CLADDING TECHNOLOGY SHANXI CO., LTDTIG Welding Arc Starting Forms and Their Effects
Literature Overview
The technical article by Xu Heshui (1997), published in Welding Technology (焊接技术), discusses the various arc starting methods used in TIG (GTAW) welding and their effects on weld quality. This practical-focused article was authored by an engineer at Nanjing Chenguang Machinery Factory and addresses a fundamental aspect of TIG welding that directly impacts weld initiation quality, porosity formation, and overall weld integrity. Understanding arc starting techniques is essential for achieving consistent, high-quality welds in production environments.
Core Technical Content
The article categorizes TIG arc starting methods into contact and non-contact types, each with distinct characteristics regarding arc stability, electrode wear, and weld initiation quality. The non-contact methods include high-frequency (HF) start, lift arc, and pilot arc methods, while contact methods involve direct electrode-to-workpiece contact. The study examines the electrical and thermal characteristics of each method during the critical arc initiation phase.
The HF arc starting method uses a high-frequency oscillator (typically 100–500 kHz) to ionize the gas between the electrode and workpiece, creating a conductive path that allows the main welding arc to establish. The lift arc method involves lifting the electrode after initial contact, creating an arc through the short circuit. The pilot arc method uses a separate small arc to pre-heat the electrode tip before main arc initiation.
Comparison of Arc Starting Methods
| Method | Arc Stability | Electrode Wear | Porosity Risk | Equipment Complexity | Application |
|---|---|---|---|---|---|
| HF Start | High | Low | Low | Medium | Stainless steel, nickel alloys |
| Lift Arc | Medium | Medium | Medium | Low | Carbon steel, general use |
| Pilot Arc | High | Low | Low | High | Precision welding, thin materials |
| Contact Start | Low | High | High | Low | Rarely used in modern practice |
The article emphasizes that the arc starting method significantly affects the initial weld pool formation, which in turn influences the final weld bead geometry, microstructure, and mechanical properties at the weld start point. Inconsistent arc starting can lead to cold starts, porosity, and incomplete fusion at the beginning of the weld, which are critical defects in pressure vessel fabrication.
Practical Recommendations for Production Welding
For cladding and overlay welding operations, the following arc starting practices are recommended based on the analysis:
- For nickel-based alloy overlays: Use HF arc starting with a minimum HF current of 5 mA to ensure stable arc initiation without electrode contamination.
- For stainless steel cladding: HF arc starting is preferred, with arc pre-heating for 1–2 seconds before introducing filler metal to establish a stable weld pool.
- For carbon steel welding: Lift arc method is acceptable for thicker sections where minor initiation irregularities are less critical.
- For thin section welding: Pilot arc or pre-heated electrode methods should be employed to prevent electrode contamination and ensure clean arc initiation.
Quality Control Implications
In bimetal pressure vessel fabrication, weld initiation quality is subject to strict inspection requirements under NB/T 47002 and ASME Section IX. The arc starting method must be documented in the welding procedure specification (WPS), and welders must demonstrate consistent arc starting technique during qualification testing. Inconsistent arc starting can result in:
- Excessive porosity at weld start (detected by RT or UT)
- Lack of fusion at weld initiation (detected by UT or MT)
- Excessive dilution at weld start (detected by chemical analysis)
- Cracking at weld start due to thermal shock (detected by PT or MT)
The article's practical guidance remains highly relevant for modern welding operations, as the fundamental physics of arc initiation has not changed despite advances in power source technology. Modern digital power sources offer improved arc starting control through programmable soft-start functions, but the underlying principles discussed in this 1997 article remain the foundation for achieving consistent, high-quality TIG welds.
Concluding Remarks on the Five Studies
These five studies collectively represent important contributions to the understanding and practice of TIG welding technology across different applications and time periods. From the fundamental thermal simulation of Invar welding to the practical arc starting techniques, each study addresses a critical aspect of welding science and engineering. The progression from basic arc starting methods (1997) through droplet transfer mechanisms (2007), temperature field simulations (2008), weaving process modeling (2008), to advanced in-situ alloying techniques (2015) demonstrates the evolution of welding research from empirical practice toward computational and materials-engineering approaches. For engineers in the cladding, bimetal, and pressure vessel industries, these studies provide a comprehensive knowledge base spanning fundamental physics, process optimization, and materials science — all essential for achieving reliable, high-integrity welded joints in demanding industrial applications.