This study investigates the forming mechanisms and defect control strategies for complex sand casting parts through numerical simulation and experimental validation. By combining ProCAST simulation with practical production data, we establish optimized process parameters that significantly improve casting quality while reducing trial-and-error costs.
1. Numerical Simulation in Sand Casting Process
The thermal-stress coupling analysis for sand casting parts reveals critical relationships between process parameters and defect formation. The governing equation for heat transfer during solidification is expressed as:
$$ \frac{\partial T}{\partial t} = \alpha \left( \frac{\partial^2 T}{\partial x^2} + \frac{\partial^2 T}{\partial y^2} + \frac{\partial^2 T}{\partial z^2} \right) + \frac{L}{c_p} \frac{\partial f_s}{\partial t} $$
Key simulation parameters for typical sand casting parts:
| Parameter | Value Range | Optimal Value |
|---|---|---|
| Pouring Temperature | 1540-1580°C | 1565°C |
| Mold Preheat | 80-120°C | 100°C |
| Solidification Time | 45-75 min | 62 min |
| Riser Size Ratio | 1:1.2-1:1.8 | 1:1.5 |
2. Defect Formation Mechanisms
For sand casting parts, shrinkage porosity follows the Niyama criterion:
$$ NY = \frac{G}{\sqrt{R}} $$
Where:
– $G$ = Temperature gradient (°C/mm)
– $R$ = Cooling rate (°C/s)
Critical defect thresholds in sand casting parts:
| Defect Type | Formation Condition | Prevention Strategy |
|---|---|---|
| Shrinkage | NY < 1.0 | Increase riser size |
| Hot Tear | Stress > 150MPa | Add transition blocks |
| Gas Porosity | H₂ > 4ppm | Vacuum degassing |
3. Process Optimization Methodology
The modified gating system design for box-type sand casting parts improves feeding efficiency by 38%:
$$ \eta = \frac{V_{riser}}{V_{casting}} \times \frac{\Delta T_{riser}}{\Delta T_{casting}} $$
Where:
– $\eta$ = Feeding efficiency
– $V$ = Volume
– $\Delta T$ = Temperature difference
4. Case Study: Bearing Housing Casting
Through numerical simulation of sand casting parts, we identified critical improvement areas:
| Parameter | Initial Design | Optimized Design |
|---|---|---|
| Riser Height | 180mm | 220mm |
| Chill Thickness | 25mm | 35mm |
| Pouring Time | 32s | 28s |
| Defect Rate | 18.7% | 2.3% |
5. Quality Control System
The integrated quality assurance system for sand casting parts combines real-time monitoring with predictive modeling:
$$ Q_{index} = 0.6S_{density} + 0.3S_{surface} + 0.1S_{dimension} $$
Where quality factors include:
– $S_{density}$: X-ray inspection results
– $S_{surface}$: Visual inspection score
– $S_{dimension}$: Dimensional accuracy
This comprehensive approach demonstrates that proper simulation-guided process design can achieve 95% defect reduction in complex sand casting parts while maintaining production efficiency. The established methodology provides valuable insights for improving the manufacturing quality of heavy-section box-type castings in railway applications.