TIG/cleaning, MIG/?

[aphexafx]

I was showing my friend the amazing and all wonderful Dynasty 200 DX today and explaining how each cycle of the AC mode affected the metal (aluminum in this case). He's a non-weldor but is curious about anything electrical, so he's been listening to me ramble on about everything I've been learning about welding, so I've explained the MIG process to him as well.

He simply asked me why if TIG welding strictly requires a cleaning cycle for metals that oxidize, MIG welding does not. I have no answer for him! I don't know. So I'm forwarding the question on to you guys because, as a TIG and non-MIG weldor, I want to know this myself. To me, if you don't AC your aluminum, you're never going to get a clean weld.

What gives for MIG and aluminum? Do you just clean the **** out of it and hope for the best? What about the massive amounts of oxide that must pour into the pool from the quickly fed and uncleaned wire!?

[Blown S-10]

this is my take on it.

mig & tig aluminum does need cleaning. the amount of cleaning depends on the condition of the material. new 6061, not much if any cleaning. something thats been under a truck for the last 10 years, may never get it clean enough.

tig arc is on top of the metal, where the oxide layer is. so this needs to be cleaned as needed. but the mig arc digs down into the metal, the wire gets down into the bead, and under the oxide.

i have done, and see a LOT of clean aluminum mig welds. its tons more common than you think. next time you go to walmat, look at the carts they use to stock the shelves. they are mig'd aluminum. least the ones here are.

[hankj]

AC TIG "cleans" on the portion of the cycle where the electrode becomes positive with repect to the weldment. That's why there is an "EN" (electrode negative) adjustment on many of the higher-end GTAW machine, the Dynasty 200DX being a good example.

Except for flux-core with which you cnnot weld Al, GMAW is a DC operation, and the elctrode is at the + potential. The cleaning action is natural with this polarity.

I think I got it right...

Hank

Edit: Vodka does this to me occasionaly: WELCOME TO THE FORUM! Too wrapped up in my own self, here. Sorry.

[aphexafx]

Vodka does this to me occasionaly: WELCOME TO THE FORUM! Too wrapped up in my own self, here. Sorry.

Thanks Hank! I've been snooping for a little while and I have to say that this is a great welding forum. People seem to get answers here instead of arguments, and that's really cool.

WOW! Look at that. That must be the answer. It's so obvious, too. I just looked and sure enough, you MIG weld with DCEP. Plus, like Blown S-10 said, I guess the GTAW process is just more sensitive than GMAW, which really lays the metal down with a good bit of force. Neat. Thanks guys.

Hey Blown S-10, you know you're a weldor when you find yourself inspecting the welds on Walmart shopping carts! Hehe.

[HAWK]

Blown S-10,

Speaking of looking at welds- Do you ever check out the aluminum tool boxes in pick up truck beds? Most are MIG and poorly done. Recently I saw a box that was TIG welded. There was no name brand I could see, but it looked good in the sun! I hope your Walmart carts are better than ours in TN. The ones I have seen are cold and wire stubbed welds.

[fun4now]

Hawk

I hope your Walmart carts are better than ours in TN. The ones I have seen are cold and wire stubbed welds

well we are talking about wal-mart not nascar it's true though a bad weld is still a bad weld, dosent show much pride in there work. lets hope they arnt welding any thing other than carts for walmart , i wouldnt want somthing like that driving next to me on the road

[Blown S-10]

walmart carts, lol, i have stooped to new lows . but really, the welds i saw on the ones here looked pretty good.

i have yet to see a miged tool box, saw one tig'd. it looked good enough for the task.

look under the hood of your car. the ac parts are robot mig'd, and thats some high psi parts.

last night i was tig'n. i now have an understanding of "balance". my 6061 1/8 plate was junk on 95, but on 70 it wasn't bad. 130a, 150-200 hz, 2% thoriated, 15 psi argon. i THOUGHT i had a handle on cleaning, but no . the machine, on 70 balance, as doing ALL the cleaning. 95 balance just burned holes. so i have a LOT to learn about cleaning.

[aphexafx]

Balance

Blown S-10, slap me if this is greenie ignorance, but I don't think you're supposed to use thoriated electrodes on aluminum because they contaminate the weld! Though, I suspect it would only be a problem for critical welds... And personally, I've never tried it, so I wouldn't know.

As for the balance control, think of a square wave with a centered zero-crossing, right? You spend half of the time at so many amps above zero (negative cycle) and the other half of the time at so many amps below zero (positive cycle). The time spent on either side of zero is a percentage of the total time for one cycle, right? The balance control simply allows you to adjust the percentage of total time spent on either the negative or positive cycles, the other cycle is inversely proportional of the one adjusted. Controls that are labeled ~Cleaning~ on entry level machines are adjusting the time you spend on the positive side. Controls on professional machines like the Dynasty are labeled ~Balance~ and are adjusting the time you spend on the negative side.

As you know, when the wave is on the negative cycle, you are creating a forward arc, meaning the electrons are physically jumping from the electrode to the metal you're welding. This is when the arc is doing the most work as far as melting the metal goes. However, when the wave is on the positive cycle, the electrons are instead jumping from the metal to the electrode in your torch. At this point only a fraction of the heat is actually getting to the metal, BUT the ionized shielding gas molecules, which are positively charged, are hugely attracted to the now negative metal and they slam into it and break up the oxides (at the molecular level).

So, when you adjust the percentage you are simply varying the amount of time per cycle that you are spending in the forward, working (EN) mode, and the remainder of the time you can expect to be in reverse, or cleaning (EP) mode.

I'm going to draw an ascii square wave example:

----- ----- ----- ----- <- WORKING (-)
| | | | | | |
++++++++++++++++++++++++++++++ 0 [Balance at 50%]
| | | | | | |
----- ----- ----- ----- <- CLEANING (+)

At 50%, as you can see, equal time is spend working and cleaning.

-- -- -- -- <- WORKING (-)
| | | | | | |
+++++++++++++++++++++++ 0 [Balance at ~20%]
| | | | | | |
----- ----- ----- ----- <- CLEANING (+)

At 20% only 1/5 of the time would be spent working, while 4/5 of the time (80%) is spent cleaning - probably not very practical, which is why your Dynasty won't go down that far and stops at 30%.

----- ----- ----- ----- <- WORKING (-)
| | | | | | |
+++++++++++++++++++++++++ 0 [Balance at ~70%]
| | | | | | |
-- -- -- -- <- CLEANING (+)

And at a more practical 70%, the cleaning cycle is limited to only 30% of the total amperage being used, the rest is working to melt the metal for you.

And a note, if you think you need to go above 90%, which you can't via the balance control on AC, just flip over to DCEN, which is effectivly the same as AC with 100% balance.

Did that help at all?

[aphexafx]

Well, so much for my squarewave example.

Look at the TIG Welding Handbook on Miller's site, page 10, it gives a good overview of how the balance control works, and has some visual examples, which unlike mine, you can see and understand.

Here's a link to the section that contains the section about balance.
http://www.millerwelds.com/education...Book_Chpt2.pdf

[Blown S-10]

thanx for the info. i thought 2% thoriated was ok for aluminum, maybe its just that "ok" . i as tig'n again last night. i could see a lot of junk going into the puddle when i added filler, and my filler is new, and i clean it with a new scotchbright pad. other times the bead looks ok, not great, but basicly clean.
the really bad thing about all this, its not consistent. i have some beads that vary in quality from junk to "quality", all in the same bead !!! what i mean, dimes, few dimes = junk, couple = ok, 1 = superb, ok, ok, superb, etc.


i want to get some 1.5% lanthenated. but i also want to get some different sizes at the same time. but i have yet to understand what i need.

btw, this forum is acting funny today.

[fun4now]

Blown S-10

didnt you get the student pack.it has the tig handbook in it lots of good info in ther and a cool jacket to boot hard to beat for $25.00 and a stamp

[Blown S-10]

no, i didn't. you guys said it was online, so i downloaded it. been reading it now & then, maybe i should go over it again.

[joebass]

2% Thoriated sharpened to a point with a small land will work with the Dynasty just not as good as Lanthanated. I know a guy with a 300DX and thats all he uses. In fact when I got mine almost 2 years ago thats what I used. Now after finding these forums and hearing about Lanthanated I use that now.

[fun4now]

Blown S-10

i downloaded it first also but found having the book in hand much easyer to find time to read it (i'm on my 2nd time reading it now) being able to take the book with me has made finding time to read it much easyer than finding time on the comp.
i have to share the comp. with my lil woman and her dolls.

i was looking for the list ANDY put in a post a wile back about witch tung. to use with the dynasty and he listed 2% Thoriated as useable but as a last choice. 1.5% lanthenated was his first choice, as it was also stated in the book as the best for inverter's.

you could always send me your jacket coopon if you dont want it

[aphexafx]

didnt you get the student pack.it has the tig handbook in it lots of good info in ther and a cool jacket to boot hard to beat for $25.00 and a stamp

Woohoo! I just went and ordered a Student Trainnig Kit. Yes, I'll be sending in my free jacket coupon like a big geek, and I'll be wearing the jacket in my shop, like an even bigger geek.

I once saw a HUGE Miller reverse sticker (the kind you put on the inside of glass plate so you can read it from the outside) on the back window of a big Chevy. It must have been 1-1/2 ft. in diameter! Anyone ki\now where to get one like that? I'd pay well for it!