In critical industries such as power generation, petrochemicals, and heavy equipment manufacturing, large bearing housings serve as fundamental components for rotating machinery. This article systematically explores the sand casting methodology for producing high-quality bearing housings with dimensions 2,486 mm × 1,639 mm × 1,340 mm, demonstrating how process optimization addresses common casting defects.
1. Material Selection and Process Parameters
The housing material ZG310-570 (equivalent to ASTM A148 90-60) requires precise control of sand casting parameters:
| Parameter | Value | Calculation Basis |
|---|---|---|
| Pouring Temperature | 1,530-1,570°C | Superheat coefficient (1.2-1.4) |
| Solidification Time | 215-240 min | Chvorinov’s Rule: $$ t = B\left(\frac{V}{A}\right)^2 $$ |
| Riser Modulus | 1.2Mc | Mr = 1.2 × 4.7 cm = 5.64 cm |
2. Gating System Design
The stepped gating system for sand casting employs empirical relationships:
$$ \Sigma A_{gate} = \frac{W}{\rho t\sqrt{2gH}} $$
Where:
W = casting weight (8,450 kg)
ρ = molten steel density (7.2 g/cm³)
H = effective metal head (1,200 mm)
t = pouring time (85 s)
| Component | Diameter (mm) | Area Ratio |
|---|---|---|
| Sprue | 140 | 1.0 |
| Runner | 100 × 2 | 1.4 |
| Ingate | 140 × 4 | 2.0 |
3. Solidification Simulation
Numerical modeling using Huacast CAE revealed critical solidification patterns:
$$ \frac{\partial T}{\partial t} = \alpha\left(\frac{\partial^2T}{\partial x^2} + \frac{\partial^2T}{\partial y^2} + \frac{\partial^2T}{\partial z^2}\right) $$
Initial simulation identified shrinkage porosity in thick sections (50-254 mm wall transitions), requiring riser optimization:
| Riser Type | Dimensions (mm) | Feed Volume (cm³) |
|---|---|---|
| Initial Cylindrical | Φ323 × 485 | 39,800 |
| Optimized Elliptical | 450 × 300 × 500 | 52,300 |
4. Process Optimization Strategy
Key improvements in sand casting process:
4.1 Modulus Correction Factor:
$$ M_{effective} = M_{riser} \times \left(1 + 0.1\frac{h}{d}\right) $$
4.2 Chill Design Formula:
$$ A_{chill} = 0.3 \times \frac{V_{hotspot}}{T_{initial} – T_{mold}} $$
4.3 Yield Improvement:
| Metric | Initial | Optimized |
|---|---|---|
| Yield Percentage | 64.2% | 72.8% |
| Shrinkage Volume | 1,850 cm³ | 420 cm³ |
5. Industrial Validation
Production trials confirmed the sand casting process effectiveness:
$$ Niyama \, Criterion: G/\sqrt{\dot{T}} \geq 1.0 \, (°C/cm\cdot s^{-0.5}) $$
Post-optimization results showed:
- X-ray inspection porosity reduction from 2.1% to 0.4%
- UT detection rate decreased from 8 defects/m² to 1.2 defects/m²
- Dimensional accuracy improved to CT12 grade
This comprehensive sand casting approach demonstrates reliable production of large bearing housings with 98.7% first-pass qualification rate, establishing a robust manufacturing framework for critical heavy-industry components.