| Exploration and development of offshore oil and gas fields need to have a large number of the original motivation to provide power. With the progress of science, the growing use of gas turbine compressor units as the key power equipments in the offshore drilling plat form operation have been applied widely in recent years. However, in the process of gas turbine compressor blade production, the forging and heat treatment process will produce a larger residual stress, which makes the blade in the subsequent buckling deformation appeared in the process of machining and eventually lead to a lot of scrap, seriously affected the normal production and delivery of the gas turbine. That is to say, the residual stress generated by hot working is a key factor to the production quality of blade.Therefore, the paper researched the relationship between the manufacturing process、 technology and residual stress of2A02aluminum alloy blade which has high strength, high toughness by using residual stress test method and finite element simulation. The paper put forward the methods to reduce residual stress effectively, and it provided the scientific basis for improving the existing manufacturing technology and the quality of blade.In the aspect of residual stress measurement, through the comprehensive comparison of several residual, micro-indentation hardness method was determined for testing the residual stress of2A02aluminum alloy.And it was appropriated in the the residual stress analysis of the tower or half tower specimens. Subsequently, the blade residual stress was tested by X-ray method compared with the micro-indentation hardness method, the results show that the trend of test results of the micro-indentation hardness method and with the X-ray method are fairly. The micro-indentation hardness method can replace X-ray method testing residual stress when the engineering cases don’t have the test conditions.Firstly, based on the complex production process、distribution and influence factors of residual stress, the forging process of2A02aluminum alloy was studied by using thermal simulation experiment via Gleeble-1500in this paper. The results showed that flow stress of2A02aluminum alloy decreased with the increasing of deformation temperature and increased with the increasing of strain rate. The constitutive equation of the alloy was constructed, so the hot deformation activation energy was obtained to be201.7kJ·mol-1. The microstructure evolution behavior was studied, when the deformation of2A02aluminum alloy was at low level (deformation was10%and20%), the main softening mechanism was dynamic recovery; when the deformation increased to40%, the softening mechanism alloys transformed from dynamic recovery to dynamic recrystallization; when the deformation increased to60%, the dynamically recrystallized grains existed in the alloy. Geometrical dynamic recrystallization was responsible for softening.The residual stress was testing under the different deformation conditions by the indentation method. The results showed that the residual stress of aluminum alloy was increased with the increasing of deformation and recrystallization.Secondly, the residual stress2A02aluminum alloy during quenching process was studied.The experimental analyzed the effects from quenching temperature, quenching holding time and cooling methods to the residual stress. The results showed that aluminum surface residual stress increased with the increasing quenching time and quenching temperature, but the magnitude of change was not great. The residual stress was introduced by water quenching process, it was a kind of thermal stress which produced by the temperature gradient.Finally, the sample surface residual was measured under different aging temperature, and time.The precipitation phase morphology and distribution at aging temperature of170、190℃was observed by means of transmission electron microscope. The results showed that the precipitation phase S with the number, the larger the sizes had a great influence on the residual stress release when the aging temperature is170℃, aging time was16h, and the residual stress reduction to around100MPa. Aging process for reducing residual stress had a certain reduction effect, but there were still remaining residual stress. The effect of190℃ageing process for reducing residual stress was not obvious. In fact, the change of residual stress during the aging process was the process for the decreasing of thermal stress and the increasing of organizational stress.In order to study the influence from the structure complexity and the constraint conditions on residual stress, I designed the tower-shaped and semi-tower-shaped samples. The quench residual stress distribution of tower-shaped and semi-tower-shaped samples is analyzed by micro-indentation hardness method and ANSYS simulation system. The correlation of quench residual stress distribution and geometrical complexity, constrained conditions is revealed. The absolute of quench residual stress decreases with constrained paramenter under the same thickness and the same trend is also observed with sample thickness under the same constrained condition. The thickness is considered to be the key factor for quench residual stress.The simulation concerning the quenching process of the2A02aluminum alloy blades is made by the virtue of ANSYS method. The results showed that the thermal stress of2A02aluminium alloy blade forging during quenching process was more complex with time changing. At the same time, the comparative analysis indicated that quenching temperature about40℃was considered to be optimum for the2A02aluminium alloy. The experiment and simulation results showed that quench stress at the bottom was the maximum and the minimum of quench stress was obtained at the top for this blade forging, and the residual compressive stress of the middle part is between of two. The results obtained by the two test methods were roughly equal, and they were consistented with the trend of the ANSYS finite element simulation conclusion. The paper also suggested that the sensitive position for quench stress was determined to be the bottom of the blade forging. In the engineering practice, under the condition of the given quenching process, the analysis should focus on the residual stressesn at the root of blades. The influence from the compression molding method on residual stress reduction degree was analysed by using the bilinear model and multi linear model of ANSYS simulation system. Obvious effect of redistributing and reducing residual stress was observed with the method of compression by mold. According to the conclusion that the1.56mm compression amount could reduce residual stress obviously in the physical experiment for blade, the moulding pressing method had been verified in the engineering project, and obtained the good results. |
PDF Full Text Request