Casting Process Optimization of Bed Castings

Based on the analysis of simulation results, the casting process needs to be optimized to eliminate the casting solidification defects.

In order to improve the inadequate liquid shrinkage of metal and eliminate depressions, several vents were added to the upper surface of the casting and the diameter of the vent was enlarged to improve the liquid shrinkage capacity. The model of the castings after initial optimization is shown in Figure 1.

The optimized scheme is simulated and the defects are shown in Figure 2.Through the observation and analysis of simulation results, some problems are found.It can be seen from Fig. 2(a) that with the addition of exhaust holes, the hole edge depressions disappear and there are no depression defects. From Fig. 2(b), it can be seen that the part of shrinkage holes near the casting system has been greatly reduced.Slicing analysis of the simulation results shows that there are shrinkage defects in parts of the casting in Figure 9 (d) ~ (f).

Because there are still some problems in the initial optimization, the second optimization of casting process is now carried out.In order to improve the internal shrinkage of casting, the selection of riser type and calculation of dimension are the key points.The main function of riser is to provide the metal liquid needed to compensate for the volume change during the casting forming process to prevent shrinkage type defects in the casting.For the determination of riser size of gray cast iron, the design method of blank holder riser can be adopted.

The shape, size and position of the riser are shown in Figure 3.

After the parts are added with exhaust holes and risers, the casting is simulated again. The model of the castings after secondary optimization is shown in Figure 4.

The optimized scheme is simulated and the defects are shown in Fig. 5.According to the simulation results, not only the depression but also the shrinkage defect disappear after adding the blank holder riser. As shown in the slice analysis, as shown in Fig. 5(c) ~(f), there is no shrinkage problem in the casting.According to Figure 5(b), it can be seen that shrinkage defects are all concentrated in riser and exhaust column, which has no effect on the part itself. Finally, the riser and exhaust column are cut off and casting defects are completely eliminated. Therefore, the modified optimization process can be considered to be relatively reasonable.

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