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Old 07-11-2004, 04:34 PM
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Red face TIG Welding Question

Another TIG Welding question. I have a 220V AC/DC welder in my garage. It works very well for stick and "scratch" TIG on steel. My question is for aluminum. My machine does not have a high frequency circuit in it.

I know that to weld aluminum you need a welder with a high freq circuit to start the arc without touching the metal. This keeps the tungsten from becoming contaminated. Can I "cheat" and use a steel scratch plate to start the arc, or will this defeat the whole thing. About the only aluminum I would like to weld would be for brackets, etc.

Thanks in advance,

H2Os50

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Old 07-11-2004, 10:15 PM
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You can buy a high freq. unit to add on. They used to be inexpensive. My first TIG setup was using a Miller welder with a Craftsman (Sears) frequency unit on it.
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Old 07-26-2004, 11:46 PM
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TIG setup

My first TIG setup was using a Miller welder with a Craftsman (Sears) frequency unit on it.

Re; I have a Century high frequncy arc stabilzer coming soon, from an ebay auction. I am curious how well did your setup work? I know century made the Craftsmen unit also. Did you have any problems at all? Thanks
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Old 07-27-2004, 09:25 PM
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I have looke at Sears and Century web sites and stores. No one seems to make or sell these units any more. I remember when I bought my welder they were available.

Maybe I'm looking in the wrong spots?

Thanks

H2Os50
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Old 07-27-2004, 10:08 PM
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TIG setup

Lincoln bought Century last october. I called lincoln and talked to Century tech to see if high freq, arc stab. is still available, NOPE He sad they they dropped them about 2 years ago I am getting mine from an ebay auction, you might try that route. I paid $301.00 with tig torch and regulator, not to bad I don't think.
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Old 07-27-2004, 10:15 PM
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Just found this web site. It shows a homemade arc stabilizer. I've got about half of this stuff laying around my garage. I may try to build one just for the hell of it.

http://www.geocities.com/CapeCanaver...tarter/hf.html

H2Os50
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Old 08-11-2004, 08:17 AM
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Ahhhhh Evil Electrickery.......

Hmmmmm the principles of TIG welding are this.....

Well it's aspro Fiziks time.

The reasons why YOU need to run High Frequency electrical overlays on basic (=sexy) arc welding machines when welding aluminimum is:

1. When things are cold such as BBQ plates, light bulb filaments etc., they (relative to their surroundings) do not radiate anything.... such as heat (Infrared light), or any visible or invisible light, Xrays or electrons.....


2. When they are cold (talking about the Steel BBQ plate here) and placed near a heat source, they absorb the energy from the heat source untill equilibrium is established - heat input = heat output from radiation and convection.

3. When STEEL is welded, the weld pool (moltern steel ~1400*c) is both hot enough to emit lots of bright white light and as it is radiant, when charged with electrons during 1/2 the sinusidal wave cycle (think tide in, tide out, tide in, tide out), and with very little provocation, the steel emits electrons back to the electrode and the arc is more or less continiously established and maintained.

4. FOUR parts to welding aluminium.

(i) Aluminium has a melting point about 650*C (I am a bit tired and forgetful right now) and the weld pool temperature is about 720*C

This is a lowish red heat, not a bright white heat. Red heat is not terribly electrically emissive when charged with electrons, so when welding with AC, during the phase of the current flowing from the job to the tungsten electrode,

As a gauge of comparison, if you were to remove the arc from weld pools of steel and aluminium, and then keep them there at that temperature, the steel would be blinding white light and the aluminium would be a dull red......

The steel is radiating everything like mad and the alumium is a dull red pool of liquid.

So the AC arc, when welding aluminium, has a wonderful tendacy to SELF EXTINGUISH, because the electrons basically refuse to run from "cold" weld pool to the electrode in the torch when welding aluminium.

(ii) To use very high voltaic pressures, that enable the arc to remain established, in the condition of LOW emissivitivity from the aluminium weld pool - well these very high voltages are not used because they have a real tendancy to kill weldors. (dead person, not welding machine)

(iii) Aluminium reacts with oxygen (elctronic reaction) to create an aluminium oxide film on the job.

This is BAD, and can create all sorts of problems in the weld quality and appearance.

However it is possible to clean aluminium in an inert atmospehere and to weld it with DC elerode negative - but most people neither have the time nor resources nor willingness to go to these lengths; and they find that just keeping the weld mechanically clean and locally shielded in Argon to be sufficient.

The AC welding cycle picks apart the aluminium and oxygen bonds to self clean the weld pool and the material surrounding the weld pool.

(it also cleans out some weld pool contaminants too)

This is good.


(iiii) Tungsten inclusions in an aluminium weld - well on one hand they can be no big deal - but on the other hand they can be real source of concern - but it all depends upon the application.

Two issues that arise when striking an arc from the aluminium surface is that the tunsten can stick into and break off into the weld and also that the aluminium tends to stick onto the electrode, which when carefully ground and shaped, has a great deal of say so about the arc shape and stability and weld quality (penetration depth and width and appearance).


So it's best to NOT strike the weld from aluminium.


5. When an High Frequency current is overlaid upon a AC welding circuit, it performs two things.

The composition of HF overlays are about 2 milliamps in power, 2000V and are about 20,000Hz (correct me if I am wrong).

So the power is stinging, but not lethal and it reignights the arc from the weld pool to the electrode.

The arc is stabilised and the HF overlay substantially aids in the deoxidation process by more forceably picking apart the electron bonds of the aluminium oxides...

And the HF tends to jump gaps so that the arc can be established without risk of contaminating the weld pool with tungsten or contaminating the tungsten electrode with aluminium crud.


Nuff said - time for a poo.

Last edited by ButtWeldor; 08-11-2004 at 08:30 AM.
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Old 08-11-2004, 10:13 AM
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Buttwelder-

Could you elaborate a little more? LOL GREAT explanation !


Jeff
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Old 12-09-2004, 12:14 AM
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I know this is short notice, there is a Century high frequency arc stabilizer unit with torch and regulator on ebay for turning an A/C or A/C-D/C buzz box type welder into a TIG unit. The auction # is 3858347486. A cheap way to go that works. the auction ends Dec-10-04 12:29:32 PST. This is not mine and I do not know the seller. Thought someone might be interested as ebay is where I found mine a few months ago.

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Old 12-11-2004, 02:28 PM
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Miller does still offer an arc stabilizer. I've never used one, but I assume it's probably the same technology that they use on their TIG machines, which we use all the time without problems. A vendor that I have used and has about the best pricing I have found carries them athttp://store.cyberweld.com/hfhigfreqarc.html
In short, I'd have to agree that you are far ahead to use a hi-freq and run on AC, especially if you are not real proficient at aluminum. There are, once in a while, good used TIG machines on the market that you can buy for not a lot of money. If you intend to do much aluminum, you may want to look at that option.
Good luck-
tjs
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Old 12-11-2004, 06:09 PM
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Yes, I am very aware of millers HF units, usually run $800.00 to $1,000.00, depending on what model you get. I know on one of the post's some one said the Miller unit was to expensive for them and that is why I posted about the Century unit on ebay. They do work well with A/C for aluminum as that is what I use.
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Old 01-19-2005, 08:53 PM
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To TIG weld aluminum ......

1. First you need to remove the surface layer of oxides. Do this with a wire wheel on a bench grinder or a drill if you don't have the grinder.

2. Preheat the aluminum with a torch to about 500 deg. F. If you do not do this the aluminum will dissipate the heat too quickly way from the pool you are attempting to make.

3. You are now ready to weld the aluminum. I trust you already are familair with shielding gasses.


There are tungsten electrodes with a red or green color code on them. ATM I cannot remember which one is the one you should use for aluminum, but it will make a difference. It has to do with how the electrode is alloyed and the resulting electrical conductive properties. I'll post that info tomorrow when I have it if no one else chimes in with it.


There's what you want and need to know without trying to impress others with theory that you are not going to be able to utilize.

Steve
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Old 01-20-2005, 11:27 AM
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Steve is correct that oxides need to be removed, as they actually melt at a higher temperature than the base metal, and cause all sorts of grief. We do not, however, preheat any of ours unless it is extremely massive. Aluminum does take a large amount of current to melt, due to the fact it disperses the heat so rapidly throughout it's mass, so you need to hit it with a substantial amount of amps to bring it to welding temp rapidly. Rapidly is a key word, too, as you want to confine the part that is melting to the weld zone, and not have the whole piece turn into a puddle at once.
As for the color bands on tungsten, green symbolizes pure tungsten, which is what you normally will want to use on AC current for aluminum. The main factor here is that it allows the tungsten to "ball" at the end, rather than retaining a sharp point like you would if tigging ferrous metals. The size of the tungsten is somewhat critical as well; if you are welding 1/16" or thinner, you probably want to go with a 3/32" tungsten or so. If you're doing up to 3/16" thick, an 1/8" works well, and over that you'll want to go with 5/32" Shielding gas cup size effects the process as well; the larger the cup (cone), the larger the heat area. A smaller one will maintain a more defined heat zone.
Hope this helps a bit...aluminum is fun to work with, and you can make some beautiful welds on it, but it does take a good bit of practice to master.
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Old 01-26-2005, 08:50 AM
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Quote:
Originally posted by Aussie XAXB
To TIG weld aluminum ......


There are tungsten electrodes with a red or green color code on them. ATM I cannot remember which one is the one you should use for aluminum, but it will make a difference. It has to do with how the electrode is alloyed and the resulting electrical conductive properties. I'll post that info tomorrow when I have it if no one else chimes in with it.



Steve
Hi guys,
i always use the green striped tungstens for aluminum Tig work. i have a piece of copper plate on my table that i use to dress the tungsten before use. and generally wipe the parts off with acetone before welding aluminum.

Bob Walker Jr.

Last edited by walkerheaders; 01-26-2005 at 08:56 AM.
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Old 01-30-2005, 09:40 AM
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I've always score the tungsten then break it folled by turning the welder to reverse polarity light up on a piece of copper until the electrode balls up then your ready to go.If it does'nt ball up you got the wrong tungsten.
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