Development prospect of low pressure casting technology

According to the principle of low pressure casting, the key of the process is the filling process. The solution of the turbulence problem of the liquid metal in the rising phase and the effective control of the fluid velocity in the filling phase are the key to ensure the quality of the castings. In the phase of liquid lift filling, compared with gravity filling, the dynamic force of liquid metal flow is different. The filling process of low-pressure casting is to control the gas pressure applied on the metal surface and push the liquid metal into the cavity along the liquid lift pipe. In order to realize the low-pressure casting preparation of large-scale thin-walled complex components, the relevant basic theories need to be further studied, the process and equipment need to be continuously improved in practice, in addition, the selection range of filling materials needs to be expanded and the corresponding materials need to be systematically studied. At present, the following problems need to be solved as soon as possible:

(1) The computer numerical simulation technology can not only help to find out the cause of the defects in the filling process, but also provide an effective optimization design of the filling parameters for the low-pressure casting process. Therefore, it is very important to study and establish a metal flow model which is consistent with the actual filling process for the accuracy of the numerical simulation results. It is necessary to fully consider the influence of other fluids (such as air flow in the cavity and air flow in the protective atmosphere) on the metal flow in the filling process, The interaction mechanism of multiphase fluid is studied systematically to solve the problem that the numerical simulation results are not consistent with the actual filling process, so as to improve the production efficiency and casting quality of low-pressure casting.

(2) The alloy system suitable for low pressure casting was developed. For a long time, the materials used in the low-pressure casting process are mainly the traditional casting aluminum alloy system and magnesium alloy system. It can be considered to design the grain refinement additive materials based on the traditional aluminum alloy and magnesium alloy system in combination with the basic theory of material thermodynamics. In this respect, there are already al-10fe-3.2p grain refinement additives [39], and more alloy system grain refinement additives should be further developed; In addition, the research and development of low-pressure casting of other alloy systems besides magnesium and aluminum alloy should be accelerated to meet the needs of industrial wide application.

(3) The newly developed low-pressure casting technology is applied to the preparation of large-scale thin-walled complex components. For example, the continuous low-pressure casting technology developed by Huazhong University of science and technology [46] divides the existing traditional low-pressure casting and heat preservation crucible into three independent crucibles, the bottom of which is connected by the aisle, and respectively completes three main actions: feeding, liquid pressure and liquid lift pouring. The improved technology ensures the continuity of production and significantly improves the production efficiency. By combining the traditional composite preparation process with the low-pressure casting technology, high-quality composite materials can be prepared. For example, the aluminum matrix composite materials can be prepared by infiltrating molten aluminum alloy liquid into fecrsi metal fiber porous preform by the low-pressure casting method in the National University of gyeongshan, South Korea [20], It is expected to improve the comprehensive properties of composite materials.