TIG welding amperage chart for steel, stainless and aluminium
Amps by material thickness, with the tungsten, filler rod, argon flow and cup size that go with them. Steel and stainless run on DC−, aluminium on AC; every figure comes from the same data the site’s TIG guide and tungsten calculator use.
Short answer
3.0 mm steel: 90–130 A DC−, 2.0–2.4 mm tungsten, 2.0–2.4 mm filler, 7–9 l/min argon, cup No. 5–6. The same 3.0 mm in stainless takes 10–20 % less, about 70–115 A. Aluminium runs on AC, and the current is limited by the tungsten: a 2.4 mm electrode carries 100–180 A on AC against 150–250 A on DC−.
TIG amperage by thickness: steel and stainless on DC−
Read across from the thinner part of the joint. The stainless column is the steel figure minus 10–20 %, rounded to 5 A: stainless conducts heat about three times worse, so the same current overheats it. Values for the flat position.
| Thickness, mm | Thickness, in | Steel, A (DC−) | Stainless, A (DC−) | Tungsten, mm | Filler, mm | Argon, l/min | Cup No. |
|---|---|---|---|---|---|---|---|
| 0.5–1.0 | 0.020–0.039 | 20–50 | 15–45 | 1.0–1.6 | 1.0–1.6 | 5–7 | 4–5 |
| 1.5–2.0 | 0.059–0.079 | 50–90 | 40–80 | 1.6 | 1.6 | 6–8 | 5 |
| 3.0 | 0.118 | 90–130 | 70–115 | 2.0–2.4 | 2.0–2.4 | 7–9 | 5–6 |
| 4.0–5.0 | 0.157–0.197 | 130–180 | 105–160 | 2.4 | 2.4–3.0 | 8–10 | 6 |
| 6.0–8.0 | 0.236–0.315 | 180–250 | 145–225 | 3.2 | 3.0–4.0 | 10–12 | 8 |
Amps by tungsten size, DC− and AC
Each electrode has a working band. Below it the arc wanders on the tip, above it the tip melts back — on AC sooner, because the positive half-cycle heats the electrode. That is why the same diameter carries less on AC. The cup and gas columns are what the tungsten calculator prints for that electrode.
| Tungsten, mm | Inch | DC−, A | AC, A | Filler, mm | Cup No. (bore, mm) | Argon, l/min |
|---|---|---|---|---|---|---|
| 1.0 | 0.040 | 15–80 | 20–60 | 1.0–1.6 | 4 (6.4) | 5 |
| 1.6 | 1/16 | 70–150 | 60–120 | 1.6–2.0 | 5 (7.9) | 6 |
| 2.0 | 5/64 | 100–200 | 80–160 | 1.6–2.4 | 5–6 (7.9–9.5)* | 6–8* |
| 2.4 | 3/32 | 150–250 | 100–180 | 2.0–3.0 | 6 (9.5) | 8 |
| 3.2 | 1/8 | 250–400 | 160–250 | 2.4–4.0 | 8 (12.7) | 10 |
| 4.0 | 5/32 | 400–500 | 200–320 | 3.0–4.0 | 10 (15.9) | 12 |
* The calculator has no 2.0 mm row: it goes from 1.6 to 2.4 mm, so a 2.0 mm electrode gets the cup and gas of its two neighbours.
Aluminium on AC
There is no thickness row for aluminium here, and that is deliberate. Aluminium takes heat away from the arc so fast that the same plate needs more current at the start of a weld than at its end, once the part has warmed up — the foot pedal does the rest. What can be tabled is the current each tungsten survives on AC, and that is the AC column above.
Starting settings from the site’s aluminium data: about 30 % cleaning on the balance control, 100–120 Hz for a tight arc on thin work, a white WZ-8 tungsten with a balled end (the tungsten calculator suggests the same), or a blue WL-20 ground to a point on a square-wave inverter, pure argon at 8–12 l/min, Ar + He on thick sections. More on the oxide film and filler choice: Welding aluminium.
Argon flow and gas cup
The cup number is its bore in sixteenths of an inch: No. 6 is 6/16 in, 9.5 mm. A larger cup gives a wider, slower gas stream and covers a longer stick-out. Flow by job:
| Job | Gas | Flow, l/min |
|---|---|---|
| TIG, steel and stainless | Ar 99.99 | 6–10 |
| TIG, aluminium (AC) | Ar 99.99 | 8–12 |
| Root purging in a pipe | Ar, N₂+H₂ | 4–8 |
Post-flow: about one second per 10 A, long enough to protect the hot tungsten and the cooling crater. Argon with 2–5 % hydrogen is for austenitic stainless only, never for carbon, ferritic or duplex steel. In a draught, screen the bay rather than turning the flow up.
Worked example: 3.0 mm butt joint, steel and stainless
- Row. 3.0 mm: 90–130 A DC−, tungsten 2.0–2.4 mm, filler 2.0–2.4 mm, argon 7–9 l/min. Start in the middle of the band, 110 A.
- Check the tungsten. At 110 A a 2.0 mm electrode is inside its band (100–200 A); a 2.4 mm one starts only at 150 A and would wander at this current. Take 2.0 mm, ground to 30–60°, and 2.0 mm filler.
- Cup and gas. No. 5–6 (7.9–9.5 mm bore), argon 7–9 l/min, post-flow about 11 s.
- Stainless, same thickness. 70–115 A from the chart; from 110 A minus 10–20 % that is 88–99 A. That is below or at the bottom of the 2.0 mm band (100–200 A), so a 1.6 mm tungsten (70–150 A) holds the arc better here.
Calculators and related pages
For a current that is not in the chart, the tungsten calculator gives diameter, grind angle, cup and flow; the gas calculator turns l/min into cylinders.
- Tungsten electrode selection
- Shielding gas selection
- Shielding gas consumption
- TIG welding
- Tungsten electrode colour codes
- Welding stainless steel
MIG/MAG settings
Amps, volts and wire feed speed for MIG/MAG by thickness are on a separate page: MIG/MAG settings chart.
Frequently asked questions
What amperage to TIG weld 3 mm (1/8 in) steel?
90–130 A on DC−, with a 2.0–2.4 mm tungsten, 2.0–2.4 mm filler and 7–9 l/min of argon. Start near the middle of the band and raise it until the pool wets both edges quickly.
How many amps can a 1.6 mm (1/16 in) tungsten take?
70–150 A on DC− and 60–120 A on AC. Near the top of the band the point erodes faster; if you work there all day, go one size up.
Does stainless need less amperage than mild steel?
Yes, about 10–20 % less at the same thickness, because stainless conducts heat roughly three times worse and the heat stays where it goes in. The chart has a separate stainless column for that reason.
What cup size for TIG?
The cup number is the bore in sixteenths of an inch. The tungsten calculator pairs No. 4 with 1.0 mm tungsten, No. 5 with 1.6 mm, No. 6 with 2.4 mm and No. 8 with 3.2 mm.
How much argon flow for TIG?
6–10 l/min on steel and stainless, 8–12 l/min on aluminium, 4–8 l/min for a root purge. More is not better: too strong a stream turns turbulent and pulls air in.
What amps for aluminium on AC?
The limit is the tungsten: 100–180 A on a 2.4 mm electrode, 160–250 A on 3.2 mm. Aluminium needs more current at the start than once the part is warm, so set the maximum on the machine and control the rest with the pedal.
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