Sand casting remains a widely used manufacturing method for steel castings due to its cost-effectiveness and adaptability. This study investigates the optimization of sand casting parameters for a ZG270-500 alloy shell component to minimize defects such as porosity, shrinkage cavities, and insufficient pouring. Three gating system designs were evaluated through numerical simulations and orthogonal experiments, with a focus on improving casting yield and mechanical properties.
1. Process Design and Numerical Modeling
The shell casting (812 mm × 525 mm × 356 mm, 392.93 kg) features variable wall thicknesses (average 8 mm) and internal surface quality requirements. The chemical composition of ZG270-500 alloy is shown in Table 1.
| Element | C | Mn | P | S | Fe |
|---|---|---|---|---|---|
| Content (wt%) | 0.4–0.5 | 0.7–0.8 | ≤0.04 | ≤0.05 | Bal. |
The initial gating systems were designed with different runner positions (base vs. cylindrical section) using open-type pouring systems. The pouring time and molten metal rise velocity were calculated as:
$$ t = \frac{G_L}{N n q} = \frac{450}{1 \times 1 \times 27} \approx 16.7\ \text{s} $$
$$ v = \frac{C}{t} = \frac{356}{16.7} \approx 21.3\ \text{mm/s} $$
2. Numerical Simulation Analysis
ProCAST simulations revealed critical defects in the initial designs:
| Design | Pouring Temp. (°C) | Velocity (m/s) | Porosity Volume (cm³) | Key Defects |
|---|---|---|---|---|
| Scheme 1 | 1,560 | 1.6 | 28.23 | Insufficient filling at top |
| Scheme 2 | 1,560 | 1.6 | 50.58 | Severe shrinkage cavities |
The modified Scheme 3 incorporated four risers (two cylindrical: Ø110×350 mm; two stepped: Ø200/135×330 mm) and demonstrated improved thermal behavior during solidification (Figure 1). The optimized temperature distribution showed sequential solidification from thin sections to riser-fed thick regions.
3. Process Parameter Optimization
An orthogonal experiment evaluated pouring parameters:
| Level | Temp. (°C) | Velocity (m/s) |
|---|---|---|
| 1 | 1,530 | 1.3 |
| 2 | 1,560 | 1.6 |
| 3 | 1,590 | 1.9 |
The range analysis revealed:
$$ R_{\text{temp}} = 2.290 > R_{\text{velocity}} = 0.844 $$
indicating temperature as the dominant factor. Optimal parameters (1,560°C, 1.6 m/s) minimized porosity to 1.416 cm³.
| Run | Temp. (°C) | Velocity (m/s) | Porosity (cm³) |
|---|---|---|---|
| 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 |
4. Production Validation
Implementation of Scheme 3 with optimized parameters achieved:
- Porosity reduction: 28.23 cm³ → 1.416 cm³
- Casting yield improvement: 81% → 96%
- Mechanical properties meeting ASTM A148 standards
This study demonstrates the effectiveness of numerical simulation in sand casting process optimization, particularly for complex shell components. The methodology reduces trial production cycles by 40–60% compared to traditional trial-and-error approaches.