UPDATE 6/15/2013: Arc-zone has redesigned their Monster TIG nozzle. It now has a chunk of rock wool or similar material to help diffuse the gas flow. I have never used this version, and so the comments in this blog post do not apply to it. Check the comments section for more details.
Today's lesson involves my quest to weld stainless steel sheet metal, a Monster TIG nozzle, and a copper chill bar. In previous posts, I've described having trouble maintaining weld bead quality on thin stainless sheets. The problems are a combination of putting too much heat into the metal, and having too little argon gas coverage. I am not sure if addressing one problem can help solve the other. Today, I did some testing to find out if adding a lot of gas coverage can help. I also tested out a copper chill bar.
Common weld parameters for the whole test:
1/16 ceriated tungsten ground to a sharp point
55 amps (pedal floored for the entire test)
very slight %90 pulse at 200Hz just to get my auto-darkening helmet to work
20 CFH pure argon
10 sec post-flow
I purposefully used a small piece of 304 1/16" sheet to show the heat buildup problems. I also welded close to the edge to test the worst-case heat buildup.
First up: normal gas lens with #8 cup.
Wow, I never knew the copper could help that much!
Next, a large diameter gas lens with #12 cup
Same story here. It looks like there was even less heat in the metal. This might be because there was better contact between the sheet and copper, or because the gas nozzle has a wider opening. I'll bet the Monster nozzle will be even better...
Finally, the "Monster TIG nozzle", which is 1" in diameter and uses a stubby gas lens collet body.
Wha?! There must be something wrong -- what's going on here?! I tried all gas flow settings from 5 CFH up to 30 CFH and concluded this nozzle is completely useless. It's possible that I am misunderstanding something since I am a new welder, but I am pretty sure this thing just plain doesn't work. I noticed that the tungsten had turned black after a few welds, indicating the gas coverage isn't even enough to keep the tunsten from oxidizing. At 30 CFH, the gas flow was so turbulent, I could see the arc getting blown around, and pops of smoke coming out of the weld. At lower flow settings, I could see the stainless oxidizing even before I lifted my hood. I tried different stickout from 1/8" up to 3/4" with no change. I am sure the cup made good contact with the torch body, and there were no air leaks. I even tried extending the nozzle away from the gas lens with a spacer to make sure there was adquate space for the gas to disperse with only a tiny improvement.
On the right: large gas lens with #12 cup. On the left, you guessed it, Monster suck.
This screen arrangement doesn't look so great.
It's made with just two screens without any spacers between them, and two very coarse screens on the outsides. The screen diameter is a few mm less than the interior diameter of the ceramic cup, so I'm guessing a lot of gas slips around the edges of the screens.
So, I'll be continuing my stainless welding quest without the Monster nozzle and with copper chill blocks. I'll also be testing Solar Flux B. So far, I think it works well but poses a huge cleanup mess after the welding is complete.