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.
Understanding Tools & Workshop Machines: TIG Welder
A TIG setup works by completing an electrical circuit between the torch and the metal workpiece. When the welder starts the arc, electricity passes through a tiny gap at the tungsten tip. This creates a very hot plasma column.
The heat is concentrated in a small area, so the welder can control the molten pool with great precision. A foot pedal or torch control often changes the current while welding. More current makes the pool larger and hotter.
Less current lets the pool cool before the metal becomes too thin or distorted. This control is especially useful near edges, corners, and thin sheet metal.
The welder usually adds filler metal by hand as a separate rod. The arc melts the edges of the joint first, forming a pool. Small amounts of filler are then fed into the front edge of that pool.
The torch angle, arc length, travel speed, and filler timing must work together. Holding the tungsten too far away spreads the arc and makes it less stable. Touching the tungsten into the molten metal can contaminate its tip.
A contaminated tip often gives a wandering arc and a dirty looking weld. It must be reground before accurate work can continue.
Shielding gas has a job that is easy to miss. Hot metal reacts quickly with oxygen, nitrogen, and water vapour in air. These reactions can make a weld weak, porous, brittle, or discoloured.
The gas flows from a cup around the electrode and pushes air away from the weld area. Good coverage is needed before the arc begins, during welding, and for a short time after the arc stops. The metal remains hot after the visible arc has ended.
Drafts, a dirty gas cup, blocked holes, or incorrect gas flow can ruin this protection. Too little flow allows air in. Excessive flow can create turbulence that pulls surrounding air into the gas stream.
Material preparation makes a major difference. Oil, paint, rust, moisture, and oxide layers can release gases or leave unwanted material in the joint. Steel and stainless steel need clean bright surfaces near the seam.
Aluminum needs extra care because its oxide coating melts at a much higher temperature than the aluminum below it. The alternating current used on aluminum helps remove this oxide during part of each cycle. Joint fit matters too.
A wide gap requires more filler and heat. More heat increases the chance of warping. Clamps, tack welds, and a sensible welding order help keep parts in position.
Students should think of TIG welding as heat management rather than simply joining metal. The amount of heat delivered depends on electrical conditions and how fast the torch moves. Moving slowly puts more heat into each part of the seam.
This can improve penetration, yet it can burn through thin metal or bend a panel. Moving too fast can leave a narrow bead that has not properly fused to both sides of the joint. Practice on scrap pieces teaches the signs of a healthy weld pool.
Safe practice is essential. The arc produces intense ultraviolet light, hot sparks, fumes, and dangerous electrical energy. A proper helmet, gloves, flame resistant clothing, ventilation, and a clear work area are necessary every time.
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.