Tig Weld aluminum lap joint (1/2" plate)

By greenchili Date 03-28-2006 02:25

I'm tig welding a part that is 6061 aluminum. It's basically a big lap joint. One piece is 1/2" X 6" X 8" and the other is about 1/2" X 4" X 10". I have to use 5356 filler because the part is going to be anodized, and they don't want a black weld to appear once it's plated. It must be welded all the way around. I usually have no problem welding that base metal thickness with 4043 filler on DCEN using straight helium. I'm using an older syncrowave that goes up to 310 amps. When I tried to use the 5356, the weld came out really ugly. It looked really "wrinkly" and it looked like I was running cold. It also looked like the toes didn't tie in very well. I was using 3/32" 2% thoriated tungsten and had the amps set to about 250. The 5356 filler is 3/32 diameter and I was shoving it in the puddle just to create a ripple. I also tried switching to AC using 1/8" 2% thoriated, but the electrode just cant handle the heat on AC no matter what my balace is set to. It could barely puddle. On both AC and DCEN I've tried mixing Argon/Helium, running pure helium AND running pure Argon. On both AC and DCEN I've tried MULTIPLE HF settings, running balanced and unbalanced, turning the arc control on and off.....I DON'T KNOW WHAT ELSE TO DO! Somebody please help!
I can't even try 5/32" tungsten because my torch only allows collets/collet bodies up to 1/8". Getting a new torch is pretty much out of the question. Can somebody lead me in the right direction as to what settings I need to get these parts done with 5356 filler, my 250 amp rated torch, and my 310amp machine? What about different tungstens? (I.E. Zirconiated maybe???) Thanks!

P.S. Everything is ultra clean...using a brush strictly for aluminum and pre cleaning with acetone.

By aevald

Date 03-28-2006 06:03

Hello greenchili, I hope this doesn't sound simplistic, but have you tried preheating the part prior to welding? I have not tried using DCEN with helium myself, but I've had good luck using preheat and an 1/8" 2% thoriated tungsten with the balance set towards the DCEN side and argon shielding gas. If you're unfamiliar with this, try it, with the torch operating on acetylene only, blacken the weld area, then use the oxygen to get a neutral flame and heat the blackened area until the black burns off, after this occurs begin to make the weld immediately. Try not to have the part in contact with anything that could act as a heat sink. I believe you will have success if you use this method. Good luck and Regards, aevald

By greenchili Date 03-28-2006 13:03

I didn't try to preheat, though I will today and post my results when I get off. I didn't know if preheating would work or not because the part gets pretty hot when I try to weld on it for a few seconds. Probably isn't getting hot enough though. Good suggestion, Thanks!

By SWP

Date 03-28-2006 15:12

Since you mention that with 4043 you "usually have no problem", I wonder if the problem is the 5356. Can you do a controlled side-by-side comparison of the two fillers? Another thought, maybe try cleaning the filler, or trying a new package/different manufacturer.
Please let us know what ever you find.

P.S. I don't see any way the tungsten type would have anything to do with it. It simply provides for the arc, thoriated or zirconiated or ceriated, no dif.

By greenchili Date 03-28-2006 23:17

Well, tungsten type and diameter does matter because certain type and diameters handle different amounts of amps. I did try cleaning the filler as well. The problem is definately in the filler type. Unfortunately my boss won't let me get any other filler manufacturer because we need to get these parts out on the fly.

Preheating definately helped (AWESOME SUGGESTION!), but I think I already contaminated the base metel so much with the previous weld that I was still getting a really dirty puddle when I tried to weld on AC w/ 1/8" 2% thoriated. I was set to about 250, AC balance on 7, HF maxed out at 100 Hz, and pure argon at 40 CFH. The tungsten was still melting and having a hard time with those settings.

I also thought that I may have preheated too much....does that sound weird, or is that possible?

Before I tried the preheating and AC welding, I had to mill off the old welds...I only left about .005 of the old weld on the part. Then I preheated, and then immediately welded. Came out very ugly. You could still see nasty stuff in the puddle.

I then decided to break the joint free, grind off all the old weld, relocate the plates, clean, preheat, and weld....still pretty ugly, but not nearly as bad. Just bad enought that It wouldn't fly though.

I spent half the day trying differnt things again, but ran out of time. The boss let me just use 4043 eventhough the weld will look black when we get it back from the plater because we need to get the part out. It's only getting clear anodized, so it won't look too too bad.

Oh well, thanks for the suggestions. I think if I could do it over, preheating is definately the key to success in my case. I should have done that in the first place and ran on AC. I think I would have a little problem with the tungsten melting, but not so much that I couldn't finish the parts. (that and a torch that can handle 5/32" or larger tungsten!)

By Lawrence (*****)

Date 03-28-2006 23:41

Better late than never

A couple more tips for getting the most out of AC GTAW

Cerium in my opinion performs best when trying to get max amperage out of AC. Zirconium is my usual choice but the Ceriated has a bit higher current carrying capcity.

Also.. Water cooled torch of course.

Full length electrode.... The heat sinking effect from a full length electrode (especially with a water cooled torch) will give you about 10 % greater heat tollerance before the tip begins to distort.

Thorium spits, and lanthanum does not make a hemisphere when it overheats so they should never be used when your at the maximum input levels.

Sharpen the largest electrode your torch will handle with a radical angle rather than a slim taper. As you weld the tip will begin to become hemispherical... Let it. When the tip becomes balled to about 1 and a half times the diameter you need to stop and redress the tip.

Little things like perfect torch angles will also have a major impact in how your puddle behaves and how much amperage it takes to get fusion.

D0 Be Careful about the pre-heating... I don't know if "overheating" is going to affect your weld as you apply it. But the greater the preheat the further you get from the original Heat treated parent material mechanicals... which may be important.

By greenchili Date 03-29-2006 03:12

good stuff dude...Never tried Cerium before...gonna have to get my hands on some.

Definately water cooled.

I've been wondering if using a larger electrode could suck up more heat

Do you taper the Cerium on AC? I thought it was supposed to be balled before you start laying the bead, no matter what tungsten....when you're welding aluminum on AC anyways. Seems like you would be going through tungsten and time if you were always having to resharpen the tip. Does it take a long time for the taper to ball?

I definately had to do some torch manipulation in order to get a puddle started....especially before I tried preheating

I tried my hardest to not change any of the characteristics of the base metal. I got the part so hot that I could pick it up with some thick ol' stick welding gloves on, welded it, and let them cool down on the table.

By Lawrence (*****)

Date 03-29-2006 04:20

Balled Tungstens are mostly an old school thing.

Unless you are using pure tungsten, in which case a ball is going to happen anyhow. Or you are dong a buildup that reqires a wide bead profile.

The sharpened electrode will keep the arc on the tip of the electrode and make the arc plasma a bit more columner and less bell shaped than with a balled electrode. This will help consentrate arc energy at a specific point.. This really can make a difference in fillets.

By SWP

Date 03-29-2006 16:22

Lawrence, Diamond Ground Products has some good information on Tungsten, some of which seems to conflict with your personal experience, although they do state "testing is the only way to determine which tungsten will otimize your welding performance".

http://www.diamondground.com/Guidebook0105.pdf

By medicinehawk (**)

Date 03-29-2006 09:33

If you have 5/32" tungsten, you could always chuck-up one end in a drill motor and spin the otherend sideways on a bench grinder to get the diameter down to 1/8" where that end will fit into your torch collet. I had a similar "bad" experience where we had problems welding 3/4" aluminum gussetts. They started mig welding and I ended up going over everything with tig and I really needed 5/32" tungsten.......what I posted is what I did to get me thru.....it worked for me.

By greenchili Date 03-29-2006 13:11

Wow...that's an awesome idea dude! definately gonna have to try that one out!