| C | Si | Mn | P | S | Cr | Mo |
| 0.32-0.42 | 0.20-0.45 | 0.50-0.80 | ≤0.025 | ≤0.025 | 0.80-1.20 | 0.20-0.30 |
The planet carrier is made of ZG42CrMo, and the overall dimension is φ 694mm × 697mm, main wall thickness 40 ～ 70mm, local wall thickness ＞ 200mm, net weight of casting 700kg, gross weight 930kg. See Table 1 and Table 2 for chemical composition and mechanical property requirements.
| Rm/MPa | Rp0.2/MPa | A(%) | Z(%) | KU/J |
| ≥800 | ≥450 | ≥10 | ≥20 | ≥45 |
Figure 1 shows the original casting process plan of the planet carrier. Due to the imperfect design of the casting process plan, the four columns connecting the upper and lower shells in the middle of the shell have casting defects such as looseness and shrinkage cavity, as shown in Figure 2.
The main reason for the casting defects is that the wall thickness of the intersection part between the upper cylinder of the planet carrier and the four columns is small. During the pouring process, the molten steel at this position cools and solidifies rapidly, thus blocking the feeder channel. Therefore, the casting defects such as looseness and shrinkage cavity are very easy to appear inside the four columns.
