Mold filling is an important stage in the. Unstable filling process of liquid metal, unreasonable filling sequence and long filling time will cause defects such as entrainment, cold shut and insufficient casting. In the process of mold filling, the heat transfer between the liquid metal and the mold wall occurs, and the unsteady temperature field is formed. Due to the limitation of laboratory area and considering the danger of centrifugal casting test process, it is difficult to carry out centrifugal casting test under laboratory conditions, and the whole process of centrifugal casting is carried out at high temperature, which is not convenient for direct observation and measurement. Therefore, the current research on filling process of centrifugal casting mainly relies on numerical simulation method, plus hydraulics The test is used for auxiliary verification.
VOF (volume of fluid) method is widely used to trace the interface between liquid metal and air (i.e. free surface) when studying the flow filling process of liquid metal in centrifugal casting. The filling process of horizontal centrifugal cast iron pipe was simulated by kaschnit 9 commercial software FLOW3D. The effects of process parameters (liquid metal inflow, mold movement, liquid metal temperature and cooling medium) on the wall thickness of the pipe were discussed, and the axial distribution of the wall thickness of the pipe was obtained.
In order to avoid too long simulation time caused by too short time step, the momentum equation was solved in rotating coordinate system. However, because the ratio of wall thickness to length is too small, each simulation still takes a long time (15-20 days). Keerthiprasad et al. Used another commercial software star-cdv4 to simulate the horizontal centrifugal casting process. Combined with cold test and real centrifugal casting test, the effects of viscosity, casting size and mold speed on the casting forming process were studied. By comparing the results of the numerical simulation with the results of the cold model test, it is found that the results of the two are in good agreement.
In their research, the lower quality polyhedral elements are avoided in meshing, so the calculation time step is greatly improved, which can reach 0.01s. However, in their research, only the continuity equation and momentum equation are solved, and the heat transfer analysis and solidification process analysis are not involved. In addition, they did not give the solution in the paper Details of the process.
It can be seen that VOF method can successfully solve the flow process of liquid metal in horizontal centrifugal casting process, but few people consider the time cost problem, and VOF method can not include the solidification process of liquid metal in the model.