I am welding 1/8 SS rods together using a TIG spot technique. I set the machine at panel control and 80 amp with HF start, DCEN. Pushing the foot control sends HF start and 80amp to the theoreated tungston tip. Quite often at start, the HF starts at the base of the tungston (up inside the cup) and travels down to the point. The amp surge grabs before the HF makes it to the point causing a wide puddle. These need to have a small weld with mimimum heat input. No filler is involved, just melting the two rods where they meet. When the HF starts at the point the weld is small and very quick. They look real nice. I cant get this to work the same way all the time. I have tried long taper on the electrode and very short taper. I even tried grinding cross wise instead of length wise. Length wise does work better.
The machine is a new Miller Syncrowave 250 DX. I am using an HP20 tig torch with .062 electrode, and argon gas. Other than the start inconsistency the machine and setup seem to work great.
Any body know what I can do to get arc to start at the tip consistently? Thanks. Happybearwelder.
Hmmmn.......I have the same machine at work and have never noticed that happening. I will look for it tommorrow. I can't quite see why that would even be possible. I have the Diamondback water cooled torch.
I have seen this many times and always wondered why it does that!!! I will be watching for answers.
Sorry that I don't have any.
Darren.
The 0.062 will work if all things are "right" (machine settings, gas, tip prep., etc.) The starting will gradually degrade with use. Oxidation will result in the starts you describe. I weld smaller diameter filler metals with an 0.062" EWTh-2 electrode w/no problems.
Try going down one electrode size to a 0.040".
I too have seen this happen often. I attribute it to accumulation of dielectric surface impurities on the electrode. When I have a delicate job, I use a spare piece of very clean base stock upon which to lightly "scratch" the electrode point (power off!!) before establishing the arc on the work piece. In your case, a piece of stainless material could be set near the work for rubbing the electrode on. Works for me.
To add to the good advice:
If the electrode appears a little "dusty" or "furry" at the tip after just a couple of arc starts a little wipe with scotch brite or emery cloth between starts might extend the life a little. This takes time and slows down production however.
If your torch is water cooled you might be able to get by with a 0.040 dia. electrode to improve arc starts. Furthermore, lanthanum electrodes in my experience provide better performance in mechanized operations that require numerous arc starts. They cost a bit more but can save considerable prep time and might be justified in your case. If your supplier has several brands of electrodes you would do well to run some trials, a brand switch can make a HUGE difference.
let us know how it goes
I tried the .040 electrode. My supplier did not have the lanthium, so i went with the 2% thoerated. I found no diffrence in the percentages of good starts to bad ones. The scratching on the SS immediately before starting each weld seems to improve the percent of good to bad. I'll keep working and if I find something that works I'll put it on the board. Thanks, the Happy bear.
After all is said, I think you'll find that the no current on scratching method the best.
Seems stainless gives off an oxide when welding. This oxide, non conducting in nature, tends to coat the tungsten electrode.
A quick scratch on a a cold electrode can often break through this oxide, ensuring good starts.
Good Luck
brande
I have asked a lot of questions and tried everything everyone said and then some (except the lanthium electrode). If I find some I will try it. For now the "no current scratch" works out the best. Thanks to all.
I have a similar problem, only with mine the HF activates and I can see the tiny arcs at the tip, but the welding arc never starts. If I just touch or scratch the tip to the workpiece I'll be able to start the arc no problem. Or if my tungsten is already hot it'll start easily. I have yet to try the lanthanated tungsten though...
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