Study On Quenching Residual Stress And Cold Compression Reduction Process Of 7050 Aluminum Alloy Frame Forgings

Solid solution quenching heat treatment is an important part of7050 aluminum alloy manufacturing process,but quenching treatment will introduce a large number of residual stresses in the material,which not only affects the service performance but also affects the manufacturing process.Therefore,it is very important to study the quenching residual stress level and reduction process of aluminum alloy.In this paper,the finite element simulation model of frame forging quenching is established.Based on the quenching analysis results,the cold pressing simulation model is established to study the stress reduction of frame forgings with different cold pressing processes.The optimization of process parameters is verified by various kinds of stress test experiments.The main research contents of this paper are as follows :1.The mechanical parameters,thermal parameters and heat transfer coefficient material parameters of 7050 aluminum alloy were tested by experiments.The relationship between aluminum alloy material parameters and temperature is established,which provides reliable material parameters for the accurate establishment of frame quenching finite element model.2.The quenching finite element model of frame forgings was established,and the influence of water entry mode and medium temperature on the quenching residual stress of forgings was carried out.The temperature field and stress field of forgings during quenching were analyzed.The water inlet mode has a great influence on the residual stress distribution of frame parts.The higher the medium temperature is,the lower the quenching residual stress is.The quenching residual stress is symmetrically distributed along the thickness,showing the distribution state of ‘external pressure and internal tension’.The correctness of the quenching model is verified by X-ray diffraction,blind hole method and contour method.3.Based on the initial quenching stress field,the finite element model of 7050 aluminum alloy forging was established,and the effects of cold pressing mode,friction coefficient,reduction and non-uniform reduction process on stress reduction were studied.Different cold pressing methods can significantly reduce the stress of window frame forgings.The results of multi-step cold pressing show that the stress reduction rate is over 75 %when the uniform pressure is 2 % and the friction coefficient is 0.1.4.The cold pressure experiment of frame forgings was carried out by using the optimized process.The accuracy of the cold pressure finite element model of window frame forgings was verified by comparing the simulation stress with the experimental stress.