The low-pressure casting simulation model of flywheel housing is established by ProCAST. The simplified three-dimensional digital model of the die is imported into ProCAST in. XT format to establish the curved surface and close the casting cavity. Generate two entities of die and low-pressure casting blank, and set the scale of surface grid and volume grid; Generate face mesh, check the face mesh and repair the face mesh. Then the volume mesh is generated based on the surface mesh, and a total of 3164585 individual meshes are generated.
Enter the castlpdc module to set relevant parameters of low-pressure casting. Including field setting, type of each volume, material setting, initial temperature, setting of heat exchange conditions at each interface, casting boundary conditions of low-pressure casting (casting speed, pressure, direction, etc.), calculation parameter setting, etc. Check the model setting before calculation, and conduct low-pressure casting calculation, part solidification calculation and advanced shrinkage cavity calculation after no error is reported. The mold adopts general die steel H13, the flywheel housing adopts alsi7mg0.3 alloy, the mold temperature is set to 325 ° C, the alloy liquid temperature is set to 725 ° C, and the mold is filled at a uniform speed within 15s. After filling, the pressure is maintained at an absolute pressure of 15kpa and cooled at room temperature.
After the simulation model is established, the simulation calculation is carried out, and finally the whole filling and condensation process of the parts is obtained. As shown in Fig. 1, the feeding block set on the die plays a good feeding role in the whole condensation process, and no independent liquid phase zone occurs on the parts body within 50s after filling.
By observing the whole condensation process, it is found that at 50.767s after mold filling, an independent liquid phase area appears on the part body, which occurs in defect a area. The detailed picture of the independent liquid phase area is shown in Fig. 5. The metal liquid in this area is not connected with the metal liquid at the casting mouth of low-pressure casting, nor with the metal liquid of feeding block. It can not be supplemented by metal liquid during condensation, resulting in shrinkage porosity. At 52.676s after mold filling, an independent liquid phase area appears again in the part body, which is located in the defect B area. The details of the independent liquid phase area are shown in Fig. 2. There is no supplement of metal liquid during condensation in this area, resulting in shrinkage.
The independent liquid phase zone can be eliminated by accelerating the cooling speed of the independent liquid phase zone or slowing down the cooling speed of the replenishment end. The position of the independent liquid phase zone is located at the connection position of the suspension point of the flywheel housing, where the connecting thread needs to be processed, and there are certain requirements for strength, Therefore, it is not advisable to speed up the cooling of the independent liquid phase area by thinning the component structure. Consider increasing the volume of the feeding block to slow down the cooling speed of the feeding liquid end, so as to eliminate the independent liquid phase area on the component body.
The thickness of the feeding block in the original area a is 25mm and the length is 34mm. The thickness of the feeding block in the original area B is 28mm and the length is 30mm. In order to slow down the cooling rate of the liquid metal of the feeding block, the thickness and length of the feeding block in area a are increased to 45mm and 65mm, and the thickness and length of the feeding block in area B are increased to 45mm and 84mm. The comparison before and after the change is shown in figure 3. Rebuild the simulation model for the changed model.
The remaining process parameters / grid scale are not adjusted, the model is re meshed, and finally 3166189 individual grid is obtained. The same calculation parameters are used for simulation calculation to obtain the improved filling and condensation process, and the condensation process is observed, No independent liquid phase area is found on the parts body. The condensation details of area a and area B before and after 50s of mold filling are shown in Fig. 4.
According to the analysis results, the mold was reformed to increase the volume of feeding block in area a and area B.