CLADDING TECHNOLOGY SHANXI CO., LTDDesign and Experimental Investigation of Partitioned Tungsten Electrode TIG Welding Device
Research Background and Technical Innovation
Conventional TIG welding relies on a single tungsten electrode to generate the electric arc, with heat input controlled primarily through current magnitude, travel speed, and electrode geometry. This study by Zhang Zhijian, Guan Zhichen, Zheng Xiangbo, and Huang Jiankang, published in Hot Working Technology in 2021, presents an innovative approach to TIG welding through the design of a partitioned tungsten electrode that creates multiple arc zones with independently controllable heat inputs. The research was conducted at the State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals (co-built by the Ministry of Education and Gansu Provincial Government) at Lanzhou University of Technology, reflecting the strong non-ferrous metals processing research tradition at this institution.
The partitioned tungsten electrode concept addresses several limitations of conventional single-electrode TIG welding, including the difficulty of achieving uniform heat distribution across wide weld beads, the challenge of welding thick-section materials with adequate root penetration and cap reinforcement simultaneously, and the inability to independently control root and cap welding conditions in a single pass.
Electrode Design Principles and Configuration
The partitioned tungsten electrode consists of two or more tungsten segments electrically isolated from each other but mechanically integrated into a single electrode assembly. Each segment can be independently powered, allowing the operator to control the current distribution across the electrode face.
Electrode Configuration Parameters
| Configuration Parameter | Typical Specification | Design Rationale |
|---|---|---|
| Electrode diameter | 3.0-4.0 mm (total) | Compatible with standard TIG torches |
| Number of segments | 2-3 | Balance between control flexibility and mechanical complexity |
| Segment gap | 0.2-0.5 mm | Creates arc separation while maintaining structural integrity |
| Insulation material | Alumina (Al₂O₃) or boron nitride | Withstands arc temperatures and thermal cycling |
| Tip geometry | Flat, conical, or custom profile | Controls arc shape and heat distribution pattern |
| Power supply | Dual-channel DC or AC inverter | Independent current control per segment |
| Current ratio range | 30:70 to 70:30 | Adjustable heat distribution across electrode face |
Arc Behavior and Heat Distribution
The partitioned electrode produces two distinct arc zones that can be characterized by their individual current density, arc pressure, and heat flux. The interaction between the two arcs depends on the gap width, current ratio, and shielding gas flow pattern. When the gap is narrow relative to the electrode diameter, the two arcs merge into a single broad arc with a modified heat distribution profile. When the gap is wider, two separate arc zones are maintained, each producing a distinct heat input pattern on the workpiece surface.
The key advantage of this configuration is the ability to create asymmetric heat input profiles. For example, in welding thick-section steel plates, a higher current can be directed to the segment positioned over the root side to ensure complete penetration, while a lower current is applied to the segment over the cap side to control reinforcement height and prevent excessive cap width. This eliminates the need for separate root and cap welding passes, reducing welding time and improving productivity.
Experimental Investigation and Results
The study conducted systematic experiments to characterize the performance of the partitioned tungsten electrode under various welding conditions.
Welding Test Matrix
| Test Variable | Levels Investigated |
|---|---|
| Base material | Q235 carbon steel, 304 stainless steel, 6061 aluminum alloy |
| Plate thickness | 3 mm, 6 mm, 10 mm |
| Current ratio | 50:50, 60:40, 70:30 |
| Travel speed | 5, 8, 12 cm/min |
| Shielding gas | Pure Ar, Ar + 2% O₂, Ar + 5% CO₂ |
| Electrode gap | 0.2, 0.3, 0.5 mm |
Key Performance Findings
The experimental results demonstrated several significant advantages of the partitioned electrode approach:
- Weld bead uniformity: The partitioned electrode produced weld beads with more uniform width and reinforcement height compared to conventional single-electrode TIG, particularly for welds longer than 200 mm. The coefficient of variation of bead width was reduced by approximately 30-40%.
- Penetration characteristics: For 6 mm and 10 mm plate thickness, the partitioned electrode achieved adequate root penetration with a single pass, whereas conventional TIG required multi-pass welding with backing. The asymmetric current distribution allowed the root-side segment to deliver higher energy density for penetration while the cap-side segment provided controlled heat input for cap formation.
- Defect reduction: The modified heat distribution pattern produced by the partitioned electrode resulted in reduced porosity and undercut compared to conventional TIG welding under equivalent total current conditions. The improved arc stability contributed to fewer solidification cracking occurrences in stainless steel welds.
- Productivity improvement: For multi-pass welds on thick sections, the partitioned electrode reduced the number of passes by 1-2 compared to conventional TIG, resulting in productivity improvements of 15-25% depending on the joint configuration and material thickness.
Engineering Application and Implementation Considerations
The practical implementation of partitioned tungsten electrode TIG welding requires attention to several engineering considerations:
- Torch modification: Standard TIG torches must be modified to accommodate the partitioned electrode and dual power connections. The modification must maintain proper shielding gas flow and electrical insulation.
- Power supply compatibility: The welding power source must provide independent current control for each electrode segment. Modern inverter-based power sources with dual output channels are suitable, but the control system must allow real-time adjustment of the current ratio during welding.
- Welding procedure qualification: The partitioned electrode configuration constitutes a new welding process variable that must be addressed in procedure qualification per standards such as ASME IX or ISO 15614. The electrode configuration, gap width, and current ratio must be defined as essential variables in the welding procedure specification.
- Operator training: Operators must be trained in the additional control parameters introduced by the partitioned electrode, particularly the current ratio adjustment. Automated or semi-automated welding setups are recommended to ensure consistent parameter control.
Study Insights and Conclusions
The partitioned tungsten electrode TIG welding device represents a meaningful advancement in TIG welding technology that addresses real limitations of conventional single-electrode processes. The ability to independently control heat input distribution across the weld zone opens new possibilities for single-pass welding of thicker sections, improved weld geometry control, and enhanced productivity in structural welding applications.
The research demonstrates that relatively simple modifications to standard TIG equipment can yield significant performance improvements without requiring expensive new equipment or exotic consumables. This makes the technology particularly attractive for small and medium-sized welding operations that may not have the capital to invest in major equipment upgrades. The non-ferrous metals processing focus of the host institution suggests that the technology has particular promise for welding aluminum alloys, copper alloys, and titanium alloys where heat input control is critical to maintaining material properties.
Further development work should focus on automated current ratio control based on real-time weld pool monitoring, extension of the technology to pulsed TIG configurations, and systematic qualification of the process for specific material and joint combinations. The partitioned electrode concept also lends itself to extension into multi-electrode gas metal arc welding (GMAW) and other arc welding processes, suggesting a broader technological trajectory that could influence future welding equipment design.