Porosity in Aluminum TIG welding

By ssbn727 (*****)

Date 05-06-2007 05:32 Edited 05-06-2007 05:35

Read the instruction manual!!! ;) Go to the Miller website!!! ;) Tell the Miller Rep to get another job!!! :(

Seriously, if you're only welding AC Aluminum use zirconiated tungsten...
1) What is the relative humidity/dew point in the environment you're working in?

2)What is the cleanliness condition of the 5052 aluminum prior to the start of welding??? in other words has every potential for contaminating the weld been eliminated? Alos, what type of Aluminum filler wire are you using?

3) What are your welding parameters/ In other words do you have the proper AC balance with respect to current percentage & dwell time in Electrode Positive and Eelectrode Negative that makes up the one squarewave complete cycle or hertz - multiplied by how many times per second the power source is set to - which makes the frequency and the amount of current (amperage or amperes) you're using???

4) What's your Shielding gas flow rate in cubic feet per hour or CFH?

5) Are you using a gas lense collet body and what size gas cup are you using?

6) Is the location you're welding at properly shielded from any wind drafts that might occur in the area?

Answer these questions and hopefully we'll be able to find the solution to your problem but if you leave anything of significance out - then it'll take longer to figure it out for you!!!

Respectfully,
Henry

By bozaktwo1 (***)

Date 05-06-2007 12:21

If you're getting minor porosity in 1/12 of your work that's pretty good for aluminum. If it was happening more often I'd worry.

I have welded a lot of 5052 with the GTAW process, and one thing I learned the hard way is that everything matters: gas, electrode, cup, lens, cleaning, filler, torch angle, right down to how shaky your hand is. There's no way to ensure 100% zero-defect welding when it comes to any aluminum alloy.

That said, I will recommend that you ditch the 2%ewth for pure tungsten or maybe cerated. Personally, I have had greater success with pure and 100% argon than with any other combination.

Good luck!

By ssbn727 (*****)

Date 05-06-2007 20:34 Edited 05-06-2007 23:18

I've got to respectfully disagree with you here Bozak!
On the older machines that had "sine wave" output characteristics, zirconiated (ZrO2 - Brown stripe) tungstens were better than pure especially when welding Aluminum!!! On the newer "squarewave" type power sources, ceriated (Orange stripe) or 2% thoriated (Red stripe) tungstens can be used but, for the best performance, lanthanated (La2O3 - Blue stripe) tungstens are recommended.

Here's an excerpt directly from Miller's website and below is the link to it which addresse the specific power source the originator of this post is using... A Miller Dynasty 300 DX:

Why would I use Ceriated or Thoriated tungsten instead of Pure?
With the introduction of new power source technologies, the use of pure tungsten is decreasing.
Pure tungsten melts at a lower temperature causing it to easily form a rounded ball at the tip. When the ball grows too large, it interferes with your ability to see the weld puddle and causes the arc to become unstable. Ceriated tungsten can withstand higher temperatures and works very well with the new squarewave and inverter machines for the following reasons:

* Holds a point longer and starts well at low amperages.

* Can be used on both AC and DC polarities. When welding aluminum, it has become very acceptable to grind a point on ceriated tungsten (especially when welding on thinner materials).

* Allows welding amperages to be increased by 25-30% compared to Pure tungsten of the same diameter.
Here's the linkthat describes just what I said above... scroll down a bit when you get to the link:
http://www.millerwelds.com/education/tech_tips/TIG_tips/hints_tips.html

Here's another link that covers the basics in GTAW of Aluminum:
http://www.millerwelds.com/education/articles/articles15.html

Hey Stratline! Check out the Miller version of their TIG (GTAW) Handbook in .pdf format... Here's the link to the main page which has links to all of the chapters online to be downloaded as a .pdf :
http://www.millerwelds.com/education/TIGhandbook/

Here's another link to their "Guidline to Gas Tungsten Arc Welding (GTAW) Handbook in .pdf format:
http://www.millerwelds.com/pdf/gtawbook.pdf

This article better explains Ac GTAW balance control and how it relates to "Squarewave" power sources
http://www.millerwelds.com/education/articles/articles82.html

Sure! one outr of twelve is'nt bad so long as we're talking about alot of weld length in between!!! For instance, if one is welding 12 parts and the total weld length of each part is 2 inches then do the math!!!

Not too impressive if this is the scenario... on the other hand if the total length for each part is 20" then that changes everything so, it's all in the details!!!

Nowadays you can achieve 100% defect free welds on Aluminum!!! I'm not talking about discontinuities here Bozak! I'm talking about defects! I mean look at the external main fuel tank on the space shuttle that NASA uses!!! that's Aluminum!!! Of course they used a Variable Polarity Plasma Arc Welding process that they came up with themselves with 100% defect free welds!!! Martin Marietta has been producing them for years down near your neck of the woods!!!

Edited 19:10: I almost forgot Stratline! Here's the link to the Miller online (GTAW) TIG Welding Calculator:
http://www.millerwelds.com/education/calculators/tig_amperage_calculator.php

Now remember that this calculator presumes that you're using a traditional sine wave output characteristic type of power source so if it recommends Green band otherwise known as pure tungsten, and you're using an inverter squarewave output characteristic type of power source - then do not follow the recommendation, and use either ceriated or lanthanated tungsten instead - especially for your Miller Dynasty 300 DX! I hope this helps!!!

Respectfully,
Henry

By bozaktwo1 (***)

Date 05-07-2007 17:08

Thanks for the info...my brain hurts now.

I prefer Ceriated, but I have had success with 5052 and pure tungsten with all sorts of machines. It it very unforgiving if you "dip" your "wick," and I suppose having no choice for many years made me respect that somewhat (we squids were never given much choice in electrodes until recent years, prior to 2000 or so it was 2%, 1% or "green"). One fine day I had to take a trip to the local AirGas shop to buy some supplies, and got into this very same conversation with the proprietor, who looked like he'd been 'round the block a few times. That was my introduction to the wonderful world of "there's more out there than just 3..." As far as Zirconated goes, I have never even seen a stick...would like to try my hand at it, however. I love the idea of putting down a skinny pjp on 22 ga. sheets.

Now on a side note: my level I welders, they're going to eat tungsten up in practice, so I am thinking start them on pure to keep costs reasonable. Most of our production aluminum is T6, and I have one level II guy and one level III guy who know how to weld it GTAW. I need more, and they want to learn, so I think I'll dust off the hood and see what I can show them.

By ssbn727 (*****)

Date 05-08-2007 03:25

Hey BozakTwo1!

I hear you loud-n-clear!!! I remember the inverter revolution back in the eighties, and that was the first sign of the changing times a comin!!!

Anywho, Do you mind me asking what type of power sources you're gonna be using to teach these youngins because you'll be eatin up alot more Pure (green) if you're using squarewave inverters?

You're also gonna have to muster up a whole lot of patience when training in GTAW Aluminum 6061T6 so, steady as she goes capish? Good Luck in your new journey!!!
We'll be here to lend a hand if needed!!!

Respectfully
Henry

By bozaktwo1 (***)

Date 05-09-2007 01:37

I have a Syncrowave 350 and an older 300. These are the only machines I have set up for GTAW now.

I have two Level II guys who do all the GTAW right now. I want them to start teaching my level I guys. I'm going to start them out on 1G scrap runs, let them learn to control the arc, then start running test coupons. Then I'll switch them to ceriated, let them run a little practice. When I think they're ready I'll run them through a 1G test, bend it, if I like what I see then on to 3G. Pretty soon I'll have the 5G tube ready for test, just sorting out the bend sample criteria now. It's always more confusing to me for pipe! I also have to get my steel welders going in 4G, we have a production run starting soon and I don't want them wasting the day flipping stuff over!

TY for the support, that's why I go here. I let my lead level II guy know that he's going to be getting some new tungsten to play with soon; I'm going to start off with ceriated, with which I have some experience, and buy a box of lanthanated as well. I'm going to run them side by side and take a look, maybe cut them and etch them. But the real test is to give them to this guy and tell him to run for a week and see how he does with it. Personally, I never really noticed any difference, but I considered myself very good on aluminum with pure. Every once in a while I would break the end off, file it flat and go to town again. I don't recall doing that with the ceriated, but I don't recall not doing it either. I get in a zone when I'm running, I guess, so I don't really pay attention to little things like that. I guess if I were paying for my own electrodes I might see it differently.

Oh, and not all my level I guys are younguns! Some are older than me! But they all have something to learn, or something to teach, I am sure. The challenge is finding out who knows what. Almost all of our production aluminum is T6, so we use it to practice and test as well.

By DaveBoyer (*****)

Date 05-09-2007 03:08

Bozak [Or anybody else with an opinion]: I was thinking of jumping up to '80s technology and getting a used Sincrowave to replace My ABP. Do You have any preference between the 300 and 350?

By bozaktwo1 (***)

Date 05-09-2007 23:28

I have never welded with a 300, only a 350, so I have no experience to share, except that the 350 is a dang reliable machine. In my opinion.

By Lawrence (*****)

Date 05-06-2007 19:12 Edited 05-06-2007 19:16

Strat

We don't really have enough data from you to determine a cause.

But I think you can be confident that your porosity is a process control problem rather than something wrong with your machine.

Minor porosity and things that may cause it.

SSBN made a good list of things to check..

Other than those I can think of one more stumbling block that is pretty common with Aluminum. When switching from a transformer rectifier (Traditional squarewave) to an inverter like Dynasty (True Squarewave) balence control settings often become an issue. Let me explane why.

Your Dynasty can control AC dwell time on the straight polarity side of the half cycle all the way to 99% dwell on DCEN.... A transformer rectifier has balence control settings usually from 1-10. Ten being a dwell time of 68% DCEN.... New users of inverters often will try to get sufficient cleaning action with a setting that is not practical... They might set that DCEN for 80% DCEN because they set their old Synchrowave 250 or Lincoln Percision Tig to 8 (about 55% DCEN) on the balence control dial. When they do this they are actually providing much more DCEN than they imagine and usually past the point of diminishing return as far as weld quality.
Having said all of this it seems unlikely that over dwelling on DCEN would only cause flaws in one out of twelve workmanship samples... Also look at shearing and bending practices...

Are the flaws occuring at the same spot in the production componant or at various spots?

Correctly prepped aluminum really should not have visible porosity problems. If your process is under control I don't think a 1 in 12 reject rate is good at all, maybe one in 120 or even fewer.

Tell us about your surface prep and fit-ups.

By ssbn727 (*****)

Date 05-06-2007 20:48 Edited 05-06-2007 23:11

Hey Larry!

Stratline! This gentleman is "Lawrence of Wufram" when it comes to GTAW!!!
I've got to defer to his expertise here because he's had much more time welding with the newer squarewave Dynasty inverters from Miller than I have!!! I've been around this business as long as Lawrence but when it comes to GTAW but, he can definitely steer you in the right direction.

Either one of us can definitely help your situation when it comes to the process but, Larry knows these Miller Dynasty's a bit longer than I do ;)

I'm more familiar with the Miller synchrowaves, 330 ABP's, Goldstars, PowCon inverters, the older P&H's, thermal Arc inverters, the venerable Linde/union Carbide/L-Tech now known as ESAB power sources, Westinghouse and those Lincoln power sources... Listen to the man! He'll steer you in the right direction!!!

Respectfully,
Henry

By Tommyjoking (****)

Date 05-10-2007 07:44

not to get into the intricacies of tungsten ....but cerated would probably work best considering its 1/4 inch plate.

Dont know your whole process but....make sure the mill finish is removed prior to welding...anal cleaning would be a good idea with a solvent that completely evaporates ...like acetone. CLEAN CUPS are a must with pure argon. On repairs try using a magnifying glass with a light in it ( like the little circle phlourescent kind) mark your holes a with a fine sharpie for repair. if you have a bead blast cabinet with fine material designed for aluminum...try blasting then inspecting under mag lens. I have similiar issues with 4130 parts that get a show chrome finish....the ONLY way to be sure before plating is to inspect with magnification after bead blasting.

Porosity in aluminum can be caused by too much heat as well as a wild arc. Try turning your frequency down to make the arc "softer"...if you are carrying a real hot puddle with a very excited arc it can cause porosity at the very least at the surface. A simple matter of the distance between your electrode and the puddle can cause issues as well. I hope somthing out of this helps your problem....please report back if it continues.

By js55

Date 05-11-2007 14:31

Dragged this out of an old WRC doc that I have in my library.
"It has been well documented that the entrapped gas which forms voids in aluminum alloy welds is almost exclusively hydrogen. Contaminants on the surfaces of the wire and base plate are the most frequent sources of hydrogen, as hydroxides, hydrocarbons, and oxides with absorbed water. But the welding atmosphere may also coantin moisture or aspired humid air. As little as 2 ppm of H2 in the motlen metal or 250 ppm of H2 in the gas are sufficient to produce significant amonts of prosity."

By Tommyjoking (****)

Date 05-12-2007 07:35

Great reply js55

I am starting to get concerned about making sure my hands are real clean before I start a weld these days and catch myself wiping my rods off too....your post validates how easy it can be to get some kind of contanminent in your weld.

By Eutectic (**)

Date 05-12-2007 07:45

I aggree with Jeff and Tommyjoking, when we dit our trials, sanded and toluened my filler rods as well, clean gloves is important.

Cheers