This study presents a comprehensive analysis of sand casting methodology applied to large hydraulic turbine volute components. Focusing on structural characteristics and operational requirements, we develop an optimized sand casting process to enhance production efficiency while reducing costs.
1. Structural Analysis and Geometric Modeling
The volute component features a spiral channel with varying cross-sections, requiring precise sand casting control. Key dimensions include:
| Parameter | Value |
|---|---|
| Maximum outer dimension | 1622.5 × 814 × 1510.3 mm |
| Wall thickness range | 25-110 mm |
| Cast weight | 1972 kg |
2. Sand Casting Process Design
The sand casting process utilizes furan resin-bonded sand with the following critical parameters:
2.1 Gating System Design
Employing a choke-poured gating system with sectional area ratios:
$$ F_{\text{runner}}:F_{\text{gate}}:F_{\text{ingate}} = 1.0:2.0:1.5 $$
Key dimensions calculated through hydrodynamic analysis:
| Component | Dimension (mm) |
|---|---|
| Sprue height | 650 |
| Runner cross-section | 94 × 112 × 144 |
| Ingate count | 6 |
2.2 Core Design
Segmented sand cores with reinforced steel骨架 ensure dimensional accuracy:
$$ M_{\text{core}} = 1.2M_{\text{casting}} $$
Where $M$ represents modulus calculated as volume/surface area ratio.
3. Solidification Simulation
Using AnyCasting software, we analyzed solidification patterns under different sand casting conditions:
| Parameter | Value |
|---|---|
| Pouring temperature | 1390°C |
| Filling time | 34 s |
| Cooling rate | 2.5°C/s |
The thermal gradient equation governs shrinkage prediction:
$$ \nabla T = \frac{\partial T}{\partial x} + \frac{\partial T}{\partial y} + \frac{\partial T}{\partial z} $$
4. Process Optimization
Key improvements in sand casting process:
4.1 Chill Design
Graphite chills effectively control solidification sequence:
$$ \delta_{\text{chill}} = (0.8 \sim 1.2)T_{\text{section}} $$
Optimized chill placement reduced shrinkage porosity by 68%.
4.2 Riser Modification
Adaptive riser sizing based on modulus calculations:
$$ H_{\text{riser}} = 1.5D_{\text{riser}} $$
Implementing necked risers improved yield rate to 82%.
5. Quality Verification
Final sand casting results demonstrated:
| Defect Type | Reduction Rate |
|---|---|
| Shrinkage cavities | 72% |
| Gas porosity | 65% |
| Sand inclusion | 88% |
The optimized sand casting process achieved dimensional accuracy of CT10 grade, confirming technical feasibility for large turbine components. This sand casting methodology provides significant advantages in cost-effectiveness and production flexibility compared to alternative manufacturing processes.