1. Orthogonal experimental design
In sand casting, pouring temperature and pouring speed are two important parameters in the sand casting process. In order to obtain a more reasonable pouring temperature and pouring speed, orthogonal experiments were conducted on the basis of the third process plan. The level of virtual orthogonal experimental factors designed is shown in Table 1.
| Horizontal | Pouring temperature/℃ | Pouring speed/(m · s ^ -1) |
| 1 | 1 530 | 1.3 |
| 2 | 1 560 | 1.6 |
| 3 | 1 590 | 1.9 |
2. Range analysis
The range analysis results of this experiment are shown in Table 2.
| Group number | Pouring temperature/℃ | Pouring speed/(m · s ^ -1) | Pore volume/cm |
| 1 | 1 530 | 1.3 | 2.368 |
| 2 | 1 530 | 1.6 | 2.201 |
| 3 | 1 530 | 1.9 | 2.503 |
| 4 | 1 560 | 1.3 | 1.553 |
| 5 | 1 560 | 1.6 | 1.416 |
| 6 | 1 560 | 1.9 | 1.818 |
| 7 | 1 590 | 1.3 | 1.984 |
| 8 | 1 590 | 1.6 | 2.066 |
| 9 | 1 590 | 1.9 | 2.206 |
| K1 | 7.072 | 5.905 | — |
| K2 | 4.782 | 5.683 | — |
| K3 | 6.256 | 6.527 | — |
| R | 2.290 | 0.844 | — |
The optimal pouring temperature is 1560 ℃ and the pouring speed is 1.6m/s
From Table 2, it can be seen that various factors have a significant impact on the pore volume of defects. The range corresponding to the pouring temperature is 2.290, which is greater than the range corresponding to the pouring speed of 0.844, indicating that the pouring temperature has a significant impact on the pore volume; As the pouring temperature increases, the pore volume first decreases and then increases, while as the pouring speed increases, the pore volume first decreases and then increases. According to range analysis, the order of the impact of two factors on the quality of shell steel castings is: pouring temperature>pouring speed. The optimal combination parameters are pouring temperature 1560 ℃ and pouring speed 1.6m/s. The pore distribution diagram is shown in Figure, indicating that the volume of pore defects in shell steel castings is 1.416cm3, which is smaller than the volume of pore defects in the first and second schemes.
After process improvement, the qualification rate of steel castings has increased from 81% to 96%, and the process yield rate is 66%.