longitudinal weld,and poor welding quality will greatly affect the performance of the profile.Based on the actual production of a square tube profiles in longitudinal seam problem,this paper uses the means of numerical simulation,studies and summarizes the influence factors and laws of the longitudinal seam weld quality,taking the automobile scaffold material as the research object to design and develop the extrusion forming process and die structure.The main work and conclusions are as follows:(1)Taking the square aluminum profile as the research object,the microstructure and strength properties of the longitudinal weld area of the actual production product were studied.Combined with the actual forming process and numerical simulation,the reason why the mechanical properties of the longitudinal weld area were lower than that of the base metal area was analyzed.(2)The influence of aluminum alloy material,extrusion process parameters and extrusion die structure on longitudinal welding during extrusion were studied by using the finite element simulation technology and the control variable method.The results show that better welding quality can be obtained during the forming process of 6061 and 6082 aluminum alloys.The change of process parameters such as extrusion speed and billet heating temperature will affect the welding process.Increasing billet heating temperature and decreasing extrusion speed will improve the welding quality.The change of mold structure shape and size,such as welding surface position,welding chamber height and welding angle,will also have an impact on the welding process.The welding quality can be improved by choosing the appropriate welding chamber height and welding surface position and reducing the welding angle.(3)The above research results were applied to the extrusion process and die design of a hollow bracket profile for an automobile,and the process parameters and die structure were improved by combining response surface method and genetic algorithm.The improved process and the shape size of the product formed by the die met the requirements.OM,SEM and other means were used to observe the microstructure of the longitudinal weld area of the profiles and analyze the tensile fracture morphology.It is found that the mechanical properties of the longitudinal weld area of the improved profiles are good and meet the requirements of use.