Numerical Simulation and Optimization of Sand Casting Process for Cast Steel Shell

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This study investigates the sand casting process optimization of ZG270-500 alloy shell components to minimize defects like porosity, shrinkage cavities, and insufficient pouring. Three gating system designs were evaluated using ProCAST simulation, with orthogonal experiments determining optimal parameters for defect reduction.

1. Introduction

Sand casting remains a cost-effective method for producing complex steel components despite challenges in controlling shrinkage and gas entrapment. This research focuses on optimizing the sand casting process for a shell structure (392.93 kg, 812×525×356 mm) through numerical simulation and experimental validation.

2. Process Design

2.1 Material Composition

The chemical composition of ZG270-500 alloy is shown in Table 1, providing balanced strength and castability for sand casting applications.

Table 1: Chemical Composition of ZG270-500 Alloy
Element C Mn P S Fe
Content (wt%) 0.4–0.5 0.7–0.8 ≤0.04 ≤0.05 Bal.

2.2 Gating System Design

Three sand casting schemes were developed:

  1. Bottom gating at base section
  2. Side gating at cylindrical section
  3. Optimized system with four risers

The pouring time was calculated using:

$$ t = \frac{G_L}{N n q} $$

Where \( G_L \) = 450 kg (total metal weight), \( N \) = 1 (number of ladles), \( n \) = 1 (number of nozzles), and \( q \) = 27 kg/s (flow rate). This yielded \( t \) = 16.7 s with metal rise velocity:

$$ v = \frac{C}{t} = \frac{356\ \text{mm}}{16.7\ \text{s}} = 21.3\ \text{mm/s} $$

3. Numerical Simulation

3.1 Simulation Parameters

Table 2: Simulation Setup
Mesh size 30 mm
Element count 45,906
Mold material Silica sand
Heat transfer coefficient 1,000 W/(m²·K)

3.2 Defect Analysis

Initial schemes showed critical defects:

Table 3: Defect Volume Comparison
Scheme Shrinkage Volume (cm³) Key Issues
1 28.23 Incomplete filling
2 50.58 Severe porosity
3 1.42 Optimal

4. Process Optimization

4.1 Orthogonal Experiment

An L9 orthogonal array evaluated pouring parameters:

Table 4: Factors and Levels
Level Temperature (°C) Velocity (m/s)
1 1,530 1.3
2 1,560 1.6
3 1,590 1.9

4.2 Range Analysis

Table 5: Range Analysis Results
Parameter K1 K2 K3 Range
Temperature 7.072 4.782 6.256 2.290
Velocity 5.905 5.683 6.527 0.844

Optimal parameters: 1,560°C pouring temperature with 1.6 m/s velocity.

5. Production Validation

The optimized sand casting process achieved:

  • Defect reduction: 96% qualification rate
  • Yield improvement: 66% process yield
  • Mechanical properties meeting ASTM A148 standards

6. Conclusion

This study demonstrates that sand casting process optimization through numerical simulation effectively reduces defects in cast steel shells. The third scheme with optimized parameters (1,560°C, 1.6 m/s) minimized shrinkage porosity to 1.416 cm³, validating sand casting as a viable method for complex steel components.

$$ J = \sum_{i=1}^{n} (T_i – T_{opt})^2 + \alpha(v_j – v_{opt})^2 $$

Where \( J \) represents the quality optimization function, \( T_i \) and \( v_j \) are process parameters, and \( \alpha \) is weighting factor.

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