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Up Topic Welding Industry / Technical Discussions / Weird ripple appearance in 1/2" 6061-t6
- - By Kix (****) Date 01-23-2009 20:11 Edited 01-23-2009 20:14
Here's what we are looking at http://i11.photobucket.com/albums/a189/vdubin474/MVC-023S.jpg  http://i11.photobucket.com/albums/a189/vdubin474/MVC-021S.jpg  http://i11.photobucket.com/albums/a189/vdubin474/MVC-024S.jpg I'm wondering what causes the that ruff back edge of the ripple.  This is the second time I have seen this in my career and have never figured out what causes it.  Could it be turbulent gas, tungsten to close or maybe a bad ground or something.  Just wondering if any of you have ever experienced this.  This is what the ripples are supposed to look like all the time  http://i11.photobucket.com/albums/a189/vdubin474/MVC-022S.jpg  When it's doing it you can hear the erratic arc like something is changing. I've had this happen to me on thinner material as well so it's not just the thick stuff.
    If you wondering it's on a 6" long 1/2" thick fillet weld coupon. We're using a Dynasty 700 at anywhere from 400 to 500 amps.  It's done in 2 passes and the cap is around 250+ amps.  Balance around 70% and freq is at 60Hz on this particular run.
Parent - - By aevald (*****) Date 01-23-2009 20:41
Hello Kix, couple of quick questions. What diameter and type of tungsten are you using? Any possibility of tungsten "spitting" being a culprit here? Your mention of sound being different and somewhat erratic would give a possible indication of not having sufficient "soak" of the welding heat, meaning that you are trying to use the heat of the arc to make the bead without allowing sufficient time for this heat to make it's way adequately through the particular joint before progression of the weld bead. I realize I may be doing a poor job of sufficiently describing this condition so I apologize beforehand. You listed your balance at 70%, which side of the polarity are you referring to?, 70% DCEN or 70% DCEP? If it's DCEP I believe that might be a tad bit too much. I know Lawrence is much better informed to comment on your particular settings. You also mentioned that you are using 60 Hz, have you tried varying this towards the upwards side? I believe you might have a bit better success by increasing this frequency setting.
     I believe this is a heat related issue and may also include some tungsten stability issues. Whenever I have not taken sufficient time to bring the heat up in the weld pool I have experienced excessive tungsten spitting or instability and I have also noticed the sounds that you have mentioned. I have also experienced tungsten issues when the balance has been too far towards, the cleaning side (DCEP). On machines that have a variable Hz control the lower Hz values have shown to agitate the end of the tungsten more than the higher values, which leads me to believe that this could also have an effect on tungsten spitting. Just a few thoughts of mine, I'll be interested to hear additional comments. Lawrence, Henry, Al, the rest of you, where are you guys? Best regards, Allan
Parent - By Kix (****) Date 01-23-2009 21:21 Edited 01-23-2009 21:32
Oh yeah, I forgot to mention one of the most important things.  We're using 5/32" 2% ceriated tungsten. The higher you go on the balance the more toward the straight pol side you go so 70% is leaning more into the - side of the wave.   As for the Hz 60Hz is what a normal A/C wave operates at and if you have no ajustment, you're stuck with what comes out of the wall.  I've seen this phenomenon with syncrowaves that have no freq adjustment.  Thing is, sometimes it runs sweet and you do not get the funk at the back of the ripple and other times you do. If you notice the begining of the cap bead has nice ripples and these funky ripples happen towards the end where the piece is cookin hot. Amperage stays about the same the length of the weld.
Parent - - By MDG Custom Weld (***) Date 01-23-2009 20:53
Ray,
I have seen this same thing on heavy plate (1/2"+) when the material is cold, like below 50f, and usually only on the first pass.  It's like the arc is really intense focusing the heat on the puddle and when it digs hard the puddle kind of splashes around and quenches before it flows smooth into the bead.  Usually it happens most when the filler is added.  It does seem to make a real harsh buzz as the AC arc is digging and making the puddle really erratic.  I have seen welders that we call "pedal pumpers" do the same thing on thinner plate as they ramp up and down on the foot pedal.  You might be able to reproduce it by running your bead and mash the pedal for a second or two and then let off.  Do that a few times and you might see the same profile.  Also too much amperage for the tungsten as Allen stated.  I can remember watching the end of the tung. starting to dance.

Mark
Parent - - By Kix (****) Date 01-23-2009 21:27
This happens toward the end when the pieces is cooking hot.  Check out the ripples in the last pic, they are from the begining of the weld and they are how it should look the whole way.  I think this phenomenon is arc related so keep the ideas coming.  Tungsten looks to be in good shape.
Parent - - By Milton Gravitt (***) Date 01-24-2009 00:52
   Kix are you using any helium if not it might help.
                    MG
Parent - - By Kix (****) Date 01-24-2009 02:43
Using 100% argon.  I wish I could use helium, but it's out of our price range.  I was able to qualify our procedures with 100% argon so I'm stuck.  I love the way a good helium mix welds on aluminum!!! Makes the welds look dam slick as well.
Parent - By Milton Gravitt (***) Date 01-24-2009 16:03
     Kix how are you cleaning the aluminum chemically etching or you scraping the oxidation off.
                        MG
Parent - - By bozaktwo1 (***) Date 01-24-2009 01:57
Just a little guesswork here.  I am going to guess you're using either 4043 or 5356 filler, since those two are most common.  I usually tend to agree with Alan on all things aluminum, but in this case I don't think your current frequency has anything to do with it.  Most of the time I have had that type of cold formation on the backside of the puddle is when I was welding with a torch for which I had no gas lens and thus had too much flow at the cup.  Most of my GTAW experience is with 5052 sheet and 5356 fillers, but I think the basic principal is the same, considering the similar melting points and density of the materials.  It doesn't take much extra gas to disturb the puddle. 

This will be an interesting thread to watch, for sure.  :)
Parent - - By Kix (****) Date 01-24-2009 02:40
I will play with the gas flow and see if I can duplicate this occurrence again.  You are correct in that I am using a 4043 filler as well.  Maybe the torch was to close where this happened and gas flow did disrupt the molten puddle causing the arc to flutter.  Like I said above, it is really cooking toward the end and the puddle is really fluid so small disturbances could cause problems.  I'll be back at er on Monday so I'll let cha guys know what I come up with.
Parent - - By Lawrence (*****) Date 01-24-2009 14:39 Edited 01-24-2009 15:14
That's a curious discontinuity.

Frequency is not the issue.. For Thicker aluminum sections an even lower frequency may benefit (try 40 Hz)

If your power supply were not an inverter I would suspect that rectification were the issue... I think I still suspect it.

The picture of "what it is supposed to look like"  has superior cathodic etching.  This leads me to question the 70% EN.. (I think Alan may be on the right track here)  The pictures of the strange discontinuities show very little etch (cleaning action).  

Rember now that "rectification" is the DCEP side of the half cycle being skipped! (Rectification = funkey etch & surface appearence)  Furthermore there may be a different "sound" when rectification occurs

With these souped up hybrid Aysemmetric power supplies the temptation is always there to take our parameters up just one more notch (because we can!!!!!) When your running on the ragged edge of physics, and that Dynasty does, just one little bump in the road (1 or 2% too much DCEN) or maybe a joint geometry that causes a different gas flow.....Believe me, a 400A Alternating Current GTAW plasma column is a pretty fierce thing.

I like the idea of

1.  If you have a second Dynasty or even a transformer power supply, roll it out and do a trial, If the same thing is occuring the problem is rectification and the Dynasty is the Culprate.   I'm thinking at those super high current levels that maybe the inverter technology (no High Freq. for AC) may have a slight weakness and make high amp operations with AC suseptable to the rectification bug-a-bo0.

2.   Checking gas flow, cup and collet setups on the offending torch.  Go big on cup size and increase argon flow above what you might think normal for aluminum operations to compensate for the crazy 400A arc plasma.

3.   If no joy...  Back off to 68% EN, do trials and reduce 2% until a proper etch and appearence is achieved

4.  Go GMAW   What could possibly be the advantage of GTAW over GMAW/P in a simple fillet of that thickness?  What are you crazy?  :)
Parent - - By Kix (****) Date 01-24-2009 22:45 Edited 01-24-2009 22:51
Lawrence,
 
    Thank you for your reply and I am willing to try anything to get to the bottom of this.  So you may be able to help me out a bit more, I must tell you I have seen this at lower amperages only one other time and it was with an older syncrowave 350 only capable of 60Hz so I to do not think it's a freq issue.  It was on thinner material and that's about all I can remember.  I thought the machine was messing up because I couldn't trouble shoot it.  So you think I'm running to far on the - side of the wave with the 70% balance?  From the picture it looks like it's etching about 1/4" out past the bead.  Is that not enough in your opinion? We do use GMAW on the thick stuff as well, but we have to weld these 3" dia solid bosses to 1/2" material with GTAW because you can't get the MIG gun in position.
     This thread and the 400 amp arc plasma will lead into another thread here shortly and I hope you (Lawrence and the rest of the crew) can help me out.  The guys are fighting the wave that gets splashed out in front of the puddle that in turn causes lack of fusion. ;-)  We'll save that discussion for the next thread though.
Parent - By 803056 (*****) Date 01-27-2009 04:54
"We're using 5/32" 2% ceriated tungsten..."

I've always used zirconiated tungsten for AC. I've used thoriated, lanthated, and ceriated for DCEN. I've seen welders use them for AC, but not with great success.

My suggestion, try either pure tungsten or zirconiated tungsten and see if there is an improvement.

As mentioned by several folks, check your cleaning before welding and your balance control.

Best regards - Al

Forgive me if the spelling is incorrect. I'm too lazy and tired to go look up the proper spelling in A5.12
Parent - - By 1fastguy (**) Date 01-27-2009 20:53
It looks to me like this is a heat issue. The 400-500 amps seems to me to be very high for GTAW of 1/2 inch T6. We use GTAW on 5083 and 6061 T6 all the time and we run at 350 amps max with a 75/25 Argon/Helium mix using 5/32 1% tungsten and .090-.125 filler rod. Just my 2 cents
Parent - - By Kix (****) Date 01-27-2009 21:28
Your argon helium mix at 350 amps is like my 400-500amps with pure argon.  The helium makes things hotter and believe me, if I could use a helium mix I would, but we're cheap.  1% what on the tungsten?  Have you done any fillet procedures proving that your 350amps gets the penetration and fusion that is required in AWS D1.2(2003)?
Parent - - By ssbn727 (*****) Date 01-29-2009 05:09
I see some "Not so clean surface" in the weld zone, and just adjacent to the weld deposit so, we can start there... I also see the points that both Alan & Lawrence make when it comes to setting your power source as they describe, and I would have to agree with Larry with respect to possibly switching to another process all together such as GMAW-P when welding that thickness of 6061-T6. Al's suggestion of using a zirconium alloyed tungsten makes a bunch of sense also!

So unless you already have a GMAW-P capable power source with push-pull feeding, then I suggest to clean the surface better, use a slight preheat if the environment is susceptable (high humidity/low temp) and finally, use either a pure or zirconium alloyed tungsten electrode of whatever color (Brown or Yellow) stripe works best for you but, don't forget to CLEAN, CLEAN, CLEAN FIRST!!!

Respectfully,
Henry
Parent - - By Lawrence (*****) Date 01-29-2009 13:21 Edited 01-29-2009 13:28
I'm going to take issue with the advice of my esteemed collegues Henry and Al, Who's feet I sit at for the other 364 days a year.

When it comes to GTAW with Alternating current and high Amperages, Pure tungsten should never be used, and Zirconium is a third alternative choice at best..

The discontinuity looks to me like it was caused by rectification... which is directly related to arc instability on the EP side of the AC half cycle...   Pure tungsten has the least favorable work function of any tungsten electrode... This low work function means that pure tungsten electrodes have fewer "emitters" to help stabalize the arc.

Cerium, Lanthanum, Thorium, Zirconium... These oxides provide excellent emitters, those helpful oxides that have more free electrons on the outside shells, ready to leap off the electrode tip and jump the arc gap, and initiate or stabalize a welding arc.

Inverter power supplies such as the Miller Dynasty switch so quickly and cleanly between DCEN and DCEP that they don't even bother with High Frequency for AC operations... This performance however, is dependent on a tungsten electrode that can support the operation... Miller discourages the use of pure tungsten in it's inverter products.

Zirconium has excellent properties for arc transmission (good emitters) however it's current carrying capacity is considerably lower than Lanthanum and Cerium.  Zirconium electrodes are not well suited for work over 250A

Cerium (which is the current electrode selected) and Lanthanum are the two best choices for electrodes for high amperage AC operations on aluminum..... Having said that, it is always possible that a bad batch of tungstens came down the pipe and are causing the rectification... If other trials continue to produce discontinuities it would be apropriate to try a Lanthanum 1.5 or 2% for an operation like this one.
Parent - - By ssbn727 (*****) Date 01-30-2009 07:50 Edited 01-30-2009 08:26
So Larry, you take issue with the possibility that the material in question doesn't need to be cleaned prior to welding? Either I'm going blind real fast here or hallucinating because after all, I do see what I believe is "magic marker" lines right about where the toes of the weld are located, and they seem to flow right into the "cathodic etching" shown adjacent to the toes of the weld. I also see some small lines of either some sort of contamination and/or corrosion of some type going on however small in size on the surface of the base material, perpendicular to the axis of the weld. Finally, I see a bit of surface porosity towards the toes of the weld also. Am I losing my eyesight here folks, or am I on to something here? :) :) ;) Oh I almost forgot... What is that stuff oozing from the bottom toe of the weld located close to the end, just before the crater shown in the first photo?

One half of an inch thick 6061-T6 tells me right off the bat so to speak, that the oxide surface layer is going to be thicker, deeper into the material than with thinner Al of the same grade... Take the time to clean that area better and I believe you'll see some improvement. BTW, what is the gas flow rate? You might want to lower it just a little in order for the gas to stay within the corner instead of bouncing off the surfaces - out of the corner you're describing - so to speak because the flow rate is too high.

The suggestion of using a zirconiated tungsten was just that... A third alternative! I believe we were just covering most, if not all of the bases with our suggestions. :)

Respectfully,
Henry
Parent - - By Lawrence (*****) Date 01-30-2009 13:29 Edited 01-30-2009 13:31
Henry,

The only issue I had... my friend for many years...  was the tungsten electrode issue.  I'm always going to chime in whenever somebody even mentions pure tungstens anymore... They should have been removed from all toolboxes about 15 years ago buddy... For an extra 5 bucks a box you can buy electrodes that really work  :)

Your other advice regarding surface prep was perfect as usual.

With the Aerowave and it's hybrid AC output, prep becomes even more important <as you rightly pointed out> when the EN balence extends beyond what can be produced by a Transformer power supply (which is about 68%EN)  It's like sailing in uncharted waters with a canoe,,, if you don't have everything perfect.

I misses the OOze... Gonna have to go back and revisit those pix !!!

PS Henry... Keep an eye on the Educators board when you have a chance to check up,  Gonna post some pix of my new lab, construction is finished and students are burnin rod!!!!!....... The Lincoln rep about went into seizures when he saw it and how Blue we seem to have become. :)
Parent - - By ssbn727 (*****) Date 01-30-2009 23:01 Edited 01-30-2009 23:12
Yes you are!!! Man I wish I could have half of your budget here :) :) :) If you see or hear from Rich Depue, please let him know that the welding program he started has hit the skids so to speak once again due to  NY State's "Draconiun" budget cuts here @ ASC!!! ;( It's a crying shame because this program is one of the few which year after year keeps growing in enrollment, has enjoyed an excellent reputation over the years, and is always running beyond full capacity which only makes sense to fully fund it and keep it current with the state of the art! :( :( :(

I guess things haven't changed much since he left here years ago when he had to put up with the obtuseness for lack of a better term used in describing the "powers that be" here in Western NY and at you know where! ;) ;) :( Thanks again for your clarification and kind words as always my friend for what seems to be "many years" - now that you mentioned it! ;) ;) :)

I hope everything is as well as expected with you and your family, and I am happy to report to you along with the rest of my friends in here my continued improvement health wise buddy. ;) I do believe it has had some indirect help from the power of prayer from which I know my friends here have practiced continually on my behalf and as a result, I am always filled with overwhelming gratitude. :) ;) Thanks again for your kind words and BTW, We stand together!!!

Respectfully,
Henry
Parent - By Lawrence (*****) Date 01-30-2009 23:22 Edited 01-30-2009 23:24
Henry,

I was working with Rich last fall on the new revision of EG2.0...  We rewrote the test bank and modularized the whole shebang... Rich was the key (did all the heavy lifting) to create/revise the new SWPS that will be provided with EG2.0.  He is also a player with the upcomming Accreditation component for SENSE that will help leverage Carl Perkins money..

Our meetings are almost always teleconference types... But when we next cross paths I'll give him your best.

PS:   Sorry for straying off the thread Ray,,,,,,,,  Tell us how the project is going and if you are seeing any more of those funny indications..  Ooozers
Parent - By Kix (****) Date 01-29-2009 13:25
   We do use GMAW as well Henry.  The TIG torch can go where no MIG gun has gone before.;-)  Saying that there are some tight places to get to on these aluminum brackets and baskets.  This could be a tungsten issue, but I highly doubt it.  I've been using 2% ceriated for a long time and have found it to be superior for heavy weldments when you want to keep a point on it to get the penetration to the root consistently with pure argon.  It doesn't spike and it doesn't leave a nasty mess when you take a direct hit.  Tomorrow I'm going to experiment with gas flows and tungsten distance and see if I can't replicate the problem.  I'll let you guys know what I come up with 2marra.
Up Topic Welding Industry / Technical Discussions / Weird ripple appearance in 1/2" 6061-t6

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