A TIG welder uses a focused electric arc to melt metal and make a strong, precise joint. TIG stands for tungsten inert gas, because the arc comes from a nonconsumable tungsten electrode and the weld is protected by an inert shielding gas. This process matters in aerospace, automotive, bicycle, art, and repair work because it gives excellent control and clean welds.
It is often chosen when weld quality and appearance are more important than welding speed.
Key Facts
- Electrical power in the arc is approximately P = VI, where P is power in watts, V is voltage, and I is current.
- Heat input per unit length can be estimated by H = VI / travel speed, using consistent units.
- The tungsten electrode does not melt into the weld under normal TIG welding conditions.
- Argon is the most common TIG shielding gas because it is inert and helps stabilize the arc.
- DC electrode negative is commonly used for steel, stainless steel, copper alloys, and titanium.
- AC TIG is commonly used for aluminum because it helps break up the oxide layer while providing heat to the workpiece.
Vocabulary
- Tungsten electrode
- A heat-resistant electrode that carries current and forms the welding arc without being intentionally consumed.
- Shielding gas
- An inert gas that flows around the arc and weld pool to keep oxygen and nitrogen from contaminating the hot metal.
- Weld pool
- The small region of molten metal where the base material and any filler metal mix before solidifying.
- Filler rod
- A separate metal rod added by hand to supply extra material to the weld joint.
- Arc length
- The distance between the tungsten electrode tip and the workpiece that affects arc stability, heat focus, and weld shape.
Common Mistakes to Avoid
- Touching the tungsten to the weld pool, because this contaminates the electrode and can leave tungsten particles in the weld.
- Using too little shielding gas, because air can reach the hot weld pool and cause porosity, discoloration, and weak joints.
- Holding too long an arc, because the heat spreads out, the arc becomes unstable, and the weld bead becomes wide and uneven.
- Choosing the wrong polarity or current type, because steel usually needs DC electrode negative while aluminum often needs AC for oxide cleaning.
Practice Questions
- 1 A TIG welder operates at 14 V and 120 A. Estimate the electrical power delivered to the arc in watts.
- 2 A welder uses 16 V and 90 A while traveling at 4 mm/s. Estimate the heat input per millimeter using H = VI / travel speed.
- 3 Explain why TIG welding uses shielding gas and why contamination is more likely when the torch is held too far from the workpiece.