Analysis of Aluminum Profile Extrusion: Metal Flow & Die

1. Fundamentals of Extrusion Forming

Extrusion forming is a plastic processing method that applies external force to a aluminum alloy billet within a barrel, overcoming die friction and metal deformation resistance to produce profiles with specific cross-sectional shapes, dimensions, and performances characteristics. This study analyzes key factors impacting extruded aluminum profile quality, emphasizing die structure optimization, metal flow uniformity, and defect mitigation.

2. Classification of Extrusion Methods

Extrusion techniques vary based on:

Stress-strain conditions
Direction (forward/backward)
Lubrication status (hot/cold)
Temperature (300°C–500°C for aluminum alloys)
Die types (flat/tapered)
Billet/product geometry

(Refer to Table 2-1 for detailed classification criteria)

3. Metal Flow Dynamics in Aluminum Profile Extrusion

3.1 Filling Extrusion Stage

Billet design: Diameter intentionally smaller than barrel inner diameter to facilitate loading.
Filling coefficient (K):
- Optimal range: 1.06–1.10
- Accounts for thermal expansion and billet-barrel bonding effects
Critical outcomes:
- Tapered billet end formation
- Linear increase in extrusion force until peak pressure

3.2 Steady-State vs. Turbulent Extrusion

Stage 1 (Filling): Barrel gap filling under axial pressure
Stage 2 (Steady): Uniform metal flow through die orifice
Stage 3 (Turbulent): Terminal phase with increased defect risks

4. Defect Mechanisms & Prevention

4.1 Common Defects in Aluminum Extrusion

Double-drum deformation: Caused by excessive billet L/D ratios
Gas entrapment: Leads to surface bubbles/skinning due to closed gas pockets
Dimensional inaccuracies: Improper die alignment or temperature gradients

4.2 Mitigation Strategies

Optimize filling coefficient (K)
Implement billet temperature gradients (100°C–150°C/mm)
Ensure smooth billet-barrier interface

5. Aluminum Profile Specifications & Limitations

5.1 Dimensional Constraints for 6063 Alloy

Minimum wall thickness: 0.5 mm (conventional extrusion)
Maximum cross-section: Determined by extruder capacity (e.g., 5000t presses at Shangli Aluminum)

5.2 Key Influencing Factors

Alloy extrudability (e.g., 6061 vs. 7075 aluminum)
Die lifespan (typically 5–50 tons per die)
Production cost-efficiency

6. Die Design & Process Optimization

Die structure: Single-/multi-port configurations for hollow aluminum profiles
Extrusion ratio (λ):
$λ = Profile Cross-Sectional Area Barrel Cross-Sectional Area$
- Primary extrusion: λ > 8–12
- Secondary extrusion: No strict limit

7. Industrial Applications & Case Studies

Aluminum alloy enclosures: High-precision profiles for EMI shielding in electronics
Architectural systems: Thermal-break profiles with <0.5 mm tolerance
Automotive: Crash-resistant 6005A-T6 alloy bumper beams

Conclusion

Mastering aluminum alloy extrusion requires synergistic control of:

Billet design (diameter, K-value)
Die engineering (structure, material)
Process parameters (temperature, speed)
Defect prevention protocols

Advances in aluminum profile extrusion technologies continue to enable thinner walls (±0.1 mm), larger sections (>500 mm diagonals), and enhanced surface finishes (Ra <0.8 μm), solidifying aluminum alloys as the premier choice for high-performance enclosures and structural components.