*CFD Optimization Method to Design Foam Residue Traps for Full Mold Casting DOI: http://dx.doi.org/10.5772/intechopen.95505*

model in which metal flows into the product part at a constant pressure from the gate was used. The inflow pressure was set at 1.425 × 105 Pa in absolute pressure, and the temperature of the pouring molten metal was set at 1623 K. The pouring temperature of the metal was set at 1.425 × 105 Pa in absolute pressure. In addition, since the shape was symmetrical, we were able to cut the analysis area in half to reduce the analysis time.

The results of the CFD analysis are shown in **Figure 3(a)**. As shown by the dashed ellipses, the metal flows by gravity from top to bottom. Due to the difference between the density of the metal and the density of the gas and residue generated by the pyrolysis, the metal would entrain the gas and residue, which would affect the occurrence of residue defects.

Then, gating system B is modified to install gates at the rim and hub to improve the flow of gating system A. To prevent the formation of defects in the residue, the pouring temperature was increased by 20 K to 1643 K.

A molten metal flow analysis was performed on the drum using this gating system B. The results of the analysis are shown in **Figure 3(b)**. The flow in the rim proceeds gradually from the bottom to the top, which makes it difficult for the metal to entrain gas and residue. In addition to the increase in temperature, these flows may actually reduce the number of residue defects.

In other words, if a gate is installed on the arm as in gating system A, a drop-in flow occurs, leading to the generation of residue defects, so the gate must be installed on the bottom of the hub and rim as in gating system B. If the

**Figure 3.** *Results of flow analysis for capstan drum.*

*Casting Processes and Modelling of Metallic Materials*

**3. CFD analysis and new gating system**

**3.1 Design of gating system based on CFD analysis**

to ρ = 16.7 kg/m3

in this study.

values expresses the difficulty of heat dissipation of the foam model. Although the model expressed by this equation does not exactly represent the generation of pyrolysis products and the thickness of the gas layer, it is thought that the flow of metal, which is close to the real phenomenon can be expressed by setting appropriate values for each parameter. In this study, casting experiments and molten metal flow analysis were conducted for the model shown in **Figure 1** to obtain the appro-

The metal was FC300 gray cast iron, and the pouring temperature was set at 1683 K. Foamed polystyrene with a foaming factor of 60 times was used for the model. A water-based mold coating agent for full-molded cast iron was used for the coating, and the coating film was about 2 mm thick. Silica sand with an AFS grain size index of 36.7 was used as the casting sand. A stopper system was used for pouring the metal. The arrival time of the metal was measured by inserting a touch sensor into the end of the model; this sensor emitted. The experimental results show that the start to the finish of pouring was 7.2 s. The casting weight was 35 kg. Next, CFD simulations were performed. The parameters in Eq. (3) were set

metal consistent with that of the experiment and the simulation, the parameter H0 was adjusted based on the definition of Eq. (3), and good results were obtained at H0 = 5500 W/(m2-K) and Eg = 0.5. We therefore use these values in the simulations

In this study, a capstan drum (**Figure 2**) is used as the product shape. Also, a casting runner with a diameter of 30 mm is used for the solution. The capstan drum was analyzed for metal flow using the two gating systems shown in **Figure 2(a)** and **(b)**. Gating system A has a gate directly on the arm, which is considered to be prone to many residue defects. Since an enormous amount of time would be required to analyze everything from the pouring to the filling of the product part, a simple

and Cp = 2100 J/(kg-K). In order to make the arrival time of the

priate values of the unknown parameters *H*0 and *E*g in Eq. (3).

**74**

**Figure 2.**

*Shape of capstan drum and gating systems.*

pouring temperature is increased to prevent residue defects, the temperature at the completion of filling will also be high, and therefore, to prevent shrinkage defects the pouring temperature should not be increased. Therefore, to prevent both residue defects and the formation of a shrinkage cavity, a new casting plan that allows the suppression of residue defects without increasing the pouring temperature is required.
