Hi, I just purchased a new Thermal Arc 185 AC/DC Tig welder and I'm having some problems laying an aluminum bead.
First some background. I'm a weekend hobbiest, not a professional. I took a training class for two semesters at the local community college that teaches welding for welding certification. At the school, I could lay an aluminum bead with both types of power sources (rectifier and inverter, the inverter was a Thermal Arc) without any problems. I had actally done some small, non critical repair welds that came out really nice.
I'm right now just working on a scrap piece of 6061 sheet about 3/8" thick practicing before I try it on any thing I don't want to mess up. I'm using 4043 filler rod I just purchased from the local welding supply store. I've tried cleaning the surface with a stainless brush (only used for aluminum) and grinding it clean. I purchased a brand new 80cf argon bottle filled.
The problem I'm having is getting a clean weld. I can seem to run a clean bead (sometimes, not all the time) without adding any filler rod. Most of the time I can see a clean puddle and the bead track looks great. The problem comes when I start trying to add filler wire to the puddle, I'm getting very rough looking welds with "black" contamination. I've done some reading and I suspect it is "weld smut", although I'm not sure. I've tried adjusting the frequency, ratio of EP/EN, amperage, pulsing, gas flow up and down, check for loose gas connection. I'm in the garage with the door closed, so there are no drafts ( I do crack the bottom from time to time to vent the room with fresh air while not welding so I don't kill myself). I cannot, for the life of me, figure out why I can't run a clean bead. The same thing happened to me one day at the welding school and I could never figure it out. Went back the next day on a different rig and everything was fine. I've tried Thoriated, pure and Zircontated Tungsten. I am grinding the tungsten to a point on an aluminum oxide griding wheel that is only used for tungsten. I've even tried using a not ground, blunt tungsten.
I can DC weld steel without any problems for the most part. I do sometime get the welds "popping" when cooling leaving holes in the weld, but I suspect the metal I'm working on is real dirty (just scraps used for practice).
Help....
Jay
One thing that jumps out at me is your use of a grinder...a huge no-no with aluminum. For preparing welds you have to use cutting tools not abrasive grinding tools.
Another minor suggestion is to use pure tungsten that has a rounded end. I don't think it is contributing to the dirty appearance, but it is probably coming off in the weld if you sharpen it.
Charles
The "grinder" I use is one of those sandpaper flap discs. The kind that have the pieces of sandpaper layed on top of one another and it's all kind of glued together I guess. I've used it before without any problems, but I'll stop. I've also tried just using a SS brush. What kind of "cutting tools"?
I had also tried the pure tungsten in a ball, didn't make any difference.
Hardened burr bits, a cut off saw, even rotor bits work; anything except abrasives. The flapper you use is inappropriate on Al, as are most abrasive devices.
For what it's worth, the color you describe is probably not caused by the flapper wheel. Contamination from the wrong prep tools usually shows up as porosity.
Another thing about aluminum. All aluminum develops a hard oxide layer that must be cleaned prior to welding. The longer it is between mfr and use, the more you have to clean it. There are chemicals that can be used but I don't know what they are. Someone else on the board will probably chime in shortly and give you some specific advice regarding the blackening of the weld in your situation.
I dunno Charles,
Aluminum oxide flappers, discs and sandpaper are all called out in Boeing, Lockheed, Alcoa and many others standard practice manuals for surface prep. However, these tools certainly should not be the cause of the above described smut.
Jay,
If you can, I would suggest applying a control to be sure you don't have contaminated argon. Take the material your working on and drop by to visit your Community college or somebody else who has good argon and run a bead on your material. Bad argon will make for bad aluminum welds while mild steel or stainless may show no visible problem or maybe a little early bluing. If you are getting clean welds on some aluminum parts and dirty welds on other aluminum parts than argon is not the culprit. You could (if your bottle was recently aquired) ask your gas supplier if they have had a bad batch lately. If they have sent out bad gas they need to know it. I've been the first customer to discover bad gas and it was a real fight to get the supplier to pay attention to me. If it is bad they should replace it with no charge.
Let us know what you find out.
Hi Lawrence, I was wondering if this might be my problem. I was a little reluctant to blame the gas as I figured it was most likely something I was doing or had the torch set up wrong or something like that. I didn't want to blame the gas when it was poor prep or technique on my part. But after spending about 2-3 hours this weekend tweaking different settings, adjusting torch angle, filler metal angle, tungsten types and lenght from the cup edge, I really had to wonder if it was me?? I can say that I'm not really getting any clean welds on any of the aluminum I've tried to weld with. That includes aluminum from three different sources. I got some at the home depot just to fiddle with for practice, no go. I went to the metal yard and picked up some 1/8 x 1 3/4 4 foot strips to play with...no go. I also got a scrap sheet of the 1/4 inch 6061 I've been working on...no go. The only "success" I've even come close to is occasionally being able to run a clean puddle/bead WITHOUT adding any filler metal. Simply heating the initial spot to a puddle and "running" the puddle down the plate. However, the moment I try to hit the puddle with the rod...blam, contaminate, pitted black/grey spotted bead.
I had thought the very same thing about running out to the CC to see if I could run a quick bead on this stuff. I'm pretty sure he would let me do that even though I'm not enrolled this semester. It's an hour drive, but right now, I'm running out of options.
FYI to you and others, I left out that I am using a 3/32 tungsten with a collect and a #6 cup. I have read that gas cups give better gas coverage and flow and I don't mind buying one if I have to. It's just I've used this same type setup before without any problems.
Thanks for the advice from all
Jay
Thanks Lawrence. My experience is limited with respect to aluminum. Cleanliness has been the issue every time we get into difficulty. I'm uncertain about the abrasives used in the flappers we had been using on aluminum, but I can say with certainty that when we got a better handle on the weld prep our problems went away.
Bad argon is usually indicated by a tan/brown smoke in the weld area.
If there is no tan/brown-look other places for your fix.
As far as abrasive use on aluminum, yes, there are special abrasive compounds specifically designed for aluminum. If you do not use these specific aluminum abrasive compounds, do not look for support from Alcoa and maybe the others.
The carbide burr or cutter is still the preferred method of weld prep-
Check out-"Aluminum Welding-Theroy and Practice" available from the Aluminum Assoc. They are the "Big Guys" in aluminum.
Many of the contributors are past Alcoa employees.
Any abrasive use on aluminum must be critically evaluated. Any abrasive grains left in the soft base aluminum will volitize (burn) under a welding arc, leading to porosity, incomplete fusion and the like.
Hope this helps
brad
Just curious, are you using a gas lense or a a collet body? If you use the latter (collet body) you should be using 15-25 cfh which may be causing the conditions you are getting if you crank it up above 25 cfh. With a gas lense, you could start out at 25 cfh and then go up to 35 cfh as a gas lense allows a more uniform "blanket" to cover the welding area.
Also, you should tilt the cup away from the direction of travel which may also help. It really shouldn't matter that much which typetungsten you are using although zirconium and pure tungsten are the norm for aluminum welding.
I hope this helps.
Be well.
Hawk
I'm using a collet body. I've tried adjusting the flow from 10 all the up to 30 with similar results.
I can tell you if I tilt the cup more than just "a little" the problem gets worse. And the problem is always there the momemnt I add any filler rod no matter what angle, gas flow or any other setting I have.
Jay
If your problems only arise when you are using filler it could be this that is causing the problem.
What grade is it.
Do you make sure you keep the end of the filler wire inside the gas shield all the time, if not it will pick up atmospheric contamination which you will then "feed" into the weldpool.
Also, what condition is the filler in, if it has been left in an opened packet for some time it can start to get an oxide coating, if this is the case it should be cleaned with stainless steel wire wool prior to using
Cheers - Bob
The filler was brand new 4043 and stays as close to the gas shield as I can keep it without it melting.
I'll trying cleaning it with stainless steel wool. Would a scotchbrite also work?
Jay
Ok, I went down the the CC where I took my welding class. Prof. told me to bring all my gear and down and we'd check it out (Can't thank him enough for this). Anyway, got everything hooked up down there and still getting bad welds. Even used his aluminum stock and filler rod and still contaminated.
Swapped out my gas for his gas. NOW, I can lay a prefect, pretty bead. So, looking at the bad welds he says, "you got Carbon contamination there". Hmmmmm.....looks like you have a tank of bad gas.
So I pack up my gear and take the tank back over to where I bought it (I purchased a brand spanking new tank with a fresh "Argon" fill). I tell them my story and the guy behind the counter proceeds into this long diatribe of how he's never seen a tank of bad gas and that it's me or my equipment. I tell him the Prof who teaches the class has 30 years experience, has done govt' contract for welding in and out of the US, welded for NASA and the US military. I say I think he has a little bit more knowledge than both of us combined and HE says I have bad gas. Guy still tells me,"come back tomorrow and tell the owner, i've never heard of bad gas".
Well, needless to say I'm a little pissed. So today I go to a different place (Metroplex welding in Dallas, Tx., free plug for them as they were more than helpful). I tell them my story and they go hmmmm...., let's check that tank. Sure enough, I've got a 75/25 tank or at least some mixture thereof as I have CO2 in that tank. They swap out the tank (going to use "my" tank as a 75/25 now) and give me a fresh Argon fill tank. I take it home, hook it up and make some very lovely welds on my scrap aluminum.
Final outcome: Someone mislabeled or mis-filled the tank. Gas probably wasn't bad, it was just the WRONG gas.
Jay
Jay,
You are not the only one who has encountered this (took us three days to figure out what was wrong), but I do believe it is a rare occurrance. Probably someone just not paying attention...
gls
Jay
I've been there.
A year ago I took a new job in the midwest at a tech college and right off the bat my local distributor delivered bad argon. Being the new fellow in town I was not believed until another customer had a similar complaint. They were very touchy at first. Thankfully their opinion has changed and now they are a bit more willing to listen.
Watch your argon.
If you are going to get a bad batch-it is usually during the summer months (condensation inside cylindeer that was not pulled down (vacum) correctly.-although it can happen in the winter as well.
If you getbrown around your weld-look for bad gas.
Good Luck
brad
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