What's inside
- What does TIG welding mean?
- How does a TIG welding machine work?
- The parts of the TIG arc
- Polarity, current, and heat control
- Joint preparation matters more with TIG
- A practical TIG setup sequence
- Why TIG suits thin and high-value metals
- Choosing a TIG setup by situation
- Ownership realities and common mistakes
- Related Guides
- What does TIG welding mean?
- How does a TIG welding machine work?
- The parts of the TIG arc
- Polarity, current, and heat control
- Joint preparation matters more with TIG
- A practical TIG setup sequence
- Why TIG suits thin and high-value metals
- Choosing a TIG setup by situation
- Ownership realities and common mistakes
- Related Guides
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How TIG welding works is simple in principle: an electric arc jumps from a non-consumable tungsten electrode to the metal, while shielding gas protects the hot weld from contamination and a separate filler rod may be added to build the joint.
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What we cover
- What does TIG welding mean?
- How does a TIG welding machine work?
- The parts of the TIG arc
- Polarity, current, and heat control
- Joint preparation matters more with TIG
- A practical TIG setup sequence
- Why TIG suits thin and high-value metals
- Choosing a TIG setup by situation
- Ownership realities and common mistakes
- Related Guides
What does TIG welding mean?
TIG stands for tungsten inert gas. The process is also called GTAW, or gas tungsten arc welding. “Tungsten” describes the electrode, which resists melting at welding temperatures, while “inert gas” normally means argon or an argon blend that does not react readily with the molten metal.
Unlike MIG welding, TIG does not continuously feed filler wire through the torch. The operator controls the arc with a foot pedal, torch button, or machine control and adds filler by hand only when the joint needs it. That separation gives TIG excellent control over heat and weld size, but it also makes the process slower and more demanding to learn.
How does a TIG welding machine work?
A TIG power source converts incoming electrical power into a controlled welding current. In broad terms, it performs four jobs:
- It supplies constant current to maintain the arc as the torch-to-work distance changes slightly.
- It starts the arc, often using high-frequency or lift-arc ignition instead of striking the tungsten directly against the work.
- It controls amperage, arc timing, gas flow, and sometimes pulse frequency and balance.
- It sends current through the tungsten while a gas valve or solenoid delivers shielding gas through the torch nozzle.
When the tungsten is brought close to the grounded workpiece, the electrical arc ionizes the gap. The arc’s heat melts a small pool of base metal. The operator moves the torch along the joint and dips filler rod into the leading edge of the pool when additional metal is required. After the arc stops, post-flow keeps argon moving over the cooling tungsten and weld puddle, reducing oxidation.
The parts of the TIG arc
Tungsten electrode
The tungsten is sharpened or shaped according to the current type and material. A pointed tungsten concentrates the arc for precise DC welding. On aluminum with AC, the tip may be prepared with a small rounded end, although modern inverter machines often allow a relatively pointed preparation.
The electrode should not touch the molten puddle. Contamination causes an unstable arc and can introduce tungsten into the weld. If contact occurs, stop, let the electrode cool, remove the contaminated section, and regrind it lengthwise on a dedicated wheel.
Shielding gas
Argon flowing from the torch forms an invisible barrier around the tungsten and weld pool. Typical starting flow is about 15–20 cubic feet per hour, or roughly 7–9 litres per minute, but the correct setting depends on nozzle size, drafts, cup design, and torch position. Excessive flow can create turbulence and pull air into the shield, so “more gas” is not automatically better.
Filler metal
Filler rod is matched to the base metal and joint requirements. Common diameters include 1.0 mm, 1.6 mm, 2.4 mm, and 3.2 mm. Thin sheet often needs no filler or a small 1.0–1.6 mm rod, while thicker steel may use 2.4 mm or larger. Keep the rod’s end inside the gas shield as it melts; withdrawing it repeatedly into room air can contaminate the weld.
Polarity, current, and heat control
Most TIG welding of steel, stainless steel, copper, and titanium uses DC electrode negative, often written DCEN. The tungsten connects to the negative terminal and the workpiece to the positive terminal. This produces a concentrated arc with good penetration and helps keep the tungsten relatively cool.
Aluminum and magnesium are commonly welded with AC. Alternating current helps break up the oxide layer on the surface while still providing useful penetration. AC machines often include balance control, which adjusts the proportion of cleaning action versus penetration, and frequency control, which changes the arc’s focus and character.
Amperage is the main heat control, but travel speed, arc length, material thickness, joint fit-up, and pulse settings matter too. A long arc spreads heat and can produce a wide, weak-looking bead. Holding the tungsten approximately 1.5–3 mm above the work keeps the arc focused. A pedal or remote amperage control lets you reduce heat near the end of a joint or when the metal begins to overheat.
| Material and thickness | Typical starting current | Common polarity | Useful tungsten range |
|---|---|---|---|
| Mild steel, 0.8 mm sheet | 25–45 A | DCEN | 1.0–1.6 mm |
| Stainless steel, 1.5 mm | 45–75 A | DCEN | 1.6 mm |
| Aluminum, 2.0 mm | 70–110 A | AC | 1.6–2.4 mm |
| Mild steel, 3.0 mm | 100–140 A | DCEN | 2.4 mm |
These are starting ranges, not guaranteed settings. The actual value changes with joint design, backing, material condition, and whether the work is flat, vertical, or overhead.
Joint preparation matters more with TIG
TIG exposes contamination that another process might hide with a larger, faster arc. Remove paint, oil, mill scale, rust, and oxide from both sides of the joint. Use a stainless-steel brush reserved for aluminum if welding aluminum; a brush previously used on carbon steel can transfer contaminants.
Fit-up should be close and consistent. A large, changing gap forces the operator to add more filler and heat, increasing distortion and burn-through risk. For thin sheet, clean sheared edges, small tack welds, and copper or aluminum backing can make a major difference. Degrease the material before final brushing, and avoid touching cleaned surfaces with oily gloves.
A practical TIG setup sequence
- Identify the metal. Choose DCEN for most steels and AC for aluminum or magnesium.
- Choose the tungsten. Select diameter for the current range, grind it lengthwise, and install it so only the appropriate amount extends from the cup.
- Install the correct filler. Match its alloy and diameter to the base metal and joint thickness.
- Set gas flow. Begin around 15–20 CFH, check for leaks, and protect the work area from fans and drafts.
- Set amperage. Start at the low end of the expected range and increase gradually on scrap.
- Practice the puddle. Establish a small, shiny pool before moving. Add filler at the leading edge with a steady dipping rhythm.
- Finish correctly. Reduce current gradually if possible, keep the torch in position during post-flow, and do not remove the torch while the tungsten is still glowing.
Why TIG suits thin and high-value metals
TIG’s low, controllable heat input makes it useful for thin stainless sheet, bicycle parts, precision brackets, food-equipment components, and visible aluminum work. The arc can be focused into a small area, and filler is added only when needed. This reduces spatter and leaves a clean weld that may require little finishing.
It is also valuable when the material is expensive or difficult to replace. The operator can carefully control penetration, avoid burying slag in the joint, and produce a neat bead with minimal cleanup. The trade-off is speed: TIG generally deposits metal more slowly than MIG, and poor technique can overheat thin material despite the machine’s precise controls.
Choosing a TIG setup by situation
| Your situation | Most suitable setup | Reason |
|---|---|---|
| Occasional steel repairs, limited budget | 160–200 A DC TIG/inverter with lift arc | Handles thin to medium steel without paying for aluminum functions. |
| Learning and frequent workshop use | 200–250 A inverter with HF start, foot control, and pulse | Easier starts and better control over thin material and heat buildup. |
| Aluminum fabrication | AC/DC machine, ideally 200 A or more | AC is required for effective aluminum oxide control and penetration. |
| Portable site work | Compact inverter with dependable input-voltage range | Lower weight and better tolerance of generator or extension-cord conditions. |
Ownership realities and common mistakes
The tungsten tip, ceramic cup, collet, collet body, gas lens, and torch hose are consumables. Cups can chip, collets lose grip, and gas lenses collect dust or spatter. Keep spare tungstens and cups available, inspect the torch lead for cuts, and replace damaged gas fittings rather than accepting a small leak.
The most common beginner errors are using too much amperage, holding too long an arc, moving too slowly, feeding filler from outside the gas shield, and welding over dirty metal. Another frequent problem is insufficient post-flow, which leaves the tungsten blue, gray, or contaminated. TIG rewards preparation and steady coordination more than brute power: clean metal, correct polarity, short arc length, controlled travel, and consistent shielding gas are the foundations of a sound weld.
