GTAW · Gas Tungsten Arc Welding
TIG Welding
TIG welding strikes an arc from a non-consumable tungsten electrode under argon shielding, with filler added by hand — the slowest process and the one that produces the highest quality welds.
- GTAW
- DCEN for steel and stainless; AC for aluminium and magnesium
- 5–300 A depending on thickness and material
- Argon or argon-helium, external gas only
How tig welding works
A tungsten electrode in a gas-cooled or water-cooled torch carries the arc but is not consumed. Argon flows around the electrode to shield both the tungsten and the puddle. The welder controls heat with a foot pedal or torch control and feeds filler rod into the leading edge of the puddle with the other hand. Because heat input and filler addition are independent, TIG gives more control than any other arc process.
At a glance
| AWS designation | GTAW — Gas Tungsten Arc Welding |
|---|---|
| Also called | TIG, GTAW, Heliarc |
| Polarity | DCEN for steel and stainless; AC for aluminium and magnesium |
| Typical amperage | 5–300 A depending on thickness and material |
| Typical voltage | 10–20 V |
| Positions | All positions |
| Deposition rate | Low — the slowest of the common processes |
| Shielding | Argon or argon-helium, external gas only |
| Skill level | The most demanding; requires coordinated use of both hands and a foot pedal |
Current types
| Mode | Description | Typical use |
|---|---|---|
| DCEN (straight polarity) | About 70% of the heat goes into the work. The standard setting for steel, stainless, titanium and nickel alloys. Allows a sharpened tungsten and a narrow, deep arc. | Steel, stainless, titanium, copper |
| AC | Alternates between electrode negative for penetration and electrode positive for oxide cleaning. Required for aluminium and magnesium, whose oxide layer melts far hotter than the metal beneath it. | Aluminium and magnesium |
| Pulsed DC | Pulses between peak and background current, reducing heat input and helping control the puddle on thin material and on open root passes. | Thin sheet, root passes, heat-sensitive alloys |
Shielding gas selection
| Gas | Used for | Notes |
|---|---|---|
| 100% argon | Almost all TIG welding | The default for steel, stainless and aluminium alike. |
| 75% Ar / 25% He | Thick aluminium and copper | Helium raises arc voltage and heat input for better penetration. |
| Ar with 2–5% H2 | Austenitic stainless only | Improves travel speed and bead wetting. Never on carbon steel, ferritic stainless, or any hydrogen-sensitive material. |
| Argon back purge | Stainless and titanium roots | Prevents sugaring on the unshielded side of a root pass. |
Starting settings
Starting points only — every machine, joint and position shifts them. Adjust by arc sound and bead profile.
| Thickness | Tungsten | Amps | Filler | Gas Flow |
|---|---|---|---|---|
| 0.030 in (22 ga) | 1/16 in | 20–40 | 1/16 in | 15 CFH |
| 1/16 in (1.6 mm) | 1/16 in | 50–75 | 1/16 in | 15 CFH |
| 1/8 in (3.2 mm) | 3/32 in | 90–130 | 3/32 in | 15–20 CFH |
| 3/16 in (4.8 mm) | 3/32–1/8 in | 130–175 | 3/32–1/8 in | 20 CFH |
| 1/4 in (6.4 mm) | 1/8 in | 175–225 | 1/8 in | 20–25 CFH |
Advantages
- The highest weld quality and the best control of any arc process
- No spatter and no slag
- Welds almost any metal, including aluminium, titanium, magnesium and nickel alloys
- Filler metal is optional — thin edges can be fused autogenously
- Precise heat control down to a few amps for very thin material
Limitations
- Slowest deposition rate of the common processes
- Steepest learning curve
- Base metal must be genuinely clean
- Cannot be used in wind without shelter
- Equipment costs more than a comparable MIG or stick machine
Where it is used
- Stainless and sanitary tube and pipe welding
- Aerospace and motorsport fabrication
- Aluminium fabrication where appearance matters
- Root passes on pipe, later filled with stick or flux-core
- Thin-wall tubing, exhaust systems and bicycle frames
Filler metals for tig welding
ER308L
AWS A5.9/A5.9M · Stainless Steel
ER308L is the bare wire and TIG rod for 304 and 304L stainless — the same low-carbon 19Cr-10Ni chemistry as E308L…
ER316L
AWS A5.9/A5.9M · Stainless Steel
ER316L is the molybdenum-bearing bare filler for 316 and 316L stainless — the standard TIG rod and MIG wire for…
ER309L
AWS A5.9/A5.9M · Stainless Steel
ER309L is the bare filler for welding stainless to carbon steel — over-alloyed at 23Cr-12Ni so the joint stays…
ER4043
AWS A5.10/A5.10M · Aluminum
ER4043 is the 5% silicon aluminum filler — fluid, crack-resistant and the default choice for welding 6061 and…
ER5356
AWS A5.10/A5.10M · Aluminum
ER5356 is the 5% magnesium aluminum filler — stronger than ER4043, stiffer to feed, and the choice when the joint…
ER70S-6
AWS A5.18/A5.18M · Carbon & Mild Steel
ER70S-6 is the default solid MIG wire for carbon steel — high silicon and manganese let it weld over mill scale and…
TIG Welding — common questions
What does TIG stand for?
Tungsten Inert Gas. The formal AWS name is Gas Tungsten Arc Welding, or GTAW. It is also called Heliarc, after the original trade name from when helium was the shielding gas.
Why does aluminium TIG need AC?
Aluminium carries a tough oxide skin that melts at roughly 3700 °F while the metal beneath melts at about 1200 °F. The electrode-positive half of the AC cycle blasts that oxide off; the electrode-negative half puts heat into the joint.
What tungsten should I use?
2% lanthanated or 2% ceriated works on both AC and DC and has replaced thoriated for most shops. Thoriated tungsten is mildly radioactive and its grinding dust is a health concern. Pure tungsten is a legacy choice for AC only.
How do you grind a TIG tungsten?
Lengthwise, with the grinding marks running along the electrode rather than around it, on a wheel dedicated to tungsten. Grinding across the electrode makes the arc wander. A point roughly 2 to 2.5 times the electrode diameter suits DC work.
Is TIG stronger than MIG?
A correctly made weld by either process develops full joint strength. TIG gives better control, lower heat input and cleaner results, which matters on thin material and exotic alloys — but a sound MIG weld is not weaker.