CLADDING TECHNOLOGY SHANXI CO., LTDVariable Polarity TIG Horizontal Welding of Aluminum Alloy: Process Parameter Investigation
Literature Overview
This study by Sun Shixuan, Zhao Yan, Jiang Yukang, Qiao Sen, Ren Hong, Guo Yunlong, and Hu Weiguo from Capital Aerospace Machinery Company, published in 2016 and supported by the National Natural Science Foundation of China (Grants 51375150 and 51205114), investigates the application of variable polarity TIG (VPTIG) welding for horizontal-position welding of aluminum alloys. Variable polarity TIG represents a significant advancement in aluminum welding technology, combining the benefits of AC TIG (oxide cleaning) with the benefits of DC TIG (deeper, more controlled penetration).
Background and Technical Rationale
Traditional TIG welding of aluminum alloys uses AC (alternating current) to achieve both cathodic cleaning (removal of the Al₂O₃ oxide layer during the negative half-cycle) and anodic heating (deeper penetration during the positive half-cycle). However, AC TIG has limitations:
- The cleaning action occurs only during the negative half-cycle, limiting the total energy available for penetration
- The positive half-cycle produces a diffuse, less controlled arc with lower energy density
- The balance between cleaning and penetration is fixed by the AC waveform and cannot be independently optimized
Variable polarity TIG (VPTIG) addresses these limitations by using a controlled switching of polarity at high frequency (typically 100–500 Hz), allowing independent control of the cleaning and penetration phases. The negative half-cycle (cathodic) provides oxide cleaning with higher current density, while the positive half-cycle (anodic) provides deeper penetration with a more concentrated arc.
Comparison of AC TIG and VPTIG for Aluminum Welding
| Parameter | AC TIG | VPTIG |
|---|---|---|
| Polarity Switching | 50/60 Hz (mains frequency) | 100–500 Hz (controlled) |
| Cleaning Action | Negative half-cycle only | Negative half-cycle (optimized) |
| Penetration | Limited by positive half-cycle | Deeper with controlled positive phase |
| Arc Stability | Moderate | High |
| Bead Profile | Wide, flat | Narrow, controllable |
| Travel Speed | 5–10 cm/min | 8–15 cm/min |
| Current | 100–200 A | 80–160 A |
| Applications | General aluminum welding | High-quality aluminum welding |
Process Parameters for Horizontal VPTIG Welding of Aluminum
The horizontal position presents specific challenges for aluminum welding due to the low melting point and high fluidity of aluminum. The molten pool tends to sag under gravity, leading to convex bead profiles and potential incomplete fusion on the upper side of the joint.
| Parameter | Recommended Value | Notes |
|---|---|---|
| Peak Current (Negative) | 80–120 A | Cleaning phase |
| Background Current (Positive) | 20–40 A | Penetration phase |
| Polarity Switching Frequency | 200–400 Hz | Higher frequency = more stable arc |
| Negative Phase Duration | 30–50% | Optimized for cleaning |
| Positive Phase Duration | 50–70% | Optim |