Study On Continuous Extrusion Welding And Forming Of Aluminum Alloy Based On LLJ400

6063 aluminum alloy is a heat treatable aluminum alloy,with the development of high-speed rail and aviation industry,aluminum alloy has been widely used.In recent years,extrusion products are changing with each passing day and are developing towards the direction of complication,abnormity,large wideband thickness ratio and high precision density.Therefore,continuous extrusion technology is adopted to produce 6063 aluminum alloy products with large wideband thickness ratio.Based on LLJ400 double-groove continuous extruder and using Hyper Xtrude numerical simulation software,this paper analyzes the variation rules of velocity,temperature,flow stress and strain rate inside the cavity in the process of double-bar continuous extrusion of6063 aluminum alloy sheet products.By changing the structure of the die,the influence of the die on the welding index and the mean square deviation of flow rate was studied,and the variation characteristics of the parameters such as pressure,flow stress,temperature and strain rate on the welding surface were analyzed.By means of orthogonal experiment method,the optimal die scheme was found by changing the structural parameters of the extended die,the flow guide die and the preformed die,aiming at improving the welding quality and balancing the flow speed of the product.Finally,the simulation results are verified by experiments.By using the numerical simulation of Hyper Xtrude,the results show that when the expansion Angle of the expansion chamber increases from 90°to 105°,the welding index will decrease gradually,and the influence on the mean square deviation of flow rate is not significant.When the opening width of the expansion die increases from 20mm to 50mm,the mean square deviation of flow rate first decreases and then increases,which has little influence on the welding index.When the height of the baffle block was increased from 2mm to 8mm,the bonding index was gradually increased and the mean square deviation of flow velocity was gradually reduced.When the inclination Angle of the guide cavity increases from 4°to 10°,the welding index is slightly improved and the mean square deviation of flow velocity is slightly reduced.When the height of the guide die and the preform die increases,the welding index increases gradually,which has little effect on the mean square deviation of flow rate.When the thickness of the extruded product is increased from 2mm to 10mm,the welding indexes and the mean variance of flow rate are gradually reduced.Through the orthogonal experiment method,the order of primary and secondary affecting the welding indexes is obtained as follows:Preforming die height(B)>Height of guide die(A)>The height of the baffle block(D)>Width of expansion die opening(C)>The inclination Angle of the mould chamber(E),The optimal combination is A₄B₄C₃D₃E₄;The primary and secondary order of SDV values affecting mean variance of flow velocity is as follows:The height of the baffle block(D)>Width of expansion die opening(C)>Inclination Angle of guide die cavity(E)>Preforming die height(B)>Height of the flow pattern(A),The optimal combination is A₄B₂C₃D₄E₄.According to the comprehensive evaluation,the optimal scheme is A₄B₃C₃D₃E₄.Finally,LLJ400 double-groove continuous extruder was used to conduct experiments,and the unoptimized scheme was compared with the optimal scheme.It was found that the optimized scheme was superior to the unoptimized scheme in the aspects of the microstructure of the weld,the mechanical properties of the weld and the uniformity of the product size,which verified the accuracy of the numerical simulation results.