We conducted a comprehensive numerical analysis on the centrifugal casting process of super-large cylinder liners using high-molybdenum ductile iron casting. Through segmented modeling and coupled calculation of temperature, flow, and pressure fields, we established an optimized process framework for industrial applications. The simulation revealed critical relationships between centrifugal parameters and casting quality, providing theoretical guidance for defect control in ductile iron casting components.
Fundamental Principles and Mathematical Modeling
The centrifugal casting process for ductile iron casting follows these governing equations:
1. Momentum conservation with rotational effects:
$$ \rho\left(\frac{\partial \mathbf{v}}{\partial t} + \mathbf{v} \cdot \nabla \mathbf{v}\right) = -\nabla p + \mu\nabla^2\mathbf{v} + \rho\omega^2\mathbf{r} $$
2. Energy conservation equation:
$$ \rho C_p\left(\frac{\partial T}{\partial t} + \mathbf{v} \cdot \nabla T\right) = \nabla \cdot (k\nabla T) + Q_{latent} $$
3. Pressure distribution in rotational system:
$$ P(r) = \frac{1}{2}\rho\omega^2(r^2 – r_0^2) $$
| Parameter | Value Range | Optimal Value |
|---|---|---|
| Rotational Speed (rpm) | 400-800 | 540±20 |
| Pouring Temperature (°C) | 1,380-1,440 | 1,410±20 |
| Mold Temperature (°C) | 150-250 | 200±50 |
Key Findings in Ductile Iron Casting Process
The simulation results demonstrate three critical aspects of ductile iron casting:
1. Flow Field Characteristics:
– Filling time: 90.3s with laminar flow pattern (Re < 2,300)
– Axial velocity gradient: 0.15-0.35 m/s
– Radial velocity distribution: $$ v(r) = \omega r \left(1 – e^{-\frac{t}{\tau}}\right) $$
2. Thermal Behavior:
– Solidification sequence: Outer surface → Inner surface
– Critical cooling rate: 12-18°C/s
– Final solidification position: Middle thick-wall section
| Position | Cooling Rate (°C/s) | Solidification Time (s) |
|---|---|---|
| Outer Surface | 18.2 | 127 |
| Mid-wall | 12.7 | 277 |
| Inner Surface | 9.4 | 808 |
3. Pressure Distribution:
– Maximum centrifugal pressure: 0.506 MPa
– Pressure gradient:
$$ \frac{dP}{dr} = \rho\omega^2r $$
– Critical pressure for defect formation: >0.3 MPa
Process Optimization Strategy
Based on simulation results, we developed an optimization model for ductile iron casting:
$$ Q_{optimized} = k_1\sqrt{\frac{\mu}{\rho\omega^2R}} + k_2\frac{T_{pour} – T_{mold}}{\delta_{wall}^2} $$
Where:
– \( k_1 = 0.78 \pm 0.05 \) (flow factor)
– \( k_2 = 1.25 \pm 0.1 \) (thermal factor)
| Diameter (mm) | Rotation Speed (rpm) | Productivity (kg/h) |
|---|---|---|
| 400 | 540 | 760 |
| 580 | 400 | 2,166 |
Industrial Validation
The implementation of optimized ductile iron casting parameters achieved:
- Defect reduction: 42% decrease in shrinkage porosity
- Mechanical improvement: Hardness increased from 210HB to 240HB
- Dimensional accuracy: ±0.25mm tolerance maintained
This study demonstrates that numerical simulation significantly enhances the quality and efficiency of ductile iron casting processes, particularly for large-scale components requiring precise microstructure control.