Design of gating system for ductile iron castings

According to the design of the riser, the riser is a hot riser, and molten iron needs to be introduced from the riser. Because the riser is placed on the top of the ductile iron castings, if the molten iron is completely fed from the top, it will have a strong scouring effect on the mold cavity, and the ductile iron castings will have various defects of the top-pouring pouring system, and the appearance quality of the ductile iron castings cannot be guaranteed. In order to solve this problem, we choose to add a runner at the bottom of the ductile iron castings at the same time. After many times of design and adjustment of the size of the runner, through computer numerical simulation, we can ensure that the advanced molten iron at the bottom can buffer the scouring of the top injection, and make the molten iron fill smoothly. In order to save the space of the molding plate and simplify the pouring system, # 1 ductile iron castings, # 2 ductile iron castings, # 3 ductile iron castings and # 4 ductile iron castings share one sprue, # 5 ductile iron castings and # 6 ductile iron castings use one sprue, and the bottom uses a 1mm thick sheet to introduce molten iron to improve the slag avoidance effect, as shown in Figure 1.

Adopt semi-closed pouring system, Σ F straight: Σ F horizontal: Σ F inner=1:0.7:1.2, the sectional areas of the sprue, transverse sprue and inner sprue are 500 mm2, 350 mm2 and 600 mm2 respectively, the initial pouring temperature is 1420 ℃, the final pouring temperature is 1370 ℃, and the pouring time of each type is 8 s.

(a) Filling 25%
(b) Filling 50%
(c) Filling 75%
(d) Filling 100%

The mold filling process and solidification process of the casting process were simulated and analyzed by using the MAGMA simulation software. Figure 2 shows the temperature field distribution diagram of the mold filling process of the ductile iron casting. It can be seen that the mold filling of the ductile iron casting is stable and there is no air entrainment. Figure 3 shows the simulation results of solidification process. It can be seen that there is no isolated liquid phase zone in ductile iron castings, which reduces the probability of shrinkage cavity and shrinkage porosity.

(a) Solidification 25%
(b) Solidification 50%
(c) Solidification 75%
(d) Solidification 100%