Arc control issues in A.C. GTAW welding

Date 08-05-2004 02:55

Hi.

This is my first post here and I have a couple of important questions.

I am using a Lincoln 355 Square Wave TIG welding supply with weldcraft crafter series torches. What I have noticed is that when I am using 1/8" pure tungsten and I poor on the power I get a good weld with the smaller gas diffusers and smaller gas nozzels. I believe, however, that a large gas lens or collet and a larger gas nozzel would provide for better shielding and cooling of the tungsten. The arc seems to wander around much more with the larger components and makes it hard to pin point welding power. Here are the specs:

Material 356 aluminium casting
4043 rod
A.C power with high frequency start and constant high frequency power
150-175 amps
2 second preflow and 10 second post flow
pure argon shielding gas at 15scfh
Balanced arc at three on the dial

I know that the collets and lenses are properly seated and there is good power transfer, but I can't control the arc well with the larger nozzels and lenses. It almost seems as if the arc is transfering to the nozzel instead of the work piece.

Any advice appreicated.

Thanks!

By Lawrence (*****)

Date 08-05-2004 07:24

You can use the search function here at the forum to find dozens of good threads about aluminum welding. Just make sure you set the days back to 999 on the search parameters.

Here is a good article

http://www.millerwelds.com/pdf/Aluminations_Ad_Package.pdf

If your torch isn't water cooled you would be better off if it were.

Forget the pointed tip and the pure tungsten. Go with a steep point with a blunt tip. Stick with the Zirconium or try Cerium

By fst951

Date 08-05-2004 14:24

Hi Lawrence.

Thanks for the advice, but when you say steep point, are you referring to a tip than ends flat at about half the diameter of the outside tungsten and then goes about 3 diameters up the tungsten. Please give me a little more info. I have the Zirconium and am trying to use it. I hae always had good luck with pure. Yes, the crafter series weldcraft torches are watercooled.

Thanks

By Lawrence (*****)

Date 08-05-2004 16:22

Here is a good article that details arc stability and penetration as it applies to tungsten electrode tip prep. Good illustrations too.

The bad about this article is that its behind the times in AC welding tip prep. They talk about DC welding but frankly the arc control factors are about the same, its only a matter of degree.

Pointed electrodes provide better control, if the taper is too slim in AC operations you risk contamination into the pool so a little blunt is provided at the tip.(I like someplace beteen 60 and 90 degrees included angle)

http://www.pro-fusiononline.com/tungsten/geometry.htm