In the past 20 years, China has vigorously developed advanced aerospace manufacturing technology, and the design structure of parts is increasingly complex, and the manufacturing accuracy is increasingly improved. Due to the availability of complex and fine aerodynamic shapes, the mass production of key aerospace components usually adopts investment casting technology. For investment castings, the dimensional accuracy can reach 5 ‰ of the nominal size, and the roughness is Ra0.8~3.2 μ m. Near-net shape castings with almost no machining can be obtained. However, for castings with large size and complex structure, the systematic and complex thermal field of investment casting technology can easily lead to defects in the internal and thin-walled parts of castings. Usually, a large number of tests are needed to optimize the process and improve the qualification rate.
Due to the high cost of investment casting test, the numerical simulation technology has been rapidly popularized in recent years, and multiple rounds of optimization have been obtained before the process is determined, which helps to reduce the cost of materials, manpower and time. In the process of determining smelting parameters, numerical simulation research shows that when the input current is constant, increasing the input frequency will weaken the effect of electromagnetic stirring, but has little effect on the temperature of the melt; When the input frequency is fixed, increasing the input current will increase the melt temperature and speed up the melt flow. During the production process, the input frequency and input current can be controlled to formulate a good smelting process. The deformation of wax patterns is also an important factor that affects the size of castings in investment casting. From the numerical simulation and test results, the shrinkage rate predicted based on the deformation of wax patterns is only 0.32% less than the test results, which is of great significance to predict the shrinkage of investment castings.
The accuracy of temperature field calculation can be verified by predicting the shrinkage porosity and shrinkage cavity of investment casting through the flow field and temperature field, and a more optimized process plan can be designed based on the comparison between the measured temperature and the numerical simulation results. In the process of numerical simulation, the thermo-mechanical coupling method can also be used to obtain the dynamic change and distribution of temperature, stress and strain of the casting, such as the simulation of differential pressure casting – air cooling – quenching process of automobile steering knuckle. Scholars improve the casting process by replacing process trial and error with numerical simulation, and use simulation calculation to design the manufacturing scheme of complex precision parts, providing reference data and guidance for actual production.
Turboguide is an important part of aeroengine, with compact structure and complex structure, which is a typical representative of aerospace parts. In view of the casting defects of the turbine guide in the actual casting process, the physical and numerical models of the investment casting process are established, the temperature field analysis and shrinkage porosity prediction are carried out, and the optimized production process is obtained through the verification of X-ray nondestructive testing.