TIG question

Try cold scratching.

Cold Scratching means just what is says. You scratch the tungsten on the base metal with no welding current flowing.

Do this every time before you try to strike the arc and you will get more reliable first strikes.

Why?

When you are TIG welding and stop, the arc collapses and in the arc stream are a certain amount of vaporized metal ions.

These ions will tend to cling to the surface of the tungsten as it cools, where they oxidize once the shielding gas stops.

So now you have a microscopically thin layer of metal oxides over the surface of your tungsten, acting as a really good electrical insulator.

When you scratch the cold tungsten on the base metal is breaks a hole in that oxide allowing the arc to strike easily.

Try it and you will find it will make your arc starts much more dependable.

No.

That is because the Dynasty uses a "capacitor discharge" high frequency generator. This creates a bigger spike of high freq with greater focus so it can pop through the oxide layer.

Transformer machines have traditional high freq generators which don't create as intense a spike of high freq.

Wow I thought it was just me that did that...I never knew the reason why it works until now. I thought it was just "luck" that when I touched the tungsten to the piece the arc would start more reliably. Learn somethin new every day...Thanks Ernie!!

I TIG weld stainless steel exhaust ducts for an aerospace company.

After tacking for a while, the HF arc has trouble establishing itself. I can 'cold scratch' for about 5-6 more starts then is becomes useless. The tungsten looks like it has been contaminated by a very thin layer of aluminium.

Since the parts are held in aluminium jigs and we work on large aluminium table tops that get scratched alot, I figure there is a little alum.dust providing the contamination.

Steph

What machine is this? You may need to pull the high freq. points, clean and reset them. It tends to boost the output a bit. The high freq capacitors also age, and may need replacing.

I believe its a Miller 350 LX ( with a great little water cooled WP20 Weldcraft torch... I love these tiny things. Can hold them any way you want ...like a pensil, upside down and by pinching the tungsten cap, whatever is comfortable.)

I'm not sure Maintenance would like me poking around the bottom of the machine but I'll see what I can do.

A 350LX should be new enough not to have that problem, unless you have a lot of grinding dust in your shop.