Research On Multi-hole Asymmetric Extrusion Process Of Aluminum Alloy Profiles For Automobile Door Frame Exterior Trim

Aluminum alloy is widely used in automobile industry because of its low density and corrosion resistance.Aluminum alloy profiles represented by exterior decoration of automobile door frame are generally characterized by thin wall,thin cross-sectional area and complex shape.It is very suitable for the use of multi-hole extrusion to improve production efficiency.However,in the multi-hole extrusion,the uneven distribution of velocity in each hole is common,which makes the extruded profiles easily warped or even bent.At present,the problems of low yield and high cost of this kind of profile extrusion have seriously restricted the production process.The study is conducted on the multi-hole extrusion of BEA191-B9 automotive door frame exterior trim aluminum alloy profile(material is AA6063).The main contents are:selecting the appropriate number of die holes and initial design of the extrusion die;simulating and analyzing the velocity and temperature fields of extrusion to optimize the die structure parameters;using the simulation analysis method to select the appropriate preheating temperature and extrusion ram speed,and verifying the simulation results by experimental methods.Firstly,according to the extrusion ratio and the size of the extrusion pressure,the number of die holes was selected as 6.According to the characteristics of the profile crosssection,the length of the bearing was initially designed,and the die holes were arranged asymmetrically to complete the initial design of a six-hole extrusion die.Secondly,the velocity field of the extrusion was simulated by Altair Inspire Extrude Metal software.The effects of bearing length,center distance and feeder holes size on the exit velocity distribution were analyzed separately.Taking into account all the influencing factors,the maximum average velocity difference between each die hole and the maximum velocity difference of each die hole was used as the optimization target.The optimization results show that the difference of the average flow rate of each hole of the six-hole extrusion die is within 1 mm/s,which meets the flow rate control requirements.Then,the temperature field of extrusion is simulated by Altair Inspire Extrude Metal software,and the effects of the preheating temperature of the extrusion container,billet,extrusion die and ram speed on the extrusion temperature were analyzed separately,and a set of suitable parameters was selected through orthogonal experiments.The final process parameters were determined as the preheating temperature of the extrusion container at450 ℃,the preheating temperature of the billet at 470 ℃,the preheating temperature of the extrusion die at 480 ℃,the ram speed at 3 mm/s.The average extrusion exit temperature was controlled at 524.3 ℃,and the production requirements were achieved.Finally,based on the results of the simulation analysis,the die structure was optimized and the experimental dies were made.The extrusion process parameters obtained from the analysis were selected for extrusion experiments,and metallographic microstructure analysis was performed.The experimental results showed that the profiles were extruded smoothly,and the extrusion speed difference and surface quality of each hole met the production requirements,which verified the correctness of the analysis results.