CLADDING TECHNOLOGY SHANXI CO., LTDDual TIG Active Arc Welding Process
Literature Overview
Dual TIG (Double Tungsten Inert Gas) active arc welding represents an advanced variation of conventional TIG welding that employs two tungsten electrodes positioned on either side of the welding torch. This configuration fundamentally alters the arc characteristics, heat distribution, and metal transfer behavior compared to single-electrode TIG welding. The literature investigates the process principles, operational parameters, and practical advantages of dual TIG active arc welding, particularly in terms of increased deposition rate, improved penetration uniformity, and enhanced process stability for cladding and overlay applications.
Process Principle and Configuration
In a dual TIG configuration, two tungsten electrodes are arranged symmetrically about the torch axis, with each electrode carrying an independent or shared electrical circuit. The arc strikes between each electrode and the workpiece (or between the electrodes and the workpiece in a three-electrode arrangement). The resulting dual-arc configuration creates a wider, more uniform heat input pattern compared to a single arc. The arc force distribution is symmetric, reducing the tendency for weld bead asymmetry and improving the geometry control of the deposited bead.
| Configuration Parameter | Single TIG | Dual TIG |
|---|---|---|
| Electrode number | 1 | 2 |
| Arc voltage (V) | 12–18 | 10–14 per arc |
| Total current (A) | 100–200 | 80–180 per arc (160–360 total) |
| Travel speed (mm/min) | 100–300 | 200–500 |
| Deposition rate (g/min) | 10–25 | 30–70 |
| Bead width (mm) | 6–12 | 10–20 |
| Penetration depth (mm) | 1.5–4.0 | 2.0–5.0 |
| Arc stability | Good | Excellent |
The active arc mode in dual TIG refers to the operation where both arcs are simultaneously active and contribute to the melting and deposition process. This is in contrast to passive modes where one electrode may serve primarily as a filler metal carrier while the other provides the primary arc.
Heat Input and Thermal Distribution
The dual-arc configuration produces a distinctive thermal profile characterized by a broader heat-affected zone with reduced peak temperature compared to single-arc TIG at equivalent total current. The thermal simulation and experimental measurements show that the maximum temperature in the dual-arc zone is approximately 80–90% of the single-arc maximum at the same total power input. This reduction in peak temperature is beneficial for cladding applications where excessive heat input can cause dilution, carbide coarsening, or phase transformation in the overlay.
The thermal cycle parameters are significantly modified in dual TIG welding. The cooling rate at the 800°C isotherm is typically 2–5°C/s lower than in single TIG at comparable deposition rates. This slower cooling rate favors the formation of equilibrium phases and reduces the likelihood of martensitic transformation in stainless steel overlays, which can be advantageous for reducing residual stresses and improving ductility.
Process Advantages for Cladding Applications
The primary advantage of dual TIG active arc welding for cladding operations is the substantially increased deposition rate. For overlay applications requiring thick deposits (5–15 mm), the productivity improvement of 2–3× compared to single TIG is economically significant. The symmetric heat input also promotes uniform dilution across the weld width, which is critical for maintaining consistent overlay composition in multi-pass cladding.
Another important advantage is the reduced risk of undercut formation at the weld edges. The dual-arc configuration provides better edge wetting and fill, resulting in cleaner bead profiles that reduce the need for mechanical finishing. In strip cladding operations, the dual TIG process can accommodate wider strips (20–40 mm) compared to single TIG (10–20 mm), further increasing productivity.
Process Challenges and Countermeasures
Despite its advantages, dual TIG active arc welding presents several technical challenges. The most significant is the potential for arc instability when the two arcs interact, particularly at low travel speeds or when the electrode spacing is insufficient. The recommended electrode spacing is 8–15 mm for standard configurations, with the gap between electrodes being 2–4 times the electrode diameter. If the spacing is too narrow, the arcs may merge into a single irregular arc, defeating the purpose of the dual configuration.
| Challenge | Cause | Countermeasure |
|---|---|---|
| Arc instability | Insufficient electrode spacing | Maintain 8–15 mm spacing |
| Uneven penetration | Asymmetric current distribution | Calibrate both circuits independently |
| Excessive spatter | High arc force at close range | Increase stand-off distance to 6–10 mm |
| Tungsten erosion | High current density per electrode | Use larger diameter electrodes (3–4 mm) |
| Porosity | Inadequate shielding gas coverage | Use wider nozzle (25–35 mm diameter) |
The shielding gas coverage is particularly critical in dual TIG welding. The wider arc zone requires a larger gas nozzle to ensure complete coverage of both arcs and the molten pool. Argon gas is typically used with a flow rate of 15–25 L/min, and helium mixtures may be employed for higher current applications to improve arc stability and penetration.
Engineering Practice Implications
For industrial cladding operations, dual TIG active arc welding is most suitable for applications requiring thick overlay deposits with controlled dilution. Typical applications include the cladding of large-diameter pipes with stainless steel or nickel-based alloys, the overlay of turbine components, and the repair of worn equipment in power generation facilities. The process is particularly effective for hardfacing applications where the combination of high deposition rate and controlled microstructure is essential.
The process setup requires specialized equipment—dual-electrode torches with independent gas flow control, dual power supplies or a single power supply with dual output channels, and precise torch positioning systems. The initial investment is higher than for single TIG, but the productivity gains typically justify the capital expenditure for high-volume cladding operations.
Study Insights and Outlook
The dual TIG active arc welding process represents a meaningful evolution of the traditional TIG welding technology, offering significant productivity improvements while maintaining the high quality and process control that TIG is known for. The key insight from this literature is that the dual-arc configuration does not merely double the deposition rate but fundamentally changes the thermal and metallurgical behavior of the process, creating opportunities for microstructure control that are not available with single-arc TIG. Future developments should focus on automated dual TIG systems with real-time arc monitoring and adaptive parameter control to fully exploit the process potential for complex cladding geometries.