Research On Extrusion Process And Transverse Weld Evolution Of A Complex Section Aluminum Profile

In the field of automobile manufacturing,lightweight body is one of the important ways to achieve energy saving and emission reduction.Aluminum alloy is one of the most ideal materials for the light weight of automobile body because of its advantages of high specific strength,good machinability,good electrical and thermal conductivity,corrosion resistance and easy recovery and regeneration.The 6xxx series aluminum alloy profiles with complex sections have complex metal flow during extrusion and the corresponding extrusion dies have many uncertainties.It is difficult to successfully test the dies at one time,which affects the trial production time and cost of new product profiles.Transverse weld seams will be formed at the junction of the two billets when the profiles are continuously extruded,the mechanical properties at the transverse weld zone of the profiles will be significantly reduced,and the length of the transverse weld will directly affect the yield of the profiles.Therefore,a complex section aluminum alloy profile used for automobile is analyzed in this paper.Physical experiment and numerical simulation are used to study the extrusion process,die structure and the evolution law of transverse weld.The main work and conclusions are as follows:(1)The thermal stress data of the material at high temperature are obtained by the thermal compression test,and the Arrhenius constitutive equation of the AA6082 alloy is established.(2)The extrusion process of the profile is studied,the finite element model of the profile extrusion process is established,and the influence of extrusion process parameters and die structure on the continuous extrusion process is analyzed.The results show that the shape and size of portholes have the greatest influence on the forming quality of the aluminum profile when the parameters is determined.Reasonable design of the number,shape and size of portholes and the appropriate addition of baffle plates can effectively improve the material flow uniformity of the profile section,meet the quality requirements,and extrude qualified profiles.(3)The influence of the extrusion process parameters and the die structure on the extension length of the transverse weld is studied by the numerical simulation method.It is found that extrusion temperature has little effect on the extension length of transverse weld,proper reduction of extrusion speed is conducive to shortening the extension length of transverse weld.And the extension length of transverse weld can be effectively reduced by improving the die structure and the size of portholes.(4)The mechanical properties,microstructure and tensile fracture morphology at the transverse weld zone of the profile are studied.The cross-section of the transverse weld is observed through optical microscope(OM),scanning electron microscope(SEM)and other means.The results show that,the mechanical strength of the transverse weld zone is significantly lower than that of the main body,and the grain size and fracture morphology are significantly different.