Development trend of investment casting technology

With the upgrading and continuous development of aerospace military equipment, civil aviation and commercial aerospace products, higher requirements are put forward for the manufacturing accuracy, forming process, production equipment, mold tooling and equipment automation and intelligence of investment precision casting technology. Investment precision casting needs to continue to improve in intelligence, reliability, accuracy, modularity and other aspects, combined with the current research status in China, Investment casting technology needs to be studied in the following five aspects in the future.

(1) Reliability control of material preparation system. Tracing back to the source, the foundation and core of any key technology is material technology. Without the development and breakthrough of material technology, it is difficult to achieve a qualitative leap in manufacturing technology. For investment casting process, the importance of material technology is self-evident. From the perspective of alloy materials, mold materials, core materials, binder materials and interface materials, the domestic material system is not as rich as that of foreign countries, especially in the details of key material control technology of special molding process. At present, foreign material design has developed from the traditional simple proportion optimization to the level of thermodynamic calculation optimization, molecular simulation optimization, and material genetic engineering design optimization. A large and complete material database has been established. The time from design to comprehensive optimization of new materials has also been shortened from more than a decade to 1-2 years. A variety of new materials have been continuously used in defense and military equipment. In recent years, China has paid more attention to the development of industrial manufacturing technology, but the investment in the research of the materials behind it is not deep enough, and the imitation will only be constantly subject to others. The blockade of material database technology in key materials and commercial material design software also makes Chinese material researchers need to start from the source of material design, improve the systematic research of material preparation system, and establish a complete and reliable material database. Only when the material preparation process is under high reliability control, can the mass production quality of corresponding manufactured products be truly and effectively controlled, The service life of structural components can be fundamentally guaranteed.

(2) Investment casting and forming – bidirectional control. With the increasing requirements for structural design of aerospace service parts, investment casting technology has been showing the trend of structural integration, precision forming and process control precision. When the investment casting process is used to form and manufacture complex components, in addition to ensuring the accurate forming of the structural dimensions of the components, it is also necessary to accurately control the internal structure of the structural components to improve the service life of the components, That is to realize “complete shape control” and “precise control” at the same time. The formability process of aerospace service parts is a process of multi-disciplinary intersection and comprehensive application of various advanced technologies, which realizes the filling, forming, microstructure and structural evolution of materials under the multi-field coupling, especially the dynamic evolution of “temperature – heat – force”. At present, the existing theoretical basis of forming is mostly based on the thermodynamic and dynamic mechanism research under the ideal state of temperature field, gravity field and external force field alone or simply combined, which is quite different from the actual special process forming process of complex components. The special process forming process is controlled by the coupling of multiple fields and affected by multiple factors, but the coupling mechanism and interaction of these factors are not completely clear at present. Therefore, the research on the microstructure evolution, size change, interface reaction, dynamic stress distribution, defect formation and growth mechanism in the precise forming process under the multi-field coupling is of great importance to guide the formability bidirectional control of complex components.

(3) Computer simulation calculation of solidification – microstructure – stress. The gradient distribution of temperature field and the flow pattern distribution of mold filling field in the solidification process directly determine the internal metallurgical quality and microstructure distribution of products. It is very important to control the grain structure in the solidification structure, especially the grain structure in the investment casting of superalloy will directly affect its high-temperature mechanical properties and corrosion resistance. In the past decades, the research of solidification process organization control has been favored by a large number of researchers at home and abroad. A variety of mathematical models and calculation methods have been introduced into the research of solidification process control to accurately predict the heat and mass transfer in the solidification process. Especially in recent years, with the continuous progress of ultra-large computing server technology, computer numerical simulation can convert complex heat and mass transfer processes into simple linear algebraic equations for accurate solution, and accurately and quantitatively describe complex problems, which not only realizes the visualization of the dynamic formation process of solidification structure, It can also quantitatively describe and analyze the dynamic evolution law and action mechanism of “temperature – heat – force” in the solidification process, realize the optimal control of material preparation process parameters, and greatly improve the qualification rate of product structure design and manufacturing process.

(4) Integrated manufacturing of functional organization structure. In order to realize the precise control of the service effectiveness of the product, the organization state of the material needs to be accurately controlled at the micro level, and the manufacturing process needs to be controllable at the macro level. The structural dimension design of the product and the organization state control of the material should be brought into the same design level, and the synchronous manufacturing should be realized at the micro and macro levels, so as to complete the integrated design of “function-structure-manufacturing” of the structural components, Realize the overall precise forming and manufacturing of functional parts. In addition to bearing capacity, equipment components serving in aerospace in the future should also meet the needs of intelligent and functional design. The preparation of materials will no longer be a simple accumulation of single metal materials. In order to achieve functional gradient, the design of materials will be the matching combination of design components with different components. New forming technologies and processes will continue to emerge, and the matching mold and core materials will also usher in revolutionary design innovation.

(5) Product manufacturing life-cycle digital design. The manufacturing of single crystal and turbine blades in the field of aero-engine needs to carry out digital design from the source of product design. The performance testing of the product should be digitally documented throughout the development and service of the product, and the service fatigue life, bearing capacity and durability period under different working conditions should be accurately estimated during the use of the product. At the same time, each process parameter in the production process of the product will be entered into the digital system, With the help of big data analysis, establish the mathematical relationship model between the production process parameters and the comprehensive performance of the product, carry out iterative analysis on the performance design of the product, optimize and improve the production process, and intelligent manufacturing will be the only way to improve the precision and precision investment products in China in the future.

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