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Posted by Brent on September 4, 2007, 2:32 pm
Please log in for more thread options > jp2express wrote:
> > 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:
> >http://www.mylincolnelectric.com/Catalog/equipmentdatasheet.asp?p=562
>
> > 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?
>
> I would be somewhat hesitant to buy tungstens from HF.
>
> Here are some notes from one of Ernie's recent TIG class lectures:
>
> Tungstens
>
> 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.
>
> AC/DC:
>
> 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.
>
> > 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?
>
> 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.
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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> 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:
> http://www.mylincolnelectric.com/Catalog/equipmentdatasheet.asp?p=562
>
> 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?