CLADDING TECHNOLOGY SHANXI CO., LTDEffect of Process Parameters on TIG-MIG Hybrid Arc Welding Process
Overview of the Literature
This 2017 publication from Tangshan Kaiyuan Welding Automation Technology Research Institute, authored by Bi Xuesong, Ma Ruifang, and Sun Xiao, investigates the effects of process parameters on TIG-MIG hybrid arc welding. The TIG-MIG hybrid process combines a non-consumable tungsten electrode arc with a consumable wire feed arc, creating a synergistic welding process with enhanced penetration and deposition characteristics. This technology has significant implications for cladding operations where deep penetration and high deposition rates are simultaneously required.
Core Technical Content
The TIG-MIG hybrid welding process operates by positioning a TIG torch at the leading edge of the weld travel direction, with the MIG gun following behind. The TIG arc provides deep penetration and acts as a guide for the MIG arc, while the MIG arc provides the bulk of the metal deposition. The interaction between the two arcs creates a deeper and more stable weld pool than either process alone.
| Process Parameter | Range Studied | Optimal Value | Effect on Weld Quality |
|---|---|---|---|
| TIG current | 80-160 A | 120 A | Penetration depth increases linearly |
| MIG current | 180-300 A | 240 A | Deposition rate increases linearly |
| TIG arc length | 2-6 mm | 3-4 mm | Arc stability and penetration balance |
| MIG arc length | 3-8 mm | 5-6 mm | Transfer mode stability |
| Travel speed | 100-300 mm/min | 200 mm/min | Heat input per unit length |
| TIG-MIG spacing | 5-15 mm | 8-10 mm | Arc interaction and penetration |
| Shielding gas flow (TIG) | 8-15 L/min | 12 L/min | Contamination prevention |
| Shielding gas flow (MIG) | 10-20 L/min | 15 L/min | Arc stability |
The key finding is that the TIG-MIG spacing of 8-10 mm creates an optimal interaction zone where the TIG arc's electromagnetic field compresses the MIG arc, resulting in deeper penetration than either process alone. At spacings below 5 mm, the arcs interfere destructively, causing instability. At spacings above 15 mm, the synergistic effect is lost, and the processes operate independently.
Parameter Interaction Analysis
The researchers identified several critical parameter interactions:
- TIG current and MIG current have a synergistic effect on penetration; increasing both simultaneously produces more than the sum of individual effects
- Travel speed has a non-linear effect on weld width; beyond 250 mm/min, the weld becomes narrow and penetration decreases rapidly
- TIG arc length primarily affects penetration, while MIG arc length primarily affects deposition profile
- Shielding gas composition affects arc behavior differently for each process; the TIG arc is more sensitive to oxygen contamination
| Parameter Combination | Penetration (mm) | Bead Width (mm) | Reinforcement (mm) | Defect Level |
|---|---|---|---|---|
| Low TIG + High MIG | 3.5 | 12 | 3.0 | Acceptable |
| High TIG + Low MIG | 5.0 | 10 | 2.0 | Acceptable |
| High TIG + High MIG | 6.5 | 14 | 2.5 | Excellent |
| Low TIG + Low MIG | 2.5 | 8 | 1.5 | Marginal |
Application to Cladding and Overlay Welding
For cladding operations, the TIG-MIG hybrid process offers unique advantages:
- The TIG arc provides a stable, deep penetration that ensures good metallurgical bonding between the overlay material and the base metal, which is critical for preventing delamination in service
- The MIG arc provides high deposition rates, reducing the number of passes required for thick cladding layers
- The combined heat input is more concentrated than either process alone, reducing the heat-affected zone width and minimizing distortion in thin-walled pressure vessels
For stainless steel overlay on carbon steel substrates, the TIG-MIG hybrid process achieves dilution ratios of 15-25%, compared to 25-40% for conventional MIG overlay alone. This lower dilution is achieved because the TIG arc's deep penetration creates a more stable weld pool boundary, reducing base metal entrainment.
Process Stability and Defect Prevention
The hybrid process requires careful attention to arc stability. The following defect prevention measures are recommended:
| Defect | Cause | Prevention Measure |
|---|---|---|
| Arc instability | Excessive TIG-MIG spacing | Maintain 8-10 mm spacing |
| Porosity | Inadequate shielding | Use 12-15 L/min for each arc |
| Undercut | Excessive travel speed | Limit to 250 mm/min |
| Excessive dilution | High MIG current with low TIG | Balance current ratio 2:1 MIG:TIG |
| Tungsten inclusion | TIG arc contact with pool | Maintain TIG arc length > 3 mm |
Summary
The TIG-MIG hybrid welding process represents a significant advancement for cladding applications where both deep penetration and high deposition rates are required. The optimal parameter windows identified in this research provide a practical foundation for process development in overlay welding operations. Engineers should note that the synergistic effect between the two arcs requires careful geometric alignment and parameter coordination, making this process more complex to set up than conventional MIG overlay but offering superior results for critical cladding applications in pressure vessel fabrication.