Hello,
I am learning to tig weld aluminum and am having some issues that I think may be related to my shielding gas. I went through my first tank of Argon this last week and just got a new refill yesterday. I am using kinda small bottles, and I see I will probably want a bigger tank soon. I went through the first one in about 5 or 6 nights of welding practice pieces.
The first image below is a little open top box/tray I built to prcatice outside corner welds. I need to do similar welds for an automotive intercooler project coming up. This first attempt had couple leaks when tested with water, but the welds were my best so far. I know, I have a long way to go, but I'm getting the hang of it.
The second image is the same box that I re-welded in a couple spots to seal up some of the leaks and fill some small holes I left. I refilled my argon tank before this second pass of welding. Now, everything I strike an arc on seems to turn black and pitted. You can see the corners where I was trying to weld in the second picture, they are black and really nasty looking.
Is this a shielding gas problem? I didn't change any settings on my machine between these welds. I cleaned the welds with a stainless brush before welding every time. And I even tried to melt a puddle on some aluminum scrap that didn't get filled with the water and soap that I tested the "box" with. It also turned out with the same black and rough look.
1st picture:
http://www.denverspeed.com/images/weld_4oct01/april7_02_practice1.jpg
2nd picutre:
http://www.denverspeed.com/images/weld_4oct01/welding_problem.jpg
Thanks for any input. Feel free to make any other criticisms. I don't have anyone around to learn from here in my shop, just books and practice. This is a great bulletin board.
-Ken Lanham
Denver, CO
Could be the gas, but, first you need to rule out all other possibilities.
1 Is your tungsten comtaminated:(touch the puddle while welding?)
2 Gas leaks: From the bottle to the torch, every thing should be tight.
3 Argon Flow: 15-25 CFH on your flow meter/ Large gas cup 1/2" I.D.
4 Hydrocarbons:Did you degrease BEFORE brushing.
1 If you touch the tungsten on the base metal, in the puddle, or on the filler rod you will get the black deposits. If that happens you need to stop and reprep your tungsten.
2 Gas leaks will pull air, which has oxygen, into the gas line giving you contaminated welds.
3 Too high of flow rate can cause turbulence which will pull air into the weld zone. Too low will also have that effect, as well as air drafts (wind)
Too small of gas cup can also give you problems.
4 Soap, wax, grease, or any hydrocarbon is poison to welding aluminum and must be removed BEFORE wire brushing, brushings' job is to remove oxides from the surface. If you wire brush with out removing hydrocarbons you can actually embed the hydrocarbons in the surface making it extremely difficult to remove.
If these checks pass, change the bottle of gas.
This will get you started, if you still have issues we'll dig deeper.
Regards, Brad
I have gotten new cylinders of argon that were contaminated and had me pulling out my hair for a few days. After eliminating the other possibilities, your gas supplier should trade you for a different cylinder. Although when I did that I still had the same problem because there was a bad batch and it affected a number of cylinders. I had a cylinder that was older and it worked fine. I was using it on aluminum and was getting the black oxides as in your photos. Good luck, Scott. BTW, what is the welder and alloy you're using? What CFH gas flow? Gas lens collet?
By wkdivr
Date 04-14-2002 05:12
Ken,
It definately looks like some kind of contamination, either by touching the tungsten, or some problem with your shielding gas. Sometimes you can touch the filler wire to the tungsten, especially if you're just working on developing your techniques, and contaminate it that way. One more tip.When fitting pieces together for tanks, or boxes, try to get your pieces to fit corner to corner. That way, you have a better weld on the outside for sealing purposes. Good luck!
Bill Simpson
If you think you have problem with your shielding gas, run a bead on some titanium, if you have bad shielding gas this will remove all doubt.
Thanks for the responses,
I swapped tanks at my local gas dealer and the problem went away immediately. I wonder if I got a tank of MIG gas, co2/argon mix or something? Anyway, it seemed to solve the problem straight away.
Bill,
Thanks for the tip on corner fit up for tanks. I'll give it a try. I am understanding that you fit the corner pieces so that there is a little 90 degree wedge to fill in, instead of overlapping the pieces like I did....?? Whew, that sounds like it makes the pieces more heat sensitive too. Anytime I get near the edge of a piece I seem to make holes.
Scott,
This is an HTP Invertig 200 AC/DC inverter machine.
The gas flow rate is in the 15-20 CFH range, on a pressure type gauge, with gas flowing, and a standard collet and cup. The aluminum is 6061 bar stock 3" wide by 1/8" thick.
Just another tip. Buy or make(PVC pipe works well) a storage container for your filler rod. It sould be air and water tight, to keep the filler as clean as possible. Also make sure you wear long sleeves or you will get a TIG-sunburn.
