Troubleshooting guide › Process troubleshooting › TIG welding problems
TIG is the cleanest process and the least forgiving. The tungsten, the gas cover and the cleanliness of the joint decide the result, and the machine can only help. This page covers the machine-side faults (arc starting, HF, gas valve) and the technique faults (contamination, wandering arc, grey welds) in one place, so the operator can tell which is which.
Reviewed by the Cruxweld technical team, October 2026. Settings are starting points to confirm on a test piece; acceptance is decided by the code or drawing the job is built to. Checks marked “call” are for our technical team.
| Symptom | Likely cause | What to do |
|---|---|---|
| No HF crackle from the machine when the trigger is pressed | Torch switch or its socket faulty or not plugged in; remote/pedal selector in the wrong position | Check the trigger plug and the panel selector (torch / pedal); try the other |
| HF crackles, no arc | Tungsten too far from the work (keep 2-3 mm); tungsten blunt, broken or poor quality; dirty work; current set very low | Bring the tungsten to 2-3 mm, regrind to a point, clean the work, raise current |
| HF crackles, no arc, machine recently overheated | Over-temperature or over-current protection active | Leave switched on for a few minutes; weld when the lamp goes out |
| Arc starts only with a scratch | HF spark gap dirty or out of adjustment; HF off in lift-arc mode | Select HF mode; the spark gap is set by our technical team |
| HF will not switch off after the arc starts | Torch switch shorted or trigger cable damaged | Check the torch lead and trigger |
| Arc starts but current cannot be adjusted | Current control or pedal fault; machine in the wrong mode (pedal connected but panel set to torch) | Check mode and the pedal plug |
| Arc starts, weld blows out, no gas | Cylinder closed or empty; solenoid not opening; hose blocked | See gas below |
Lift-arc start (touch the tungsten, lift) is for machines or jobs where HF would interfere with nearby electronics or CNC controls. It works well on steel; on aluminium HF is preferred to keep the tungsten clean.
| Tungsten | Use | Tip for DC | Tip for AC |
|---|---|---|---|
| 2 % lanthanated (blue) | All-round: steel, stainless, aluminium on inverters | Sharp point, 20-30 degree included angle | Slightly blunted point; a small ball forms |
| 2 % thoriated (red) | DC steel and stainless; avoid grinding dust | Sharp point | Not for AC |
| 2 % ceriated (grey) | Low-current DC, thin stainless | Sharp point | Not usual |
| Zirconiated (white) / pure (green) | AC aluminium on transformer machines | – | Balled end |
| Tungsten diameter | DC current range | AC current range (balanced) |
|---|---|---|
| 1.0 mm | 15-80 A | 20-60 A |
| 1.6 mm | 70-150 A | 60-120 A |
| 2.4 mm | 150-250 A | 100-180 A |
| 3.2 mm | 250-400 A | 160-250 A |
| 4.0 mm | 400-500 A | 200-320 A |
Typical ranges for lanthanated tungsten with argon. AC ranges depend on balance; more cleaning (EP) time needs a thicker tungsten.
Argon below 5 L/min does not cover the pool; the weld oxidises and goes grey or black.
Flow drops as the pressure falls below about 5 bar.
A split hose, a loose torch connection, or coolant leaking into the gas line.
The weld end and the tungsten are still hot when the gas stops; both oxidise.
Argon is heavy and easily blown away.
Oil, paint, marker ink and moisture burn into the pool.
A tungsten that touched the pool carries steel into every weld.
Industrial argon below 99.99 % or a contaminated cylinder.
| Symptom | Likely cause | What to do |
|---|---|---|
| No gas when the trigger is pressed | Cylinder valve or flow meter closed; hose blocked or crushed; solenoid valve or its relay faulty | Open both valves; check the hose end to end; if the solenoid does not click, call service |
| Gas flows all the time | Solenoid stuck open or trigger shorted | Call service; do not leave the cylinder open overnight |
| Flow meter reads but no gas at the nozzle | Torch body leak, split torch hose, blocked gas lens | Replace the hose or gas lens |
| Porosity at the start of the weld | Pre-flow too short | Set 0.5-1 s pre-flow; purge the line after changing cylinders |
| Weld black at the end | Post-flow too short | See above |
| 1 mm sheet | 1.6 mm tungsten, 1.0-1.6 mm filler, 30-50 A, 6-8 L/min |
| 2 mm | 1.6-2.4 mm tungsten, 1.6 mm filler, 60-90 A, 7-9 L/min |
| 3 mm | 2.4 mm tungsten, 1.6-2.4 mm filler, 90-130 A, 8-10 L/min |
| 5 mm | 2.4-3.2 mm tungsten, 2.4 mm filler, 140-200 A, 10-12 L/min |
| 8 mm | 3.2 mm tungsten, 3.2 mm filler, 200-280 A, 12-15 L/min, water-cooled torch |
| Pulse (thin sheet) | Peak = set current, base 30-50 %, 1-3 Hz, 40-50 % on time |
| Down-slope / post-flow | 2-5 s / 8-15 s |
Starting points. Stainless runs about 10 % lower current than mild steel. For aluminium see the aluminium guide.
Post-flow is too short or the gas flow is low, so the hot tungsten oxidises in air. Set post-flow to 1 s per 10 A and check the flow at the cup.
No. DC+ on TIG puts most of the heat into the tungsten and melts it in seconds. The torch always goes to negative for DC TIG; AC alternates automatically.
It replaces the standard collet body with a screened one that gives a smooth, laminar gas column. It allows a longer stick-out and a lower flow, and it is the first thing to fit when welding stainless corners or titanium.
Above about 200 A for more than a few minutes, or on long production seams, yes. An air-cooled torch run at its limit overheats the handle and the tungsten, and the operator slows down.
Lamps, fault codes and the checks an operator can do outside the cabinet, for the machines this page applies to.
A DC TIG with HF start, adjustable post-flow, down-slope and pulse covers steel and stainless. Aluminium needs AC with adjustable balance and frequency. Above about 200 A continuous, or on long seams, a water-cooled torch with a cooling unit stops the torch overheating and lets a smaller, more controllable tungsten run at full current.
Send a photo of the weld or cut, your machine model, consumable and plate thickness. Our technical team replies on WhatsApp with the likely causes and the next checks to make.
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