Investigation Of Deformation Behavior And Design Of Forging Process For Aluminum Alloy Axis Box

Aluminum alloy forgings have attracted more and more attention in the application of lightweight vehicles for their superiority in light weight,low density,good mechanical properties,corrosion resistance and other excellent performance.High-speed trains mainly focus on the development of lightweight and higher speed.The axis box on the high-speed train is an important bearing component and a transition joint in the movement.In recent years,people prefer using 7050 aluminum alloy which has high-strength and high-toughness to replace the traditional steel and common aluminum alloy in the manufacturing of high-speed trains.Since the 7050 aluminum alloy has poor castability and the axis box is easy to form defects such as shrinkage hole,shrinkage and hot cracks during the traditional casting process,so the forging forming process has become an important method for manufacturing aluminum alloy axis box.But the axis box's volume is large and its shape is very complicated,and defects such as folding and filling dissatisfaction are easily generated during the forging forming process.Therefore,the aluminum alloy axis box's forging forming process is very complicated.However,the current research about this technology is not very sufficient,especially for the structure of die and the design of pre-forgings in different processes.Therefore,the forging process of the aluminum alloy axis box still faces many difficulties and challenges.On the other hand,the current numerical simulation software generally incomplete material database,and the thermal rheological behavior and true stress-strain of 7050 aluminum alloyare not yet provided,which will inevitably affect the accuracy and practicality of the numerical simulation of the forging forming process.Focusing on the existing problems,the objective of this paper is to design the forming scheme and dies of forging for 7050 aluminum alloy axis box.Hot compression experiments of 7050 aluminum alloy was firstly conducted for the establishment of Arrhenius constitutive model with Strain compensation and hot processing map,the stress-strain curves at different strain rates and deformation temperatures were obtained.The temperature and strain rate intervals for the stable deformation of the material were determined.The microstructure changes of 7050 aluminum alloy at different rates and temperatures were studied.Then,the numerical simulation models of aluminum axis box has been established,based on the constitutive model of 7050 aluminum alloy,analyzed the law of material deformation in detail,revealed the influence of shapes of pre-forging and parameters on forging's quality,optimized the shape of pre-forging and the preform process,designed and developed the forging process and dies for 7050 aluminum axis box.A new manufacturing process for forgings of axis boxes combined with forging and extrusion was proposed,ensuring the materials are finally filled.As for the problems of material waste and performance degradation caused by the large hole machining after the unidirectional forging,this paper proposed a bi-directional forging process of the axis box,which realized the large hole of box is formed during forging,this way can greatly improve the material utilization and product's quality.The flow behavior of metal in the forging process of the axle box was studied by numerical simulation method.The deformation law and the distribution of stress and strain were analyzed in forging processes.Based on the above-mentioned regularity study,the bi-directional forging process of the axis box was designed.