DP-TIG High-Speed Welding Process Research for Intelligent Equipment Manufacturing

Literature Overview

The study by Liu Zigang, Chen Fei, Tang Haihong, and Chen Liang, published in 2020 in the "Journal of Lanzhou University of Technology," investigates the Double-Pulse TIG (DP-TIG) welding process for high-speed fabrication of intelligent logistics equipment components. The research is funded by Noli Intelligent Equipment Co., Ltd. and the Zhejiang Province Engineering Technology Research Center for Intelligent Logistics Equipment, reflecting a strong industry-academia collaboration. The primary motivation is to increase welding productivity while maintaining or improving weld quality, which is a persistent challenge in mass-production environments where thin-walled structural components are welded at high travel speeds.

Core Technical Points

DP-TIG welding employs two distinct pulse types within each welding cycle: a high-energy pulse (H-pulse) for melting and penetration, and a low-energy pulse (L-pulse) for solidification control and bead shaping. This dual-pulse approach decouples the melting and solidification processes, allowing independent optimization of penetration depth and weld bead geometry. For high-speed welding applications, the key parameters are the H-pulse current (150–300 A), L-pulse current (40–100 A), H-pulse frequency (5–20 Hz), L-pulse frequency (20–50 Hz), and travel speed (600–1500 mm/min).

The authors demonstrate that DP-TIG welding can achieve travel speeds up to 1200 mm/min on 3 mm carbon steel plates while maintaining full penetration and acceptable weld bead profiles. The cooling rate in the weld metal is significantly higher than in conventional TIG welding, which can lead to a fine-grained microstructure with improved mechanical properties, provided that the cooling rate does not exceed the threshold for martensitic transformation and hydrogen-induced cracking.

Process Analysis and Engineering Implications

From a manufacturing standpoint, the DP-TIG process offers several advantages for high-volume production of equipment frames and structural components. The high travel speed reduces welding time by 50–70 percent compared to conventional pulsed TIG, which directly translates to lower labor costs and higher throughput. However, the process also introduces challenges related to arc stability at high speeds, gas coverage of the solidifying pool, and potential porosity formation.

The authors recommend using a nozzle with a 7–8 mm diameter and a torch-to-plate distance of 4–6 mm to ensure adequate gas shielding at high travel speeds. They also suggest a slight torch angle of 5–10 degrees forward to improve gas coverage of the trailing edge of the weld pool. The mechanical properties of DP-TIG welds are comparable to or better than conventional TIG welds, with tensile strength in the range of 480–560 MPa and elongation of 20–28 percent for typical carbon steel grades.

Key Questions and Reflections

A critical question is the scalability of DP-TIG welding to thicker sections and different material grades. While the study focuses on thin carbon steel plates, the applicability to low-alloy steels, stainless steels, and aluminum alloys requires further investigation. The high cooling rates achieved in DP-TIG welding may be beneficial for carbon steels but could promote brittle martensite in higher-alloy materials. Additionally, the study does not extensively address the long-term fatigue performance of DP-TIG welds, which is essential for structural components subjected to cyclic loading.

Another reflection is the cost-benefit analysis of DP-TIG equipment. The specialized power source and control electronics required for DP-TIG welding are more expensive than conventional TIG power sources. However, the productivity gains and reduced post-weld machining requirements may justify the capital investment in high-volume production environments.

Summary

This research demonstrates that DP-TIG welding is a viable and productive alternative to conventional TIG welding for thin-section structural components in intelligent equipment manufacturing. The dual-pulse approach provides superior control over the welding process, enabling high travel speeds without sacrificing weld quality. For engineering practice, the key parameters to optimize are the H-pulse and L-pulse frequencies and current levels, which must be matched to the plate thickness and material grade. The work represents a meaningful step toward high-productivity welding technologies that can meet the demands of modern manufacturing while maintaining the quality standards required for safety-critical applications.