Three process schemes of sand casting were numerically simulated by ProCAST software. The model is modeled by Pro / E software and exported as IGS format. Meshcast module is used to divide the grid. The number of grids has a great impact on the simulation accuracy. Generally, the more the number of grids, the smaller the size, the more accurate the calculation results. However, the amount of calculation is very huge. When the number of grids exceeds a certain value, the calculation efficiency will be reduced, but the accuracy will not change greatly. Therefore, when dividing the grid, the grid size of sand casting, cold iron, gating system and riser is 10mm, and the grid size of mold part is 40mm. At the same time, non-uniform adaptive grid is adopted to reduce the amount of grid division calculation of complex parts of the model and improve the simulation accuracy. After the grid division is completed, the grid quality needs to be checked and repaired. Check whether there are neg-jac negative Jacobian elements with severe distortion and whether there are bad elements with radius ratio less than 0.001. When a bad cell appears, it needs to be smoothed. If it cannot be repaired, you need to modify the original solid model.
The figure shows the finite element model of sand casting and mold after meshing.
Set material parameters, boundary conditions, initial conditions, etc. in ProCAST pre-processing. The specific pre-processing parameters are as follows:
(1) Set the type of material: the sand casting material is cast steel ZG25, and the sand core and mold material are carbon dioxide hardened sodium silicate sand.
(2) Set the interface exchange coefficient: 2000 W / (m · 2K) between cold iron and sand casting; 300 W / (m · 2K) between mold and sand mold; The interface between sand casting and mold, cold iron and mold is general.
(3) Boundary condition setting (initial simulation setting): the pouring time is 25 s, the pouring temperature is 1565 ℃, and the surface heat dissipation condition is air cooling.
(4) Gravity normal pressure pouring, calculated termination temperature 1132.8 ℃.