Due to the defects of insufficient pouring at the upper part of the shell barrel in Scheme 1 and Scheme 2, through the analysis of Fig. 1 and Fig. 2, there are also many pore-like defects in Scheme 1 and Scheme 2, and shrinkage and porosity also occur at the base in actual production. Therefore, the third scheme is designed (see Fig. 3), the position of the inner gate is adjusted, and four open risers are designed, two of which have a diameter of 110mm and a height of 350mm. The other two exposed risers are stepped, with the lower diameter of 200mm and height of 32.5mm, and the upper diameter of 135mm and height of 330mm.
The filling process of the third process scheme is shown in Figure 4. When the molten metal enters the mold cavity, the molten metal fills the lower part of the inner gate and the right side of the inner gate at the same time, and then fills from the bottom to the top. The filling process is from the bottom to the top, which is conducive to the discharge of gas in the mold cavity and reduces the formation of air holes in the steel castings. From the temperature distribution of the filling process, during the whole filling process of the steel casting, the temperature of the base part of the steel casting is basically low, and the temperature of the cylindrical part is high. When the initial pouring temperature is 1560 ℃, the minimum temperature at the end of the filling process is about 1100 ℃. It can be seen from the temperature field during mold filling that the temperature of molten metal at the inner runner is slightly higher. At the initial stage of pouring, the temperature of molten metal drops rapidly, while with the continuous pouring, the temperature drop rate of molten metal decreases and is basically at a stable stage. That is, at the beginning of pouring, the heat loss of molten metal is relatively serious, while with the increase of pouring time, the heat loss is relatively small.
The solidification process of molten metal is shown in Figure 5. On the whole, the time required for complete solidification of steel castings is relatively long, and the solidification speed is much slower than that of mold filling. The temperature distribution of the steel castings during the whole solidification process basically increases gradually from the base to the cylindrical part. The temperature of the base part is lower, and the temperature of the cylindrical part is higher, that is, the thin-wall part of the steel castings is solidified first, and the larger part of the wall thickness is solidified later, and the riser is set at the post-solidification part to strengthen the feeding. After the solidification, the steel castings have no defects, which proves that this process is reasonable.
