This study investigates the sand casting process optimization for high-pressure steam chamber steel castings (ZG15Cr2Mo1) using numerical simulation. The research focuses on addressing shrinkage defects through systematic process design and computational analysis, demonstrating the effectiveness of sand casting technology in producing complex industrial components.
1. Casting Characteristics and Process Requirements
The steam chamber exhibits a maximum wall thickness of 153 mm and minimum thickness of 30 mm, with critical dimensions of 1648 mm × 620 mm × 1077 mm. Key material properties include:
| Property | Value |
|---|---|
| Density | 7.8 g/cm³ |
| Liquidus Temperature | 1501°C |
| Linear Shrinkage | 1.8% |
The chemical composition of ZG15Cr2Mo1 is critical for high-temperature performance (565°C, 8.28 MPa):
| Element | C | Mn | Si | Cr | Mo | S | P |
|---|---|---|---|---|---|---|---|
| Content (%) | ≤0.18 | 0.40–1.20 | ≤0.60 | 2.00–2.75 | 0.90–1.20 | ≤0.030 | ≤0.030 |
2. Sand Casting Process Design
The horizontal pouring position was selected to optimize feeding efficiency and minimize sand core complexity. Key parameters were calculated using fundamental sand casting principles:
Pouring time calculation:
$$ t = \frac{G_L}{N \cdot n \cdot v_{pour}} $$
where \( G_L \) = 2094.846 kg (total molten metal weight), \( N \) = 1 ladle, \( n \) = 1 sprue, \( v_{pour} \) = 120 kg/s.
Metal flow velocity verification:
$$ v_L = \frac{h_C}{t} = \frac{620}{18} \approx 34.44 \, \text{mm/s} $$
confirming adequate mold filling capability.
3. Numerical Simulation and Defect Analysis
ProCAST simulations revealed critical solidification patterns:
| Defect Type | Location | Volume (%) |
|---|---|---|
| Macroshrinkage | Base section | 4.2 |
| Microporosity | Top bosses | 1.8 |
The thermal modulus calculation identified critical sections:
$$ M = \frac{V}{A} $$
where \( M \) > 2.5 cm indicates high shrinkage risk zones.
4. Process Optimization Strategy
Modified sand casting design incorporated:
- Four cylindrical risers with modulus \( M_{riser} = 1.2M_{casting} \)
- Chromite sand chills (thickness = 0.6Tcasting)
- Gating ratio optimization to 1:1.8:2.2
Final shrinkage porosity reduced to 2.71% with complete elimination of macroshrinkage. The optimized sand casting process demonstrates:
| Parameter | Initial | Optimized |
|---|---|---|
| Total Porosity (%) | 6.3 | 2.7 |
| Yield (%) | 68.4 | 75.2 |
5. Conclusion
This study validates sand casting as an effective manufacturing method for high-pressure components through:
- Systematic thermal analysis using modulus calculations
- Strategic placement of risers and chills
- Numerical simulation-guided process optimization
The methodology demonstrates significant improvement in casting quality while maintaining the inherent advantages of sand casting – flexibility, cost-effectiveness, and suitability for large-scale components.
$$ \text{Process Efficiency Gain} = \frac{\eta_{optimized} – \eta_{initial}}{\eta_{initial}} \times 100 = 9.9\% $$
Future work will focus on integrating artificial cooling channels and advanced feeder designs to further enhance sand casting performance for high-integrity applications.