1. Pretreatment before simulation
After the gating system is drawn, use ProCAST software to mesh the shell and select the appropriate mesh step to ensure accurate total time and simulation results in the numerical simulation analysis process. Import steel castings under the Visual － Mesh working page. The mesh step of steel castings is set to 30mm. The total number of divided face meshes is 12722, and the total number of volume meshes is 45906. Use Mesh’s Checks process to check the crack, intersection, damage, overlap, joint surface matching and other problems in mesh division from 1D, 2D to 3D, and comprehensively repair these defects at the mesh division stage to complete the establishment of the final volume mesh. In the pre-treatment stage, the steel casting material is set as Medium-CarbonAISI1040 (ZG270-500), resin sand molding and core making, and the molding sand and core material are silicon sand. The sand mold temperature is 25 ℃, the cooling mode is COINC, and the heat transfer coefficient of metal and sand mold is 1000W/(m2 · K). Set parameters such as gravity acceleration, boundary conditions and cooling mode in turn.
2. Simulation and analysis of filling and solidification process of molten metal
The pouring temperature is 1560 ℃ and the pouring speed is 1.6m/s. After setting, use simulation software to simulate the two schemes, and the simulation results are shown in Figure 1 and Figure 2. It can be seen from Fig. 1 and Fig. 2 that there is insufficient pouring defect above the cylindrical part of the shell. Therefore, two open risers are designed and simulated at the insufficient pouring part. The temperature field of Scheme 1 is shown in Fig. 3, and the pore distribution diagram is shown in Fig. 4. The temperature field of Scheme 2 is shown in Figure 5, and the pore distribution diagram is shown in Figure 6. The pore volume of Scheme 1 is 28.23cm3, and that of Scheme 2 is 50.58cm3. Due to too many defects, the shell steel castings cannot be used.