The pump cover, a critical component in marine dredging pumps, functions by forming a sealed cavity with the volute to guide fluid from the inlet to the impeller and subsequently direct discharged media to the outlet. Key challenges in steel casting for this component include eliminating shrinkage porosity, shrinkage cavities, and inclusions in critical mating surfaces. This article details the casting process design, simulation validation, and production practices for a ZG270-500 steel pump cover with a diameter of 2,600 mm and height of 260 mm.
1. Process Design for Steel Casting
The pump cover’s structural complexity requires specialized casting solutions. Key considerations include:
| Parameter | Value |
|---|---|
| Material | ZG270-500 |
| Pouring Temperature | 1,530°C |
| Riser Type | Elliptical Exothermic + Conventional |
| Process Yield | 65.8% |
The modulus method forms the basis of riser design. For critical sections:
$$
M_{\text{casting}} = \frac{V}{A}
$$
$$
M_{\text{riser}} = (1.0 \sim 1.2) \times M_{\text{casting}}
$$
Where \( M_{\text{casting}} \) represents the casting modulus, \( V \) the volume, and \( A \) the cooling surface area. Key riser dimensions:
| Riser Location | Dimensions (mm) |
|---|---|
| Impeller Junction | Φ200/300×500 |
| Volute Interface | Φ160/240×350 |
2. Feeding System Optimization
The gating system employs a bottom-pouring design with open-channel configuration:
$$
F_{\text{sprue}}:F_{\text{runner}}:F_{\text{ingate}} = 1:1.5:1.5
$$
Using standardized ceramic components:
| Component | Dimension |
|---|---|
| Sprue | Φ110 mm |
| Runner | 100×120 mm |
| Ingates | 15×60 mm (10 channels/side) |
3. Solidification Simulation
CASTsoft analysis confirms the effectiveness of the steel casting process:
$$
t_{\text{solidification}} = \frac{(M)^2}{\pi \cdot k^2}
$$
Where \( k \) represents the solidification constant (2.5 cm/min½ for ZG270-500). Simulation results show complete feeding without shrinkage defects when:
$$
\frac{M_{\text{riser}}}{M_{\text{casting}}} \geq 1.15
$$
4. Production Challenges and Solutions
Critical issues in steel casting production:
| Issue | Solution | Effectiveness |
|---|---|---|
| Sand Burning | Chromite Sand Layer (20mm) | Reduced defect rate by 82% |
| Microporosity | Directional Solidification Design | Achieved 99.9% soundness |
5. Quality Verification
Mechanical properties of final steel casting:
| Property | Requirement | Result |
|---|---|---|
| Tensile Strength | ≥500 MPa | 620 MPa |
| Yield Strength | ≥270 MPa | 320 MPa |
| Impact Energy | ≥27 J | 28 J |
This steel casting process demonstrates that through scientific modulus calculation, advanced simulation, and proper feeding system design, large-scale pump covers can achieve defect-free production while meeting stringent marine application requirements. The successful implementation of exothermic risers and chromite sand reinforcement provides valuable insights for similar steel casting components in heavy machinery manufacturing.