The mold filling process has a great influence on the quality of iron mold sand coated castings, which is one of the key factors to control the quality of iron mold sand coated castings. Generally, the filling process of iron mold sand coated casting requires it to ensure the rapid and stable filling of liquid metal; It is conducive to the concentration and elimination of slag and gas in molten metal; The temperature field distribution in the mold cavity is adjusted to make the iron mold sand coated castings cool and solidify according to certain solidification rules, which is conducive to the densification of iron mold sand coated castings. If serious turbulence or eddy current occurs in the mold filling process, it may lead to defects such as pores, slag holes, shrinkage holes, cracks, sand inclusion and slag inclusion, which directly affect the quality and yield of iron mold sand coated castings. Most casting defects are formed in the tens of seconds to minutes of pouring. Especially for iron mold sand coated casting, the gating system is limited by iron mold, the structure is relatively simple, and there is usually no riser, so it is difficult to fully realize the above requirements.
The cooling process of iron mold sand coated casting determines its final microstructure, and then affects the mechanical properties of the casting. When the iron mold sand coated casting changes from austenite state, the faster the cooling speed, the more pearlite, the finer the pearlite and the denser the structure. Iron mold sand coated casting process can create better heat dissipation conditions than sand mold by adjusting the thickness of iron mold and sand coated layer. At present, most iron mold sand coated castings still need subsequent heat treatment process, which can not well realize the batch stable production of as cast castings. Therefore, this paper will study these two key links of iron mold sand coated casting combined with computer numerical simulation. Computer numerical simulation is based on numerical calculation, combined with the research of physical chemistry, heat transfer, rheology, elastic-plastic mechanics and hydrodynamics, to simulate the flow field, temperature field and stress field of iron mold sand coated casting during mold filling and solidification, and to predict the microstructure of iron mold sand coated casting. The introduction of computer numerical simulation technology makes the process design more scientific and fast. The trial production cost of iron mold sand coated casting process is very large. The process design of stable production of high-quality castings still faces many problems, such as the elimination of shrinkage casting defects, the provision of blank parts with stable composition, matrix structure and mechanical properties for high-performance castings, and the as cast production of nodular iron castings. Therefore, it is urgent to introduce computer simulation into process optimization design.
The importance of computer numerical simulation in production has been widely recognized by all countries. The next generation manufacturing plan released by the United States in 1996 includes the key project of modeling and simulation. In the joint efforts of various countries, continuous research results show that the method of computer simulation of casting filling process and solidification process is feasible, and the calculation results can be applied to production to optimize the process. The simulation results make people re understand the molding process of iron mold sand coated casting and improve the casting process design process, so that computer-aided design can gradually replace the traditional design method relying on theoretical formula and experience. The research content of casting process design is based on computer simulation. It is one of the nine hotspots of computer simulation research in China. Others include casting stress and deformation simulation research, microstructure and defect simulation research, advanced solidification and material processing process simulation, material performance measurement and simulation, mold filling simulation and experimental verification, development and application of CAE system, heat transfer and solidification simulation of iron mold sand coated castings, continuous casting simulation, etc.