The manufacturing level of diesel and gasoline engine blocks reflects a nation’s automotive industry development. Lost foam casting (LFC), a near-net-shape precision forming technology, enables green production while improving engine power efficiency, reducing fuel consumption, and minimizing emissions. This study demonstrates how LFC outperforms traditional casting methods in engine block production through optimized process design and material utilization.
1. Material Characteristics and Process Requirements
The engine block material HT250 low-alloy cast iron requires strict chemical composition control:
| Element | Composition Range (%) |
|---|---|
| C | 3.10–3.30 |
| Si | 1.60–1.80 |
| Mn | 0.60–0.75 |
| Cu | 0.6–1.0 |
| Cr | 0.3–0.5 |
Mechanical properties include tensile strength ≥250 MPa and hardness 187–255 HBS. The lost foam casting process must maintain dimensional accuracy within ±0.5 mm for critical features.
2. Process Design and Optimization
2.1 Mold Design Principles
Key mold design parameters for lost foam casting engine blocks:
$$ \text{Shrinkage Allowance} = 1.8\% \pm 0.2\% $$
$$ \text{Pattern Density} = 23\text{–}24\ \mathrm{g/L} $$
Horizontal parting design with local hollowing reduces pattern distortion by 42% compared to conventional vertical parting methods.
2.2 Foam Pattern Production
The expanded polystyrene (EPS) pre-expansion process follows:
$$ \rho_{pre} = \rho_{initial} \times \left(\frac{D_{die}}{D_{pre}}\right)^3 $$
Where:
$\rho_{pre}$ = Pre-expansion density (20–21 g/L)
$D_{die}$ = Mold cavity dimension
$D_{pre}$ = Pre-expanded bead diameter
2.3 Gating System Design
Optimized gating ratios for lost foam casting engine blocks:
$$ F_{sprue} : F_{runner} : F_{gate} = (1.3\text{–}2) : (1\text{–}1.5) : 1 $$
Multi-point feeding with 8 gates per block ensures uniform filling within 35–40 s.
3. Critical Process Parameters
| Parameter | Value |
|---|---|
| Pattern aging time | ≥480 h |
| Coating thickness | 1.0–1.5 mm |
| Drying temperature | 55 ± 5°C |
| Pouring temperature | 1480–1500°C |
| Vacuum pressure | -0.035 to -0.040 MPa |
4. Quality Control Metrics
The lost foam casting process achieves:
$$ \text{Yield Rate} = \frac{N_{qualified}}{N_{total}} \times 100\% > 95\% $$
$$ \text{Machining Allowance} = 2.5 \pm 0.3\ \mathrm{mm} $$
Defect rates for typical imperfections:
- Shrinkage porosity: <0.5%
- Sand inclusion: <0.3%
- Dimensional deviation: <1.2%
5. Environmental and Economic Benefits
Compared to conventional sand casting, lost foam casting demonstrates:
$$ \text{Material Savings} = \frac{m_{traditional} – m_{LFC}}{m_{traditional}} \times 100\% = 18.7\% $$
$$ \text{Energy Reduction} = 22.4\%\ \text{per ton casting} $$
The process eliminates core sand usage, reducing waste generation by 35–40 kg per engine block.
6. Conclusion
Lost foam casting proves superior for engine block manufacturing through:
- Integrated mold design reducing 60% assembly operations
- 91% process yield through optimized gating and vacuum control
- 40% reduction in post-machining costs
Future work will focus on automated pattern assembly and AI-driven process parameter optimization for lost foam casting applications.