TIG Welding Guide - Process, Equipment & Best Practices

Introduction to TIG Welding (GTAW)

Tungsten Inert Gas (TIG) welding — formally Gas Tungsten Arc Welding (GTAW) — is the most precise arc welding process. It uses a non-consumable tungsten electrode to create the arc, with optional filler rod addition, and relies on an inert shielding gas (typically high-purity argon) to protect the arc and weld pool from atmospheric contamination. The absence of flux and the clean shielding environment mean no slag, minimal spatter, and excellent metallurgical integrity.

Because TIG focuses heat input tightly and allows independent control of filler, it is chosen when joint quality and appearance are critical — aerospace components, pharmaceutical and food-grade stainless pipework, nuclear and chemical processing equipment, precision automotive and motorsport fabrications.

TIG Welding Process Fundamentals

The TIG arc is established between a sharpened tungsten tip and the workpiece. Tungsten’s melting point (~3,422 °C) ensures the electrode does not melt into the pool; the arc supplies heat to fuse the base metal. Autogenous welds fuse joint edges without filler and are common on thin stainless or titanium. Where reinforcement, gap filling, or tailored properties are needed, a matching filler rod is added manually to the pool’s leading edge, always inside the gas envelope.

Arc length is typically controlled within 1–3 mm; excessive length causes arc wandering, oxidation, and porosity. Torch angle of ~10–15° in the travel direction improves visibility and gas coverage. Dipping the tungsten into the pool or touching the filler to the electrode contaminates the tip, destabilising the arc and risking tungsten inclusions.

TIG Welding Equipment and Power Sources

TIG requires a constant-current (CC) power source with a drooping volt–ampere characteristic: current remains stable despite small changes in arc length. Most sets provide DC, AC, or AC/DC. DC electrode negative (DCEN) concentrates ~70% of heat into the workpiece; AC alternates polarity to clean oxide films and penetrate, essential for aluminium and magnesium.

Arc initiation is achieved via high-frequency (HF) start (non-contact) to avoid tungsten contamination, or lift-arc where HF is unavailable. Controls (foot pedal or torch-mounted) allow real-time current modulation for crater fill, variable thickness, or position changes. Torches are air-cooled for light/medium duty or water-cooled for high current and long duty cycles. Gas lenses and appropriately sized nozzles improve shielding.

Tungsten Electrodes and TIG Filler Rods

Tungsten Electrodes

Choice of tungsten influences arc start, stability, and life:

• Pure (Green): Favourable for AC aluminium; tip “balls” for oxide cleaning.
• 2% Thoriated (Red): Stable DC arcs for steels and nickel alloys; slightly radioactive — follow safe handling.
• Ceriated (Grey): Excellent low-current starts; ideal for thin sheet, AC/DC.
• Lanthanated (Blue/Gold): Versatile AC/DC performance, long life; common modern replacement for thoriated.

Tip geometry is critical: a ground cone produces a narrow, concentrated arc (DCEN steels/stainless), while a slightly balled tip is used for AC aluminium.

TIG Filler Rods

Supplied in cut lengths (typ. 1.6–3.2 mm). Composition generally matches the base metal with alloying to tune toughness/corrosion resistance (e.g., ER70S-2 carbon steel, ER308L stainless, ER5356 aluminium-magnesium). Feed the rod to the pool’s leading edge within the gas shroud; remove surface oxides and oils prior to welding.

Shielding Gases for TIG Welding

Argon (Ar) is the universal first choice: easily ionised, smooth arcs, good cleaning and coverage at modest flow rates. Helium (He) raises arc voltage and heat input, increasing penetration and travel speed on thick sections (higher flow rates required). Ar/He blends combine stability with heat for aluminium and copper alloys. Ar/H₂ (1–5%) improves surface finish and penetration on austenitic stainless and Cu-Ni alloys, but must not be used on hydrogen-sensitive materials.

Set flow to achieve laminar coverage: too low risks oxidation/porosity; too high creates turbulence and entrains air. Use post-flow to protect hot tungsten and fresh weld metal until dull red/black, preventing oxidation and colouration.

TIG Welding Modes of Operation (DCEN, DCEP, AC, Pulsed)

• DCEN: Work-directed heat for deep penetration on steels, stainless, nickel, titanium, copper alloys.
• DCEP: Shallow penetration, high electrode heating; niche use on very thin sheet.
• AC: Alternating cleaning (EP) and penetration (EN); standard for aluminium and magnesium.
• Pulsed TIG: Alternates peak/background current to reduce overall heat input, stabilise small pools, and improve out-of-position control — ideal for thin stainless, titanium, and intricate joints.

Common TIG Welding Defects and Remedies

Typical discontinuities and how to address them:

Defect	Example	Cause	Remedy
Porosity		Low/erratic gas flow, contamination, long arc length	Clean materials, correct flow & nozzle, maintain short arc
Lack of Fusion / Penetration		Low current, high travel speed, poor torch angle	Increase current, reduce speed, optimise angle; consider He or Ar/He
Undercut		Excess current, fast travel, incorrect filler manipulation	Reduce current, slow travel, feed rod at pool leading edge

Advantages of TIG Welding vs Other Processes

TIG delivers the highest weld quality with excellent surface finish, no slag and virtually no spatter. Independent control of heat and filler metal allows fine control on thin material, reactive alloys (Ti, Zr), and code-critical joints. Pulsed capability widens usability to positional and thin-gauge work. Compact torches and gas lenses improve access and shielding in confined geometries.

TIG Welding Applications in Industry

Common applications include aerospace (titanium/nickel alloy structures and engine parts), pharmaceutical and food-grade stainless pipework, nuclear and chemical pressure systems, motorsport and performance automotive fabrications (exhausts, roll cages, alloy tanks), and general fabrication of thin sheet or prototypes where aesthetics and integrity are paramount.

Conclusion: Why TIG Welding Remains Essential

TIG welding is the benchmark for precision fabrication: clean, slag-free welds, fine control of heat and filler, and compatibility with a wide range of materials including reactive alloys. While slower and more skill-intensive than MIG or MMA, it delivers the weld integrity demanded by aerospace, nuclear, pharmaceutical, and high-spec manufacturing.

Explore ESAB’s AC/DC TIG power sources, precision torches, tungsten electrodes, and filler rods to achieve code-compliant, repeatable quality.

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