Use orthogonal experiments to investigate the influence of various factors on the maximum shrinkage porosity. Based on 9 sets of experimental results, calculate the mean of the maximum shrinkage porosity and porosity under different levels of each factor, and calculate the range Rx of each factor by subtracting the minimum value from the maximum value of the mean. After calculation, RA=0.1363, RB=1.4563, and RC=0.7954 are obtained. From a range perspective, the influence of various factors on the shrinkage porosity is RB>RC>RA, indicating that the pouring speed plays a major role in the shrinkage porosity, followed by the preheating temperature of the mold shell, and the pouring temperature has the smallest effect on the shrinkage porosity.
| Factor | Sum of squares | Freedom | Mean square | F-Value |
| Pouring temperature | 0.0104 | 2 | 0.0052 | 13.96 |
| Pouring speed | 1.0637 | 2 | 0.5319 | 119.30 |
| Shell preheating temperature | 0.3422 | 2 | 0.1711 | 38.41 |
| Error | 0.0356 | 2 | 0.0178 | — |
| Sum | 1.4519 | 8 | — | — |
Considering that in investment casting, the preheating temperature of the mold shell should not be too high, appropriately reducing the preheating temperature of the mold shell can avoid the formation of shrinkage defects. Based on the results of orthogonal experiments and the influence of various factors, the optimal process parameter group is determined as A2B1C2, which includes pouring temperature of 1550 ℃, pouring speed of 1.0 kg/s, and shell preheating temperature of 1150 ℃. From the analysis of variance (as shown in the table), the effect of pouring speed on shrinkage porosity is the most significant, followed by the effect of shell preheating temperature on shrinkage porosity. The effect of molten metal pouring temperature on shrinkage porosity is the weakest, indicating that the optimal solution group is A2B1C2, which is consistent with the range analysis results.