This study investigates the optimization of lost foam casting (LFC) processes for high manganese steel (ZGMn13) ball mill liners to mitigate shrinkage defects. Three distinct LFC configurations—top-gated 8-liner (Process A), step-side-gated 10-liner (Process B), and side-gated 4-liner with risers (Process C)—were analyzed using ProCAST to simulate filling dynamics, solidification behavior, and defect formation. The methodology integrates thermal-physical property calculations, porosity prediction criteria, and empirical validation to establish process superiority.
Thermal-Physical Modeling and Process Parameters
The ZGMn13 alloy’s thermal properties were derived using ProCAST’s Back-diffusion module (cooling rate: 5°C/s). Key parameters include:
$$ \rho(T) = 7,850 – 0.65T \quad (\text{kg/m}^3) $$
$$ k(T) = 28 + 0.02T \quad (\text{W/m·K}) $$
where \( \rho \) is density and \( k \) is thermal conductivity. The EPS foam (density: 25 kg/m³) and resin sand (permeability: 1e-7) were modeled with gasification thresholds (330–350°C) and interfacial heat transfer coefficients (20–250 W/m²·K).
| Parameter | Process A | Process B | Process C |
|---|---|---|---|
| Gating Type | Top | Step-Side | Side + Riser |
| Liners per Cast | 8 | 10 | 4 |
| Pouring Temp (°C) | 1,420 | 1,420 | 1,420 |
| Fill Time (s) | 44.9 | 35.8 | 27.7 |
Filling Dynamics and Thermal Analysis
Process A exhibited turbulent flow at 30% fill (11.95 s), with gas entrapment delaying final filling (44.9 s). Process B showed amplified turbulence due to multi-stage gating, causing temperature disparities up to 50°C between liners. In contrast, Process C achieved laminar flow with uniform thermal distribution (±10°C), attributed to reduced foam decomposition interference.
Solidification and Porosity Prediction
Defect susceptibility was evaluated using POROS and Niyama criteria:
$$ \text{POROS} = \frac{\Delta V}{V_0} \times 100\% \quad (\text{Critical threshold: 1\%}) $$
$$ \text{Niyama} = \frac{G}{\sqrt{R}} \quad (\text{Critical threshold: 1.0 K^{1/2}s^{1/2}mm^{-1}}) $$
Process A and B liners exhibited scattered shrinkage near surfaces (POROS > 3%, Niyama < 0.8), while Process C localized defects to cores (POROS: 1.2–1.5%, Niyama: 0.9–1.1).
| Process | Max POROS (%) | Min Niyama (K¹/²s¹/²/mm) | Defect Location |
|---|---|---|---|
| A | 3.8 | 0.6 | Surface/Core |
| B | 4.5 | 0.4 | Surface |
| C | 1.5 | 0.9 | Core |
Empirical Validation
Process C was prototyped, revealing sub-surface defects (<2 mm depth) via cross-sectional analysis, aligning with simulation results. Core porosity (diameter: 0.5–1.2 mm) posed minimal impact on wear resistance compared to surface defects in Processes A/B.
Conclusion
Lost foam casting optimization for ZGMn13 liners demonstrates that side-gated systems with risers (Process C) minimize turbulence and defect criticality. The methodology establishes a framework for LFC process design in high-shrinkage alloys, prioritizing thermal uniformity and defect localization.