Thread: Unstable arc

In tig welding, what is the main cause of unstable arc.?

Originally Posted by awpy

In tig welding, what is the main cause of unstable arc.?

Now that's a very big question, somewhat along the line of "what's the meaning of life."
Are you running AC or DC current?
Generally speaking, TIG loves clean. By this I mean, good earth, good connections, stable gas flow, clean parent metal and electrode.
My next question is what do you call unstable? AC current at low amperages can appear "fluffy" and the arc can walk around the electrode tip while welding.If you can describe exactly what's happening, then I'm pretty sure we can sort you out. Give us polarity, amperage, balance, frequency and any other settings as well as telling us what you are welding.

Welding AC on 1.5mm aluminium, I tried higher amps and that has fixed the problem,

Electrons can escape from the surface of your electrode easier when it is hot. If you have imperfections in your tungsten grind, these small ridges and points can heat up more than the tip of your electrode and the electrons will tend to flow out through that path. This happens more at low amps as the whole electrode isn't as hot as at high amps. The arc wanders because electron flow causes magnetic fields and these fields in turn affect the path of electrons pushing the arc point to new hot spots. At higher amps, the arc will go from the tip (or point of shortest distance to the job) and the arc will wander less because everything is in symmetry.