CLADDING TECHNOLOGY SHANXI CO., LTDNumerical Simulation of TIG Welding Arc with Argon and Helium Shielding Gases
Literature Overview
Published in the Journal of Henan Institute of Technology (2026), this study by researchers from Henan Institute of Technology presents numerical simulation results comparing the TIG welding arc characteristics under argon and helium shielding gases. The work is supported by the Henan Institute of Technology Innovation Education Course Project (CX-2020-005, CX-2021-004). Understanding arc behavior is fundamental to process optimization, particularly for cladding and overlay applications where arc stability directly affects deposit quality.
Physical Principles of TIG Arc Behavior
The TIG welding arc is a complex plasma phenomenon governed by electromagnetic forces, thermal convection, and gas dynamics. The governing equations include:
- Maxwell's equations: Describe electromagnetic field distribution
- Navier-Stokes equations: Govern gas flow dynamics
- Energy equation: Accounts for Joule heating, radiation, and convection
- Species transport equations: Track ionization states and plasma composition
The shielding gas composition profoundly influences arc properties through its effect on:
| Property | Argon (Ar) | Helium (He) | Engineering Significance |
|---|---|---|---|
| Atomic mass | 40 g/mol | 4 g/mol | Affects gas flow dynamics |
| Thermal conductivity | 0.0177 W/(m·K) | 0.1513 W/(m·K) | Determines heat transfer rate |
| Ionization potential | 15.76 eV | 24.59 eV | Influences arc stability |
| Arc voltage | Lower | Higher (~10-15% higher) | Affects energy input |
| Penetration depth | Shallower | Deeper | Critical for thick-section welding |
| Arc column diameter | Wider | Narrower | Affects bead profile |
Simulation Results and Analysis
The numerical model typically employs a finite volume method with coupled electromagnetic and thermal-fluid solvers. Key simulation findings include:
Arc Temperature Distribution
The arc temperature profile shows that helium produces a hotter core temperature (approximately 15,000–20,000 K) compared to argon (12,000–15,000 K), while the arc boundary temperature is lower due to helium's higher thermal conductivity distributing heat more uniformly.
Current Density Distribution
The current density distribution reveals that helium produces a more concentrated current density at the arc root (cathode spot), leading to deeper penetration. The peak current density for helium can be 20–30% higher than for argon at equivalent welding parameters.
Gas Flow Velocity
The lower molecular weight of helium results in higher gas flow velocities within the arc column. The axial velocity at the arc center can reach 200–400 m/s for helium compared to 150–300 m/s for argon, which affects the cooling rate of the weld pool.
Practical Implications for Cladding and Overlay Applications
For weld overlay and cladding operations, the choice of shielding gas has direct consequences:
- Dilution control: Helium's deeper penetration increases base metal dilution, which may be undesirable when maintaining overlay alloy chemistry. For nickel-based alloy cladding on carbon steel, argon is typically preferred to minimize dilution.
- Bead profile: Argon produces wider, flatter beads suitable for corrosion-resistant overlay layers, while helium produces narrower, more convex beads with deeper penetration.
- Multi-pass welding: For thick overlay deposits, helium may reduce the number of passes required, but the increased dilution must be compensated by adjusting filler metal composition.
- Cost considerations: Helium is significantly more expensive than argon (typically 3–5 times the cost), which must be factored into production economics.
Process Window Optimization
The simulation results enable process window mapping for different application scenarios:
| Application | Recommended Gas | Current Range (A) | Travel Speed (cm/min) | Rationale |
|---|---|---|---|---|
| Carbon steel base cladding with SS304 | Ar or Ar-5%He | 120–200 | 8–15 | Moderate penetration, good wetting |
| Nickel alloy overlay (Inconel 625) | Ar | 100–180 | 6–12 | Minimize dilution |
| Thick-section austenitic steel welding | Ar-50%He or Ar-75%He | 150–250 | 5–10 | Enhanced penetration |
| Thin-section titanium welding | Ar | 80–150 | 10–20 | Controlled heat input |
Study Insights
This numerical study provides valuable theoretical foundation for process parameter selection in TIG welding operations. The simulation approach allows prediction of arc behavior under conditions that may be difficult to measure experimentally due to extreme temperatures and rapid dynamics. For engineers involved in weld overlay qualification per NB/T 47014 or ASME Section IX, understanding the fundamental arc physics enables more rational process development rather than purely empirical parameter selection.
The research also highlights the importance of considering shielding gas properties as a process variable rather than a fixed parameter. In cladding applications where deposit chemistry is critical, the dilution behavior governed by shielding gas selection must be incorporated into the overall process design from the outset.