TIG Welding - tungsten and argon

I have not operated a TIG machine since I was in my early 20s (now approaching my 40s), and back then we had a shop manager that kept our parts available for us.

Recently, I purchased a TIG torch for an Inverter machine, so I will be limited to DC welding (no aluminum).

My TIG torch is the Lincoln PTA-17V, and won on eBay:

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How do I select tungsten?

Looking in Harbor Freight's catalog, I see 2 options for 1/16" tungsten:

1) #93724-0 - EWTH-2 "1.7-2.2% thorium dioxide" 2) #93725-0 - EWCE-2 "1.8-2.2% cerium oxide"

What's the difference between thorium dioxide and cerium oxide? The price is the same. Is one for aluminum and one for steel?

Here is part 2: I have an argon/CO2 tank that I use for MIG. Since I do not intend to do a lot of TIG or MIG, I had planned to use this same cylinder for TIG welding. However, a guy at the local welding store said that I must use argon only for TIG welding and that I needed a separate meter for TIG welding than the meter I had for my MIG setup. I've never heard this! Is this true? I see meters on eBay that say they are for MIG and TIG, so I think the guy at the welding store did not know what he was talking about. Can someone verify this?

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I would be somewhat hesitant to buy tungstens from HF.

Here are some notes from one of Ernie's recent TIG class lectures:


Only 4 companies actually make tungstens. Ernie cautions that some companies have poor quality assurance especially on the outside diameter tolerance.

Pure Tungsten Don't use pure tungsten except when you're welding pop cans. Pure tungsten gives the smoothest arc of any electrode.

DC only: 2% thoriated Works OK, but thoria is radioactive so you can be exposed when grinding it. May go off the market soon.


Lanthanated: works on steel, stainless or aluminum Ernie recommends 1.5% or 1% because he says he thinks the 2% has QA issues

Ceriated: also works on most metals, but won't take as much current useful for really thin stuff because it will start an arc with the lowest amperage of any tungsten

AC only (esp. high amperage): Zirconiated Buy 1/8" in whatever doping percentage they come in, Ernie suggests, and use these in high amperage AC applications like aluminum.

Of interest also are "triple strike" tungstens by Huntington Fusion - these are supposedly doped with lanthanum, cerium, and zircon.

Tungsten Grinding

For roughing, use a silicon carbide (green) wheel. For fine, use AlOx in about 120 grit. These go well on the 2 sides of a bench grinder. Or, you can use a sanding belt, the blue kind (ZrAlOx) to rough quickly, and a diamond wheel for touching up or polishing.

The ideal angle is about like a pencil, and you don't want it dead sharp for any job requiring 150 amps or more. The tip can erode and fall off and wind up in the weld, where Ernie says it is like "a marble in cookie dough". As the weld flexes, it can tear around the tungsten inclusions.

He's partly correct. You can't use a gas that's part CO2 for TIG. But your flowmeter will work fine for a straight argon cylinder.

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Grant Erwin

Thanks Grant! That was a lot of info!

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Look an Ebay for tungstens. Nothing against Harbor Freight, but I think you can get a better price and selection on Ebay.


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the "thorium is radioactive" concern is junk

So is carbon so is graphite so are smoke detectors

Last i checked the half life of thorium is 15 billion years. That means that it takes almost 3 times the age of the earth for thorium to give off half its radiation

Uranium 235 (Fuel uranium) gives off half its radiation in 500 years (Half life)

Polonium 135 (the russian spy killer form last year) gives off half its radiation in something like 3 months

And inactive U235 fuel rod pellets are safe to handle (they also weigh more than a tungsten)

Just because it gives off "radiation" doesnt make it dangerous

if that was the case cigarettes would have been banned decades ago since they do send radioactive meterials directly into the bloodstream through the lungs.

There are many labs dealing with actual "radioactive materials" and once that can actually be dangerous

If the government and nuclear regulatory bodies don't require the users of thoriated tungsten to be registered and issued a "Dosimeter" youre safe from the radiation side.

Dont get me wrong its not good to inhale tungsten but dont blame the radiation. Heavy metal contamination and the associated "grinder scuzz" will hurt your health LONG before the "radiation" of thoria alminium and iron oxide and tungsten and oter associate chemicals thrown off the grinder are always best left out of your lungs.

Brent Ottawa Canada

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Breathing its dust while grinding is what supposedly makes it dangerous.

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Howdy! I'm a weldor at PSNS, so I don't know how well this applies to the real world....

We use the same flowmeters for four different shielding gases- just rotate the floating ball chamber until you see the correct guage markings.

Do not use CO2 in your gas mix for tig, unless it is a very small percentage (like 1% or less). It's not as bad as forgetting your shielding gas (tungsten goes puff in a yellow haze), but you will see some very quick degredation of your tungsten. Shop 26 uses pure argon for virtually all tig work, with a few special applications using 95/5 argon/helium, or custom mixing stations for exotic metals.

Remember, grind your tungsten longitudinally, not radially. Put a pencil point on it, then take the sharp tip off the point. I've got a tungsten in my torch that's lasted me for several months now, but admittedly I only get a tig assignment about once a week.

Lanthanated- Yuk! We don't like it at PSNS, and it is no longer in use here after a short trial period.

2% Thoriated- Great stuff, we use it all the time, and while it is radioactive and will set off the detectors, it is not so radioactive as to pose a risk to personnel.

Just wear your respirator while you grind it.

LOW POINT VENT!! Argon is heavier than air, and if you are doing any work in any kind of depression, be sure to vent out the argon- it will displace O2 and kill you before you realize what is happening.


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Hey TinLizzied,

Ok, so I need the pure Argon for TIG so that I don't burn up my tungsten.

Any idea why I can't use the same pure Argon for MIG?


"TinLizziedl" pitched this into the mix:

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No, that is 703 million years, otherwise there would be not enough left on earth for it to be a practical nuclear fuel.

Just comparing the half life of the different elements gives an incomplete picture. You could be holding several grams of thorium atoms in a pack of tungstens, which is a much, much larger number of atoms than the americum in a smoke detector etc. and even the smoke detector would be quite unhealthy if you ground it up and inhaled it. If you borrow a geiger counter and hold it near the thoriated rods, you will notice quite a lot of clicking, compared to any other common object that you would allow to enter your body.

and the lethal dose is about 1 microgram

Yeah well I would not grind them up unless I had a very good reason to.

I don't see the connection - cigarettes do kill people. The reason that they are not banned is not because they don't kill people, it's because some people like smoking them, and other people like selling them.

Well if there is an alternative rod that is just as good for welding as the thoriated rod, then why not use it? Are the alternatives any good?

I for one wish that I had not used thoriated rods in the past - especially because I was not much good at welding so I did quite a bit of grinding!


Reply to
Chris Jones

I see some questionable statements herein. I'll type within. Martin

Mart> >>> I have not operated a TIG machine since I was in my early 20s (now

Be cautious - the error is below! I have a degree in Physics and took Atomic from a Manhattan PhD Tech.

Carbon by nature can be made but isn't naturally. Graphite likewise. Soft coal is dangerous it contains Thorium naturally. So a soft coal plants emit more radiation than a 'nuke'(negative name) power plant does.

The half life means this : During the first half most of the radiation is active and by the half life the dose is 1/2 the value.

Therefore you want a half life of 3.5 years and in 4 and 8 years it might be safer. The watches that used heavy water sort to speak was 3.5 years. They started to get dark and then after the 2x or 7 the watch still worked but the background was to dark to see.

It doesn't take half of the lifetime to give it off - it decays to half intensity.

You confuse half life as something it isn't.

Inactive Huh U235 fuel rod pellets are safe ?? not.

Depleted is used as bullet cores for war. Tank busters.. All of it is picked up and that means cutting it out of busted tanks and sand. It is not safe - they hunt for it by instruments, not eyes.

Alpha particles won't get into the skin or paper. It is to thick. However the small thin layers in the lung can be passed through. So the rad stuff in cigs does get people and contribute to the cancer.

Beta goes through skin and then some it can kill.

Gamma goes through the body and through thick layers of some materials.

The best Neutron absorber - e.g. shield from a strong 'bullet' is paraffin wax. Concrete block and wax and other chemicals are better shields.

I helped build a neutron gun in school. Had to help build the containment...

No you are wrong again. Go ahead for yourself. One simply doesn't do what can hurt themselves. Like sound - often they are late. And some places have laws for protection.

Reply to
Martin H. Eastburn

Howdy! You can use pure argon for mig, but you will note a difference in how your beads run. When I did my pulse tests, we used a mix of 95% argon, 5% CO2. This gave us a good bead profile, good penetration, low spatter, and in general it just "ran" better than pure argon. For spray we used the same mix, and the results were again better than running pure argon.

We were using gas mixers, and we got to play around a little with our settings just so we could see why the shipyard has specified what mix we use on the waterfront.

If you would like some photos of what the difference is in how the beads look and what kind of penetration you get, I'm sure I could either find them in my books or call up my trade instructor and ask him if I could borrow a pic or two...

Try it out! If you have a decent vendor, they may well be willing to set up an experiment for you, or you can go to most any place that teaches welding (here in Bremerton, Olympic College) and I'm sure they would be happy to not just explain what you should use but also be able to show you why.

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Fellow physics guy here. I only went as far as my BS at the University of Texas in Arlington (UTA).

Took my first year of grad school thinking I'd get the harder stuff our of the way first: Quantum Mechanics, Math Methods, Thermodynamics, and Classical Electricity and Magnetism. The titles to these courses mimicked classes I had completed as an undergrad. Ha! Going off the axis introduced hours and hours of extra mathematics!

I finished the year with a C average, losing my Teaching Assistantship and grants.

The department told me I could write a letter requesting to be re-admitted and that loans were available to me, but that wasn't for me.

So, I dr> Be cautious - the error is below! I have a degree in Physics and took > Atomic

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However, IIRC, the amount of ionizing radiation emitted by the Th is inversly proportional to the half-life, right? So a material with a 3 year half life is considerably more radioactive over the short term than a material with a much longer half-life.


Reply to
Scott Lurndal

I lived several blocks away and and ate sometimes at the Wataberger(sp) just off campus - and in 70 - have some docs yet (dumb me :-) ) was a charter member of the North Texas Computer Club hosted at UTA. Gosh Physics at an Engineering school - how could you :-)

I was mostly an E&M Electro & Magnetic type. Was moving into High Energy and had an assistance ship when my mother-in-law became terminal. SO I taught for 12 years and then moved into industry.


Mart> Martin,

Reply to
Martin H. Eastburn

I'd have to get out the books but that in general doesn't sound right.

I can have some really hot very long life stuff that burns forever almost and some short stuff that isn't nearly as hot and depletes it self in a short time.

Mart> "Mart>>> >

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Martin H. Eastburn

E&M was always my favorite subject (although gravity was becoming more and more interesting).

My main problem was that I never could see the symmetry when it came to solving the math problems. If the problem said there was an infinitely long line charge, I *always* tried to calculate the charge from theta = 0 to pi. On homework problems, I could see the symmetry and just treat it as a point source - but not come test time!

Though I loved E&M, there aren't really any studies going on in that area these days. I spent most of my time hanging out with the High Energy guys there: Dr. Andrew White and Dr. Ransom Stephens. Of course, that was back when they were still building the super collider that eventually became the big abandoned hole in the ground.

So, what do you do with physics these days? Are you a Welding Engineer? I was trained to be a welder before college while I was in the Marine Corps. Had I known there was such a field as a Welding Engineer back then when I was going to college, I certainly would have gone that route! Career councilors that the government uses aren't worth a crap. They only know 5 to

10 of the big main areas that people typically go into. I spoke with them to try to find out what I'd be good going into. I told them I was interested in physics, so they said I should go into physics. {sigh} Idiots.

Saw your post above about "Force of Impact = M * A." I suppose whenever a mass suddenly stops, it does have an instant negative acceleration, but it seems like a better expression would be for the kinetic energy: KE = 1/2 M * V^2. Your formula works out to be the same after taking the derivative of mine, so its just a preference. F = MA is certainly more common! :)

I haven't talked physics >I lived several blocks away and and ate sometimes at the Wataberger(sp)

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I just finished (tonight) cutting out 4 12x12 squares with 2" round corners and will weld a pipe flange in the center (post cleaning and acid washing both the

1/4" steel and flanges. For an artist type doing something with balloons...

I use Hf as a electron and element source blasting out of my plasma torch. It was a hobby that I make a little money on the side to keep life fun. My wife and several art types are biggest customers. But I ship targets Nation wide.

Write a little and give advice. Fix stuff and design a few things.

Give my dad the biggest push - keep his mind and mine going - he gets back - I send something about the machine in Cern and I get "String Theory and M-Theory" Becker(s) and Schwarz for 'light' reading in return!

Serve as a science adviser to one group and just completed being a Science adviser to a private school. We moved. It was into Hydrogen fuel cells and got :-) a department of Energy a grant for research. Mostly development, investigation and nation wide display and use. I built the test gear that verified operation and measurement points.

But being an IC and PCB designer which both jobs (overlapping) required some high tech understanding. Use of Smith charts and exotic instruments was my game. Solving a problem of whatever.

I was trained to think. To observe and think. Provide solutions or pathways to a solution.

But lately, being semi-retired, I'm a Conchologist, metal cutter/welder, cabinet maker and having fun re-loading using my high tech scale.

Oh - I do send email to department and division heads back at school - the division head was starting his teaching about the time I graduated. I sent them how to generate ball lighting in the lab. That was something that might be fun and a good experiment.

Mart> E&M was always my favorite subject (although gravity was becoming more and

Reply to
Martin H. Eastburn

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