Dual TIG Reactive Arc Additive Manufacturing Method and Process

Literature Overview

This paper by Zhang Jia, Shao Peize, Wang Xinxin, Huang Jiankang, and Fan Ding, published in the Transactions of the China Welding Society in 2024 (Vol. 45, No. 8, pp. 62–69), proposes a novel additive manufacturing method using dual TIG reactive arcs as the heat source. The method employs two TIG torches with a small amount of active oxygen gas added to the shielding gas, using 1.2 mm diameter SUS304 austenitic stainless steel wire to deposit thin-walled components. The study investigates the effects of oxygen introduction, deposited current distribution, arc travel speed, and wire feed speed on the deposited layer average width and height, and examines the microstructure and mechanical properties of the deposited metal.

Core Technical Insights

The dual TIG configuration provides two distinct advantages over single TIG additive manufacturing: increased heat input and the ability to distribute deposited current between front and rear torches. The introduction of reactive oxygen gas into the shielding atmosphere reduces the surface tension of the deposited metal and molten pool, enhancing wetting and spreading characteristics. This results in improved bead geometry and higher deposition efficiency.

Under equivalent current conditions, the dual TIG reactive arc additive manufacturing process achieves a deposition efficiency of 2.7 kg/h, which is a significant improvement over conventional single TIG arc deposition. The microstructure of the deposited metal consists of columnar dendritic crystals oriented perpendicular to the deposition direction, with no significant change in morphology due to oxygen introduction. However, the tensile strength and elongation at break of the deposited wall decrease slightly with increasing oxygen content.

Engineering Practice Implications

The dual TIG reactive arc additive manufacturing method has direct relevance to pipe and fitting manufacturing, particularly for producing thin-walled components with complex geometries. The high deposition efficiency of 2.7 kg/h makes this method competitive with conventional fabrication processes for medium-scale production. The improved wetting characteristics resulting from oxygen introduction are particularly beneficial for building thin-walled structures where layer adhesion and geometric accuracy are critical.

For pipe fitting production, the ability to control deposited current distribution between front and rear torches provides a powerful means of shaping the deposited wall geometry. By adjusting the current ratio, engineers can optimize the width-to-height ratio of deposited layers to match the desired component dimensions. This is particularly valuable for producing reducers and elbows where wall thickness varies along the component length.

The slight decrease in mechanical properties with oxygen introduction is a trade-off that must be carefully managed. For non-critical structural applications, the improved deposition efficiency and bead geometry may outweigh the minor strength reduction. For critical applications, the oxygen content should be minimized while still achieving acceptable wetting characteristics.

Key Questions and Reflections

The interaction between the two TIG arcs in the dual configuration raises important questions about process stability and reproducibility. The authors' study demonstrates that the process can produce consistent results under controlled conditions, but the sensitivity of the deposited geometry to torch spacing, arc interaction effects, and gas flow interference needs further investigation. In a production environment, maintaining precise torch positioning and gas flow symmetry is essential for consistent quality.

The use of oxygen as an active gas in stainless steel welding requires careful consideration of metallurgical consequences. While the authors report only slight changes in microstructure and mechanical properties, the long-term effects of oxygen inclusion on corrosion resistance, fatigue behavior, and creep performance are not addressed. For pipe applications in corrosive or high-temperature service, these factors must be evaluated before adopting the reactive arc approach.

Study Insights and Implications

This research demonstrates a promising approach to increasing the productivity of arc-based additive manufacturing for stainless steel components. The dual TIG reactive arc method combines the high deposition rate of multi-arc welding with the improved wetting of reactive gas welding, achieving a deposition efficiency that makes it competitive with conventional fabrication methods. For engineers working on pipe and fitting production, this technology offers a pathway to manufacturing complex, thin-walled components with reduced material waste and improved geometric accuracy. The parameter interaction effects identified in this study provide a practical guide for process optimization, and the microstructural analysis confirms that the deposited metal retains the desirable austenitic characteristics of SUS304 stainless steel.