torker
05-25-2009, 04:52 PM
Another thread prompted me to write you guys this blurb..
Undercut...not matter how small is NOT acceptable when welding.
It's a real problem with tig...as it's a slow process and the "flow" is entirely up to the operator's dexterity.
There's three main reasons you get undercut with tig.
The first and very common is an arc length that is too long.
By this I mean...the tungsten should ALMOST be dunked in the puddle. When I'm practiced up I can actually drag the tip of the tungsten in the puddle. As long as I don't break the surface tension of the molten metal I won't foul the tungsten.
Why would we do this? Ultimate control...I can zig zag the tip across the puddle and really bite into the edges by pausing slightly to let the metal curl around the tip and fill in the undercut or flow out to the edge of my cap.
A longer arc length doesn't have this kind of control. The further you lift the electrode off the puddle...the farther out the heat is broadcast. Now you don't have that metal flowing around the tip...this is where you are getting some undercut.
Another reason...if you are trying to fill too much with a too small rod. It takes great skill to feather out a smallish dab of metal to fill in the edges.
You should change up to a bigger rod or perhaps use two smaller ones side by side.
The other main reason you get undercut is simply going too fast and not letting the edges fill in.
Good luck with that...
Russ
Undercut...not matter how small is NOT acceptable when welding.
It's a real problem with tig...as it's a slow process and the "flow" is entirely up to the operator's dexterity.
There's three main reasons you get undercut with tig.
The first and very common is an arc length that is too long.
By this I mean...the tungsten should ALMOST be dunked in the puddle. When I'm practiced up I can actually drag the tip of the tungsten in the puddle. As long as I don't break the surface tension of the molten metal I won't foul the tungsten.
Why would we do this? Ultimate control...I can zig zag the tip across the puddle and really bite into the edges by pausing slightly to let the metal curl around the tip and fill in the undercut or flow out to the edge of my cap.
A longer arc length doesn't have this kind of control. The further you lift the electrode off the puddle...the farther out the heat is broadcast. Now you don't have that metal flowing around the tip...this is where you are getting some undercut.
Another reason...if you are trying to fill too much with a too small rod. It takes great skill to feather out a smallish dab of metal to fill in the edges.
You should change up to a bigger rod or perhaps use two smaller ones side by side.
The other main reason you get undercut is simply going too fast and not letting the edges fill in.
Good luck with that...
Russ