Study On The Mechanism Of Hot Ring In Temperature Gradient Rolling For Large-scale Aluminum Alloy Ring Used In Aerospace

With the increasing development of national aerospace science and technology projects,the demand for new-generation launch vehicles has become increasingly urgent for large-scale lightweight circular structures.Due to its low density,high strength and good plasticity,aluminum alloys are widely used in aerospace applications.High-performance large-scale aluminum alloy ring parts are mainly used for key structural components such as connecting frames,transition rings,transfer frames,and fuel tank connection rings between the rocket bay sections.Ring rolling,one of plastic processing technology,is an advanced manufacturing technology.With ring rolling equipment,it makes ring shape workpiece thinner,the diameter bigger and section profile formed.In the ring rolling process,especially for large-scale annular parts,when the ratio of the wall thickness of the ring to the contact arc length is larger,the rolling deformation is concentrated on the inner and outer surfaces of the ring.After multi-pass radial compression,it results in circumferential elongation and axial compression of the ring's core,causing a fishtail defect on the ring's end face.At the same time,because ring diameter and wall thickness is larger,the internal and external deformation is not uniform,and the permeation of the heart is not sufficient,resulting in defects such as large residual stress of the ring and coarsening of the core grains,which are difficult to be effectively controlled.Regarding the 2219 aluminum alloy material as the research object,through the thermal compression simulation test,the effects of deformation temperature,strain,and strain rate on the plastic rheological behaviors are studied.Based on the True stress True strain curve of the material,the constitutive equations and processing maps of the material were determined.Through the analysis of the processing map,the suitable material processing window can be intuitively obtained,and the optimal processing area of the 2219 aluminum alloy material under different strains is obtained.Aiming at large aluminum alloy rings,this paper presents a method of hot ring rolling with temperature gradient.Based on ultra-fast cooling technology,high-speed jet nozzles are used to rapidly spray cool the inside and outside circumferential surfaces of hot-rolled blanks to avoid film boiling and transition boiling caused by low cooling rates,and to directly enter the high-heat-exchange nucleate boiling stage.The temperature gradient of the hot-rolled blank from the centripetal portion of the inner and outer circumferential to the surfaces is rapidly increasing.Based on the ABAQUS finite element software,the constitutive equations of the material are introduced into the VUMAT subroutine.And the finite element models for the normal and the temperature gradient hot rolling of the large-scale aluminum alloy rings are established.Through the simulation and analysis of the hot ring rolling process,the forming mechanism of large-scale aerospace aluminum alloy ring during hot ring rolling with temperature gradient is identified,and the effect of the temperature gradient rolling on the rheological inhomogeneous behavior and the macro forming quality of the annular parts is revealed.The theoretical basis is provided by optimizing the forming process parameters of large-scale aerospace aluminum alloy ring.