A common defect that occurs during the casting process can have a significant impact on the performance of the casting. During the filling process, liquid metal often experiences spraying and splashing due to its high flow rate, causing it to roll or convection, resulting in a large amount of gas trapped in the mold cavity entering the liquid metal. If the gas trapped in the metal liquid cannot be discharged in a timely manner, it will remain inside the metal, forming gas defects that seriously affect the performance of the casting. Numerical simulation technology can predict the occurrence of casting defects based on the evolution law of liquid metal during filling and solidification processes, which is an effective means of process optimization. At present, many studies have been conducted on the formation mechanism of gas entrapment and the prediction of gas entrapment defects in castings. However, there is still a lack of quantitative prediction of gas entrapment during the metal filling process in single-phase flow systems.
Huazhu software uses single-phase flow simulation, which assumes that the cavity wrapped by the curled metal liquid is vacuum and does not calculate the pressure and movement trend of the gas involved. Therefore, during subsequent calculations, the cavity will gradually disappear into the metal liquid. Huazhu software adopts a single-phase flow model and does not consider the involvement of gas in the simulation process of metal liquid filling. Therefore, at the final moment of filling, the casting is completely filled. In the previous chapter, by comparing the flow field files at two different time points, we identified the isolated gas connected communication area that disappeared during the filling process due to the lack of consideration for the velocity and pressure of the gas involved. For this disappearing isolated gas connected communication domain, it is necessary to retain it in the flow field file at a later time to predict the location of the gas defect, so it is necessary to correct the flow field file.
The shape of castings is often complex. In order to further verify the prediction system for gas entrapment during the casting process, the internal structure of castings is complex, with many wall barriers. The metal liquid enters the mold cavity from below, and there are many pouring inlets. Gas entrapment is prone to occur at the intersection of several metal liquid flows and at the pouring inlet. Simulate the filling calculation of castings and obtain a series of flow field data. Input these data into the coiling gas prediction system for calculation, and then use the continuation calculation function of Huazhu software for continuation calculation. Select a more typical filling stage and compare the calculation results of the coiling gas prediction system with the original calculation results of Huazhu software.