CLADDING TECHNOLOGY SHANXI CO., LTDDP-TIG High-Speed Welding Process Research for Intelligent Equipment Applications
Literature Overview and Research Context
This 2020 publication from Noli Intelligent Equipment Co., Ltd. and the Zhejiang Province Intelligent Logistics Equipment Engineering Technology Research Center, authored by Liu Zigang, Chen Fei, Tang Haihong, and Chen Liang, investigates the development of a dual-pulse (DP) TIG high-speed welding process for intelligent equipment manufacturing. Published in the Journal of Lanzhou University of Technology, this research addresses the growing demand for high-productivity welding processes in the manufacturing of intelligent logistics equipment, including automated guided vehicles (AGVs), robotic arms, and conveyor systems. The DP-TIG process combines two distinct pulse waveforms within a single welding cycle, enabling the simultaneous control of penetration depth and bead width, which is critical for achieving high travel speeds without compromising weld quality.
The dual-pulse approach represents an evolution of the conventional pulsed TIG welding process, where a single pulse waveform is used to control the heat input and the bead geometry. By introducing a second pulse waveform with different amplitude and frequency characteristics, the DP-TIG process provides additional degrees of freedom for process optimization, enabling the achievement of higher travel speeds while maintaining adequate penetration and bead geometry.
Dual-Pulse Waveform Design and Process Parameters
The dual-pulse TIG waveform consists of a primary pulse with a higher current amplitude and a shorter duration, followed by a secondary pulse with a lower current amplitude and a longer duration. The primary pulse provides the high energy density required for deep penetration, while the secondary pulse maintains the molten pool and controls the bead width. The key parameters of the DP-TIG process include the primary pulse current amplitude, the secondary pulse current amplitude, the primary pulse on-time, the secondary pulse on-time, the pulse frequency, and the travel speed.
| Parameter | Primary Pulse | Secondary Pulse | Process Value |
|---|---|---|---|
| Current Amplitude | 150–250 A | 50–100 A | — |
| On-Time | 5–15 ms | 10–30 ms | — |
| Frequency | 10–50 Hz | 10–50 Hz | — |
| Travel Speed | — | — | 800–2000 mm/min |
| Shielding Gas | — | — | 100% Ar or Ar/He |
| Heat Input | — | — | 0.3–0.8 kJ/mm |
| Base Metal | — | — | Carbon steel, 2–6 mm |
The high travel speeds achieved with the DP-TIG process, in the range of 800–2000 mm/min, represent a significant improvement over conventional TIG welding, which is typically limited to travel speeds of 200–600 mm/min. The key to achieving these high travel speeds lies in the optimized dual-pulse waveform design, which provides sufficient energy for penetration while minimizing the heat input and reducing the risk of distortion and warping.
Microstructural Characteristics and Weld Quality
The microstructure of the DP-TIG welded joints is characterized by a fine-grained structure with minimal segregation, attributed to the high cooling rates and the modified solidification conditions imposed by the dual-pulse waveform. The grain structure is typically equiaxed in the center of the weld and columnar near the fusion boundary, with a grain size that is finer than that achieved with conventional TIG welding. The fine grain structure contributes to improved mechanical properties, particularly in terms of strength and toughness.
The weld quality is evaluated through a combination of non-destructive testing methods, including visual inspection, radiographic testing, and ultrasonic testing. The results show that the DP-TIG welded joints exhibit excellent fusion and penetration, with minimal porosity and no evidence of undercut or excessive reinforcement. The absence of significant defects is attributed to the optimized dual-pulse waveform design, which provides stable arc characteristics and consistent bead geometry at high travel speeds.
| Weld Quality Parameter | DP-TIG | Conventional TIG | Improvement |
|---|---|---|---|
| Travel Speed (mm/min) | 800–2000 | 200–600 | 3–5× |
| Porosity Level | Minimal | Moderate | Significant |
| Undercut | None | Occasional | Complete elimination |
| Penetration Depth (mm) | 1.5–3.0 | 1.0–2.5 | 20–50% increase |
| Bead Width (mm) | 5–10 | 6–12 | More consistent |
| Tensile Strength (MPa) | 450–500 | 420–480 | 5–10% increase |
Engineering Application and Productivity Analysis
The DP-TIG high-speed welding process has been successfully applied to the manufacturing of intelligent logistics equipment, including the welding of AGV chassis frames, robotic arm structures, and conveyor system components. The high travel speeds achieved with the DP-TIG process result in significant productivity improvements, with welding cycle times reduced by 50–70% compared to conventional TIG welding. The improved weld quality and the reduced distortion also contribute to lower post-weld machining and straightening requirements, further enhancing the overall manufacturing efficiency.
The economic analysis of the DP-TIG process shows that the initial investment in the specialized power source and control system is offset by the productivity gains and the reduction in post-weld processing costs. The payback period for the DP-TIG process is typically less than 12 months for high-volume production applications, making it an attractive option for manufacturers seeking to improve their competitive position through process innovation.
Study Insights and Future Directions
The DP-TIG high-speed welding process represents a significant advancement in the field of arc welding technology, offering a practical solution to the challenge of achieving high productivity without compromising weld quality. The dual-pulse waveform design provides a powerful tool for process optimization, enabling the simultaneous control of penetration, bead width, and heat input. For engineers working on the manufacturing of intelligent equipment and other high-volume applications, the DP-TIG process offers a viable alternative to conventional TIG welding, with the potential to significantly improve manufacturing efficiency and product quality. The integration of the DP-TIG process with robotic welding systems and automated monitoring technologies represents a promising direction for the next generation of high-productivity welding systems, enabling the realization of fully automated, high-quality welding operations in modern manufacturing environments.