Study On Forming Technique And Quenching Processing Of Large Aluminum Forgings With Multi-rib And Thin-web

With the rapid development of the aerospace industry,the requirement of lightweight,large-scale,integrated is becoming more and more urgent.As one of the most important structural materials,aluminum has been applied in aviation field widely because of its light weight property.In order to lighten its weight further,aluminum alloy component with web-rib section has been designed usually;However,un-filling,partial draining and large load often appear in the forming process for this kind of forgings.Due to the large size and complicated structure,a lot of residual stress exist in the internal of the forging during quenching heat treatment,which reduces the dimensional stability of the part in the subsequent machining.In this work,a certain large 7050 aluminum alloy component with multi-rib and thin-web structure is taken as an example to solve the above question.With the CAD software,the structure of forging,finish and preform mould have been designed firstly;Then,the numerical simulation of preforming and finish forming is preformed via CAE software to predict the possible problems during the process of forming,and optimization is taken timely aiming at these problems.Meanwhile,the process of cold forming to eliminate residual stress has been researched by using CAD/CAE software;And at the same time,the impact on residual stress and properties for forging of different quenching medium has been explored combining with experiment.The main conclusions of this paper are as following:(1)In this work,the structure characteristics of the part is analyzed firstly,and the cold forging is designed based on three dimensional modeling software.Then,the forming process has been obtained after considering the structure feature of forging and the initial finite element model has been established as well.The filling performance,velocity field and forming load have been analyzed according to the FEM results.The optimization scheme of pre-forging has been proposed aiming at the problems,and the hollow structure of forging is finally identified through CAE analysis.In the next work,the finite element model of pre-forging is established with CAD/CAE software,and the original billet is achieved through numerical simulation analysis.(2)Considering that the forming quality,especially forming force,is affected by the process parameters deeply,the influence of different initial temperature of billet,mold temperature,forming speed and lubrication on finish forging load are investigated in this work via finite element method.Result shows that: improve forging temperature,mold temperature or lubrication condition can effectively reduce the finish forging forming load.However,the forming load will increase if the speed of hydraulic press is too slow or too fast.(3)Taken the cross section of forging,the effect of different cold deformation on transition fillet and reinforcement on residual stress within the forging has been researched in this paper.It shows that 4% cold deformation on transition fillet can effectively eliminate the residual stress.(4)The influence of air,water,salt water and different concentration of PAG polymer on the residual stress of 7050 aluminum alloy is studied.The volume fraction and morphology of the second phase particles for different samples are effected by quenching medium significantly,and the mechanical properties of samples are different from each other as well after T74 aging heat treatment.The quenching residual stress,microstructure morphology and mechanical properties are related with cooling property of medium closely.