The application ofsimulation should not only find out the causes of defects, but also put forward solutions or measures. When the simulation is completed, it is necessary to compare the sand casting simulation results with the actually observed defects. If the simulation results of sand casting are more accurate, the appropriate conditions for eliminating defects can be found by adjusting process parameters and repeating sand casting simulation.
For example, if the defect occurs at the thick wall, it may be a shrinkage defect. Considering the time and cost according to the actual situation, run the sand casting simulation again after changing the riser, cavity size, cold iron or pouring temperature. If the simulation result of sand casting is not ideal and the defect position of sand casting simulation is quite different from the actual observation, the sand casting simulation shall be carried out again after modifying the following input parameters:
a) Check the change of gating and riser system and cavity size. Their original design has been changed for various reasons, such as defect control, wear, maintenance and customer requirements.
b) Check which functions in the sand casting simulation software are used. This requires guessing the cause of the defect. If the defect looks like a gas defect and the gas content in the molten metal is higher than usual, we should choose those functions that consider the gas content.
c) Check the changes of pouring mode, pouring temperature, pouring speed and mold, including the changes of mold coating. The actual pouring temperature usually changes with time and date, even for the same casting. Especially when manual pouring is used, it is usually necessary to observe the pouring operation, such as pouring time interval and other factors that may cause the change of pouring temperature.
d) Check other input parameters, including physical properties of liquid metal and mold, thermal conductivity of casting and mold, shrinkage rate, critical solid rate of liquid metal flow and criteria used to evaluate defects, such as niyama criterion, etc. In fact, the correctness of initial conditions, boundary conditions and physical properties can be evaluated by comparing sand casting simulation and measured temperature.
e) Analyzing the simulation results of sand casting requires rich casting experience and theoretical knowledge, including the formation mechanism of casting defects. For example, if the real defect is located above the sand casting simulation results, these differences may be caused by bubble floating or thermal convection during solidification. Consider these phenomena in sand casting simulation, check the input parameters and rerun the simulation.