Numerical Simulation And Experimental Study On Cold Extrusion Forming Of 3003 Aluminum Alloy Rectangular Box Parts

With the proposal of the goal of peaking carbon dioxide emissions and carbon neutralization,the electric vehicle industry is developing rapidly,and the demand for power battery case is increasing.At present,multi-step deep drawing process is usually used to form aluminum alloy battery shell in China.However,there are many problems in this process,such as too many forming processes,long time consuming for die matching in different processes,and high difficulty in die debugging.There have been researches on cold extrusion + thinning drawing process for forming power battery case in foreign countries,but there are few related researches in China.In this paper,cold extrusion of3003 aluminum alloy rectangular box battery case was studied by numerical simulation and forming experiment.The influencing factors of cold extrusion forming process were analyzed,and cold extrusion die was designed and improved.Through numerical simulation and forming experiment,it was determined that the best condition of workpiece is formed by using flat top blank and vertical working belt punch.Through the analysis and comparison of microstructure and hardness of 3003 hot rolled aluminum alloy before and after annealing,it was concluded that 3003 aluminum alloy billet after annealing at 460? for 8h is more conducive to cold extrusion.Based on the analysis of the problems of the test piece formed by the guide pillar and guide sleeve mold base,the die positioned by unloading device was designed.According to the problems discovered in the experiment,the positioning mode of die was improved,and the sheet positioning die was designed,which could accurately control the gap between punch and die and was easy to operate.By analyzing and comparing the simulation results of cold extrusion forming of battery case with uneven gap between punch and die,it was concluded that the formed part does not meet the precision requirements when the gap between punch and die is more than 0.05 mm.The optimum fit size and guide length of the die structure for the matching and positioning of unloading device were determined by calculation.The simulation results of cold extrusion of battery case with different side wall thickness were analyzed and compared.The results showed that it is difficult to directly form the workpiece with a side wall thickness of 0.6 mm in one cold extrusion process.The forming process was modified to one cold extrusion for forming part with wall thickness of 1.0mm followed by one thinning and deep drawing process to obtain the shell with wall thickness of 0.6 mm.Through numerical simulation and forming experiment,it was confirmed that the lubrication effect of graphite + engine oil lubricant with smaller friction coefficient is better than that of zinc stearate lubricant.In this paper,when the extrusion speed is 7mm/s,it is suitable for forming cold extrusion parts with wall thickness of 1.0mm.Through strength check of die,it was calculated that the Cr12 Mo V punch with 61 HRC hardness after heat treatment does not lose stability and the 5Cr Ni Mo upper and lower base plate which hardness is 50 HRC after heat treatment had no yield deformation in the experiment.