CLADDING TECHNOLOGY SHANXI CO., LTDEffect of Tungsten Electrode Spacing on Dual-Tungsten Electrode TIG Arc Characteristics
Literature Overview
This 2025 publication by Guo Chao-bo, Cui Lu-lu, Tao Kai, Li Xing-xia, Ma Tian-feng, and Wu Zhe from Henan Institute of Technology investigates how the spacing between two tungsten electrodes affects the arc characteristics in dual-tungsten electrode TIG welding. The research is supported by the Henan Provincial Natural Science Foundation (232300420365) and the Key Research Project of Higher Education Institutions (20B430003). Dual-electrode TIG welding is a promising technique for increasing deposition rates while maintaining the quality benefits of TIG welding, particularly relevant for cladding and overlay applications.
Core Technical Content
The dual-tungsten electrode configuration involves two non-consumable tungsten electrodes positioned symmetrically or asymmetrically on either side of the weld seam. Both electrodes are electrically connected to the same power supply, creating a combined arc with higher energy input than a single electrode. The spacing between electrodes (typically 5-25 mm) is a critical parameter that determines arc stability, heat distribution, penetration profile, and bead geometry.
Arc Characteristics as a Function of Electrode Spacing
| Electrode Spacing (mm) | Arc Voltage (V) | Arc Current (A) | Penetration (mm) | Bead Width (mm) | Bead Height (mm) |
|---|---|---|---|---|---|
| 5 | 18-22 | 120-150 | 3.2-3.8 | 8-10 | 3.5-4.5 |
| 10 | 20-24 | 140-170 | 2.8-3.4 | 10-13 | 3.0-4.0 |
| 15 | 22-26 | 160-190 | 2.5-3.0 | 12-16 | 2.5-3.5 |
| 20 | 24-28 | 180-210 | 2.2-2.8 | 14-18 | 2.0-3.0 |
| 25 | 26-30 | 200-230 | 2.0-2.5 | 16-20 | 1.8-2.8 |
The data reveals a clear trend: as electrode spacing increases, arc voltage and current increase due to the larger arc area, but penetration decreases because the heat input becomes more distributed. The optimal spacing for deep penetration is 5-10 mm, while wider spacing (15-25 mm) is better suited for surface cladding where a wider, shallower bead is desired.
Arc Stability and Plasma Behavior
High-speed imaging and optical emission spectroscopy reveal that the arc structure changes significantly with electrode spacing. At narrow spacings (5-10 mm), the two arcs merge into a single, stable plasma column with intense central heat concentration. At intermediate spacings (10-15 mm), the arcs interact but maintain distinct cores, producing a bimodal heat distribution. At wide spacings (15-25 mm), the arcs operate largely independently, with minimal interaction and a broad, flat heat profile.
The arc stability is highest at 10-15 mm spacing, where the interaction between the two arcs provides a self-stabilizing effect. At spacings below 5 mm, the arcs tend to merge completely, creating an unstable, oscillating plasma that can lead to porosity and uneven penetration. At spacings above 25 mm, the arcs are too independent, resulting in two separate weld beads with an unmelted zone between them.
Engineering Practice Implications
For cladding and overlay applications, the dual-electrode TIG technique offers a significant advantage in deposition rate. Compared to conventional single-electrode TIG welding, the dual-electrode configuration can increase deposition rate by 40-80% while maintaining equivalent or better weld quality. This is particularly valuable for thick cladding layers where productivity is a major cost driver.
The optimal electrode spacing depends on the specific application:
- Deep penetration cladding (e.g., corrosion-resistant overlay on carbon steel): 5-10 mm spacing
- Surface cladding (e.g., wear-resistant overlay): 15-20 mm spacing
- Bimetallic strip cladding preparation: 10-15 mm spacing
The study also demonstrates that the dual-electrode technique produces a more uniform microstructure across the weld width compared to single-electrode welding, due to the more even heat distribution. This results in more homogeneous mechanical properties and reduced susceptibility to cracking in the cladding layer.
Key Questions and Reflections
A significant practical challenge is the need for specialized electrode holders and torch designs to accommodate two electrodes at precise, adjustable spacings. The study proposes a novel torch design with interchangeable electrode spacing modules, which could be integrated into existing welding equipment with minimal modification.
Another important consideration is the effect of electrode spacing on dilution in cladding applications. At narrow spacings, the higher heat concentration increases dilution, which may be undesirable when cladding a low-dilution alloy (such as Hastelloy C276 or Inconel 625) onto a carbon steel base. At wider spacings, dilution decreases, making the technique more suitable for low-dilution cladding requirements.
The study raises the question of whether the dual-electrode technique can be extended to three or more electrodes for even higher deposition rates. While theoretically possible, the complexity of arc interaction and the need for precise electrode positioning make multi-electrode configurations challenging for industrial implementation.
In conclusion, this study provides valuable quantitative data on the relationship between electrode spacing and arc characteristics in dual-tungsten TIG welding, offering practical guidance for optimizing the technique for specific cladding and overlay applications.